Updated on 2024/03/29

写真a

 
OHKAWA Masashi
 
Organization
Academic Assembly Institute of Science and Technology JOUHOU DENSHI KOUGAKU KEIRETU Professor
Graduate School of Science and Technology Electrical and Information Engineering Professor
Faculty of Engineering Department of Engineering Professor
Title
Professor
External link

Degree

  • 工学博士 ( 1989.3   大阪大学 )

Research Areas

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electron device and electronic equipment

Research History

  • Niigata University   Faculty of Engineering Department of Engineering   Professor

    2017.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

  • Niigata University   Faculty of Engineering Department of Biocybernetics   Professor

    2004.4 - 2017.3

  • Niigata University   Faculty of Engineering   Lecturer

    1993.4 - 1995.5

  • Niigata University   Faculty of Engineering   Research Assistant

    1989.4 - 1993.3

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Papers

  • Response of the underground environment of the KAGRA observatory against the air pressure disturbance from the Tonga volcanic eruption on January 15, 2022

    Tatsuki Washimi, Takaaki Yokozawa, Akiteru Takamori, Akito Araya, Sota Hoshino, Yousuke Itoh, Yuichiro Kobayashi, Jun'Ya Kume, Kouseki Miyo, Masashi Ohkawa, Shoichi Oshino, Takayuki Tomaru, Jun'Ichi Yokoyama, Hirotaka Yuzurihara

    Progress of Theoretical and Experimental Physics   2022 ( 11 )   2022.11

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    Publishing type:Research paper (scientific journal)  

    On January 15, 2022, at 04:14:45 (UTC), the Hunga Tonga-Funga Ha'apai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, erupted and generated global seismic, shock, and electromagnetic waves, which also reached Japan, situated more than 8000 km away. KAGRA is a gravitational wave telescope located in an underground facility in Kamioka, Japan. It has a wide variety of auxiliary sensors to monitor environmental disturbances that obstruct the observation of gravitational waves. The effects of the volcanic eruption were observed by these environmental sensors both inside and outside of the underground facility. In particular, the shock waves made it possible to evaluate the transfer functions from the air pressure wave in the atmosphere to the underground environmental disturbances (air pressure and seismic motion).

    DOI: 10.1093/ptep/ptac128

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  • The Current Status and Future Prospects of KAGRA, the Large-Scale Cryogenic Gravitational Wave Telescope Built in the Kamioka Underground

    Homare Abe, Tomotada Akutsu, Masaki Ando, Akito Araya, Naoki Aritomi, Hideki Asada, Yoichi Aso, Sangwook Bae, Rishabh Bajpai, Kipp Cannon, Zhoujian Cao, Eleonora Capocasa, Man Leong Chan, Dan Chen, Yi Ru Chen, Marc Eisenmann, Raffaele Flaminio, Heather K. Fong, Yuta Fujikawa, Yuya Fujimoto, I. Putu Wira Hadiputrawan, Sadakazu Haino, Wenbiao Han, Kazuhiro Hayama, Yoshiaki Himemoto, Naoatsu Hirata, Chiaki Hirose, Tsung Chieh Ho, Bin Hua Hsieh, He Feng Hsieh, Chia Hsuan Hsiung, Hsiang Yu Huang, Panwei Huang, Yao Chin Huang, Yun Jing Huang, David C.Y. Hui, Kohei Inayoshi, Yuki Inoue, Yousuke Itoh, Pil Jong Jung, Takaaki Kajita, Masahiro Kamiizumi, Nobuyuki Kanda, Takashi Kato, Chunglee Kim, Jaewan Kim, Young Min Kim, Yuichiro Kobayashi, Kazunori Kohri, Keiko Kokeyama, Albert K.H. Kong, Naoki Koyama, Chihiro Kozakai, Jun’Ya Kume, Sachiko Kuroyanagi, Kyujin Kwak, Eunsub Lee, Hyung Won Lee, Ray Kuang Lee, Matteo Leonardi, Kwan Lok Li, Pengbo Li, Lupin Chun Che Lin, Chun Yu Lin, En Tzu Lin, Hong Lin Lin, Guo Chin Liu, Ling Wei Luo, Miftahul Ma’arif, Yuta Michimura, Norikatsu Mio, Osamu Miyakawa, Kouseki Miyo, Shinji Miyoki, Nozomi Morisue, Kouji Nakamura, Hiroyuki Nakano, Masayuki Nakano, Tatsuya Narikawa, Lan Nguyen Quynh, Takumi Nishimoto, Atsushi Nishizawa, Yoshihisa Obayashi, Kwangmin Oh, Masatake Ohashi, Tomoya Ohashi, Masashi Ohkawa, Yoshihiro Okutani, Ken Ichi Oohara, Shoichi Oshino, Kuo Chuan Pan, Alessandro Parisi, June Gyu Park, Fabián E. Peña Arellano, Surojit Saha, Kazuki Sakai, Takahiro Sawada, Yuichiro Sekiguchi, Lijing Shao, Yutaka Shikano

    Galaxies   10 ( 3 )   2022.6

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    KAGRA is a gravitational-wave (GW) detector constructed in Japan with two unique key features: It was constructed underground, and the test-mass mirrors are cooled to cryogenic temperatures. These features are not included in other kilometer-scale detectors but will be adopted in future detectors such as the Einstein Telescope. KAGRA performed its first joint observation run with GEO600 in 2020. In this observation, the sensitivity of KAGRA to GWs was inferior to that of other kilometer-scale detectors such as LIGO and Virgo. However, further upgrades to the detector are ongoing to reach the sensitivity for detecting GWs in the next observation run, which is scheduled for 2022. In this article, the current situation, sensitivity, and future perspectives are reviewed.

    DOI: 10.3390/galaxies10030063

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  • Physical-random number generation via a diode laser's frequency noise: an investigation into frequency discriminator Reviewed

    Arai Hideaki, Sato Takashi, Doi Kohei, Ohdaira Yasuo, Sakamoto Shuichi, Ohkawa Masashi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 ( 1 )   2019.1

  • Space gravitational-wave antennas DECIGO and B-DECIGO

    Seiji Kawamura, Takashi Nakamura, Masaki Ando, Naoki Seto, Tomotada Akutsu, Ikkoh Funaki, Kunihito Ioka, Nobuyuki Kanda, Isao Kawano, Mitsuru Musha, Kazuhiro Nakazawa, Shuichi Sato, Takeshi Takashima, Takahiro Tanaka, Kimio Tsubono, Jun’ichi Yokoyama, Kazuhiro Agatsuma, Koh suke Aoyanagi, Koji Arai, Akito Araya, Naoki Aritomi, Hideki Asada, Yoichi Aso, Dan Chen, Takeshi Chiba, Toshikazu Ebisuzaki, Satoshi Eguchi, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Rina Gondo, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Kiwamu Izumi, Shinya Kanemura, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Sachiko Kuroyanagi, Kei ichi Maeda, Hideo Matsuhara, Nobuyuki Matsumoto, Yuta Michimura, Osamu Miyakawa, Umpei Miyamoto, Shinji Miyoki, Mutsuko Y. Morimoto, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama, Shigeo Nagano, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Naoko Ohishi, Masashi Ohkawa, Kenshi Okada, Norio Okada, Koki Okutomi, Kenichi Oohara, Norichika Sago

    International Journal of Modern Physics D   28 ( 12 )   2018.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WORLD SCIENTIFIC PUBL CO PTE LTD  

    © 2018 World Scientific Publishing Company DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna. The most important objective of DECIGO, among various sciences to be aimed at, is to detect gravitational waves coming from the inflation of the universe. DECIGO consists of four clusters of spacecraft, and each cluster consists of three spacecraft with three Fabry–Perot Michelson interferometers. As a pathfinder mission of DECIGO, B-DECIGO will be launched, hopefully in the 2020s, to demonstrate technologies necessary for DECIGO as well as to lead to fruitful multimessenger astronomy. B-DECIGO is a small-scale or simpler version of DECIGO with the sensitivity slightly worse than that of DECIGO, yet good enough to provide frequent detection of gravitational waves.

    DOI: 10.1142/S0218271818450013

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  • Output characteristics for high-order resonance modes in resonance-type guided-wave optical acoustic emission sensors Reviewed

    Kenta Shimizu, Masashi Ohkawa, Takashi Sato

    22nd Microoptics Conference, MOC 2017   2017-   238 - 239   2018.1

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Electrical and Electronics Engineers Inc.  

    A resonance-type guided-wave optical acoustic emission (AE) sensor consists of a diaphragm and a single-mode optical waveguide. In order to increase detectable frequency, the feasibility of application of high-order resonance modes was examined by their measured output characteristics using acoustic pulses or continuous waves instead of AE pulses.

    DOI: 10.23919/MOC.2017.8244574

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  • Diaphragm thickness-dependent sensitivity in a glass-based guided-wave optical microphone Reviewed

    Yutaro Karasawa, Masashi Ohkawa, Takashi Sato

    22nd Microoptics Conference, MOC 2017   2017-   248 - 249   2018.1

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Electrical and Electronics Engineers Inc.  

    Our original guided-wave optical microphone consists of a diaphragm and a single-mode optical waveguide. Sensitivity is an important specification for microphones, and is theoretically known to be dependent on diaphragm thickness. In this study, we fabricated three microphones with different diaphragm thicknesses, and experimentally examined the diaphragm thickness-dependent sensitivity.

    DOI: 10.23919/MOC.2017.8244579

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  • Fast physical-random number generation for laser range finders using a laser diode's frequency noise -Comparison of the used lasers for fast random number generation- Reviewed

    Kasuya Yuki, Suzuki Masamichi, Matsumoto Kouhei, Arai Hideaki, Sato Takashi, Sakamoto Shuichi, Ohkawa Masashi, Ohdaira Yasuo

    MULTISPECTRAL, HYPERSPECTRAL, AND ULTRASPECTRAL REMOTE SENSING TECHNOLOGY, TECHNIQUES AND APPLICATIONS VII   10780   2018

  • Optical distance measuring system using a laser diode's fast frequency noise as a detection signal Reviewed

    Suzuki Masamichi, Kasuya Yuki, Kawakami Daiki, Sato Takashi, Ohkawa Masashi, Ohdaira Yasuo, Sakamoto Shuichi

    MULTISPECTRAL, HYPERSPECTRAL, AND ULTRASPECTRAL REMOTE SENSING TECHNOLOGY, TECHNIQUES AND APPLICATIONS VII   10780   2018

  • Fast physical-random number generation using laser diode's frequency noise -Influence of frequency discriminator- Reviewed

    Matsumoto Kouhei, Kasuya Yuki, Yumoto Mitsuki, Arai Hideaki, Sato Takashi, Sakamoto Shuichi, Ohkawa Masashi, Ohdaira Yasuo

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XXVI   10526   2018

  • Physical-random number generator using an oscillation frequency stabilized laser diode Reviewed

    Hirai Kyohei, Taoka Toshihiro, Sato Takashi, Doi Kohei, Ohdaira Yasuo, Sakamoto Shuichi, Ohkawa Masashi

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XXVI   10526   2018

  • Optical distance measuring method using fast frequency noise characteristics of a laser diode Reviewed

    Kawakami Daiki, Suzuki Masamichi, Kimura Ryotaro, Sato Takashi, Saito Takahiro, Ohkawa Masashi, Ohdaira Yasuo, Sakamoto Shuichi

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XXVI   10526   2018

  • The status of DECIGO Reviewed

    Shuichi Sato, Seiji Kawamura, Masaki Ando, Takashi Nakamura, Kimio Tsubono, Akito Araya, Ikkoh Funaki, Kunihito Ioka, Nobuyuki Kanda, Shigenori Moriwaki, Mitsuru Musha, Kazuhiro Nakazawa, Kenji Numata, Shin Ichiro Sakai, Naoki Seto, Takeshi Takashima, Takahiro Tanaka, Kazuhiro Agatsuma, Koh Suke Aoyanagi, Koji Arai, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei Ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shinji Mukohyama, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Norio Okada, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shihori Sakata, Misao Sasaki

    Journal of Physics: Conference Series   840 ( 1 )   2017.6

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    © Published under licence by IOP Publishing Ltd. DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present..

    DOI: 10.1088/1742-6596/840/1/012010

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  • Study on the resolution improvement of a range finder using the chaotic frequency characteristics of a laser diode Reviewed

    Takahiro Saito, Shinya Maehara, Kohei Doi, Takashi Sato, Yasuo Ohdaira, Shuichi Sakamoto, Masashi Ohkawa

    OPTICAL ENGINEERING   56 ( 6 )   1 - 6   2017.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

    An optical range finder system that relies on laser diodes' frequency noise, instead of intensity or frequency modulations, and its improvement in resolution are reported. The distance to the target is measured by calculating the cross-correlation of two signals reflected from the target and reference mirrors. These two signals are converted from the laser diodes' frequency noise signals by frequency/intensity converters, such as a Fabry-Perot etalon. We obtained the distance to the target by checking time lags between the target and reference beams at the highest correlation coefficient. We also measured the change in the correlation coefficient around the peak sampling point by adjusting the reference-path length, achieving a resolving power of +/- 3 mm. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

    DOI: 10.1117/1.OE.56.6.064101

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  • Design guidelines for a guided-wave optical pressure sensor based on dependences of sensitivity and resonance frequency on diaphragm dimensions Reviewed

    Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    OPTICAL ENGINEERING   56 ( 5 )   2017.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

    Design guidelines for a guided-wave optical pressure sensor based on dependences of sensitivity and resonance frequency on diaphragm dimensions were considered. The guided-wave optical pressure sensor consists of a diaphragm and a single-mode waveguide on the diaphragm. According to our theoretical study, the edge of the diaphragm was found to be the best position to obtain the highest sensitivity. Also, sensitivity is proportional to the cube of the side length of the diaphragm but inversely proportional to the square of the diaphragm thickness. On the other hand, resonance frequency of the diaphragm is proportional to the diaphragm thickness and inversely proportional to the square of the side length. Dependences were experimentally examined for fabricated sensors with different diaphragm dimensions to confirm theoretical predictions. The experimental results agreed well with the theoretical predictions. Moreover, a design assistant chart for the sensor was proposed based on the dependences. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

    DOI: 10.1117/1.OE.56.5.057108

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  • Beat Signal Generation between Two Rubidium Absorption-Line-Stabilized Diode Lasers in GHz-Frequency Band Reviewed

    Tomoyuki Uehara, Shinya Maehara, Kohei Doi, Toshiya Nimonji, Takahiro Saito, Hideaki Arai, Takashi Sato, Yasuo Ohdaira, Shuichi Sakamoto, Masashi Ohkawa

    International Journal of Modern Physics and Applications   2 ( 1 )   1 - 6   2016.3

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    Language:English   Publishing type:Research paper (scientific journal)  

    A stable microwave source using frequency stabilized diode lasers was developed. The Doppler-free spectra of Rb atoms produced by saturated absorption spectroscopy were used to obtain highly-sensitive control signals and lock the frequency of diode lasers to it. The beat frequencies between two independently stabilized diode lasers were 1.2 GHz and 2.9 GHz. The fluctuations in beat frequencies were 40 kHz and 400 kHz respectively in the best stability.

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  • Silicon-based guided-wave optical flow sensor using a diaphragm with a small opening as an orifice Reviewed

    Masashi Ohkawa, Takashi Sato

    OPTICAL ENGINEERING   55 ( 1 )   2016.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

    Our proposed silicon-based guided-wave optical flow sensor consists of a diaphragm with a small opening used as an orifice and a waveguide across the diaphragm. The sensor operates based on Bernoulli's theorem and the elasto-optic effect. A sensor, which had a 10 x 10-mm(2), 50-mu m-thick diaphragm with a 0.34 x 0.34-mm(2) opening, was fabricated to demonstrate and confirm the sensor operation. Measured output power as a function of flow rate using oxygen gas agreed quite well with the theoretical prediction although slight deviation was seen in the high flow rate region. Moreover, according to Bernoulli's theorem, sensitivity is strongly dependent on sectional area of opening. So, three sensors with different opening areas, such as 0.28 x 0.28, 0.34 x 0.34, and 0.55 x 0.55 mm(2), were fabricated to examine such a dependence, which would be helpful to design the sensor. The measured sensitivity was found to be almost proportional to area of the opening, similar to the theoretical prediction. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

    DOI: 10.1117/1.OE.55.1.017102

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  • Development of laser intensity stabilization system for the gravitational wave observation III

    Sugimoto Yusuke, Moriwaki Yoshiki, Matsushima Fusakazu, Kobayashi Kaori, Kambara Shougo, Furuhata Takayuki, Kawamura Seiji, Miyakawa Osamu, Kokeyama Keiko, Nakano Masayuki, Telada Souichi, Akutsu Tomotada, Aso Youichi, Ueda Akitoshi, Ohishi Naoko, Michimura Yuta, Somiya Kentaro, Yano Kazushiro, Sato Takeshi, Ohkawa Masashi, Saitou Takahiro, Shiga Kazunari, Uehara Tomoyuki, Ohmae Noriaki, Yoon Tai Hyun

    Meeting Abstracts of the Physical Society of Japan   71   526 - 526   2016

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_526

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  • 19aBA-5 Development of laser intensity stabilization system for KAGRA

    Kagawa T., Moriwaki Y., Matsushima F., Kobayashi K., Sugimoto Y., Kambara S., Fujisawa M., Furuhata T., Kawamura S., Miyakawa O., Kokeyama K., Nakano M., Telada S., Akutsu T., Aso Y., Ueda A., Ohishi N., Michimura Y., Somiya K., Yano K., Sato T., Ohkawa M., Saitou T., Shiga K., Uehara T., Ohmae N., Yoon Tai Hyun

    Meeting Abstracts of the Physical Society of Japan   70   568 - 568   2015

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    DOI: 10.11316/jpsgaiyo.70.2.0_568

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  • Frequency noise characteristics of a diode laser and its application to physical random number generation

    Shinya Maehara, Kohei Kawakami, Hideaki Arai, Kenji Nakano, Kohei Doi, Takashi Sato, Yasuo Ohdaira, Shuichi Sakamoto, Masashi Ohkawa

    OPTICAL ENGINEERING   52 ( 1 )   2013.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

    We describe a method of generating physical random numbers by means of a diode laser that has an extremely wide-band frequency-noise profile. Fluctuations in the laser frequency affect the intensity of the light transmitted through the optical frequency discriminator, detected thereafter as random fluctuations. This allows us to simultaneously generate 8 random bit streams, due to the parallel processing of 8-digit binary numbers sampled by an 8-bit analog-to-digital converter. Finally, we generated physical random numbers at a rate of 3 Gbit/s, by combining one data stream with another stream that is delayed by 2 ms, by exclusive-OR. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.OE.52.1.014302]

    DOI: 10.1117/1.OE.52.1.014302

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  • Output Response Characteristics of Resonant-Type Guided-Wave Optical Acoustic Emission Sensor Reviewed

    Sotaro Tachibana, Masashi Ohkawa, Takashi Sato

    2013 IEEE SENSORS   1875 - 1878   2013

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    Our group has proposed a resonant-type guided-wave optical acoustic emission (AE) sensor, which consists of a diaphragm and a single-mode optical waveguide on the diaphragm. In this study, we examined output response characteristics of the AE sensor using an acoustic sound pulse, instead of an AE pulse. Output responses of a fabricated AE sensor were investigated for each parameter, namely pulse duration, sound pressure (amplitude) and frequency. A larger output signal was obtained due to resonance effect, but it lacked similarity to the original target pulse due to a narrow bandwidth and required approximately 10 ms to reach the steady state. However, based on the experimental results, a formula was derived to determine pulse duration and amplitude. In the case of out-of-resonance, output signal is more complex, but the frequency deviation from the resonance frequency could be determined from the beat-like phenomenon for long-duration pulse.

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  • Scale-reduction rule without drop in the sensitivity of a silicon-based guided-wave optical pressure sensor using a micromachined diaphragm Reviewed

    Masashi Ohkawa, Takashi Sato

    OPTICAL ENGINEERING   51 ( 1 )   014401-1 - 6   2012.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

    In this study, an original scale-reduction rule without a drop in the sensitivity of a guided-wave optical pressure sensor was obtained using a micromachined diaphragm. The sensor has a rectangular diaphragm as a pressure-sensitive structure and a sensing waveguide across the diaphragm. Its sensitivity is theoretically known to be strongly dependent on the dimensions of the diaphragm. According to the theoretical results, the sensitivity can be kept constant even if the diaphragm dimensions are reduced as long as both the aspect ratio and the characteristic length of the diaphragm remain constant. Here, the characteristic length is introduced as the cube of either width or length of the rectangular diaphragm divided by the square of its thickness. Such a scale-reduction rule would be very useful for miniaturizing a sensor without reducing sensitivity, although it has not been experimentally confirmed. In this study, the scale-reduction rule was experimentally examined using three fabricated sensors with the same aspect ratio and the same characteristic length. The measured sensitivities of the three sensors were quite similar to each other, as theoretically predicted. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.OE.51.1.014401]

    DOI: 10.1117/1.OE.51.1.014401

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  • Evaluation of Damping Ratio in a Glass-Based Guided-Wave Optical Microphone with a Diaphragm

    Masashi Ohkawa, Kazuya Murata, Takashi Sato

    INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES XVI   8264   82641I   2012

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:SPIE-INT SOC OPTICAL ENGINEERING  

    In a guided-wave optical microphone with a diaphragm used as a vibration plate, damping of diaphragm vibration is very significant in order to realize broad flat frequency response. In this study, a glass-based guided-wave optical microphone without a damping structure was experimentally examined to evaluate the damping ratio as the first phase in the optimization of damping. Damping ratio and resonance frequency were successfully evaluated to be 0.009 and 3.5 kHz, respectively, for a fabricated microphone with a diaphragm of 20 mm x 20 mm x 0.15 mm.

    DOI: 10.1117/12.910286

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  • Design Study of a Guided-Wave Optical Microphone with a Diaphragm

    Kazuya Murata, Masashi Ohkawa, Takashi Sato

    2012 IEEE SENSORS PROCEEDINGS   2160 - 2163   2012

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    Our guided-wave optical microphone consists of a diaphragm and a single-mode optical waveguide on the diaphragm. Since sensitivity and frequency response are strongly dependent on waveguide position and diaphragm dimensions, designing the microphone is relatively complicated without a design guideline. In this report, a convenient and helpful chart diagram when designing the microphone is proposed based on theoretical and experimental results on dependences of sensitivity and resonance frequency on diaphragm dimensions. In addition, since damping of diaphragm vibration is also vital in obtaining a broader flat frequency response, squeeze-film air damping is discussed.

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  • Silicon-Based Guided-Wave Optical Accelerometer: Experimental Consideration to Establish its Design Guideline

    Natsumi Saito, Yusuke Miura, Takuya Oshima, Masashi Ohkawa, Takashi Sato

    2012 IEEE SENSORS PROCEEDINGS   453 - 456   2012

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    Our group has proposed and demonstrated a silicon-based guided-wave optical accelerometer with a proof mass centered on a diaphragm. It is strongly suggested that sensitivity is related to many factors, such as waveguide position, diaphragm dimensions, and size and weight of proof mass. These relationships need to be clearly identified in order to establish a design guideline. In this study, sensitivity dependences on waveguide position and diaphragm dimensions were experimentally examined. Regarding waveguide position, phase sensitivity was highest for the waveguide at the diaphragm edge, and was also relatively high for the waveguide at the edge of proof mass. Regarding diaphragm dimensions, phase sensitivity was found to be inversely proportional to the square of the diaphragm thickness, and proportional to the side length of the diaphragm.

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  • Oscillation wavelength shifts observed in vertical cavity surface emitting lasers exposed to magnetic fields

    Y. Yamagishi, S. Tabira, Y. Matsumoto, K. Doi, T. Sato, M. Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XX   8255   825522   2012

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:SPIE-INT SOC OPTICAL ENGINEERING  

    Even as long ago as the 1960's, scientists understood that diode lasers' oscillation wavelengths demonstrated significant shifts to the shorter wavelength side, when subjected to strong magnetic fields, at extremely low temperatures. When we exposed Fabry-Perot type diode lasers oscillating at 780 nm to weak magnetic fields, at room temperature, the oscillation wavelength was observed to have shifted to the longer wavelength side. In discussions of shift mechanisms aimed at explaining how/why our results differ from those obtained in studies conducted in the 1960's, we noted a rise in temperature and an increase in the carrier density, and how it affected the characteristic shifts observed, when a magnetic field was applied to the Fabry-Perot type laser diodes parallel to the injection current. In the present work, we tested the oscillation wavelength shift of a vertical-cavity surface-emitting laser (VCSEL) in a magnetic field, because we expected that, by doing so, the VCSEL would show a shorter wavelength side shift.

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  • Fast Random-Number Generation Using a Diode Laser's Frequency Noise Characteristic

    Hiroki Takamori, Kohei Doi, Shinya Maehara, Kohei Kawakami, Takashi Sato, Masashi Ohkawa, Yasuo Odaira

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XX   8255   825521   2012

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    Random numbers can be classified as either pseudo- or physical-random, in character. Pseudo-random numbers are generated by definite periodicity, so, their usefulness in cryptographic applications is somewhat limited. On the other hand, naturally-generated physical-random numbers have no calculable periodicity, thereby making them ideal for the task. Diode lasers' considerable wideband noise gives them tremendous capacity for generating physical-random numbers, at a high rate of speed. We measured a diode laser's output with a fast photo detector, and evaluated the binary-numbers from the diode laser's frequency noise characteristics. We then identified and evaluated the binary-number-line's statistical properties. We also investigate the possibility that much faster physical-random number parallel-generation is possible, using separate outputs of different optical-path length and character, which we refer to as "coherence collapse".

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  • Oscillation frequency stabilization and narrowing of a laser diode by using an external cavity

    Minoru Iwahori, Kohei Doi, Hideaki Arai, Takashi Sato, Masashi Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XX   8255   825529   2012

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    External cavity diode laser (ECDL) systems are presently experiencing a surge in popularity as laser light-sources, in advanced optical communications- and measurement-applications. Because such systems require that their external reflectors be precisely controlled, to eliminate low frequency fluctuations in optical output, we conducted experiments with a two-cavity version of the ECDL system for a vertical cavity surface emitting laser (VCSEL). This technique brings the added advantages of a narrower linewidth than would be achievable via a single optical feedback. VCSELs are characterized by wider oscillation linewidths than edge emitting types, so the larger effect of double optical feedback system is expected.

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  • THz wave generation using frequency stabilized laser diodes

    Yasuhito Minamisawa, Tosiya Nimonji, Kenji Nakano, Takashi Sato, Masashi Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XX   8255   82551L   2012

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    A laser diode (LD) has been used in many areas, such as optical communication systems. However, its oscillation frequency changes, with variations in ambient temperature and injection current, so its frequency stabilization is of vital importance. In these situations, Rb saturated absorption spectroscopy is the method of choice. We use the beat signal, both for the purpose of evaluating frequency stability between two independently stabilized LDs, and for generating THz waves. This work shows a basic experiment using our beat signal observation, by high-speed photodetector. In addition, we have also used a frequency-stabilized etalon, to improve frequency selectivity.

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  • Damping ratio in a glass-based guided-wave optical microphone without a damping structure

    Kazuya Murata, Kazuaki Yoshida, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 17th Microooptics Conference   H-59   2011.11

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  • The Japanese space gravitational wave antenna: DECIGO Reviewed

    Seiji Kawamura, Masaki Ando, Naoki Seto, Shuichi Sato, Takashi Nakamura, Kimio Tsubono, Nobuyuki Kanda, Takahiro Tanaka, Jun'ichi Yokoyama, Ikkoh Funaki, Kenji Numata, Kunihito Ioka, Takeshi Takashima, Kazuhiro Agatsuma, Tomotada Akutsu, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Dan Chen, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Kiwamu Izumi, Isao Kawano, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Sachiko Kuroyanagi, Kei-ichi Maeda, Hideo Matsuhara, Nobuyuki Matsumoto, Yuta Michimura, Osamu Miyakawa, Umpei Miyamoto, Shinji Miyoki, Mutsuko Y. Morimoto, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama, Mitsuru Musha, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Kazuhiro Nakazawa, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Kenshi Okada, Norio Okada, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Ryo Saito, Masaaki Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Ayaka Shoda, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Nobuyuki Tanaka, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Yasuo Torii, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka Wakabayashi, Kent Yagi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino, Ke-Xun Sun

    CLASSICAL AND QUANTUM GRAVITY   28 ( 9 )   094011   2011.5

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    The objectives of the DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) are to open a new window of observation for gravitational wave astronomy and to obtain insight into significant areas of science, such as verifying and characterizing inflation, determining the thermal history of the universe, characterizing dark energy, describing the formation mechanism of supermassive black holes in the center of galaxies, testing alternative theories of gravity, seeking black hole dark matter, understanding the physics of neutron stars and searching for planets around double neutron stars. DECIGO consists of four clusters of spacecraft in heliocentric orbits; each cluster employs three drag-free spacecraft, 1000 km apart from each other, whose relative displacements are measured by three pairs of differential Fabry-Perot Michelson interferometers. Two milestone missions, DECIGO pathfinder and Pre-DECIGO, will be launched to demonstrate required technologies and possibly to detect gravitational waves.

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  • Oscillation frequency shifts observed in vertical cavity surface emitting lasers exposed to magnetic fields

    T. Kobayashi, Y. Yamagishi, H. Arai, Y. Matsumoto, T. Sato, M. Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XIX   7933   79331O   2011

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    As long ago as the 1960's, scientists understood that Diode lasers' oscillation wavelengths showed a significant shift to the shorter wavelength (high frequency) side, when exposed to strong (<4[T]) magnetic fields, at extremely low temperatures (<80[K]). Not surprisingly, then, in preliminary tests, when we exposed Fabry/Perot-type diode lasers oscillating at 780[nm] to weak magnetic fields (<1.4[T]), at room temperature (300[K]), we observed that the oscillation wavelength shifted to the longer (low frequency) wavelength side. In the present work, we used vertical-cavity surface-emitting lasers (VCSEL) to check whether its change into the shorter wavelength side takes place.
    In discussions of shift mechanisms, we consider how wavelength (frequency) and optical output-power shifts are correlated. Our expanded knowledge base has forced us to use a completely different mechanism to explain how/why our results differ from those obtained in studies conducted in the 1960's. We are now introducing a mechanism that affects a rise in temperature and an increase in the carrier density, affect the characteristic shifts observed in our experiments, when a magnetic field is applied to the laser diodes parallel to the injection current.

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  • Super fast physical-random number generation using laser diode frequency noises

    Tetsuro Ushiki, Kohei Doi, Shinya Maehara, Takashi Sato, Masashi Ohkawa, Yasuo Ohdaira

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XIX   7933   79332F   2011

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    Random numbers can be classified as either pseudo- or physical-random in character. Pseudo-random numbers' periodicity renders them inappropriate for use in cryptographic applications, but naturally-generated physical-random numbers have no calculable periodicity, thereby making them ideally-suited to the task. The laser diode naturally produces a wideband "noise" signal that is believed to have tremendous capacity and great promise, for the rapid generation of physical-random numbers for use in cryptographic applications. We measured a laser diode's output, at a fast photo detector and generated physical-random numbers from frequency noises. We then identified and evaluated the binary-number-line's statistical properties. The result shows that physical-random number generation, at speeds as high as 40Gbps, is obtainable, using the laser diode's frequency noise characteristic.

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  • Consideration of sensitivity with respect to diaphragm thickness and waveguide position in silicon-based guided-wave optical accelerometer

    Yusuke Miura, Hideto Endo, Takuya Oshima, Masashi Ohkawa, Takashi Sato

    INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES XV   7941   79410P   2011

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    Our group has developed a silicon-based guided-wave optical accelerometer with a proof mass centered on a diaphragm. For this type of accelerometer, it is strongly suggested that sensitivity is related to waveguide position, diaphragm dimensions, and size and weight of proof mass. In this study, sensitivity dependences on waveguide position and diaphragm thickness were considered experimentally. Experimental results demonstrated that the highest sensitivity could be obtained for the waveguide at the diaphragm edge and is inversely proportional to the square of the diaphragm thickness.

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  • Modeling of fluid dynamics and thermo-chemical system in halogen lamp operation Reviewed

    Makoto Bessho, Masashi Ohkawa

    Journal of Light and Visual Environment   35 ( 1 )   7 - 22   2011

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    One of the key elements in improving lamp efficiency is understanding and controlling the halogen transport process. Therefore, it is worthwhile to build a model that depicts this process and can be applied to the study of various types of lamps. We examined the halogen transport process in a lamp by using a hybrid simulation model based on fluid dynamics and chemical equilibrium.

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  • Examination of tungsten transport in operating halogen lamp by fluid dynamics and thermo chemical simulation Reviewed

    Makoto Bessho, Masashi Ohkawa

    Journal of Light and Visual Environment   35 ( 1 )   23 - 33   2011

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    Tungsten transport in halogen lamp operation was examined by fluid dynamics and thermo-chemical simulation. Partial pressures of almost all species dramatically increased around the coil leads. The cause appears to be a stagnant flow of filling gases. Results of a life test showed that tungsten was slightly deposited at the coil leads. Such a tungsten deposit can be attributed to a high concentration of tungsten compounds during the gas phase.

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  • Sensitivity dependences on waveguide position and diaphragm thickness in silicon-based guided-wave optical accelerometer

    Masashi Ohkawa, Hideto Endo, Takuya Oshima, Yusuke Miura, Takashi Sato

    Technical Digest of the 16th Microooptics Conference   WP-30   2010.11

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  • Double External Cavity Single-Mode VCSEL system for DWDM applications

    Kohei Doi, Hideaki Arai, Shinya Maehara, Takashi Sato, Masashi Ohkawa

    International Symposium on Organic and Inorganic Electronic Materials and Related Nanotechnologies (EM-NANO2010)   B1-2   2010.6

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  • Physical-Random Number Generation Using Frequency Noises of Laser Diode

    Shinya Maehara, Kohei Doi, Takashi Sato, Yasuo Ohdaira, Masashi Ohkawa

    International Symposium on Organic and Inorganic Electronic Materials and Related Nanotechnologies (EM-NANO2010)   110 ( 66(LQE2010 1-15) )   P3-12   2010.6

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  • DECIGO and DECIGO pathfinder Reviewed

    Masaki Ando, Seiji Kawamura, Naoki Seto, Shuichi Sato, Takashi Nakamura, Kimio Tsubono, Takeshi Takashima, Ikkoh Funaki, Kenji Numata, Nobuyuki Kanda, Takahiro Tanaka, Kunihito Ioka, Kazuhiro Agatsuma, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Kiwamu Izumi, Isao Kawano, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Umpei Miyamoto, Shinji Miyoki, Mutsuko Y. Morimoto, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama, Mitsuru Musha, Shigeo Nagano, Isao Naito, Kouji Nakamura, Masahiro Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Kazuhiro Nakazawa, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Kenshi Okada, Norio Okada, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Ryo Saito, Masaaki Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Yasuo Torii, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka Wakabayashi, Kent Yagi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino, Ken-Xun Sun

    CLASSICAL AND QUANTUM GRAVITY   27 ( 8 )   2010.4

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    A space gravitational-wave antenna, DECIGO (DECI-hertz interferometer Gravitational wave Observatory), will provide fruitful insights into the universe, particularly on the formation mechanism of supermassive black holes, dark energy and the inflation of the universe. In the current pre-conceptual design, DECIGO will be comprising four interferometer units; each interferometer unit will be formed by three drag-free spacecraft with 1000 km separation. Since DECIGO will be an extremely challenging mission with high-precision formation flight with long baseline, it is important to increase the technical feasibility before its planned launch in 2027. Thus, we are planning to launch two milestone missions. DECIGO pathfinder (DPF) is the first milestone mission, and key components for DPF are being tested on ground and in orbit. In this paper, we review the conceptual design and current status of DECIGO and DPF.

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    Other Link: http://orcid.org/0000-0003-1318-2635

  • Double optical feedback system for a single-mode vertical-cavity surface-emitting laser Reviewed

    Kohei Doi, Takashi Sato, Masashi Ohkawa

    OPTICAL ENGINEERING   49 ( 1 )   014202   2010.1

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    Ongoing tests involving the application of double optical feedback to a vertical-cavity surface-emitting laser (VCSEL) are resulting in demonstrable and significant improvements in oscillation linewidth and frequency stability. We look into the workings of a double optical feedback system for a Fabry-Perot-type diode laser. We describe a single-mode VCSEL that is characterized by a narrow oscillation linewidth and a stable output intensity that shows no trace of the low-frequency fluctuation (LFF) that so often occurs in single optical feedback diode lasers. Initial tests use a beat note to do this. From there, we calculate the square root of the Allan variance to determine the level of frequency stability. We also evaluate the degree of LFF suppression achieved using its spectrum density and compare those results with what we obtained through single and double optical feedback and with no feedback whatsoever. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3284784]

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  • VCSEL's frequency stabilization of an external cavity diode laser - Countermeasures against atmospheric temperature variations

    Mutsuki Motojima, Kohei Doi, Takashi Sato, Masashi Ohkawa, Takamasa Suzuki

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVIII   7597   75972A   2010

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    We introduced the vertical cavity surface emitting laser (VCSEL) as the laser diode in tour external cavity system. Because VCSELs are now commercially available, and the External cavity diode laser (ECDL) systems using them are expected to improve their frequency stability, we have replaced a Fabry-Perot type laser diode with a VCSEL, and examined its oscillation-frequency stability. Therefore we were able to expect that the VCSELs with our double optical feedback system have good oscillation frequency stability. The obtained VCSEL's oscillation-frequency stability, i.e., the square root of Allan variance sigma was 4x10(-10), at an averaging time of tau = 1 sec.

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  • Semiconductor laser oscillation-frequency stabilization using the Faraday effect

    Hideaki Arai, Akira Sato, Ayumi Sato, Kenji Nakano, Takashi Sato, Masashi Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVIII   7597   75971D   2010

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    The semiconductor lasers in use today are on one hand, prized, and highly praised, for their small size, light weight, longevity and energy-efficiency, -and on the other, criticized for their susceptibility to frequency-fluctuations brought about by changes in temperature and driving current. Once this "wrinkle" is ironed out, semiconductor lasers will become the default light-sources, for satellites' onboard interferometers. Our studies have been directed at stabilizing oscillation frequency to the atomic absorption line, and using negative electrical feedback to the injection current. Frequency stabilization is accomplished, by either; a) applying direct modulation to the semiconductor laser's driving current, or b) modulating the reference frequency, to obtain the error signal needed for stabilization. In this instance, Faraday effect-based stabilization was used. This indirect oscillation frequency stabilization has no discernable effect on spectra width, but, stability was no better than that observed in the system using the direct modulation.
    When we compared Faraday effect-and direct modulation-based methods of stabilization, in order to uncover the root-cause of the discrepancy, sensors picked up system noise, the source of which was heat generated by the heavy current applied to a magnetic coil used to apply the Faraday effect. We also substituted a permanent magnet for the electromagnet.

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  • Physical-random number generation using laser diodes' inherent noises

    Hiroki Nishimura, Kohei Doi, Tetsurou Ushiki, Takashi Sato, Masashi Ohkawa, Yasuo Odaira

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVIII   7597   75970M   2010

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    Random numbers can be classified as either pseudo- or physical-random in character. This work demonstrates how laser diodes' inherent noise can be exploited for use in generating physical-random numbers in cryptographic applications. In the initial stages of the experiment, we measured a laser diode's output, at a fast photo detector and generated physical-random numbers from intensity noises. We then identified and evaluated the binary-number-line's statistical properties. Our preliminary results show that fast physical-random numbers are obtainable, using the laser diode's frequency noise characteristics.

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  • Frequency stabilization of a laser diode using Rb saturated absorption lines

    Ayumi Sato, Kenji Nakano, Hideaki Arai, Takashi Sato, Masashi Ohkawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVIII   7597   79571N   2010

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    We have succeeded, thus far, in stabilizing laser diode (LD) frequencies to Rb absorption lines, by means of negative electrical feedback. While the absorption lines were stable over the long term, the Doppler Effect's influence was evident, in broadened spectrum linewidth. To avoid the problem in subsequent tests, we used Rb-saturated absorption signals.
    In this work, we demonstrated potentials of two applications; one was as a reference signal source for estimation of other LD's frequency stabilization system, and the other was a light source for generation of THz radiation.

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  • Characteristics of a glass-based guided-wave optical microphone

    Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 15th Microoptics Conference   296 - 297   2009.10

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  • Diaphragm size-dependent resonance frequency in a glass-based optical microphone

    Mizuki Nakajima, Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 15th Microoptics Conference   298 - 299   2009.10

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  • Sensitivity dependences of silicon-based guided-wave optical flow sensors

    Masashi Ohkawa, Yusuke Kudo, Masafumi Adachi, Takashi Sato

    Integrated Photonics and Nanophotonics Research and Applications (IPNRA) 2009   JTuB7   2009.7

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  • DECIGO pathfinder Reviewed

    Masaki Ando, Seiji Kawamura, Shuichi Sato, Takashi Nakamura, Kimio Tsubono, Akito Araya, Ikkoh Funaki, Kunihito Ioka, Nobuyuki Kanda, Shigenori Moriwaki, Mitsuru Musha, Kazuhiro Nakazawa, Kenji Numata, Shin-ichiro Sakai, Naoki Seto, Takeshi Takashima, Takahiro Tanaka, Kazuhiro Agatsuma, Koh-suke Aoyanagi, Koji Arai, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shinji Mukohyama, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Taiga Noumi, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Norio Okada, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Yasuo Torii, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka Wakabayashi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

    CLASSICAL AND QUANTUM GRAVITY   26 ( 9 )   2009.5

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    DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory), which is a future space gravitational wave antenna. DECIGO is expected to provide fruitful insights into the universe, particularly about dark energy, the formation mechanism of supermassive black holes and the inflation of the universe. Since DECIGO will be an extremely challenging mission, which will be formed by three drag-free spacecraft with 1000 km separation, it is important to increase the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. In this paper, we review the conceptual design and current status of the first milestone mission, DPF.

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  • Comparison of three semiconductor laser systems for gravitational wave detection Reviewed

    Tomoyuki Uehara, Akira Sato, Shinya Maehara, Toshiya Nimonji, Takashi Sato, Masashi Ohkawa, Takeo Maruyama, Seiji Kawamura

    OPTICAL ENGINEERING   48 ( 3 )   034302   2009.3

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    The primary objective of the Decihertz Interferometer Gravitational Wave Observatory (DECIGO) mission is to detect and observe black holes' and galactic binaries' gravitational waves (GWs), at frequencies ranging from 10(-2) to 10(1) Hz (from 0.1 to 100 s in averaging time). This low-frequency range is inaccessible to ground-based interferometers, due to unshieldable background noise and to the fact that ground-based interferometers are limited to a few kilometers in length. Our research is focused on efforts to stabilize semiconductor, Nd:YAG, and fiber lasers, for use as GW detectors' optical sources. In present-day and future detectors, frequency and phase noise may place certain limitations on sensitivity and stability. Our goal is primarily to design robust experiments. In this report, we compare existing methods: Faraday, Faraday peak, and saturated absorption spectroscopy. In these, the laser frequency is stabilized to Rb as an atomic frequency reference by a feedback-loop control system. From the frequency stability of these models, we can predict the characteristics of the three systems through dynamic stability analysis, by analyzing the dynamic Allan variance. We find the optical frequency stability, expressed as the Allan deviation (the square root of the Allan variance), to be 3.3 x 10(-11), 2.9 x 10(-12), and 1.2 x 10(-12) in the respective methods. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3089887]

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  • Modeling of fluid dynamics and thermo chemical system in operating halogen lamp

    Makoto Bessho, Masashi Ohkawa

    Lux Pacifica Conference 2009   197 - 202   2009.1

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  • 平成20年度リフレッシュ理科教室(北陸・信越支部新潟会場)開催報告 Reviewed

    大河正志, 鈴木孝昌, 坪井望, 新保一成, 大平泰生, 馬場暁, 岩野春男, 丸山武男

    応用物理教育   33 ( 1 )   35 - 38   2009.1

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  • Modeling of Fluid Dynamics and Thermo-Chemical System in Halogen Lamp Operation Reviewed

    Makoto Bessho, .Masashi Ohkawa

    Journal of the Illuminating Engineering Institute of Japan (Shomei Gakkai Shi)   93 ( 11 )   814 - 826   2009

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    One of the key elements in improving lamp efficiency is understanding and controlling the halogen transport process. Therefore, it is worthwhile to build a model that depicts this process and can be applied to the study of various types of lamps. We examined the halogen transport process in a lamp by using a hybrid simulation model based on fluid dynamics and chemical equilibrium.

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  • Oscillation frequency stabilization of a semiconductor laser by an indirect modulation method using the Faraday effect

    Akira Sato, Shinya Maehara, Tomoyuki Uehara, Hideaki Arai, Takashi Sato, Tadashi Tamura, Masashi Ohkawa, Seiji Kawamura

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVII   7211   72110A   2009

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    Scientists throughout the world are seeking to enhance the capabilities of satellite-to-satellite tracking laser interferometer-based optical systems used to measure the alterations in earth's gravitational field that indicate critical changes in the environment. These systems must be able to measure infinitesimal fluctuations in the relative velocities of two satellites, using a light source that oscillates at a level of frequency stability rated better than 10-13 in the square root of the Allan variance. In our experiments, semiconductor laser frequency stabilization that typically requires a brief direct modulation of the laser injection current to obtain an error signal, was accomplished using the Faraday effect of Rb absorption lines. This effectively modulates the reference frequency of the stabilization system, i.e., the Rb absorption line, by modulating the magnetic field applied to the Rb absorption cell, instead of the oscillation frequency of the laser diode. Most recently, we used the Faraday method, in conjunction with a precision temperature controller. For present purposes, we also use the PEAK method, to obtain the most accurate signal possible, comparing it with saturated absorption spectroscopic readings, to determine the noise-source.

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  • Examination of tungsten transport in operating halogen lamp by fluid dynamics and thermochemical simulation Reviewed

    Makoto Bessho, Masashi Ohkawa

    Journal of the Illuminating Engineering Institute of Japan (Shomei Gakkai Shi)   93 ( 11 )   827 - 837   2009

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    Tungsten transport in halogen lamp operation was examined by fluid dynamics and thermo-chemical simulation. Partial pressures of almost all species dramatically increased around the coil leads. The cause appears to be a stagnant flow of filling gases. Results of a life test showed that tungsten was slightly deposited at the coil leads. Such a tungsten deposit can be attributed to a high concentration of tungsten compounds during the gas phase.

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  • Dependence of resonance frequency on diaphragm dimensions in a guided-wave optical pressure sensor Reviewed

    Mizuki Nakajima, Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    IEEJ Transactions on Sensors and Micromachines   129 ( 10 )   357 - 362   2009

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    The resonance frequencies of various diaphragms in glass-based guided-wave optical pressure sensors were examined experimentally. In this study, acoustic sound pressure was applied to six fabricated sensors with square diaphragms of different dimensions to evaluate frequency characteristics as well as resonance frequency. The measured resonance frequencies were proportional to the diaphragm thicknesses, and inversely proportional to the square of the side-length of diaphragms, as theoretically predicted. © 2009 The Institute of Electrical Engineers of Japan.

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  • Sensitivity dependences on side length and aspect ratio of a diaphragm in a glass-based guided-wave optical pressure sensor Reviewed

    Hiroyuki Nikkuni, Yu Watanabe, Masashi Ohkawa, Takashi Sato

    Optics Express   16 ( 19 )   15024 - 15033   2008.9

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    According to our previous theoretical study, sensor sensitivity is proportional to the cube of the side length of the diaphragm in a guided-wave optical pressure sensor consisting of a glass diaphragm and a single-mode waveguide on the diaphragm. Also, to obtain higher sensitivity, an aspect ratio of the diaphragm should be approximately 1 for two waveguide positions: the center and the edge of the diaphragm. In this study, sensitivity dependences on side length and aspect ratio of the diaphragm were experimentally examined. The obtained experimental results strongly supported the theoretical predictions. © 2008 Optical Society of America.

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  • Resonance frequency of diaphragm in glass-based guided-wave optical pressure sensor

    Hiroyuki Nikkuni, Mizuki Nakajima, Masashi Ohkawa, Takashi Sato

    Techinical Digest of the 14th Microoptics Conference   P-71   2008.9

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  • Characteristics of a guided-wave optical microphone with a micromachined diaphragm

    Noriyuki Watanabe, Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 14th Microoptics Conference   P-70   2008.9

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  • Feasibility of a silicon-based guided-wave optical microphone

    Masashi Ohkawa, Manabu Hayashi, Hiroyuki Nikkuni, Noriyuki Watanabe, Takashi Sato

    ◦Integrated Photonics and Nanophotonics Research and Applications (IPNRA) 2008   JMB34   2008.7

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  • Sensitivity dependence with respect to diaphragm thickness in guided-wave optical pressure sensor based on elasto-optic effect Reviewed

    Hiroyuki Nikkuni, Yu Watanabe, Masashi Ohkawa, Takashi Sato

    OPTICAL ENGINEERING   47 ( 4 )   044402   2008.4

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    We experimentally investigated the relationship between sensitivity and diaphragm thickness in a glass-based guided-wave optical pressure sensor using intermodal interference between the fundamental TM-like and TE-like modes. The sensor consists of a rectangular diaphragm and a straight single-mode waveguide on the diaphragm. The sensitivity is theoretically known to be inversely proportional to the square of the diaphragm thickness. In this study, to examine this relationship, four sensors with diaphragm thicknesses of 0.30 mm, 0.22 mm, 0.20 mm, and 0.15 mm were fabricated. The area of the diaphragm was 10 mm x 10 mm. For the waveguide position nearest to the center of the diaphragm, the measured sensitivities almost agreed with the theoretical ones. (C) 2008 Society of Photo-Optical Instrumentation Engineers.

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  • Semiconductor laser frequency-stabilization; influence of multi-position temperature controls

    M. Yanagisawa, K. Nakano, S. Maehara, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVI   6889   688917   2008

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    The precise interferometric systems employed in today's artificial satellites require semiconductor lasers of the highest callibur. But, one particularly large obstacle has stood in the way of their broad application; the stabilization of their oscillation frequencies. While a number of different approaches have been tested, none have provided overall, long-term stability. Most recently, we used a Doppler-free absorption line of Rb atoms with a precision temperature controller and an improved laser mount; in this instance, relative optical frequency stability rated 9.07x10(-13)<=sigma(2,tau)<= 7.54x10(-10), in averaging time for 0.01s <=tau <= 23s. Furthermore, we heated the Rb cell to up to 313K, in order to enhance the control signal and improve oscillation frequency stability.

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  • Analytical discussion of semiconductor lasers for Gravitational-wave detection

    T. Uehara, A. Sato, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    ADVANCED MATERIALS AND DEVICES FOR SENSING AND IMAGING III   6829   68291H   2008

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    The primary objective of the Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) mission is to detect and observe black holes' and galactic binaries' gravitational waves (GWs), at frequencies ranging from 10(-2) to 10(1) HZ. This low-frequency range is inaccessible to ground-based interferometers, due to unshieldable background noise, -and the fact that ground-based interferometers are limited to a few kilometers in length. Our research is focused on efforts to stabilize semiconductor-, Nd:YAG- and fiber- lasers, for use as GW detectors' optical sources. In present-day- and future detectors, frequency- and phase-noise may place certain limitations on sensitivity and stability. Our goals (shared with scientists around the world) are; first, to design robust experiments that will measure a variety of noises (- random-walk FM, flicker-FM, white FM, flicker PM and white PM), in order to verify existing models, and second, -to find ways to reduce sensitivity to spurious noise. Current models predict a variety of frequency- and phase-dependent noise slopes, but, a conclusive distinction between noise-models can only be made when the exact points at which the noises occurred are known. In order to increase the sensitivity of the experiment, the laser frequency is stabilized to an atomic-frequency-reference by a feedback-loop control system.

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  • Frequency stabilization of a semiconductor laser using both Rb saturated absorption profiles and double optical feedback systems

    K. Nakano, S. Machara, M. Yanagisawa, K. Doi, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    ADVANCED MATERIALS AND DEVICES FOR SENSING AND IMAGING III   6829   68290R   2008

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    The precise interferometric systems employed in today's artificial satellites require semiconductor lasers of the highest callibur. But, one particularly large obstacle has stood in the way of their broad application; the stabilization of their oscillation frequencies. While a number of different approaches have been tested, none have provided overall, long-term stability. Most recently, we used a Doppler-free absorption line of Rb atoms with a precision temperature controller and an improved laser mount; in this instance, relative optical frequency stability rated 9.07 x 10(-13) <=sigma(2,tau)<= 7.54 x 10(-10), in averaging time for 0.01s <=tau <= 23s. By introducing optical feedback, which narrows the laser's linewidth, we obtained improved frequency stability.

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  • Frequency stabilization of semiconductor lasers for onboard interferometers using both Rb-saturated absorption profiles and double-optical feedback systems

    K. Nakano, S. Maehara, M. Yanagisawa, A. Sato, K. Doi, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    SPACE TELESCOPES AND INSTRUMENTATION 2008: OPTICAL, INFRARED, AND MILLIMETER, PTS 1 AND 2   7010   701047   2008

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    The precise interferometric systems employed in today's artificial satellites require semiconductor lasers of the highest caliber. To this end, efforts to stabilize their oscillation frequencies and narrow spectrum line-widths continue relentlessly. While a number of different approaches have been tested, none have provided overall, long-term stability. Most recently, we employed a Doppler-free absorption line of Rb atoms, with a precision temperature controller and an improved laser mount. In this instance, relative optical frequency stability rated 9.07 x 10(-13)<=sigma(2,tau)<= 7.54x10(-10), in averaging time for 0.01s <=tau <= 23s. By introducing an optical feedback, which narrows the laser's linewidth, we obtained improved frequency stability.

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  • Frequency stabilization of an external cavity diode laser - Countermeasures against atmospheric temperature variations

    Yuta Minabe, Kohei Doi, Takashi Sato, Takeo Maruyama, Masashi Ohkawa, Tsuneya Tsubokawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XVI   6889   688918   2008

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    External cavity diode lasers (ECDL) are presently experiencing a surge in popularity, as laser light-sources for advanced optical measurement systems. While these devices normally require external optical-output controls, we simplified the setup, a bit, by adding a second external cavity. This technique boasts the added advantage of having a narrower oscillation-linewidth than would be achievable, using a single optical feedback. Because drive-current and atmospheric temperature directly impact the ECDL systems' oscillation frequency, during frequency stability checks, it was necessary, in this instance, to construct a slightly smaller ECDL system, which we mounted on a Super-Invar board, to minimize the influence of thermal expansion. Taking these and other aggressive and timely measures to prevent atmospheric temperature-related changes allowed us to achieve an improvement in oscillation-frequency stability, i.e., to obtain the square root of Allan variance sigma =2 x 10(-10), at averaging time tau = 10(-1).
    We introduced a vertical-cavity surface-emitting laser (VCSEL) to the setup, for the simple reason that its frequency is far less susceptible to changes in temperature, than other lasers of its type. And, because VCSELs are widely available, and the ECDL systems that use them improve frequency stability, we replaced the Fabry-Perot semiconductor laser with a VCSEL.

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  • Sensitivity dependence on waveguide position in silicon-based optical flow sensor

    Masafumi Adachi, Yusuke Kudo, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 13th Microoptics Conference   2007.10

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  • Sensitivity dependence with respect to diaphragm dimensions in a glass-based guided-wave optical pressure sensor

    Yu Watanabe, Hiroyuki Nikkuni, Masashi Ohkawa, Takashi Sato

    Technical Digest of the 13th Microoptics Conference   2007.10

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  • Improvement of S/N ratio of a Glass-Based Guided-Wave Optical Microphone Reviewed

    Manabu Hayashi, Hiroyuki Nikkuni, Yoshiaki Mogi, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    International Symposium on Fusion Technology   123 - 123   2007.1

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  • Laser diode frequency stabilization by means of optical feedback and the Faraday effect Reviewed

    T. Uehara, S. Maehara, T. Nimonji, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    International Symposium on Fusion Technology   58 - 58   2007.1

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  • Semiconductor laser frequency stabilization using satulated absorption spectroscopy system Reviewed

    K. Nakano, S. Maehara, M. Yanagisawa, Y. Sekiya, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    International Symposium on Fusion Technology   57 - 57   2007.1

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  • Evaluation of frequency stability in compact double optical feedback laser diode systems Reviewed

    Kohei Doi, Yuta Minabe, Toshiya Kaizaka, Takashi Sato, Takeo Maruyama, Masashi Ohkawa, Tsuneya Tsubokawa

    International Symposium on Fusion Technology   59 - 59   2007.1

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  • Improvement of the signal-to-noise ratio in a glass-based guided-wave optical microphone Reviewed

    Hiroyuki Nikkuni, Yoshiaki Mogi, Manabu Hayashi, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES XI   6475   647519   2007

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    In this study, the signal-to-noise ratio of a glass-based guided-wave optical microphone was successfully improved by both increasing sensitivity and reducing noise. The optical microphone has a square diaphragm as a pressure-sensitive structure and a straight single-mode waveguide across the diaphragm. Sensitivity of the microphone and resonance frequency of the diaphragm are dependent on the area and thickness of the diaphragm. In this study, in order to increase sensitivity, the diaphragm dimensions were enlarged from 16 mm x 16 mm x 0.15 mm in the previous study to 20 mm x 20 mm x 0.15 mm. According to theoretical calculations, the phase sensitivity and resonance frequency were 2.5 mrad/Pa and 3.4 kHz for a 20 mm x 20 mm x 0.15 mm diaphragm, respectively. The sensitivity was theoretically expected to be twice as high as that in the previous study. To reduce noise, a bandpass filter with passband from 300 Hz to 3 kHz was employed. After fabrication of the optical microphone, sound pressure, ranging from 100 to 122 dB-SPL, was applied to the microphone with a frequency of I kHz. The measured output of the optical microphone was almost proportional to the sound pressure, and the minimum detectable sound pressure level of the microphone was experimentally evaluated to be 100 dB-SPL.

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  • Rb-saturated-absorption-profile-based enhancement of semiconductor laser frequency stability Reviewed

    K. Nakano, S. Maehara, M. Yanagisawa, Y. Sekiya, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XV   6468   64680C   2007

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    Laser interferometers detect gravitational waves with a degree of accuracy and efficiency unimaginable even a few years ago. The semiconductor lasers that are the primary light source for these devices are small, lightweight, durable and energy-efficient. On the downside, the devices currently available are still marked by broad oscillation spectra, and heightened sensitivity to fluctuations in injection current and /or ambient temperature. By applying a small sine wave to the injection current, we modulate the oscillation frequency. This frequency-modulated beam is introduced to the Avalanche photo diode through the Rb cell in the saturated absorption optical setup. The resulting signal and a reference signal are detected simultaneously and combined, to produce an error signal, which, when fed back to the injection current, stabilizes the diode's oscillation frequency at 2.12x10(-12) <= sigma(2,tau)<= 5.88x10(-11) in the averaging time between 0.4s to 65s. An optical feedback method, which introduces the laser beam reflected by a mirror or a grating to the semiconductor laser itself, is reported to narrow oscillation linewidth and improve frequency stability. We are now combining these two techniques to further improve frequency stability.

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  • Laser diode frequency stabilization by means of optical feedback and the magneto-optical effect Reviewed

    T. Uehara, S. Maehara, T. Nimonji, T. Sato, M. Ohkawa, T. Maruyama, S. Kawamura

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XV   6468   64680D   2007

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    A method of detecting gravitational-field variations using laser diodes is described. While the GRACE project is currently using the Doppler microwave system to measure the velocities of satellites flying in tandem, in the future, more advanced laser interferometry will be employed. It is hoped that we will be able to measure infinitesimal changes in their velocities, by using frequency-stabilized lasers rated at better than 10(-13) in the square root of the Allan variance (sigma) for Is < tau < 100s. As laser light sources, these devices will be notable for their compactness, energy efficiency, lightweight and high frequency-stability. This thesis describes the improved frequency stabilization obtained through the use of the magneto-optical effect of the Rb-D-2 absorption line, and the adaptation of the PEAK method, in order to obtain a precise control signal. The method allows us to modulate the reference frequency of the stabilization system (the absorption spectrum of the Rb-D-2 absorption line) by modulating the magnetic field applied to the Rb absorption cell, instead of the oscillation frequency of the laser diode. In so doing we are able to achieve a frequency stabilized laser diode (sigma = 9 x 10(-12)), while maintaining its linewidth, at an averaging time of 40s. In the next stage, we will test frequency-stabilized laser optical sources that are to be used in detecting and observing gravitational waves.

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  • Compact double optical feedback external-cavity diode laser system and its frequency stabilization Reviewed

    Kohei Doi, Yuta Minabe, Takashi Sato, Takeo Maruyama, Masashi Ohkawa, Tsuneya Tsubokawa

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XV   6468   64680E   2007

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    External cavity diode laser (ECDL) systems are presently experiencing a surge in popularity as laser light-sources, in advanced optical communications- and measurement-systems. Because such systems require that their external reflectors be precisely controlled, to eliminate low frequency fluctuations (LFF) in optical output, we conducted experiments with a two-cavity version, which easily eliminated LFFs, as expected. The technique has the added advantage of a narrower oscillation-linewidth than would be achievable, using a single optical feedback. However, the ECDL's oscillation frequency is susceptible to the influences of the drive-current, as well as changes, both in the refractive index, and the overall length of the external reflector that results from fluctuations in atmospheric temperature. We made every effort to maintain the length of the ECDL cavity, while evaluating oscillation-frequency stability. We used a Super-Invar board as the platform for our compact ECDL system to minimize the influence of thermal expansion, because of its low expansion coefficient. We then compared the effect of atmospheric temperature variations between two experimental conditions, with the Super-invar board and without it, and finally took note of the improvement in performance, using the board.

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  • The Japanese space gravitational wave antenna - DECIGO Reviewed

    Seiji Kawamura, Takashi Nakamura, Masaki Ando, Naoki Seto, Kimio Tsubono, Kenji Numata, Ryuichi Takahashi, Shigeo Nagano, Takehiko Ishikawa, Mitsuru Musha, Ken-ichi Ueda, Takashi Sato, Mizuhiko Hosokawa, Kazuhiro Agatsuma, Tomotada Akutsu, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Kunihito Ioka, Koji Ishidoshiro, Yousuke Itoh, Shogo Kamagasako, Nobuyuki Kanda, Nobuki Kawashima, Hiroyuki Kirihara, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Yasufumi Kojima, Keiko Kokeyama, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Hiromi Mizusawa, Toshiyuki Morisawa, Shinji Mukohyama, Isao Naito, Noriyasu Nakagawa, Kouji Nakamura, Hiroyuki Nakano, Atsushi Nishizawa, Yoshito Niwa, Choetsu Nozawa, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Akira Okutomi, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shihori Sakata, Misao Sasaki, Shuichi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Hideyuki Tagoshi, Tadayuki Takahashi, Hirotaka Takahashi, Ryutaro Takahashi, Tadashi Takano, Takahiro Tanaka, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Masao Tokunari, Shinji Tsujikawa, Yoshiki Tsunesada, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

    CLASSICAL AND QUANTUM GRAVITY   23 ( 8 )   S125 - S131   2006.4

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    DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. It aims at detecting various kinds of gravitational waves between 1 mHz and 100 Hz frequently enough to open a new window of observation for gravitational wave astronomy. The preconceptual design of DECIGO consists of three drag-free satellites, 1000 km apart from each other, whose relative displacements are measured by a Fabry-Perot Michelson interferometer. We plan to launch DECIGO in 2024 after a long and intense development phase, including two pathfinder missions for verification of required technologies.

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  • Evaluation of frequency stability in double optical feedback ECDL systems - art. no. 61150O Reviewed

    Kohei Doi, Yurnie Kobayashi, Shinya Maehara, Takashi Sato, Takeo Maruyama, Masashi Ohkawa, Tsuneya Tsubokawa

    Physics and SImulation of Optoelectronic Devices XIV   6115   O1150 - O1150   2006

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    External cavity diode laser (ECDL) systems are presently experiencing a surge in popularity as laser light-sources, in Z 4:1 advanced optical communications- and measurement-applications. Because such systems require that their external reflectors be precisely controlled, to eliminate low frequency fluctuations (LFF) in optical output, we conducted experiments with a two-cavity version of the ECDL system. This technique brings the added advantages of a narrower linewidth than would be achievable via a single optical feedback. However, the ECDL's oscillation frequency is susceptible to the influences of the driving current, changes in the refractive index, and changes in external-reflector length that result from fluctuations in atmospheric temperature. We made every effort to maintain the length of the ECDL cavity, while evaluating oscillation-frequency stability. We used a Super-Invar board as the platform for our ECDL system, in order to minimize the influence of thermal expansion. Moreover, our ECDL system combines an Rb cell within an external cavity; an arrangement designed to improve stability by restricting the LD frequency within both the external cavity mode and the Rb-saturated absorption spectrum. We used the square root of the Allan variance, when evaluating oscillation frequency stability, observing, in the process, that it improved stability by about one order of magnitude.

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  • Guided-wave optical pressure sensor with semi-closed space under the diaphragm: step response in relation to the area of a small hole of a semi-closed space Reviewed

    Kaoru Sato, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    PHOTONIC APPLICATIONS FOR AEROSPACE, TRANSPORTATION, AND HARSH ENVIRONMENTS   6379   637908-1 - 637908-8   2006

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    An original guided-wave optical pressure sensor, which has a semi-closed space with a small hole under a diaphragm, can be used even under high quasi-static pressure without sacrificing sensitivity, unlike conventional pressure sensors. Moreover, the sensor possesses characteristics of a high-pass filter, so that it responds to only the high-frequency components of pressure change. The cutoff frequency of the high-pass filter of the sensor property is a key factor in designing the sensor, and is acquired from the step response of the sensor. In a step-like change in ambient pressure, a pressure difference is induced on the diaphragm for a short while because the small hole restricts fluid flow between the semi-closed space and the surroundings. The reciprocal of the duration of the induced pressure difference corresponds to the cutoff frequency. In this study, the step response in relation to the cross-sectional area of the small hole was examined experimentally, and the measured durations were compared with the theoretical ones. In the experiment, the duration was approximately inversely proportional to the area of the small hole as theoretically predicted although the measured durations are larger by a factor of thousands than the calculated ones.

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  • Stability of holographic gratings recorded on photopolymer using different dyes Reviewed

    Keiichi Tsuchida, Masashi Ohkawa, Seishi Sekine

    PRACTICAL HOLOGRAPHY XX: MATERIALS AND APPLICATIONS   6136   613610-1 - 613610-8   2006

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    In this study, stability of holographic gratings recorded in four photopolymer films with different dyes was experimentally examined. Also, dye concentration was optimized to get high diffraction efficiency. Each film contains triethanolamine and acrylamide in polyvinyl alcohol matrix, and one type of dye: eosin Y, methyl violet, rhodamine B or rose bengal. Dye concentrations were adjusted so that transmittances of the four films 60 mu m thick were approximately 94%. The photopolymer films were exposed by two intersecting beams of a YVO laser at 532 nm to form holographic grating with spatial frequency of 653 line/mm until the diffraction efficiency reached its maximum. The power of each recording beam was 10 mW, and its diameter was 2.25 mm each.
    Diffraction efficiency was measured using a YVO laser beam for the recorded films undergoing either 300 sec reconstruction or 5-day dark storage. The photopolymer film containing eosin Y showed the best stability both for a 300 sec reconstruction and for 5-day storage. Regarding optimization of dye concentration, the diffraction efficiencies of more than 60% were obtained when an amount of eosin Y is between 1 mg and 50 mg, which was solved in 9.1 % polyvinyl alcohol aqueous solution of 110 g.

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  • Frequency stabilization of laser diode light-sources in satellite-to-satellite laser interferometers - art. no. 611529 Reviewed

    S. Maehara, Y. Kurosaki, T. Sato, M. Ohkawa, T. Maruyama, T. Yoshino, H. Kunimori, M. Hosokowa, H. Ito, Y. Li, S. Nagano, S. Kawamura

    Physics and SImulation of Optoelectronic Devices XIV   6115   11529 - 11529   2006

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    The present work discusses methods of stabilizing the frequencies of commercially-available laser diodes. Laser diodes are generally compact and long-lived. The frequency stability, which makes them ideal for onboard laser interferometer light-sources, in applications such as the satellite-to-satellite tracking systems used to verify fluctuations in earth's gravity field, which, in turn, indicate other critical changes in the environment, is the key characteristic of this work. We used the devices typically operating at 780nm, and their frequencies can be stabilized using either of two systems; one, employing the Doppler-free absorption line of Rb atoms and another, using the Faraday effect of the Rb absorption line. In both cases, the use of the proper modulation frequency and amplitude improved frequency stability, overall, attaining 2.05 x 10(-12) and 2.73 x 10(-11), respectively, in the square root of the Allan variance, by measuring the beat-note between two independently-stabilized laser diodes.

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  • An investigation into changes observed in the oscillation characteristics of semiconductor lasers exposed to magnetic fields - art. no. 61150Z Reviewed

    T. Miyamoto, J. Chiba, T. Sato, M. Ohkawa, T. Maruyama

    Physics and SImulation of Optoelectronic Devices XIV   6115   Z1150 - Z1150   2006

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    Semiconductor lasers' oscillation wavelengths respond to temperature-, injection current-, and magnetic field-fluctuations. As reported in the 1960's, the oscillation wavelength shortened, under magnetic fields stronger than 4T, at temperatures lower than 80K. However, when we exposed bulk-type semiconductor lasers oscillating at 780nm to relatively weak magnetic fields (less than 1.4T), at room temperature (300K), we observed that the oscillation wavelength shifted to the longer (lower frequency) side. In this work, we focused on the longer oscillation wavelength shift, the lower power side optical output-power shift, and the higher voltage side terminal voltage shift of a number of multi-quantum-well (MQW) laser diodes oscillating at 780nm, under the same experimental conditions as those used in our previous works. In discussions of these shift mechanisms, we consider how wavelength (frequency), optical output-power, and terminal voltage shifts are correlated. Because our new knowledge arrows us to employ mechanisms completely different from those used in studies dating as far back as the 1960's, we have introduced one whereby the shifts observed in our experiments result from temperature rises and longitudinal magneto-resistance effects. Also discussed, are the results of experiments conducted near the threshold current.

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  • Frequency stabilization of a semiconductor laser using the Rb saturated absorption spectroscopy - art. no. 61150P Reviewed

    Y. Ohta, S. Maehara, K. Hasebe, Y. Kurosaki, T. Sato, M. Ohkawa, T. Maruyama, T. Tsubokawa

    Physics and SImulation of Optoelectronic Devices XIV   6115   P1150 - P1150   2006

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    We report on the stabilization of a semiconductor laser's frequency, using Rb absorption lines. In order to improve overall frequency stability within our system, we adjusted the setup used in Rb- saturated absorption spectroscopy, and optimized modulation parameters such as modulation - frequency and -width, to more accurately detect the error signal. When we stabilized laser frequency using a Doppler-free absorption line of Rb atoms, a time-constant of 0.01sec, and a modulation frequency of 7.77kHz, relative optical frequency stability of 2.12x10(-12)<=sigma(2,tau)<= 5.88x10(-11) was achieved, in averaging time for 0.04s <=tau <= 65s.

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  • Evaluation of frequency stability in double optical feedback ECDL systems Reviewed

    Kohei Doi, Yumie Kobayashi, Shinya Maehara, Takashi Sato, Takeo Maruyama, Masashi Ohkawa, Tsuneya Tsubokawa

    Proceedings of SPIE - The International Society for Optical Engineering   6115   70 - 76   2006

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    External cavity diode laser (ECDL) systems are presently experiencing a surge in popularity as laser light-sources, in advanced optical communications- and measurement-applications. Because such systems require that their external reflectors be precisely controlled, to eliminate low frequency fluctuations (LFF) in optical output, we conducted experiments with a two-cavity version of the ECDL system. This technique brings the added advantages of a narrower linewidth than would be achievable via a single optical feedback. However, the ECDL's oscillation frequency is susceptible to the influences of the driving current, changes in the refractive index, and changes in external-reflector length that result from fluctuations in atmospheric temperature. We made every effort to maintain the length of the ECDL cavity, while evaluating oscillation-frequency stability. We used a Super-Invar board as the platform for our ECDL system, in order to minimize the influence of thermal expansion. Moreover, our ECDL system combines an Rb cell within an external cavity
    an arrangement designed to improve stability by restricting the LD frequency within both the external cavity mode and the Rb-saturated absorption spectrum. We used the square root of the Allan variance, when evaluating oscillation frequency stability, observing, in the process, that it improved stability by about one order of magnitude.

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  • Development of a simulator of a satellite-to-satellite interferometer for determination of the Earth's gravity field Reviewed

    S Nagano, M Hosokawa, H Kunimori, T Yoshino, S Kawamura, M Ohkawa, T Sato

    REVIEW OF SCIENTIFIC INSTRUMENTS   76 ( 12 )   124501-1 - 124501-10   2005.12

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    A satellite-to-satellite laser interferometer is essential for a future gravity-field mission to improve the accuracy and spatial resolution of the Earth's gravity model. We have designed a ground-based simulator of a satellite-to-satellite interferometer, which aims to evaluate instrument error reflecting on the accuracy of the gravity-field retrieval and achieve the essential technologies required to measure the intersatellite range rate. The developed simulator was successfully operated with a range-rate sensitivity of 40 nm/s/<radical><radicand>Hz</radicand></radical> in the measurement band of 10(-2)-1 Hz. From a primary demonstration, it was confirmed to be available for experimental simulation of the satellite-to-satellite interferometer in the laboratory. The simulator will be a powerful tool for establishing guidelines for the development of future gravity missions. (c) 2005 American Institute of Physics.

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  • Silicon-based guided-wave optical flow sensor based on Bernoulli's Theorem Reviewed

    Yusuke Ohara, Masanori Tsuchiya, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    6th Japan-Finland Joint Symposium on Optics in Engineering   77 - 78   2005.9

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  • Guided-wave optical pressure sensor responding only to changing pressure Reviewed

    Yoshisumi Endo, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    Progress in Biomedical Optics and Imaging - Proceedings of SPIE   5728   309 - 316   2005

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    In this paper, an original guided-wave optical pressure sensor that responds only to rapid pressure change is described. The proposed sensor is based on a conventional guided-wave optical pressure sensor using intermodal interference, with an added semi-closed space with a small hole under the bottom side of the diaphragm. By the addition of this semi-closed space, the sensor, unlike conventional sensors, can withstand high static pressure. When there is a sudden change in ambient pressure, pressure within the semi-closed space cannot quickly adjust due to the small hole that restricts fluid flow. So, pressure difference is induced on the diaphragm for a short while. Thus, the sensor shows a response only to changes in pressure, not to static pressure. We examined the step response of the sensor, that is, the output characteristics for sudden pressure change. The diaphragm dimensions of the fabricated sensor were 14 mm×14 mm×0.22 mm. Also, the volume of the semi-closed space was 14 mm×14 mm×1.8 mm, and the sectional area of the small hole was 93 μm×25 μm. In this experiment, the pressure in a 30 cm×28 cm×30 cm closed box, in which the fabricated sensor was placed, was suddenly increased by 0.78 kPa. Due to the pressure change, the output intensity decreased by approximately 20% of the initial intensity level. Approximately 1.4 sec after the step-like change in pressure, output intensity returned to the initial level.

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  • Guided-wave optical pressure sensor responding only to changing pressure Reviewed

    Y Endo, M Ohkawa, S Sekine, T Sato

    Integrated Optics: Devices, Materials, and Technologies IX   5728   309 - 316   2005

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    In this paper, an original guided-wave optical pressure sensor that responds only to rapid pressure change is described. The proposed sensor is based on a conventional guided-wave optical pressure sensor using intermodal interference, with an added semi-closed space with a small hole under the bottom side of the diaphragm. By the addition of this semi-closed space, the sensor, unlike conventional sensors, can withstand high static pressure. When there is a sudden change in ambient pressure, pressure within the semi-closed space cannot quickly adjust due to the small hole that restricts fluid flow. So, pressure difference is induced on the diaphragm for a short while. Thus, the sensor shows a response only to changes in pressure, not to static pressure. We examined the step response of the sensor, that is, the output characteristics for sudden pressure change. The diaphragm dimensions of the fabricated sensor were 14 mmx14 mmx0.22 mm. Also, the volume of the semi-closed space was 14 mmx14 mmx1.8 mm, and the sectional area of the small hole was 93 mu mx25 mu m. In this experiment, the pressure in a 30 cmx28 cmx30 cm closed box, in which the fabricated sensor was placed, was suddenly increased by 0.78 kPa. Due to the pressure change, the output intensity decreased by approximately 20 % of the initial intensity level. Approximately 1.4 sec after the step-like change in pressure, output intensity returned to the initial level.

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  • Holographic characteristics of two different films using methyl violet dyes in polyvinyl alcohol matrices Reviewed

    K Tsuchida, M Ohkawa, S Sekine

    Practical Holography XIX: Materials and Applications   5742 ( 1 )   250 - 258   2005

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    Holographic characteristics of two different films using methyl violet dyes in polyvinyl alcohol matrices are reported. One of the films, Film A, contains only methyl violet in the matrix. The other film, Film B, contains methyl violet, triethanolamine and acrylamide in the matrix. Diffraction efficiencies of the two films were measured and compared. Mechanisms of holographic recording and the functions of the dyes are discussed. The films were 8 pm thick.. Holographic gratings were recorded in the films by two intersecting YVO laser beams at 532 nm. The recording intensity of each beam was 25 mW, 50 mW and 100 mW, and the beam diameter was 2.25 mm. The spatial frequency of the grating was 653 line/mm. During recording, intensity of the diffracted light was simultaneously measured using a He-Ne laser at 633 nm. Regarding Film A, diffraction efficiency reaches a peak at a specific exposure time. This means that holographic grating grows according to exposure time in low exposure, but vanishes when over-exposed. In bright regions of the interference fringe on the film, the dyes are bleached. Changes of absorption and refractive index due to bleaching would result in the holographic grating. Regarding Film B, the diffraction efficiency was saturated in high exposure, and the maximum diffraction efficiency was not strongly dependent on the concentration of methyl violet. In the bright regions of the interference fringe on the film, excited methyl violet and triethanolamine cause polymerization of acrylamide. Changes in the refractive index due to the polymerization build the holographic grating.

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  • Holographic characteristics of two different films using methyl violet dyes in polyvinyl alcohol matrices Reviewed

    K Tsuchida, M Ohkawa, S Sekine

    Practical Holography XIX: Materials and Applications   5742   250 - 258   2005

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    Holographic characteristics of two different films using methyl violet dyes in polyvinyl alcohol matrices are reported. One of the films, Film A, contains only methyl violet in the matrix. The other film, Film B, contains methyl violet, triethanolamine and acrylamide in the matrix. Diffraction efficiencies of the two films were measured and compared. Mechanisms of holographic recording and the functions of the dyes are discussed. The films were 8 pm thick.. Holographic gratings were recorded in the films by two intersecting YVO laser beams at 532 nm. The recording intensity of each beam was 25 mW, 50 mW and 100 mW, and the beam diameter was 2.25 mm. The spatial frequency of the grating was 653 line/mm. During recording, intensity of the diffracted light was simultaneously measured using a He-Ne laser at 633 nm. Regarding Film A, diffraction efficiency reaches a peak at a specific exposure time. This means that holographic grating grows according to exposure time in low exposure, but vanishes when over-exposed. In bright regions of the interference fringe on the film, the dyes are bleached. Changes of absorption and refractive index due to bleaching would result in the holographic grating. Regarding Film B, the diffraction efficiency was saturated in high exposure, and the maximum diffraction efficiency was not strongly dependent on the concentration of methyl violet. In the bright regions of the interference fringe on the film, excited methyl violet and triethanolamine cause polymerization of acrylamide. Changes in the refractive index due to the polymerization build the holographic grating.

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  • Magnetic fields' effect on semiconductor lasers' characteristics Reviewed

    Y Seto, T Miyamoto, T Sato, M Ohkawa, T Maruyama

    Physics and Simulation of Optoelectronic Devices XIII   5722   90 - 97   2005

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    Semiconductor lasers' oscillation wavelengths respond to temperature- and magnetic field-fluctuations. As reported in the 1960's, these wavelengths shortened, at lower than 80K, under a magnetic field larger than 4T. This phenomenon attracted our attention, during preliminary experiments, because, when we exposed bulk-type semiconductor lasers oscillating at 780nm to relatively weak magnetic fields (less than 1.4T), at room temperature (300K), we observed that the oscillation wavelength shifted to the longer (lower frequency) side. For this work, we focused on the longer oscillation wavelength shift, the lower power side optical output-power shift, and the higher voltage side terminal voltage shift of a number of multi-quantum-well (MQW) laser diodes oscillating at 780nm, under the same experimental conditions as those used in our previous works. In discussions of these shift mechanisms, we consider how wavelength (frequency), optical output-power, and terminal voltage shifts are correlated. Our expanded knowledge base has forced us to employ mechanisms completely different from those used in studies dating as far back as the 1960's. We are now introducing a mechanism in which temperature rise and the longitudinal magneto-resistance effect cause the shifts observed in our experiments.

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  • Oscillation frequency stabilization of a semiconductor laser using the Faraday effect of Rb absorption lines and the double optical feedback Reviewed

    H Kobayashi, T Nimonji, S Maehara, T Sato, M Ohkawa, T Maruyama, T Yoshino, H Kunimori, M Hosokawa, H Ito, Y Li, S Nagano, S Kawamura

    Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications IV   5710   83 - 90   2005

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    Currently in the initial stages of development, the endeavor aims to use satellite-to-satellite tracking laser interferometer-based optical technique, to document fluctuations in earth's gravitational field indicating other critical changes in the environment. This system must be able to measure infinitesimal changes in the relative velocity of the two satellites, using a laser light source, which oscillates at frequency stability better than 10(-13) in the square root of the Allan variance. We have stabilized the laser's oscillation frequency using the Faraday effect of Rb absorption lines. This method modulates the reference frequency of the stabilization system by modulating the magnetic field applied to the Rb, absorption cell, instead of the oscillation frequency of the laser diode. Furthermore, we have adapted the "double optical feedback" to the laser diode for narrowing its oscillation spectrum and improving its frequency stability. In recent years, a "femtosecond optical comb generator" has been developed as a new reference frequency source for absolute frequency measurement. This optical comb generator is controlled by the microwave frequency standards systems and provides stability of 4 x 10(-13) at an averaging time of 1s and at the order of 10(-15) at 1000s averaging time. We have measured the frequency stability of our system using the optical comb. We obtained the best spectrum narrowing effect using two gratings as external reflectors in the double optical feedback setup. The obtained results were 6.269 x 10(-11) <= sigma <= 1.516 x 10(-10)(24.11kHz <= f <= 58.31kHz) from Is to 39s in the averaging time.

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  • Feasibility of guided-wave optical microphone based on elasto-optic effect Reviewed

    Hiroyuki Nikkuni, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    Proceedings of SPIE - The International Society for Optical Engineering   6049   56 - 63   2005

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    In this paper, the feasibility of a glass-based guided-wave optical microphone is described. The optical microphone consists of a rectangular diaphragm and a straight waveguide on the diaphragm. The sensitivity of the microphone and the resonance frequency of the diaphragm are dependent on the diaphragm dimensions. In this study, to confirm operation of the proposed optical microphone, the target values for phase sensitivity and resonance frequency were set at 1.3 mrad/Pa and 5 kHz, respectively. By design considerations, the diaphragm dimensions were determined to be 16 mm× 16 mm×0.15 mm. After fabrication, a sound wave of 1 kHz and 25 Pa, corresponding to 122 dB-SPL (sound pressure level), was applied to the microphone. In the experiment, the intensity-modulated output with the same frequency as the applied sound wave was obtained, but the observed output was unexpectedly caused by misalignment of the optical components due to mechanical vibration. The estimated output signal by the normal operation of the microphone for a sound pressure of 25 Pa was 1/10 - 1/100 of the noise level, according to the measured output characteristic to static pressure. In order to detect normal speech ranging from 55 to 65 dB-SPL, the S/N ratio should be improved by a factor of more than 104.

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  • Optical microphone using a silicon-based guided-wave optical pressure sensor Reviewed

    Hiroyuki Nikkuni, Shuuichi Dokko, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    Progress in Biomedical Optics and Imaging - Proceedings of SPIE   5728   317 - 324   2005

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    In this paper, an optical microphone using a silicon-based guided-wave optical pressure sensor as an opto-mechanical transducer is reported. The pressure sensor consists of a rectangular diaphragm and a straight waveguide on the diaphragm. The sensitivity of the sensor and the resonance frequency of the diaphragm are important factors to determine the characteristics of the microphone, and depend on the diaphragm dimensions. In this study, to examine a feasibility of the proposed optical microphone, the target values of phase sensitivity and resonance frequency were set at 1.6 mrad/Pa and 7 kHz, respectively. By design considerations, the diaphragm dimensions were determined to be 7 mm× 7 mm× 23 μm. After fabrication of the optical microphone, sound pressure from 5 to 25 Pa, with a frequency of 1 kHz, was applied to the fabricated microphone with a 7 mm× 7 mm× 27 μm diaphragm. During measurement, a lock-in detection was taken because the fabricated pressure sensor had an unexpected low sensitivity, which resulted in an extremely low S/N ratio. The measured output voltage from the lock-in amplifier was proportional to the sound pressure as expected although the lock-in detection is not practical for the microphone.

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  • Optical microphone using a silicon-based guided-wave optical pressure sensor Reviewed

    H Nikkuni, S Dokko, M Ohkawa, S Sekine, T Sato

    Integrated Optics: Devices, Materials, and Technologies IX   5728   317 - 324   2005

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    In this paper, an optical microphone using a silicon-based guided-wave optical pressure sensor as an opto-mechanical transducer is reported. The pressure sensor consists of a rectangular diaphragm and a straight waveguide on the diaphragm. The sensitivity of the sensor and the resonance frequency of the diaphragm are important factors to determine the characteristics of the microphone, and depend on the diaphragm dimensions. In this study, to examine a feasibility of the proposed optical microphone, the target values of phase sensitivity and resonance frequency were set at 1.6 mrad/Pa and 7 kHz, respectively. By design considerations, the diaphragm dimensions were determined to be 7 mm x 7 mm x 23 mu m. After fabrication of the optical microphone, sound pressure from 5 to 25 Pa, with a frequency of 1 kHz, was applied to the fabricated microphone with a 7 mmx 7 mmx 27 gm diaphragm. During measurement, a lock-in detection was taken because the fabricated pressure sensor had an unexpected low sensitivity, which resulted in an extremely low S/N ratio. The measured output voltage from the lock-in amplifier was proportional to the sound pressure as expected although the lock-in detection is not practical for the microphone.

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  • Evaluation of Complex Refractive Index of Metal Clusters by Scattering Ellipsometry Reviewed

    Ayumu Sato, Yasunari Harada, Seishi Sekine, Masashi Ohkawa

    IEEJ Transactions on Fundamentals and Materials   125 ( 5 )   461 - 465   2005

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    A scattering ellipsometry is a newly developed method to measure a complex refractive index of metal clusters at a high temperature region. The complex refractive index is required to determine a luminous efficacy, which is one of the most important factors to develop lamps, of cluster lamps. In this study, we built a scattering ellipsometer, and considered its accuracy of measurement through evaluations of the complex refractive index of gold particles at room temperature. In measurement, a Nd: YAG laser of 532 nm was used as the light source. The measured complex refractive index of gold particles was 0.31 in real part and 1.75 in imaginary part. A repeatable accuracy was evaluated 0.01 in real part and 0.02 in imaginary part from a standard deviation in measuring the complex refractive index 10 times in the same condition. Also, the size parameter of gold particles was 1.71, and its repeatable accuracy was 0.02. Such accuracy is sufficient to estimate characteristics of the cluster lamps, such as the spectral radiant flux, the luminous efficacy and so on. © 2005, The Institute of Electrical Engineers of Japan. All rights reserved.

    DOI: 10.1541/ieejfms.125.461

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  • Evaluation of oscillation frequency stability of a diode laser using a fs laser optical comb Reviewed

    H Kobayashi, T Nimonji, A Sawamura, T Sato, M Ohkawa, T Maruyama, T Yoshino, H Kunimori, M Hosokawa, H Ito, Y Li, S Nagano, S Kawamura

    ULTRAFAST PHENOMENA XIV   79   849 - 851   2005

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    We have stabilized the oscillation frequency of a diode laser using the Faraday effect of Rb absorption lines. The stabilized laser frequency was measured by means of a femtosecond mode-locked pulse laser optical comb generator.

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  • Frequency stabilization of a semiconductor laser using the spectrum of a Fabry-Perot etalon controlled by the Rb absorption line Reviewed

    Y Kurosaki, S Maehara, K Hasebe, Y Ohta, T Sato, M Ohkawa, T Maruyama, T Tsubokawa

    Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications IV   5710   73 - 82   2005

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    We report on the stabilization of a semiconductor laser's frequency, using spectra-controlled etalon. As the spectra of an etalon are controlled by, one of the Rb absorption lines.. they provide highly stable reference frequencies in a broad frequency range. When we adapted the PEAK method to the etalon's spectra and used a Doppler-free absorption line of Rb atoms as the control signal for the newest model of our system, relative optical frequency stability of 2.91 x 10(-11) <= sigma(2,tau) <= 3.72 x 10(-10) was achieved in averaging time for 0.04 <= tau <= 100s.

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  • Measurement of Complex Refractive Index of Tungsten by Using Ellipsometry — Study of the Accuracy of Ellipsometer — Reviewed

    Ayumu Sato, Seishi Sekine, Masashi Ohkawa

    Journal of Light and Visual Environment   29 ( 2 )   55 - 61   2005

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    Tungsten microcavity light sources and tungsten cluster light sources have interested us as light sources for next-generation having high luminous efficacy and long lifetime. The complex refractive index of tungsten requires the operating temperatures from 2000 K to 6500 K to evaluate the luminous efficacy and lifetime. Little is, known however, about the complex index of tungsten at such high temperatures. Since ellipsometry has a non-contact measurement technique, the complex refractive index of any metal can be measured even under extremely high temperature with high accuracy. We consider that ellipsometry is an effective measuring method. We thus designed and fabricated the ellipsometer to measure the complex refractive index of tungsten at room temperature. As the result, we established the ellipsometer improved from measurement of the complex refractive index of tungsten from 2000 K to 6500 K. In this paper, we report on the problems to measure the complex refractive index of tungsten using the ellipsometry, and the achieved accuracy of measurement. KEYWORDS: microcavity light source, cluster light source, tungsten, complex refractive index, ellipsometry. © 2005, The Illuminating Engineering Institute of Japan. All rights reserved.

    DOI: 10.2150/jlve.29.55

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  • タングステンクラスター光源のハロゲン化物に因る放射特性の検討 Reviewed

    佐藤歩, 保坂和幸, 久保博樹, 関根征士, 大河正志

    照明学会誌   88 ( 5 )   281 - 287   2004.12

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    DOI: 10.2150/jieij.88.281

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  • Displacement measuring technique for satellite-to-satellite laser interferometer to determine Earth's gravity field Reviewed

    S Nagano, T Yoshino, H Kunimori, M Hosokawa, S Kawamura, T Sato, M Ohkawa

    MEASUREMENT SCIENCE AND TECHNOLOGY   15 ( 12 )   2406 - 2411   2004.12

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    We present a new displacement measuring technique with simplicity, robustness, high sensitivity and wide measurement range. A set of a frequency shifter and a voltage-frequency converter is used to lock a homodyne interferometer on the half-bright fringe by eliminating the Doppler fringe resulting from mirror motion. The mirror displacement is directly retrieved from the feedback signal of a fringe control loop. By developing a table-top interferometer, we successfully demonstrated signal recovery without significant degradation. The achieved displacement sensitivity and measurement range of the interferometer were 24 nm Hz(-1/2) and 1.3 mm at a Fourier frequency of 0.1 Hz, respectively. This technique was found to have a potential for application to precise displacement measurements. It is, in particular, suitable for a satellite-to-satellite laser interferometer to determine Earth's gravity field.

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  • Evaluation of the Artificial Neural Network for Color Discrimination-Discrimination of Non-learned Colors- Reviewed

    Yasuko Tayagaki, Satoko Sekiya, Seishi Sekine, Masashi Ohkawa

    Journal of Light and Visual Environment   28 ( 2 )   101 - 103   2004.9

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    Our research purpose is to build an artificial neural network with an excellent color discrimination capability like human being on a computer. In this study, we built the network, which was trained to learn 10 colors with different hues in the Munsell color system. Then, we examined the response of the trained network when the network was interrogated about 10 non-learned colors. The network showed a good color discrimination capability, close to that of human being. © 2004, The Illuminating Engineering Institute of Japan. All rights reserved.

    DOI: 10.2150/jlve.28.101

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  • Holographic characteristics of two different films using methyl violet dyes in polyvinyl alchohol matrices Reviewed

    Keiichi Tuchida, Masashi Ohkawa, Seishi Sekine

    EM-NANO 2004   124 - 124   2004.6

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  • Guided-wave optical pressure sensor with sensitivity for sudden pressure change only Reviewed

    Yoshisumi Endo, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    EM-NANO 2004   228 - 228   2004.6

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  • Development of a light source in a satellite-to-satellite laser interferometer for the precise measurement of their relative velocity Reviewed

    Toshiya Nimonji, shinya Maehara, Hiromichi Kobayashi, Takeshi Sato, Masashi Ohkawa, Takeo Maruyama

    EM-NANO 2004   224 - 224   2004.6

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  • Ground simulator for future satellite gravity mission by inter-satellite laser interferometer Reviewed

    Taizoh Yoshino, Shigeo Nagano, Hiroo Kunimori, Mizuhiko Hosokawa, Seiji Kawamura, Takashi Sato, Masashi Ohkawa

    1st European Geosciences Union(EGU) General Assembly   1   P0823   2004.4

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  • Measurement of Complex Refractive Index of Tungsten by Using Ellipsometry Reviewed

    Ayumu Sato, Seishi Sekine, Masashi Ohkawa

    IEEJ Transactions on Fundamentals and Materials   124 ( 2 )   114 - 119   2004

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    In development of tungsten microcavity illuminants and tungsten cluster illuminants, the Complex Reractive Index of tungsten at the operating temperature of 2000–6000 K is necessary to evaluate their luminous efficacy and lifetime. Little is, however, known about the complex index of tungsten in such a high temperature region. In this study, we have determined the complex index of tungsten using an ellipsometer at room temperature. In measurement, a He-Ne laser of 633 nm and a Nd:YAG laser of 532 nm were used as the light sources. The measured complex index of tungsten was 2.0 to 3.0 in real part and 2.5 to 3.0 in imaginary part at 633 nm. Also, the corresponding components at 532 nm were 1.8 to 2.8 and 2.4 to 2.8. Repeatable accuracy was estimated about 1% in measuring the complex index repeatedly at the same point on individual tungsten plates. It was, however, found that the measured complex index was linearly proportional to the reflectivity. This dependence is attributed to surface conditions such as oxidation and roughness on a microscopic scale. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

    DOI: 10.1541/ieejfms.124.114

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  • Oscillation frequency stabilization of a diode laser for the laser interferometer in a satellite-to-satellite tracking system Reviewed

    S Maehara, H Kobayashi, T Sato, M Ohkawa, T Maruyama, T Yoshino, H Kunimori, M Hosokowa, H Ito, Y Li, S Nagano, S Kawamura

    SEMICONDUCTOR LASERS AND APPLICATIONS II   5628   113 - 120   2004

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    Currently in the initial stages of development, the endeavor aims to use satellite-to-satellite tracking laser interferometer-based optical technique, to document fluctuations in earth's gravitational field indicating other critical changes in the environment. This system must be able to measure infinitesimal changes in the relative velocity of the two satellites, using a laser light source, which. oscillates at frequency stability better than 10(-13) in the square root of the Allan variance. The constraints placed upon the system will ultimately require that the interferometer's light-source be small, lightweight, extremely efficient, durable, and possess high frequency-stability. Present-day technology of a laser diode possesses all of these characteristics, except the last and most critical one; frequency stability. So, our ongoing efforts are all focused on the search for a method of stabilizing the oscillation frequency of the satellite-to-satellite laser-diode light source. We used a Rubidium absorption line as a frequency reference of the frequency stabilization system and the "double optical feedback" method to narrow the laser diode's oscillation linewidth, in order to improve its frequency stability. We have measured the frequency, to determine its degree of stability, by comparing the "femtosecond optical comb generator"- and laser diode-frequencies.

    DOI: 10.1117/12.576544

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  • New frequency stabilization method of a semiconductor laser using the Faraday effect of the Rb-D2 absorption line Reviewed

    Toshiya Nimonji, Shin-Ichi Ito, Akihiko Sawamura, Takashi Sato, Masashi Ohkawa, Takeo Maruyama

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers   43 ( 5 A )   2504 - 2509   2004

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    We have applied a precise amount of electrical feedback into laser injection current to stabilize the oscillation frequency of a semiconductor laser. This feedback method usually requires a small direct modulation to the laser injection current to obtain an error signal. This broadens the oscillation width of the laser diode, but certain applications, such as those related to coherent optical communications and measurements, require a narrower oscillation linewidth. Thus, we have attempted to obtain the error signal and stabilize the laser oscillation frequency in a narrower oscillation linewidth using the Faraday effect of the Rb absorption line. Our next task for the Faraday-effect-based method involves frequency stabilization, which we accomplish using a large frequency discrimination gain Gd. By incorporating our "PEAK" circuit, which utilizes the envelope detection method to determine the switching points between two different absorption signals, we increase Gd in our improved PEAK methods.

    DOI: 10.1143/JJAP.43.2504

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  • New frequency stabilization method of a semiconductor laser using the Faraday effect of the Rb absorption line Reviewed

    S Ito, T Nimonji, A Sawamura, T Sato, M Ohkawa, T Maruyama

    OPTICAL DEVICES FOR FIBER COMMUNICATION IV   4989   78 - 87   2003

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    We normally apply a precise amount of electrical. feedback into the laser injection current, to stabilize the oscillation frequency of a semiconductor laser. This feedback method usually needs a small direct modulation to the laser injection current, to obtain an error signal. This broadens the oscillation width of the laser diode, but certain applications, such as those related to coherent optical communications, benefit from, and in fact require narrower oscillation linewidth. We obtain the error signal, and stabilize the laser oscillation frequency in narrower oscillation linewidth, using the Faraday effect of the Rb absorption line. Our next task involves frequency-stabilization, which we accomplish, using a large frequency discrimination gain (G(d)). By incorporating our "PEAK" circuit, which utilizes the envelope detection method to determine the switching points between two different absorption signals corresponding to the different magnetic fields and different polarization conditions, we increases the G(d) in our stabilization system.

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  • Sensitivity dependence with respect to diaphragm dimensions in a glass-based integrated optic pressure sensor Reviewed

    Y Iwase, Y Okamoto, M Ohkawa, S Sekine, T Sato

    INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES VII   4987   256 - 263   2003

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    In this paper, the relationship between sensitivity and diaphragm dimensions in a glass-based integrated optic pressure sensor is described. The sensor has a rectangular diaphragm as a pressure-sensitive structure and a straight sensing waveguide across the diaphragm. The sensor operation is based on the phenomenon that a phase difference between two orthogonal guided modes is induced by the elasto-optic effect in the presence of applied pressure. The sensitivity of the sensor is theoretically known to be dependent on the thickness and side length of the diaphragm. Such dependencies are worth investigating to obtain helpful design rules for miniaturization of the sensor, but have not been examined experimentally in detail. In this study, to examine the relationship between sensitivity and thickness, two sensors were fabricated with 10 mm x 10 mm x 0.3 mm (sensor #1) and 10 mm x 10 mm x 0.22 mm (sensor #2) diaphragms.. The sensitivity of sensor #2 was larger than that of sensor #1 by a factor of 1.72, which closely agreed with the theoretical factor of 1.86. Moreover, to determine the relationship between sensitivity and side length, two more sensors, besides sensor #2, with 7mm-square (sensor #3) and 14mm-square (sensor #4) diaphragms, were fabricated with a diaphragm thickness of 0.22 mm. The measured sensitivities agreed approximately with the theoretical ones although there was a slight difference in sensor #4.

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  • Scale-reduction rule for diaphragm dimensions to miniaturize a silicon-based integrated optic pressure sensor without reducing sensitivity Reviewed

    A Yamada, T Tokita, M Ohkawa, S Sekine, T Sato

    INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES VII   4987   248 - 255   2003

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    In this paper, an original scale-reduction rule without sensitivity loss in integrated optic pressure sensors based on the elasto-optic effect is described. The sensor has a rectangular diaphragm as a pressure-sensitive mechanical structure and a sensing waveguide on the diaphragm. In this type of sensor, sensitivity is theoretically known to be strongly dependent on the dimensions of the diaphragm. According to the theoretical results, the sensitivity can be kept constant even if the diaphragm dimensions are reduced as long as both the side length ratio and the characteristic length remain constant. Here, the characteristic length is introduced as the cube of the shorter side length of the diaphragm divided by the square of the thickness. Such a scale-reduction rule would be very significant in the miniaturizing of a sensor without reducing sensitivity, but it has not been experimentally confirmed. In this study, the scale-reduction rule was experimentally examined using three fabricated sensors, which had the same side length ratio. and the same characteristic length. The exact dimensions of the sensors were 2.0 mm X 10 mm X 35 mum, 2.5 mm X 12.5 mm X 49 mum and 3.0 mm X 15 mm X 64 mum. The measured sensitivities of the three sensors were quite similar to each other as theoretically predicted.

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  • Silicon-based integrated optic sensor using intermodal interference between fundamental TM-like and TE-like modes Reviewed

    Masashi Ohkawa, Seishi Sekine, Takashi Sato

    Recent Research Developments in Electronics and Communications Part-I   1   137 - 148   2002.12

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  • Sensitivity dependence with respect to diaphragm thickness in integrated optic pressure sensor Reviewed

    Yumi Okamoto, Masahiro Nanasawa, Masashi Ohkawa, Seishi Sekine, Takashi Sato

    Proceedings of APLS 2002   482 - 485   2002.10

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  • Relationship between sensitivity and waveguide position on the diaphragm in integrated optic pressure sensors based on the elasto-optic effect Reviewed

    Masashi Ohkawa, Kazuhiko Hasebe, Seishi Sekine, Takashi Sato

    Applied Optics   41 ( 24 )   5016 - 5021   2002.8

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    The sensitivities of integrated optic pressure sensors with diaphragms theoretically are known to be strongly dependent on the position of the sensing waveguide on the diaphragm. According to the theoretical results, the diaphragm edge is the best position for the waveguide of a sensor based on the elasto-optic effect. The relationship between sensitivity and the waveguide position, however, has not been investigated experimentally, although it is important in the designing of such a sensor and in determining the misalignment tolerance of the sensing waveguide. In this study, this relationship in a glass-based integrated optic sensor by use of an intermodal interference was examined experimentally. © 2002 Optical Society of America.

    DOI: 10.1364/AO.41.005016

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  • Silicon-based integrated optic pressure sensor using intermodal interference between TM-like and TE-like modes Reviewed

    M Ohkawa, Y Shirai, T Goto, S Sekine, T Sato

    FIBER AND INTEGRATED OPTICS   21 ( 2 )   105 - 113   2002

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    In this paper, a silicon-based integrated optic pressure sensor using an intermodal interference between the fundamental TM-like and TE-like modes is described. The sensor consists of a micromachined rectangular diaphragm and a straight polystyrene optical waveguide passing over the diaphragm. Its sensitivity is theoretically known to be strongly dependent on the position of the waveguide over the diaphragm. To experimentally investigate such dependence, we fabricated a sensor with a 1.2 mm x 10 mm x 20 mum diaphragm, over which waveguides were placed at 50 mum intervals. The measured phase sensitivity was 98 mrad/kPa for the waveguide nearest to the diaphragm edge. The measurement was also carried out for the other waveguides. As theoretically expected, the largest sensitivity was obtained for the waveguide nearest to the edge.

    DOI: 10.1080/014680302317244807

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  • Frequency stabilization of a semiconductor laser using the Faraday effect of the Rb absorption line - Magnatic modulation strength and stability - Reviewed

    T. Saga, T. Nimonji, S. Ito, T. Sato, M. Ohkawa, T. Maruyama, M. Shimba

    6th Symposium on Frequency Standards & Metrology   629 - 631   2001.6

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  • Increase of the inner second harmonic light of 1.5mm semiconductor lasers - Effect of two optical feedback loops - Reviewed

    M. Sakai, T. Ichiba, T. Seki, Y. Ohsawa, T. Sato, M. Ohkawa, T. Maruyama, M. Shimba

    6th Symposium on Frequency Standards & Metrology   635 - 637   2001.6

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  • Frequency stabilization of a semiconductor laser using both etalon and atomic spectra as frequency refrences Reviewed

    T. Aiba, Y. Ohsawa, T. Sasaki, T. Sato, M. Ohkawa, T. Maruyama, M. Shimba

    6th Symposium on Frequency Standards & Metrology   632 - 634   2001.6

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  • Silicon-based integrated optical pressure sensor using intermodal interference between TM-like and TE-like modes Reviewed

    Y Shirai, T Goto, M Ohkawa, S Sekine, T Sato

    INTEGRATED OPTICS DEVICES V   4277   411 - 418   2001

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    A silicon-based integrated optical pressure sensor using an intermodal interference between the fundamental TM-like and TE-like modes is described. The sensor consists of a micromachined rectangular diaphragm and a straight polystyrene optical waveguide passing across the diaphragm, The use of the intermodal interference has the potential advantage of shortening the sensor length since it needs neither a Y-branch nor a 3-dB coupler. In the presence of the pressure difference on the diaphragm, the phase difference is yielded between the two guided modes by an anisotropic index change induced by the elasto-optic effect. The phase difference is finally transformed into a change in light intensity by an analyzing polarizer. We fabricated a sensor with a 1.2 mm X 10 mm x 20 mum diaphragm over which the waveguides were formed at 50 mum intervals. In the experiment, a linearly-polarized He-Ne laser beam at 633 nm was coupled to the two guided modes at equal intensity. The output intensity through a polarizer was sinusoidally changed at a period of 64 kPa, corresponding to a phase sensitivity of 98 mrad/kPa, for the waveguide nearest to the diaphragm edge. The measurement was carried out for other waveguide positions. The largest sensitivity was obtained for the waveguide nearest to the diaphragm edge as theoretically expected.

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  • An experimental investigation of sensitivity dependence with respect to waveguide position on a micromachined diaphragm in a silicon-based integrated optic pressure sensor Reviewed

    T Goto, A Yamada, M Ohkawa, S Sekine, T Sato

    ELECTRONICS AND STRUCTURES FOR MEMS II   4591   337 - 344   2001

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    We have been developing a silicon-based integrated optic pressure sensor using an intermodal interference between the fundamental TM-like and TE-like modes. The sensor has a micromachined diaphragm with a sensing waveguide as a pressure-sensitive structure. The sensor is theoretically known to have a strong dependence of sensitivity on the sensing waveguide on the diaphragm. According to the theoretical prediction for the sensor based on the elasto-optic effect, the waveguide should be placed along the diaphragm edge to maximize sensitivity. To date, such dependence has not been experimentally examined in detail. In this study, two sensors with 20 or more waveguides placed at 0.1 mm intervals on the diaphragm were fabricated to determine the relationship between sensitivity and waveguide position. The diaphragm dimensions were (1) 2.0 mm x 10 mm x 35 mum and (2) 3.0 mm x 15 mm x 64 mum. The ratio between width and length of each diaphragm was 1:5. The maximum sensitivity of 100 mrad/kPa was obtained for the waveguide nearest to the diaphragm edge with a wavelength of 633 nm. In addition, the measured sensitivities were very similar for the corresponding waveguide positions in the two sensors since a scaling factor, which is defined as the cube of the either side length divided by the square of the thickness, was set as a constant.

    DOI: 10.1117/12.449164

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  • Relationship between sensitivity and waveguide position on diaphragm for silicon-based integrated optic pressure sensor Reviewed

    A Yamada, Y Shirai, T Goto, M Ohkawa, S Sekine, T Sato

    CLEO(R)/PACIFIC RIM 2001, VOL I, TECHNICAL DIGEST   420 - 421   2001

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    We have experimentally investigated how sensitivity is dependent on the position of a waveguide passing over a diaphragm in a silicon-based integrated optic pressure sensor based on the elasto-optic effect.

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  • Integrated optic pressure sensor using intermodal interference between two mutual orthogonal guided-modes Reviewed

    M Ohkawa, K Hasebe, C Nishiwaki, S Sekine, T Sato

    OPTICAL REVIEW   7 ( 2 )   144 - 148   2000.3

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    we theoretically and experimentally investigated fundamental characteristics of an integrated optic pressure sensor using intermodal interference between the lowest-order TM-like and TE-like modes. The sensor consists of a rectangular diaphragm and a straight single-mode waveguide along an edge of the diaphragm. Its operation is based on a difference of phase retardations produced in the two guided modes through the photoelastic effect. The sensor was fabricated by bonding two glass substrates together: a Coming 0211 glass 300 mu m thick to form a waveguide and a thick substrate with a 10 mm x 10 mm square hole to define the diaphragm. The fabricated sensor was successfully tested using a He-Ne laser at 633 nm. The halfwave pressure was measured to be 77 kPa which is almost double the theoretical estimate.

    DOI: 10.1007/s10043-000-0144-4

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  • Glass-based integrated optic pressure sensors with a Mach-Zehnder interferometer and with an intermodal interferometer Reviewed

    M Ohkawa, C Nishiwaki, K Hasebe, S Sekine, T Sato

    INTEGRATED OPTICS DEVICES IV   3936   309 - 318   2000

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    We have theoretically and experimentally investigated the fundamental characteristics of glass-based integrated optic pressure sensors with a conventional Mach-Zehnder (MZ) interferometer and with an intermodal (IM) interferometer consisting of a straight waveguide. Each sensor has a rectangular diaphragm as a pressure-sensitive mechanical structure. The sensing path of the MZ interferometer and the waveguide of the IM interferometer should be placed along the diaphragm edge to maximize the sensitivity of the sensors based on the elasto-optic effect, if the deflection of the diaphragm is small, the phase difference either between the sensing and reference waves for the MZ interferometer or between the fundamental TM-like and TE-like modes for the IM interferometer is proportional to the applied pressure. The sensors were fabricated using two glass substrates: a 0.3mm-thick Coming 0211 glass and a thick soda-lime glass with a 10mm X 10mm hole. After forming the waveguide on the 0211 glass, both substrates were bonded together with optical cement. For each sensor, the dimensions of the diaphragm were 10mm X 10mm X 0.3mm and the interaction length was 10mm. The sensitivities measured at 633mm in wavelength were 0.053rad/kPa for the MZ interferometer using the TM-like mode and 0.041rad/kPa for the IM interferometer. Each result was, however, half its theoretical estimate.

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  • Oscillation wavelength shifts of laser diodes with or without a package in a Magnetic Field Reviewed

    T Sato, T Nakagawa, A Nishiie, Y Ohsawa, M Ohkawa, T Maruyama, M Shimba

    LASER DIODES AND LEDS IN INDUSTRIAL, MEASUREMENT, IMAGING, AND SENSORS APPLICATIONS II; TESTING, PACKAGING AND RELIABILITY OF SEMICONDUCTOR LASERS V   3945   231 - 238   2000

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    We have measured the oscillation characteristic shifts of laser diodes originated from a magnetic field. We observed wavelength shifts toward the longer wavelength side, i.e., a red shift, by using the beat note between test and reference lasers at room temperature in more than five different laser types, whereas the experiments in early 60's showed a blue shift at extremely low temperature and in a very strong magnetic field. We also observed output power shifts toward the lower power side. Both characteristic shifts showed the same tendencies at increased temperature. So, we considered the magnetic field increases the temperature of the laser diodes and then two characteristics will change. Our experiment, however, showed that the amounts of changes in temperature, estimated from each characteristic shift, do not coincide with each other. At the first stage of our experiment, we removed the packaging parts of laser diodes because they are made of ferromagnetic materials. However, we recently observed the wavelength shifts using the laser diodes with the packaging parts. We are now expecting the changes of the current flow around the active region in the magnetic field can explain this discrepancy by using the correlation analysis between these two shifts.

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  • Faraday effect-based semiconductor laser-frequency stabilization at the Rb absorption line. Reviewed

    T Kato, T Nimonji, T Sato, M Ohkawa, T Maruyama, M Shimba

    LEOS 2000 - IEEE ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS. 1 & 2   826 - 827   2000

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  • 情報検索ホログラムメモリーのレンズ系設計と情報量限界 Reviewed

    土田 恵一, 関根征士, 大河正志, 三田元仁

    光学   28 ( 3 )   149 - 154   1999.3

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  • Integrated optic pressure sensor using intermodal interference between TM-like and TE-like modes Reviewed

    K Hasebe, M Ohkawa, C Nishiwaki, S Sekine, T Sato

    OPTICAL ENGINEERING FOR SENSING AND NANOTECHNOLOGY (ICOSN'99)   3740   517 - 520   1999

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    An integrated optic pressure sensor based on intermodal interferometry is described. The sensor consists of a straight waveguide supporting the lowest-order TM-like and TE-like modes and a rectangular diaphragm as a pressure sensitive region. The waveguide is placed along an edge of the diaphragm to maximize the sensitivity of the sensor. The output intensity of the sensor system is dependent on a difference of phase retardations induced in the two guided modes by the applied pressure via the photoelastic effect. The sensor was fabricated using two glass substrates: a Coming 0211 glass with a thickness of 300 mu m and a thick substrate with a 10mm x 10mm square hole to define the diaphragm. The two substrates were finally bonded together by UV curing adhesion after the waveguide was formed on the thin substrate. The fabricated sensor was tested using a He-Ne laser at 633nm. We successfully obtained the sinusoidal change of the output power versus the applied pressure. The halfwave pressure was evaluated to be about 80kPa experimentally.

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  • Theoretical analysis of spectral power distributions from microcavity radiators Reviewed

    S. Sekine, T. Kashiwagi, M. Ohkawa

    Proceedings of the 8th International Symposium on the Science & Technology of Light Sources   182 - 183   1998.12

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  • Bandwidth enhancement of second-harmonic generation with quadratic spatial-soliton generation versus conventional methods Reviewed

    M Ohkawa, RA Fuerst, GI Stegeman

    JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS   15 ( 11 )   2769 - 2772   1998.11

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    A detailed numerical comparison of the bandwidth-efficiency trade-off for second-harmonic generation (SHG) achieved by the formation of two-dimensional quadratic spatial solitons versus the more conventional method of gentle focusing in the middle of a nonlinear crystal is presented. Numerical simulations for type II SHG in potassium titanyl phosphate with constant wave-vector mismatch show that the 3-dB drop-off in SHG conversion efficiency can be many multiples of pi in detuning from the phase-match condition over a large range of walk-off angles and focal positions. (C) 1998 Optical Society of America [S0740-3224(98)01911-0].

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  • Frequency stabilization of a semiconductor laser under direct FSK modulation: The modulation method and evaluation of stability Reviewed

    H Watanabe, H Azuma, H Nakano, T Sato, M Ohkawa, T Maruyama, M Shimba

    ELECTRICAL ENGINEERING IN JAPAN   125 ( 2 )   44 - 51   1998.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SCRIPTA TECHNICA-JOHN WILEY & SONS  

    The frequency stability of a semiconductor laser deteriorated under direct frequency shift keying (FSK) when stabilization depended entirely upon an external frequency reference. Therefore, the PEAK method was devised for the purpose of improving frequency stability.
    This method requires two distinct frequency components and, therefore, will not work effectively in a communications system that produces a succession of identical frequencies, as does the FSK method on occasion. This paper, then, explains the results of our comparative analysis of the two modulation methods.
    The evaluation of frequency stability requires us to use a beat note between two stabilized laser beams, referred to here, as "signal" and "reference" lasers. The reference laser is stabilized by a method that takes advantage of the magneto-optical effect. This laser restrains the tendency of the beat note frequency to broaden in other stabilization methods, and even makes it possible to predetermine the beat frequency to be employed. The improvement in frequency stability obtained is about one order of magnitude. (C) 1998 Scripta Technica.

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  • Oscillation wavelength shift characters of a semiconductor laser in a magnetic field: Observation by using a beat note Reviewed

    S Matsuda, K Shibata, H Nakano, T Sato, M Ohkawa, T Maruyama, M Shimba

    ELECTRICAL ENGINEERING IN JAPAN   122 ( 3 )   46 - 54   1998.2

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    In papers published previously, we discussed the oscillation wavelength shift of a semiconductor laser in a magnetic field at room temperature. Observations were carried out by means of a monochromator that was able to measure the oscillation wavelength shift in a steady state only and that was subject to a certain degree of measurement error. In this work, we used the beat note between two semiconductor lasers as a means of observing the wavelength shift. This method reduces the overall measurement error to about one tenth that obtained when using the monochromator-and enables us to observe the time dependence of the wavelength shift, after establishing a magnetic field. The observed wavelength shift was delayed in comparison with the square of the magnetic flux density, which is proportional to the wavelength shift in a steady state. The delay was about 0.07 s, which is much longer than we actually expected, when changing the temperature in an active layer. (C) 1998 Scripta Technica.

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  • Oscillation frequency stabilization of a semiconductor laser under direct FSK by using the PEAK method Reviewed

    H Nakamura, K Tamura, K Hosoya, H Nakano, T Sato, M Ohkawa, T Maruyama, M Shimba

    LASER DIODES AND APPLICATIONS III   3415   182 - 191   1998

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    The oscillation frequency of a semiconductor laser must be stabilized in coherent optical communications systems that use such devices, because the frequency fluctuates according to variations in either temperature or injection current. Therefore, we set about the task of stabilizing it, using the Rb-D-2 absorption line as an external frequency reference and negative feedback control. This method of stabilization requires the application of small sine wave modulation to obtain error signal by synchronous detection method While the highly sensitive control ensures improved signal stability, frequency stability is deteriorated under direct FSK (Frequency Shift Keying), because the oscillation spectrum of a semiconductor laser is broadened. We, therefore, devised the. "PEAK method", which improves frequency stability under direct FSK. The accurate measurement of frequency stability requires that the beat note between two stabilized laser frequencies, the signal and reference lasers, be measured. But beat note was sometimes outside the limits of our measuring equipment The reference laser frequency was therefore adjusted by using the magneto-optical effect to control the beat note frequency within measurable limits of this work. We calculated the square root of the Allan variance to estimate the frequency stability, thereby confirming the effectiveness of PEAK method.

    DOI: 10.1117/12.326633

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  • Oscillation frequency stabilization of a semiconductor laser using the magneto-optical effects of Rb-D-2 absorption line Reviewed

    T Nimonji, K Ishikawa, H Nakano, H Nakamura, T Sato, M Ohkawa, T Maruyama, M Shimba

    LASER DIODES AND APPLICATIONS III   3415   17 - 28   1998

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    The oscillation frequency of semiconductor lasers fluctuates by a temperature or an injection current change. Semiconductor lasers are now used in many application fields such as optical fiber communications systems, compact disk and laser disk systems, and others, because these application fields don't need the high frequency stability in their light source. Therefore, we must stabilize the oscillation frequency of semiconductor lasers if we use them in a coherent optical communications or other coherent systems.
    Some frequency stabilization experiments of semiconductor lasers using external frequency references have been reported in recent years. We have also stabilized them using the Rb-D-2 absorption line as an external frequency reference. Applying a small modulation directly to the injection current usually performs these stabilization methods. But the oscillation spectrum of the semiconductor laser is broadened by the modulation in this method.
    So we devised two stabilization methods without any direct modulation, which use the magneto-optical effects called the Zeeman and the Faraday effects, and stabilized the oscillation frequency of the semiconductor laser. As a result, we got high frequency stability without any spectrum broadening caused by the modulation. The stabilized frequency was tuned in a wide range at almost the same stability condition.
    Moreover, we devised an optical setup, which produces a high sensitive error signal between the reference frequency and the laser oscillation frequency. This method, which we named "PEAK method", is also combined with the Zeeman effect to improve the frequency controllability.

    DOI: 10.1117/12.326635

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  • Theoretical Evaluation of Spectral Power Distributions of Radiant Energy from Microcavities Reviewed

    Seishi Sekine, Masatoshi Ueno, Hiroaki Suzuki, Masashi Ohkawa

    Journal of Light and Visual Environment   22 ( 1 )   12 - 16   1998

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    Characteristics of radiation from microcavities are investigated to verify the luminous efficacy of microcavity radiator that was estimated by John F. Waymouth in 1989. Electromagnetic waves in a rectangular microcavity and a cylindrical microcavity were analyzed based on the waveguide theory. The modes of electromagnetic waves in the microcavities are analyzed using a normalized eigenfunction. The conductivity and permittivity of metals are obtained by analyzing the motion equation of the free electron in the metals. The skin depth of tungsten is estimated with the emissivity of tungsten based on electromagnetic theory. Accordingly it is estimated that the luminous efficacy of radiation from the microcavity is expected to reach 118 Im/W. © 1998, The Illuminating Engineering Institute of Japan. All rights reserved.

    DOI: 10.2150/jlve.22.1_12

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  • Oscillation wavelength shifts of visible and infrared laser diodes in a magnetic field Reviewed

    T Sato, K Matsumoto, S Toujou, T Nakagawa, H Nakano, M Ohkawa, T Maruyama, M Shimba

    LASER DIODES AND APPLICATIONS III   3415   173 - 181   1998

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    The shift, which occurs in the oscillation wavelength of a semiconductor laser in a magnetic field, has been the subject of great interest, since the early 60's. During the course of the investigation, the observed shift was toward the short wavelength side, i.e., a blue shift, which was well accounted for, in terms of the Landau level. At present, we are studying how wavelength shift is affected, by applying, at room temperature, a relatively weak magnetic field, using recently developed visible and infrared diode lasers. By doing so, we have observed a red shift and a decrease in laser output-power, under a certain magnetic field conditions in its strength and direction. Since these two changes in wavelength and output power correspond to those observed at higher temperatures, we assumed that the orientation of the magnetic field affects current density in laser diodes. And then it alters temperatures around the active layer, which in turn influence oscillation wavelength and laser output-power. Also of note, was the fact that the red shift and the decrease in laser output-power occurred simultaneously, revealing an almost linear dependency on one another. This might possibly explain the heat, which developed as the result of applying the magnetic field. However, we recently observed an instance, in which visible MQW laser diodes did not exhibit this linear dependence. Because this phenomenon cannot be traced simply to the effects of heat, we are now examining it in terms of current-density alteration.

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  • Zeeman effect-based control-signal improvement for frequency stabilization of a semiconductor laser Reviewed

    H Nakano, N Watanabe, T Sato, M Ohkawa, T Maruyama, M Shimba

    ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS   80 ( 8 )   20 - 29   1997.8

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    We have stabilized the oscillation frequency of a 780-nm-band semiconductor laser using the D-2 absorption line of Rb atoms. The absorption line has a spectral width due to the natural width and Doppler width, which limits the stability of laser performance. In order to minimize the spectral spread of the absorption line, a Doppler effect-free absorption line whose spectral spread is close to the natural width was obtained by saturated absorption spectroscopy and was used for stabilization of the laser oscillation frequency However, the spectral width of the absorption line could not be further narrowed by optical means alone. In this study, the spectral width of the reference signal was further narrowed using the Zeeman effect of the Rb atomic absorption line and the newly developed PEAK and BOTTOM methods. Using this reference signal, the width of the frequency discrimination curve was narrowed. As a result, the laser oscillation frequency more accurately tracks the reference frequency. In addition it was confirmed that the frequency discrimination curve could be swept. (C) 1998 Scripta Technica.

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  • Integrated optic micropressure sensor using ring resonator Reviewed

    M Ohkawa, T Abe, S Sekine, T Sato

    ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS   79 ( 4 )   1 - 10   1996.4

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    In this paper, sensitivity improvement of integrated optic micropressure sensors is discussed. The sensor is composed of a diaphragm and a ring resonator that is a multiple interference optical circuit. A part of the waveguide of the ring resonator is on the diaphragm. When a pressure is applied to the sensor, the diaphragm is deformed and the refractive index changes slightly so that a phase shift is induced on the guided wave propagating on the diaphragm. From the change of the resonant frequency caused by this phase change, the magnitude of the applied pressure is detected. In this study, particular emphasis is on the relationship between the diaphragm dimensions and the sensor sensitivity. From the analysis of the sensor operation, it is concluded that the use of a square-shaped diaphragm with a waveguide of the ring resonator at the edge in addition to employing the TM-like mode is most suited for a highly sensitive sensor. Further, from the evaluation of the minimum detectable pressure, it is expected that an integrated optic microprocessor sensor can be realized which is sensitive to such low pressure as underwater acoustics.

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  • FREQUENCY STABILIZATION OF A SEMICONDUCTOR-LASER UNDER DIRECT FREQUENCY-SHIFT KEYING USING THE SATURATED ABSORPTION SIGNAL Reviewed

    T SATO, J MIZUMOTO, Y KOBAYASHI, M ISHIGURO, M OHKAWA, T MARUYAMA, M SHIMBA

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS   33 ( 3B )   1608 - 1613   1994.3

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    The oscillating frequency of a semiconductor laser was stabilized at the Rb-D2 absorption line under direct frequency shift keying (FSK). The control system equipped with a peak-hold circuit provided the frequency stability of 10(-9) > sigma(2, tau) > 10(-12) at the averaging time 0.05 s < tau < 40 s when the Doppler-limited absorption line was used as a frequency reference. This stability was better than that obtained by the traditional control system without the peak-hold circuit under direct FSK. Using the saturated absorption signal, the frequency stability was improved more than one order of magnitude in comparison with that obtained using the Doppler-limited absorption signal.

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  • OSCILLATION WAVELENGTH SHIFTS OF DIODE-LASERS IN A MAGNETIC-FIELD Reviewed

    T SATO, H KAWASHIMA, T HOSHI, S YAMAMOTO, M OHKAWA, T MARUYAMA, M SHIMBA

    LASER DIODE TECHNOLOGY AND APPLICATIONS VI   2148   431 - 439   1994

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  • Oscillation wavelength shift of GaAlAs laser diodes in a magnetic field Reviewed

    Takashi Sato, Hidetoshi Kawashima, Toshio Nakamura, Masashi Ohkawa, Takeo Maruyama, Minoru Shimba

    Electronics and Communications in Japan (Part II: Electronics)   76 ( 4 )   13 - 21   1993

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    The wavelength shift of laser diodes in a magnetic field has been known for a long time. However, most of the studies have been performed at very low temperatures in a strong magnetic field. An experiment is carried out using laser diodes which oscillate at room temperature and found that the wavelength shift changed significantly, being sensitive to an inner structure. Further, the wavelength shift occurred depending on a magnetic field direction. Previously, the wavelength shift was explained on the basis of the Landau level at very low temperatures in a strong magnetic field. However, such Landau levels are not formed in a relatively weak magnetic field at room temperature
    and, thus, the present result cannot be accounted for by the existing theories. This paper describes the experimental results of various types of GaAlAs laser diodes and discusses the mechanism of the wavelength shift and the wavelength control. Copyright © 1993 Wiley Periodicals, Inc., A Wiley Company

    DOI: 10.1002/ecjb.4420760402

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  • Integrated Optic Accelerometer Employing a Cantilever on a Silicon Substrate

    Ohkawa Masashi, Izutsu Masayuki, Sueta Tadasi

    Jpn J Appl Phys   28 ( 2 )   287 - 288   1989.2

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    A novel integrated optic accelerometer employing a cantilever on a silicon substrate is proposed. An analysis is carried out to demonstrate the feasibility of the proposed sensor and obtain the basic design concept. The sensitivity and the detectable frequency range of the acceleration can be set by proper selection of the cantilever dimensions and the added weight.

    DOI: 10.1143/JJAP.28.287

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  • マイクロオプトメカトロニクスハンドブック

    大河正志, 井筒雅之, 五十嵐伊勢美, 江刺正喜, 藤田博之編( Role: Joint author ,  3.3節 光集積回路センサ)

    朝倉書店  1997.12 

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  • Light Scattering and Reflection Characteristics Measurement System Using Michelson Interferometer-Measurement of Amplitude Reflectance of Glass Surfaces for Operation Test-

    石井千皓, 中川瑞輝, 大河正志, 鈴木孝昌

    Optics & Photonics Japan講演予稿集(CD-ROM)   2022   2022

  • Output responses of narrow-band guided-wave optical Acoustic Emission (AE) sensor

    32   1 - 4   2015.10

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  • Output Response in guided-wave optical pressure sensor using semi-closed space under diaphragm

    32   1 - 4   2015.10

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  • FEM Analysis on Sensor Sensitivity in a Silicon-Based Guided-Wave Optical Accelerometer : Sensitivity Dependences on Waveguide Position and Diaphragm Thickness

    32   1 - 4   2015.10

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  • Optical range finder using semiconductor laser frequency noise

    T. Saito, K. Kondo, Y. Tokutake, S. Maehara, K. Doi, H. Arai, T. Sato, M. Ohkawa, Y. Ohdaira, S. Sakamoto

    Proceedings of SPIE - The International Society for Optical Engineering   9576   2015.1

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    © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. Semiconductor laser range-finder systems use so-called time-of-flight methods that require us to modulate semiconductor lasers intensity and frequency, and detect those of reflected lights, in order to compare optical paths to the reference and the target. But, accurate measurement requires both high-speed modulation and detection systems. By taking advantage of semiconductor lasers broad-spectrum frequency noise, which has a range of up to a few GHz, and converting it to intensity noise, we were able to generate a set of high-speed physical random numbers that we used to precisely measure the distance. We tuned the semiconductor lasers oscillation frequencies loosely to the Rb absorption line and converted their frequency noise to intensity noise, in the light transmitted. Observed through a frequency discriminator, beams traveling along two different paths will always share intensity noise patterns, but there is a time lag. We calculate the cross-correlation of the two signals by sweeping their time lags. The one with the highest degree of correlation was that corresponding to the difference in the length of the two optical paths. Through our experiments, we confirmed that the system was accurate up to a distance of 50 m, at a resolution of 0.03 m, when the sampling rate was adjusted to 0.2 ns.

    DOI: 10.1117/12.2187963

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  • Physical-random number generation using a semiconductor laser diode's frequency noise characteristics : Influence of lights source characteristics

    MIZUTANI Naohiro, HASEGAWA Masatoshi, ARAI Hideaki, MAEHARA Shinya, DOI Kohei, SATO Takashi, OHDAIRA Yasuo, OHKAWA Masashi, SAKAMOTO Shuichi

    Technical report of IEICE. OPE   114 ( 186 )   59 - 62   2014.8

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    The encryption technique is necessary for the internet community. The encryption using the pseudo-random numbers is considered safe because it takes a lot of time to decode it. However, since high speed processing computers are emerging in these days, it may not safe anymore. On the other hand, quantum cryptographic communications which are theoretically impossible to decode have been advanced and need a large number of physical random numbers. This paper describes a method, whereby semiconductor laser diodes' frequency noise-signatures generate a series of physical random numbers. As a result, we generated random number bit strings at 40Gb/s in a VCSEL and at 50Gb/s in a FPLD.

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  • Examination of an Optical Range Finder using Semiconductor Laser Frequency Noises

    Kondo Katsuki, Saito Takahiro, Tokutake Yuuya, Arai Hideaki, Maehara Shinya, Doi Kohei, Sato Takashi, Ohdaira Yasuo, Ohkawa Masashi, Sakamoto Syuuichi

    Technical report of IEICE. OPE   114 ( 186 )   63 - 66   2014.8

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    Because of their low cost, light weight, low power consumption and durability, semiconductor lasers are ideal, for use as optical range finder light-sources. Their oscillation-frequency fluctuations generate the physical random numbers, which are used to measure distances. While normal range finders use modulation signals, such as sharp pulses, the method we devised employs semiconductor lasers' frequency noise, and a frequency to intensity converter, such as the rubidium absorption profile, to produce physical random numbers. This allowed us to construct an optical range finder that requires no additional modulation of the semiconductor laser, - has a range of up to 50 meters, and resolution of 0.06 meters. We also consider the resolving power of this method without changing its sampling rate.

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  • Oscillation Characteristic Changes of a Vertical Cavity Surface Emitting Laser in a Magnetic Field

    IIJIMA Otohiro, DOI Kohei, SATO Takashi, OHKAWA Masashi

    IEICE technical report. Component parts and materials   114 ( 185 )   67 - 70   2014.8

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    Laser diodes' oscillation characteristics vary according to types of materials used in their composition, injection current, laser temperature, and the strength of an applied magnetic field. Regarding the applied magnetic field, other researchers have thus far conducted their tests using up to 4T magnetic fields, at a temperature less than 80K; figures cited in Landau level theory. We have studied the effect of a magnetic field on the oscillation characteristics at "room temperature (300K) and a relatively weak magnetic field (〜0.5T)". This work describes the shifts in oscillation frequency-, injection current- and voltage, of a vertical cavity surface emitting laser diode (VCSEL), and the mechanism by which the device's oscillation characteristics shift, when exposed to a magnetic field.

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  • C-4-14 半導体レーザの周波数雑音特性を用いた物理乱数生成 : 発振幅狭窄化が物理乱数生成への影響に関する考察(C-4.レーザ・量子エレクトロニクス,一般セッション)

    酒井 翔太, 新井 秀明, 齋藤 高大, 大河 正志, 大平 泰生, 坂本 秀一, 佐藤 孝

    電子情報通信学会総合大会講演論文集   2014 ( 1 )   250 - 250   2014.3

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  • C-3-8 Examination of the design method in design support system of a guided-wave optical pressure sensor

    Sato Ryosuke, Ohkawa Masashi, Sato Takashi

    Proceedings of the IEICE General Conference   2014 ( 1 )   163 - 163   2014.3

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  • D-2-3 Transform of RGB color system to L^* a^* b^* color system using neural network

    Shinozaki Hitoshi, Ohkawa Masashi

    Proceedings of the IEICE General Conference   2014 ( 1 )   15 - 15   2014.3

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  • 21aSB-4 スペース重力波アンテナDECIGO計画(55) : DECIGO/DPFの概要(21aSB 重力波(KAGRA,DECIGO,TOBA,検出器),宇宙線・宇宙物理領域)

    安東 正樹, 川村 静児, 瀬戸 直樹, 中村 卓史, 坪野 公夫, 佐藤 修一, 田中 貴浩, 船木 一幸, 沼田 健司, 神田 展行, 井岡 邦仁, 高島 健, 横山 順一, 阿久津 智忠, 武者 満, 上田 暁俊, 麻生 洋一, 新谷 昌人, 坂井 真一郎, 青柳 巧介, 我妻 一博, 浅田 秀樹, 新井 宏二, 池上 健, 石川 毅彦, 石崎 秀晴, 石原 秀樹, 和泉 究, 市來 淨與, 伊東 宏之, 伊藤 洋介, 井上 開輝, 植田 憲一, 牛場 崇文, 歌島 昌由, 江口 智士, 江尻 悠美子, 榎 基宏, 戎崎 俊一, 江里口 良治, 大石 奈緒子, 大河 正志, 大橋 正健, 大原 謙一, 大渕 喜之, 岡田 健志, 岡田 則夫, 奥富 弘基, 河島 信樹, 川添 史子, 河野 功, 木内 建太, 岸本 直子, 國中 均, 國森 裕生, 黒田 和明, 黒柳 幸子, 小泉 宏之, 洪 鋒雷, 郡 和範, 穀山 渉, 苔山 圭以子, 古在 由秀, 小嶌 康史, 固武 慶, 小林 史歩, 権藤 里奈, 西條 統之, 齊藤 遼, 阪上 雅昭, 阪田 紫帆里, 佐合 紀親, 佐々木 節, 佐藤 孝, 柴田 大, 柴田 和憲, 正田 亜八香, 真貝 寿明, 末正 有, 杉山 直, 鈴木 理恵子, 諏訪 雄大, 宗宮 健太郎, 祖谷 元, 高野 忠, 高橋 走, 高橋 慶太郎, 高橋 弘毅, 高橋 史宜, 高橋 龍一, 高橋 竜太郎, 高森 昭光, 田越 秀行, 田代 寛之, 田中 伸幸, 谷口 敬介, 樽家 篤史, 千葉 剛, 陳 たん, 辻川 信二, 常定 芳基, 豊嶋 守生, 鳥居 泰男, 中尾 憲一, 中澤 知洋, 中須賀 真一, 中野 寛之, 長野 重夫, 中村 康二, 中山 宜典, 西澤 篤志, 西田 恵里奈, 西山 和孝, 丹羽 佳人, 能見 大河, 橋本 樹明, 端山 和大, 原田 知広, 疋田 渉, 姫本 宣朗, 平林 久, 平松 尚志, 福嶋 美津広, 藤田 龍一, 藤本 眞克, 二間瀬 敏史, 細川 瑞彦, 堀澤 秀之, 前田 恵一, 松原 英雄, 松本 伸之, 道村 唯太, 宮川 治, 宮本 雲平, 三代木 伸二, 向山 信治, 森澤 理之, 森本 睦子, 森脇 成典, 八木 絢外, 山川 宏, 山崎 利孝, 山元 一広, 吉田 至順, 吉野 泰造, 柳 哲文, 若林 野花

    日本物理学会講演概要集   69 ( 0 )   49 - 49   2014

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  • 周波数安定化半導体レーザーによる物理乱数生成システムの構築

    新井秀明, 前原進也, 土井康平, 佐藤孝, 大平泰生, 坂本秀一, 大河正志

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   74th   ROMBUNNO.16P-P2-3   2013.8

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  • Physical random number generation using a frequency noise characteristic of a semiconductor laser : An influence of narrower oscillation width on physical random number generation

    FRUKAWA Genichi, SAITOU Takahiro, SAKAI Shota, ARAI Hideaki, MAEHARA Shinya, DOI Kouhei, SATO Takashi, OHKAWA Masashi, SAKAMOTO Shuichi, OHDAIRA Yasuo

    Technical report of IEICE. LQE   113 ( 190 )   5 - 10   2013.8

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    The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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  • High-speed physical-random number generation using a laser diode's frequency noise characteristics

    KONDO Takanobu, MAEHARA Shinya, MIZUTANI Naohiro, ARAI Hideaki, DOI Kohei, SATO Takashi, SAKAMOTO Syuichi, OHDAIRA Yasuo, OHKAWA Masashi, SHIMIZU Naoya

    Technical report of IEICE. LQE   113 ( 190 )   1 - 4   2013.8

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    Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode's frequency noise characteristic.

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  • Optical Distance Measurement Using Frequency Noises of a Semiconductor Laser

    Shimizu Naoya, Maehara Shinya, Doi Kouhei, Arai Hideaki, Sato Takashi, Ohkawa Masashi, Ohdaira Yasuo, Sakamoto Shuichi

    Technical report of IEICE. LQE   113 ( 190 )   11 - 14   2013.8

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    A semiconductor laser's frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser's frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser's frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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  • Oscillation frequency stabilization of a semiconductor laser diode using the direct modulation method and its application

    MATSUKI Kohei, NIMONJI Toshiya, TSUKAMOTO Syoya, SATO Takashi, OKAWA Masashi

    IEICE technical report. Component parts and materials   113 ( 188 )   15 - 18   2013.8

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    Because a semiconductor laser's oscillation frequency changes easily, its frequency stabilization is necessary for many application fields. We stabilized semiconductor laser's oscillation frequency using the direct modulation method and measured two stabilized laser's relative frequency stability using the beat signal between two laser beams. Recently THz wave generationis focused, so we think we can use the semiconductor laser as the THz wave source. We measure the beat signal of 1.2GHz as abasic experiment.

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  • Physical-random number generation using laser diode's frequency noise : Consideration about the influence of laser diode's linewidth

    Saito Takahiro, Arai Hideaki, Furukawa Genichi, Sakai Shota, Sato Takashi, Sakamoto Shuichi, Ohkawa Masashi

    Technical report of IEICE. LQE   113 ( 49 )   17 - 21   2013.5

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    We have been constructed a physical random number generator which utilizes laser diode's frequency noise characteristics. A linewidth of a laser diode indicates the range in which its oscillation frequency fluctuates. In this study, we generate random numbers using a laser diode which operates in a free-running condition and in an external cavity diode laser system which have a narrow linewidth. We used the "FIPS140-2" test as a statistical test suitable for the evaluation of random numbers and compared the random numbers which are generated in our two laser systems so that we consider the influence of linewidth of laser diodes.

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  • Shorter Wavelength Side Shift of a Vertical Cavity Surface Emitting Laser in a magnetic field

    KONO Keiko, Iijima Otohiro, DOI Kohei, TABIRA Shinichi, SATO Takashi, OKAWA Masashi

    Technical report of IEICE. LQE   113 ( 49 )   23 - 26   2013.5

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    The output characteristic of a diode laser is changed by the conditions of its injection current, its temperature, and the applied magnetic fields. We made a research on a Fabry-Perot type diode lasers, especially its oscillation frequency characteristic in a room temperature and relatively weak magnetic fields in our previous work. This work reports the characteristic of a VCSEL in a magnetic field. The obtained result is different from that of a Fabry-Perot type diode laser's case and the VCSEL's oscillation frequency shifted to the higher oscillation frequency side.

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  • 半導体レーザーの周波数雑音を利用した物理乱数生成と距離計測

    土井康平, 前原進也, 新井秀明, 佐藤孝, 大平泰生, 坂本秀一, 大河正志

    応用物理学会学術講演会講演予稿集(CD-ROM)   73rd   ROMBUNNO.12A-PA1-1   2012.8

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  • Physical-random number generation using laser diode's noise characteristics : Consideration about the influence of laser diode's oscillation frequency stabilization

    SAITO Takahiro, FURUKAWA Genichi, ARAI Hideaki, SATO Takashi, SAKAMOTO Shuichi, OHKAWA Masashi

    Technical report of IEICE. LQE   112 ( 184 )   5 - 8   2012.8

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    The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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  • Random-Number-Generation Using a VCSEL's Frequency Noise Characteristic

    KAWAKAMI Kohei, MAEHARA Shinya, DOI Kohei, ARAI Hideaki, KONDO Takanobu, SHIMIZU Naoya, SATO Takashi, SAKAMOTO Shuichi, OHDAIRA Yasuo, OHKAWA Masashi

    Technical report of IEICE. LQE   112 ( 184 )   9 - 12   2012.8

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    The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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  • Oscillation frequency stabilization of a semiconductor laser diode using the Rb saturated absorption spectroscopy and advanced technology

    TAKADA Kohei, NIMONJI Toshiya, MATSUKI Kohei, SATO Takashi, OKAWA Masashi

    IEICE technical report. Reliability   112 ( 180 )   17 - 20   2012.8

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    Because a semiconductor laser's oscillation frequency changes easily, its frequency stabilization is necessary for many application fields. We measured this frequency stability using the beat signal between frequencies of two semiconductor lasers. We studied the generation method of terahertz waves by means of semiconductor laser's beat signals because this method has the potential of low cost, small size, and high performance Terahertz wave sources for medical and communication fields.

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  • Oscillation characteristic changes of a vertical cavity surface emitting laser in a magnetic field

    TABIRA Shinichi, KONO Keiko, DOI Kohei, SATO Takashi, OKAWA Masashi

    IEICE technical report. Reliability   112 ( 180 )   13 - 16   2012.8

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    The Output characteristic of a diode laser is changed by the its conditions of injection current, temperature, and magnetic fields. So far, we researched on a Fabry-Perot type diode lasers, especially its t oscillation frequency characteristic in room temperature and relatively weak the magnetic fields. We studied the characteristic of a VCSEL in magnetic field. That result differed from the Fabry-Perot type diode laser's case and the VCSEL's oscillation frequency shifted to the higher oscillation frequency side.

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  • 24pGJ-6 Space Gavitational-Wave Antenna DECIGO (36) : DECIGO/DPF

    Ando Masaki

    Meeting Abstracts of the Physical Society of Japan   67 ( 0 )   126 - 126   2012

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  • 半導体レーザーの周波数雑音を利用した高速物理乱数生成

    土井康平, 松本良彦, 新井秀明, 前原進也, 佐藤孝, 大平泰生, 坂本修一, 大河正志

    応用物理学関係連合講演会講演予稿集(CD-ROM)   59th   2012

  • Physical Random Number Generation by Means of Diode Lasers' Frequency Noise

    DOI Kohei, ARAI Hideaki, MAEHARA Shinya, TAKAMORI Taiki, MATSUMOTO Yoshihiko, SATO Takashi, OHDAIRA Yasuo, SAKAMOTO Shuichi, OHKAWA Masashi

    IEICE technical report   111 ( 56 )   9 - 12   2011.5

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    Diode lasers are characterized by wideband frequency-noise output that is easily detected by frequency-selective elements, that convert frequency deviation into intensity fluctuation. Any such intensity noise can be digitized by means of A/D converters; so, some of these digital signals demonstrate physical-random number characteristics. We demonstrated physical random number generation and evaluated the physical random numbers using NIST standard tests.

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  • 28aGS-1 Space Gravitational Wave Antenna DECIGO (30) : Design, Project

    Kawamura Seiji

    Meeting Abstracts of the Physical Society of Japan   66 ( 0 )   124 - 124   2011

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  • Fast Physical-Random Number Generation Using Frequency Noises of a Semiconductor Laser

    MAEHARA Shinya, DOI Kohei, USHIKI Tetsurou, SATO Takashi, OHDAIRA Yasuo, OHKAWA Masashi

    IEICE technical report   110 ( 66 )   23 - 26   2010.5

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    Pseudo-random numbers' periodicity renders them inappropriate for use in cryptographic applications, but, naturally-generated physical-random numbers have no calculable periodicity, thereby making them ideally-suited to the task. Some experiments about physical-random number generation have reached to Gbps range by using laser diode's (LD's) intensity noises in recent years. The laser diode naturally produces a wideband "noise" signal that is believed to have tremendous capacity and great promise, for the rapid generation of physical-random numbers for use in cryptographic applications. The result shows that the fast physical-random number generation, as fast as 5Gbps, is obtainable, using the laser diode's frequency noise characteristic.

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  • BI-1-7 Space gravitational wave detector : DECIGO & DPF

    Sun Ke-Xun, Musha Mitsuru

    Proceedings of the IEICE General Conference   2010 ( 1 )   SS_85 - SS-86   2010.3

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    本文データは学協会の許諾に基づきCiNiiから複製したものである

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  • 21aBH-1 Space Gravitational Wave Antenna DECIGO (24) : Design, Project

    Kawamura Seiji

    Meeting Abstracts of the Physical Society of Japan   65 ( 0 )   108 - 108   2010

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  • C-3-8 Characterization of a Silicon-Based Guided-Wave Optical Microphone

    Watanabe Noriyuki, Ohkawa Masashi, Sato Takashi

    Proceedings of the Society Conference of IEICE   2009 ( 1 )   163 - 163   2009.9

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  • C-3-17 Relationship between diffraction efficiency and spacial frequency in acrylamide-based photopolymer holographic film

    Ogashiwa Keisuke, Ohkawa Masashi, Sato Takashi

    Proceedings of the Society Conference of IEICE   2009 ( 1 )   172 - 172   2009.9

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  • C-3-25 Silicon based guided-wave optical accelerometer : Dependence of sensor sensitivity on thickness of diaphragm

    Oshima Takuya, Endo Hideto, Ohkawa Masashi, Sato Takashi

    Proceedings of the Society Conference of IEICE   2009 ( 1 )   180 - 180   2009.9

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  • Oscillation frequency stabilization of a semiconductor laser using the Faraday effect : Consideration about the temperature fluctuation of our experimental setup

    ARAI Hideaki, MAEHARA Shinya, SATO Akira, KUWABARA Hideyuki, SATO Takashi, OHKAWA MASASH

    IEICE technical report   109 ( 49 )   59 - 63   2009.5

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    Recently, the compact and highly coherent laser light source is required to be developed for the use in the laser interferometers on the artificial satellite. The semiconductor laser is a promising candidate of these light sources, but there is the defect that the oscillation frequency varies with the change of driving current and atmospheric temperature. Therefore we are using the atomic absorption line as a frequency reference, and stabilize the oscillation frequency of the semiconductor laser. We describe the oscillation frequency stabilization in which we used the magneto-optic effect for obtaining the error signal for the stabilization without directly modulating the injection current of the laser diode, i.e., without broadening the oscillation width of the diode laser. We tried to improve the frequency stability by reducing the temperature fluctuation using a permanent magnet instead of the electromagnet for obtaining the Faraday effect.

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  • 10aSE-4 Space Gravitational Wave Antenna DECIGO (20) : Design, Project

    Kawamura Seiji

    Meeting Abstracts of the Physical Society of Japan   64 ( 0 )   32 - 32   2009

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  • 30pSC-1 Space Gravitational Wave Antenna DECIGO (17) : Design, Project

    Kawamura Seiji

    Meeting Abstracts of the Physical Society of Japan   64 ( 0 )   100 - 100   2009

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  • 応用物理学会の教育・公益事業の取組みとして~北陸・信越支部による「リフレッシュ理科教室」~

    坪井望, 鈴木孝昌, 大河正志, 新保一成, 大平泰生, 馬場暁, 岩野春男, 丸山武男

    応用物理学会学術講演会講演予稿集   70th   2009

  • Decigo: The japanese space gravitational wave antenna

    Masaki Ando, Seiji Kawamura, Takashi Nakamura, Naoki Seto, Kimio Tsubono, Kenji Numata, Ryuichi Takahashi, Mitsuru Musha, Ken Ichi Ueda, Ikkoh Funaki, Shigenori Moriwaki, Takeshi Takashima, Shin Ichiro Sakai, Takashi Sato, Nobuyuki Kanda, Shigeo Nagano, Mizuhiko Hosokawa, Takehiko Ishikawa, Shuichi Sato, Yoichi Aso, Mutsuko Y. Morimoto, Kazuhiro Agatsuma, Tomomi Akutsu, Tomotada Akutsu, Tomotada Akutsu, Koh Suke Aoyanagi, Koji Arai, Yuta Arase, Akito Araya, Hideki Asada, Takeshi Chiba, Toshikazu Ebisuzaki, Motohiro Enoki, Yoshiharu Eriguchi, Feng Lei Hong, Masa Katsu Fujimoto, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Hideyuki Horisawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Kunihito Ioka, Koji Ishidoshiro, Hiroyuki Ito, Yousuke Itoh, Shogo Kamagasako, Nobuki Kawashima, Fumiko Kawazoe, Hiroyuki Kirihara, Naoko Kishimoto, Kenta Kiuchi, Werner Klaus, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei Ichi Maeda, Hideo Matsuhara, Yasushi Mino, Jun Ichi Miura, Osamu Miyakawa, Shinji Miyoki, Tomoko Morioka, Toshiyuki Morisawa, Shinji Mukohyama, Isao Naito, Noriyasu Nakagawa, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Akira Okutomi, Kouji Onozato, Kenichi Oohara, Norichika Sago

    11th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proc. of the MG11 Meeting on General Relativity   120   2393 - 2397   2008.12

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    DECIGO (DECI-hertz interferometer Gravitational wave Observatory) is the future Japanese space gravitational wave antenna with observation band around 0.1 Hz. It aims at detecting gravitational waves from various kinds of sources, with sufficient sensitivity to establish the gravitational wave astronomy. In the pre-conceptual design, DECIGO is formed by three drag-free spacecraft, 1000 km apart from one another. The relative displacements between proof masses housed in these spacecraft are measured by Fabry-Perot interferometers. We plan to launch DECIGO in 2024 after research and development phase, including two milestone missions (DECIGO pathfinder and Pre-DECIGO) for verification of required technologies. © 2008 World Scientific Publishing Co. Pte. Ltd.

    DOI: 10.1088/1742-6596/120/3/032004

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  • C-3-31 Frequency response of glass-based guided-wave optical microphone

    Nakajima Mizuki, Nikkuni Hiroyuki, Ohkawa Masashi, Sato Takashi

    Proceedings of the Society Conference of IEICE   2008 ( 1 )   153 - 153   2008.9

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  • Frequency stabilization of semiconductor lasers for onboard interferometers using both Rb-saturated absorption profiles and double optical feedback systems

    NAKANO Kenji, MAEHARA Shinya, SATO Ayumi, DOI Kohei, SATO Takashi, OHKAWA Masashi, KAWAMURA Seiji

    IEICE technical report   108 ( 192 )   93 - 98   2008.8

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    We expect that semiconductor lasers are useful for precise interferometric systems employed in artificial satellites, by virtue of their overall compactness, lightweight, durability and energy-efficiency. However, stability of their oscillation frequency and broad-spectrum linewidth are obstacles in this area. Once we find a way to sidestep that issue by stabilization, satellite-to-satellite tracking laser interferometers will measure fluctuations in earth's gravitational field with a level of precision we can now only dream of. Thus far, we have succeeded in stabilizing semiconductor lasers' frequencies to Rb-saturated absorption lines. In order to narrow oscillation linewidth, we introduced "Double Optical Feedback". This double optical feedback system reduces oscillation linewidth and also reduces fluctuations in intensity and frequency, without resorting to mechanical control elements.

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  • Oscillation frequency stabilization of a semiconductor laser by an indirect modulation method using the Faraday effect

    SATO Akira, MAEHARA Sinya, UEHARA Tomoyuki, ARAI Hideaki, SATO Takashi, TAMURA Tadashi, OHKAWA Masashi, KAEAMURA Seiji

    IEICE technical report   108 ( 192 )   99 - 102   2008.8

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    Research, using tandem satellites' on-board tracking laser interferometers, is aimed at gauging the infinitesimal variations in the relative velocities of these orbiting bodies, to accurately measure fluctuations in earth's gravitational field. A major part of this effort has involved the stabilization of semiconductor lasers' frequencies to Fabry-Perot etalons and atomic absorption lines, and obtaining from them, the requisite control signal, by directly modulating the oscillation frequency. Taking advantage of the etalon's short-term stability and tunability over a wide frequency range, and the Rb absorption line's stability over the long term, we succeeded in stabilizing the frequency of a semiconductor laser.

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  • Consideration about characteristic improvements of a VCSEL using an external cavity system

    DOI Kohei, MINABE Yuta, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi

    IEICE technical report   108 ( 51 )   59 - 62   2008.5

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    The recent development of FTTH (Fiber To The Home) can provide not only an Internet service but also IP phone and Cable TV system services. But, the faster communication links will be required for these services in the near future. So, we are interested in the fast modulation characteristics of a VCSEL (Vertical Cavity Surface Emitting Laser) and investigate the optical feedback method for improving the VCSEL's oscillation characteristics, which is important to use the VCSEL in the wavelength division multiplex system. Our experimental results showed that this system could narrow its oscillation linewidth and stabilize its oscillation frequency.

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  • 25pZW-6 Space Gravitational Wave Antenna DECIGO XIII : Overview, Roadmap, Path Finder

    Ando M, Kawamura S, Nakamura T, Tsubono K, Tanaka T, Seto N

    Meeting Abstracts of the Physical Society of Japan   63 ( 0 )   116 - 116   2008

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  • 23aSF-1 Space Gravitational Wave Antenna DECIGO XV : Overview, Roadmap, Path Finder

    Ando M, Kawamura S, Seto N, Tanaka T, Nakamura T, Tsubono K

    Meeting Abstracts of the Physical Society of Japan   63 ( 0 )   91 - 91   2008

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  • Frequency stabilization of an external cavity diode laser : Countermeasure against atmospheric temperature variations

    MINABE Yuta, DOI Kohei, KAIZAKA Toshiya, SATO Takashi, TAMURA Tadashi, OHKAWA Masashi, MARUYAMA Takeo

    IEICE technical report   107 ( 198 )   123 - 126   2007.8

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    External cavity diode lasers are presently experiencing a surge in popularity, as laser light-sources for advanced optical measurement systems. While these systems normally require an active cavity-control device, we removed this active element from the setup, by adding a second external cavity. This technique boasts the added advantage of having a narrower oscillation-linewidth than would be achievable, using a single optical feedback.

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  • Influence of the frequency stability from temperature controls at several points in our frequency stabilization of a semiconductor laser

    YANAGISAWA Mitsusuke, NAKANO Kenji, MAEHARA Sinya, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi, KAEAMURA Seiji

    IEICE technical report   107 ( 198 )   119 - 122   2007.8

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    Semiconductor lasers used as light sources for satellite-to-satellite tracking interferometers measure fluctuations in earth's gravitational field, accurately gauging infinitesimal variations in the relative velocities of satellites flying in tandem, at better than 10nm/s ; a feat that requires frequency stability better than 10^<-13> in the square root of Allan variance σ. Having stabilized semiconductor lasers' frequencies to external Fabry-Perot etalon- and atomic absorption line- references, we are able to take maximum advantage of the Fabry-Perot etalon's short-term stability and the Rb absorption line's stability over the long term, to create a robust, frequency-stabilized semiconductor laser system. We obtained the stability 9×10^<-13> by improving the temperature stability of our laser mount.

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  • Design for glass-based guided-wave optical microphone with a diaphragm : Sensitivity dependence with respect to thickness and side length ratio of the diaphragm

    NIKKUNI Hiroyuki, WATANABE Yu, OHKAWA Masashi, SEKINE Seishi, SATO Takashi

    IEICE technical report   107 ( 124 )   53 - 58   2007.6

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    Sensitivity of a guided-wave optical microphone is theoretically found to be inversely proportional to the square of the diaphragm thickness. Also, according to the theoretical analysis, sensitivity increases with an increase in side length ratio for the side length ratio of less than unity, but the sensitivity shows a plateau for the ratio of more than unity. These dependencies, however, have not been demonstrated experimentally, although they are important in the designing of the optical microphone. In this study, these dependencies were examined experimentally. Based on the sensitivity dependence with respect to the diaphragm dimensions, the optical microphone with a 20 mm×20 mm×0.15 mm diaphragm was fabricated, and then successfully detected a sound wave of 100 dB-SPL.

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  • Design for glass-based guided-wave optical microphone with a diaphragm : Sensitivity dependence with respect to thickness and side length ratio of the diaphragm

    NIKKUNI Hiroyuki, WATANABE Yu, OHKAWA Masashi, SEKINE Seishi, SATO Takashi

    IEICE technical report   107 ( 125 )   53 - 58   2007.6

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    Sensitivity of a guided-wave optical microphone is theoretically found to be inversely proportional to the square of the diaphragm thickness. Also, according to the theoretical analysis, sensitivity increases with an increase in side length ratio for the side length ratio of less than unity, but the sensitivity shows a plateau for the ratio of more than unity. These dependencies, however, have not been demonstrated experimentally, although they are important in the designing of the optical microphone. In this study, these dependencies were examined experimentally. Based on the sensitivity dependence with respect to the diaphragm dimensions, the optical microphone with a 20 mm×20 mm×0.15 mm diaphragm was fabricated, and then successfully detected a sound wave of 100 dB-SPL.

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  • Study of the natural random number generation using a noise characteristic of a semiconductor laser

    CHIBA Jun, DOI Kohei, SATO Takashi, OHDAIRA Yasuo, OHKAWA Masashi, MARUYAMA Takeo

    IEICE technical report   107 ( 71 )   45 - 48   2007.5

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    Random numbers can be classified as either pseudo-random or physical random in character. Pseudo-random numbers' periodicity renders them inadequate for coding purposes, in an age of ultra high-speed calculation, whereas Naturally-generated physical random numbers have no calculable periodicity. This work demonstrates how semiconductor lasers' inherent noise can be exploited for use in generating the physical random number and applying it in the field of cryptography.

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  • Frequency stabilization of a semiconductor laser using the PEAK method : Discussion about the effect of experimental condition on frequency stability

    UEHARA Tomoyuki, MAEHARA Shinya, NIMONJI Toshiya, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, KAWAMURA Seiji

    IEICE technical report   107 ( 71 )   41 - 44   2007.5

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    In 1916, Albert Einstein argued for the existence of gravitational waves. But, confirmation of his ideas would not come, until 1991, when the binary neutron star, PSR1913+16 was discovered. We now understand that gravitational waves carry information of ultimate states in space to us. And, while we know that these tide-like forces move at the speed of light, we have yet to detect them directly. To verify the existence of gravitational waves, we need laser interferometers that are far more powerful than those currently in uses, and have been conducting experiments with frequency-stabilized atomic absorption line-based semiconductor lasers. While these devices hold some promise, we are still contending with their absorption lines' broad linewidths. In the interim, we are using the PEAK method, to obtain a stabilization point.

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  • Investigation of characteristic improvements in an external cavity diode laser system using a double optical feedback method

    DOI Kohei, MINABE Yuta, KAIZAKA Toshiya, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi

    IEICE technical report   107 ( 71 )   49 - 52   2007.5

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    Wavelength stability and spectrum purity are crucial, when a semiconductor laser is used as a light source, in precision optical measurement systems. This paper reports the improvements of a semiconductor laser's characteristics using the double optical feedback system, which consists of two mirrors or two diffraction gratings. The double optical feedback can lessen the laser linewidth and improve the frequency stability. However, a long-term stability level worsens because the length of an external resonator changes by the atmospheric temperature variation. Some experiments, which can suppress the influence of the temperature change, are reported in this paper.

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  • 21aZH-2 Space Gravitational Wave Antenna DECIGO XII (Path Finder)

    Ando M, Kawamura S, Seto N, Nakamura T, Tsubono K, Tanaka T

    Meeting Abstracts of the Physical Society of Japan   62 ( 0 )   95 - 95   2007

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  • 21aZH-3 Space Gravitational Wave Antenna DECIGO XI (Science)

    Seto Naoki

    Meeting Abstracts of the Physical Society of Japan   62 ( 0 )   96 - 96   2007

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  • 21aZH-1 Space Gravitational Wave Antenna DECIGO X (Design, Project)

    Kawamura Seiji

    Meeting Abstracts of the Physical Society of Japan   62 ( 0 )   95 - 95   2007

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  • P02 Verification of conjecture ability of color by neural networks(2)(Special Issue 38th Annual Meeting)

    Kondo Akiko, Sekine Seishi, Ohkawa Masashi

    31   80 - 81   2007

  • C-3-66 ガラス基板光導波型マイクロホンに関する研究 : S/N比の改善(光記録・計測(2),C-3.光エレクトロニクス,一般講演)

    林 学, 茂木 良晃, 新國 広幸, 大河 正志, 関根 征士, 佐藤 孝

    電子情報通信学会ソサイエティ大会講演論文集   2006 ( 1 )   188 - 188   2006.9

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  • C-3-62 おもり付きダイヤフラムを用いたシリコン基板光導波型加速度センサ : センサ感度の導波路位置依存性(光記録・計測(1),C-3.光エレクトロニクス,一般講演)

    外川 徹郎, 大河 正志, 関根 征士, 佐藤 孝

    電子情報通信学会ソサイエティ大会講演論文集   2006 ( 1 )   184 - 184   2006.9

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  • Evaluation of frequency stability in compact double optical feedback ECDL systems

    DOI Kohei, MINABE Yuta, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi, TSUBOKAWA Tsuneya

    IEICE technical report   106 ( 90 )   53 - 58   2006.5

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    Wavelength stability and spectrum purity are crucial, when a semiconductor laser is used as a light source, in precision optical measurement systems. This paper reports the frequency stabilization of a semiconductor laser using the double optical feedback system, which is consist of two mirrors or two diffraction gratings. The double optical feedback can lessen the laser linewidth and improve the frequency stability. However, a long-term stability level worsens because the length of an external resonator changes by the atmospheric temperature variation. Some experiments, which can suppress the influence of the temperature change, are reported in this paper.

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  • Influence of modulation characteristics on oscillation frequency stability of a semiconductor laser using the direct modulation method : Frequency stabilization using the saturated absorption line of the Rb atom

    NAKANO Kenji, MAEHARA Shinya, SEKIYA Yasuhiro, YANAGISAWA Mitsusuke, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi, TSUBOKAWA Tsuneya

    IEICE technical report   106 ( 90 )   75 - 80   2006.5

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    We have improved the frequency stabilization system of a semiconductor laser, which uses a Fabry-Perot etalon as a frequency reference, by controlling the etalon spectrum using the Rb absorption line. Because the stabilization system using the etalon has a wide control range but a defect in its long-term stability, we combined the etalon system with the atomic absorption system, which can provide the control signal for the long-term stabilization. This paper reports an experiment using the saturated absorption spectroscopy of the Rb absorption line to obtain the control signal for the etalon and then to improve the frequency stability of the semiconductor laser

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  • B1-5 Verification of conjecture ability of color by neural networks(Special Issue 37th Annual Meeting)

    Kondo Akiko, Sekine Seishi, Okawa Masashi

    30   68 - 69   2006

  • Constructing of light engine lighting system and the making to highly effective : Examination of system configuration and use material

    Tomiyama Kazuya, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   38   68 - 68   2005.7

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  • Estimation of complex refractive index of clusters by Mie-Scattering Ellipsometry

    Harada Yasunari, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   38   270 - 271   2005.7

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  • Characteristic evaluation of cluster luminescence : Characteristic of Molybdenum cluster radiation

    Kondo Kazuya, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   38   67 - 67   2005.7

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  • Evaluation of stability of oscillation frequency of a double optical feedback system

    DOI Kohei, KOBAYASHI Yumie, MAEHARA Shinya, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi, TSUBOKAWA Tsuneya

    Technical report of IEICE. LQE   105 ( 52 )   37 - 40   2005.5

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    Wavelength stability and spectrum purity are crucial, when a semiconductor laser is used as a light source, in coherent optical communications systems and precision optical measurement systems. This paper reports the frequency stabilization of a semiconductor laser using the double optical feedback system, which is consist of two mirrors or two diffraction gratings. The double optical feedback can lessen the laser linewidth and improve the frequency stability. However, a long-term stability level worsens because the length of an external resonator changes by the atmospheric temperature variation. Some experiments, which can suppress the influence of the temperature change, are reported in this paper.

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  • 27aXH-13 Development of a ground simulator for a satellite-to-satellite laser interferometry IV

    Nagano S., Kunimori H., Hosokawa M., Yoshino T., Kawamura S., Sato T., Ohkawa M.

    Meeting abstracts of the Physical Society of Japan   60 ( 1 )   103 - 103   2005.3

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  • 28aSE-5 Development of a ground simulator for a satellite-to-satellite laser interferometry III

    Nagano S, Kunimori H, Hosokawa M, Yoshino T, Kawamura S, Sato T, Ohkawa M

    Meeting abstracts of the Physical Society of Japan   59 ( 2 )   76 - 76   2004.8

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  • Development of a Ground Simulator of a Satellite-to-Satellite Interferometry for the Earth's Gravity Field Determination

    NAGANO Shigeo, KUNIMORI Hiroo, HOSOKAWA Mizuhiko, YOSHINO Taizoh, KAWAMURA Seiji, SATO Takashi, OHKAWA Masashi

    Technical report of IEICE. SANE   104 ( 271 )   23 - 26   2004.8

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    A satellite gravity mission is proposed to monitor the Earth's environment in Japan. In the mission, a satellite-to-satellite laser interferometer (SSI) will be employed to amplify the gravitational signal by measuring the relative velocity of twin satellite in the low earth orbit. The maximum range-rate we must measure is predicted to be 0.1 m/s, whereas the required sensitivity is lOnm/s in the measurement band of 10^<-2> 〜 1 Hz to detect the changes in the geoid with millimeter-level accuracy. We are developing a ground simulator to study the feasibility of the SSI for the future mission.

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  • Some characteristics changes of a semiconductor laser in a magnetic field : Consideration of the shift mechanism by changing the injection current

    SETO Yoshio, MIYAMOTO Tetsuya, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo

    Technical report of IEICE. LQE   104 ( 270 )   71 - 75   2004.8

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    Semiconductor laser's oscillation wavelengths are altered significantly, when semiconductor laser are exposed to magnetic fields. When we set some bulk type semiconductor lasers oscillating at 780nm in weak magnetic fields (〜1.4T), at room temperature (300K). When the magnetic field is applied to the laser diodes parallel to the injection current, we observed that the oscillation wavelength shifted to the longer wavelength (low frequency) side in our preliminary works. In this work, we report the longer wavelength side shift, the lower optical output-power side shift, and the higher side terminal voltage shift of some multi-quantum-well (MOW) laser diodes oscillating at 780nm. We are now introducing the mechanism, in which the temperature rise and the longitudinal magneto-resistance effect cause the characteristics shifts observed in our experiments.

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  • Frequency stabilization of a semiconductor laser using the spectrum of a fabry-perot etalon controlled by the Rb absorption line

    KUROSAKI Yoshiharu, MAEHARA Shinya, HASEBE Keiki, OHTA Yuichi, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, TSUBOKAWA Tsuneya

    Technical report of IEICE. LQE   104 ( 270 )   65 - 70   2004.8

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    In this work, in order to employ semiconductor lasers as light sources for optical frequency-, or phase-based systems, we constructed an external frequency reference system that boasted high stability in a wide frequency range. While, ino our previous experiments, we stabilized the oscillation frequency of a laser diode using one of the spectra of an etalon, and controlled its spectrum, using the Rb-D_2 absorotion line, this paper describes the outcome of a trial, where an adapted version of the PEAK method improved the laser diode's frequency stability, to one of the etalon spectra, by using a saturated Rb-D_2 absorption he as the control signal for the etalon.

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  • Estimation of complex refractive index of clusters by Mie-Scattering Ellipsometry

    Harada Yasunari, Sato Ayumu, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   37   247 - 248   2004.8

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  • Development of a light source in a satellite-to-satellite laser interferometer for the global observation of the environmental changes : Improvement of a frequency stability of a semiconductor laser by narrowing a linewidth using an optical feedback

    MAEHARA Shinya, KUROSAKI Yoshiharu, SATO Takashi, OHKAWA Masashi, YOSHINO Taizoh, KUNIMORI Hiroo, HOSOKAWA Mizuhiko, ITO Hiroyuki, RI Ying, NAGANO Shigeo, KAWAMURA Seiji

    Technical report of IEICE. LQE   104 ( 98 )   43 - 46   2004.5

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    There is an idea to measure the time varying gravity field for the global observation of the environmental changes, using the laser interferometric technique for satellite-to-satellite tracking instead of using the radio technique as used in the current inter-satellite system, GRACE. It is required to measure the changes of the relative velocity between the twin satellites better than lOnm/s in averaging time for 1s ≦ τ ≦ 100s by using a frequency-stabilized laser light source which oscillates in frequency stability better than 10^<-12> in the square root of the Allan variance in this optical system. We are investigating availability of a diode laser as a light source of a laser interferometer in satellite by stabilizing its oscillation frequency using "double optical feedback" method to narrow its oscillation linewidth.

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  • High Luminous Efficacy and Long Lifetime Incandescent Lamps

    SEKINE Seishi, SATO Ayumu, OHKAWA Masashi

    2004 ( 1 )   13 - 18   2004.3

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  • C-4-11 エタロンによる半導体レーザの発振周波数安定化 : 光フィードバック法を用いた直接変調方式における安定化(C-4.レーザ・量子エレクトロニクス)

    黒崎 芳晴, 長谷部 圭紀, 太田 悠一, 佐藤 孝, 大河 正志, 丸山 武男, 坪川 恒也

    電子情報通信学会総合大会講演論文集   2004 ( 1 )   339 - 339   2004.3

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  • C-4-13 Some Characteristics Changes of a Semiconductor Laser in a Magnetic Field

    Seto Y., Kondo M., Hatakeyama J., Sato T., Ohkawa M., Maruyama T.

    Proceedings of the IEICE General Conference   2004 ( 1 )   341 - 341   2004.3

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  • C-4-12 Rb吸収線のファラデー効果を用いた半導体レーザの発振周波数安定化 : 長期の安定度の測定(C-4.レーザ・量子エレクトロニクス)

    小林 寛道, 二文字 俊哉, 澤村 明彦, 佐藤 孝, 大河 正志, 丸山 武男, 坪川 恒也

    電子情報通信学会総合大会講演論文集   2004 ( 1 )   340 - 340   2004.3

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  • 30aZG-12 Development of a ground simulator for a satellite-to-satellite laser interferometry II

    Nagano S, Yoshino T, Kunimori H, Kawamura S, Hosokawa M, Sato T, Ohkawa M

    Meeting abstracts of the Physical Society of Japan   59 ( 1 )   99 - 99   2004.3

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  • Color Discrimination by Artificial Neural Network Using Digital Camera

    SEKIYA Satoko, SEKINE Seishi, OHKAWA Masashi

    28   128 - 129   2004

  • Evaluation of Impression for Interior Color of Medical Facilities by Artificial Neural Network

    AIZAKI Tomoyasu, SEKINE Seishi, OHKAWA Masashi

    28   22 - 23   2004

  • Evaluation of incandescent radiation from tungsten cluster : Comparison of cluster radiation in various metal oxides

    Kubo Hiroki, Sato Ayumu, Kondo Kazuya, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   84 - 84   2004

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  • Frequency stabilization of a semiconductor laser using a magneto-optical effect of the Rb absorption line : Evaluation of the frequency stability using the fs laser optical comb and stabilization with an optical feedback

    SAWAMURA A., NIMONJI T., KOBAYASHI H., SATO T., OHKAWA M., MARUYAMA T., YOSHINO T., KUNIMORI H., HOSOKAWA M., ITO H., LI Y., NAGANO S., KAWAMURA S.

    Technical report of IEICE. LQE   103 ( 526 )   17 - 20   2003.12

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    We have stabilized the oscillation frequency of a laser diode using the magneto-optical effect of the Rb absorption line with "PEAK" method. In recent years, a "femto second mode lock pulse laser optical comb generator" has been developed as a new reference frequency source. We used the "double optical feedback" method to narrower the oscillation line width of our stabilized laser diode and measured the stability by using the optical comb.

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  • Changes of semiconductor laser characteristics in a magnetic field and their mechanisms

    KONDO Mitsumasa, SETO Yoshio, OHSAWA Yasuaki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo

    Technical report of IEICE. LQE   103 ( 526 )   21 - 24   2003.12

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    We have measured the optical output power and the oscillation wavelength shifts of visible and infrared semiconductor lasers of some different inner structures in a magnetic field. From the experimental result of our early experiments, we thought that the characteristic changes of semiconductor lasers are due to temperature increase inside thesemiconductor laser. We, however, obtained the result that needs the explanation using not only the effect of a temperature butalso that of carrier density by the experiment of semiconductor lasers oscillating at different wavelengths and having different inner structures. We report our experiment to examine the shift mechanism in detail.

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  • Improvement of a semiconductor laser wavelength stability using an optical feedback technique

    HOUGA Y., NARITA S., MAEHARA S., SATO T., MARUYAMA T., OHKAWA T., YOSHINO T., KUNIMORI H., HOSOKAWA M., ITO H., NAGANO S., LI Y., KAWAMURA S.

    Technical report of IEICE. LQE   103 ( 526 )   25 - 28   2003.12

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    We have studied the oscillation frequency stabilization of a semiconductor laser in a 1.5μm wavelength region using an inner second harmonic generation of 1.56μm laser light and the Rb D_2 absorption line as an external frequency reference. However, the output power of the inner SHG is too weak for the frequency stabilization, so we tried to increase it by introducing an optical feedback method. This method is also effective for decreasing the oscillation linewidth and improving the semiconductor laser frequency stability. In this experiment, we decreased the fundamental spectrum width of a semiconductor laser and examined the improvement of the semiconductor laser frequency stability by using the optical feedback method.

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  • C-4-13 半導体レーザの発振周波数安定化 : エタロンと Rb 吸収線の組み合わせによる周波数基準の構築

    黒崎 芳晴, 長谷部 圭紀, 佐藤 孝, 大河 正志, 丸山 武男, 坪川 恒也

    電子情報通信学会ソサイエティ大会講演論文集   2003 ( 1 )   289 - 289   2003.9

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  • C-4-12 Rb 吸収線のファラデー効果を用いた半導体レーザの発振周波数安定化 : 光コムを用いた安定度の評価

    小林 寛道, 二文字 俊哉, 澤村 明彦, 佐藤 孝, 大河 正志, 吉野 泰造, 国森 裕生, 細川 瑞彦, 伊東 宏之, 長野 重雄

    電子情報通信学会ソサイエティ大会講演論文集   2003 ( 1 )   288 - 288   2003.9

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  • Some Characteristics Changes of a Semiconductor Laser in a Magnetic Field

    Seto Y., Kondo M., Sato T., Ohkawa M., Maruyama T.

    Proceedings of the Society Conference of IEICE   2003 ( 1 )   290 - 290   2003.9

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  • Evaluation of the artificial neural network for color discrimination : discrimination of a non-learned color

    TAYAGAKI Y., SEKIYA S., SEKINE S., OHKAWA M.

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   36   167 - 167   2003.8

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  • Estimation of the complex refractive index of the cluster using by Mie-Scattering Ellipsometry

    Sato Ayumu, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   36   196 - 196   2003.8

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  • Development of a ground simulator for a satellite-to-satellite laser interferometry

    Nagano S., Yoshino T., Kunimori H., Kawamura S., Hosokawa M., Sato T., Ohkawa M.

    Meeting abstracts of the Physical Society of Japan   58 ( 2 )   91 - 91   2003.8

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  • Measurement of Complex Index of Refraction of Tungsten by Using Ellipsometry : Study of the Accuracy of the Ellipsometer

    SATO Ayumu, SEKINE Seishi, OHKAWA Masashi

    Journal of the Illuminating Engineering Institute of Japan   87 ( 5 )   328 - 334   2003.5

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    The tungsten microcavity light source and the tungsten cluster light source have recently attracted interest as next-generation light sources that have a high luminous efficacy and a long lifetime. The complex index of refraction of tungsten requires a 2000 to 6500K operating temperature to evaluate the luminous efficacy and lifetime. Little is, known however, about the complex index of tungsten at such high temperatures. We consider that ellipsometry is an effective measuring method because it can measure complex index of refraction without metallic contact at these temperatures. We thus designed and fabricated an ellipsometer and used it to measure the complex index of refraction of tungsten at room temperature. As a result, we established that with an improved ellipsometer the complex index of refraction of tungsten could be measured at 2000-6500K. In this paper, we report on the problems of measuring metallic complex index of refraction precisely using ellipsometry and on the achieved measurement accuracy.

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  • Verification of a general theory of relativity by observing a movement of a pendulum : For construction of an interferometer using semiconductor lasers

    Maehara S., Ohsawa Y., Suenaga T., Sato T., Maruyama T., Ohkawa M., Tsubokawa T.

    Proceedings of the IEICE General Conference   2003 ( 1 )   303 - 303   2003.3

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  • Examination to wavelength stabilization of a semiconductor laser using optical feedback

    Houga Yuusuke, Seki Takeo, Hafiza BintiHad, Ohsawa Yasuaki, Sato Takasi, Maruyama Takeo, Ohkawa Masasi

    Proceedings of the IEICE General Conference   2003 ( 1 )   308 - 308   2003.3

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  • Frequency stabilization of a semiconductor laser applying the Faraday effect of the Rb absorption line : Examination to long-term stabilization using PEAK method

    Sawamura A., Nimonji T., Ito S., Kobayashi H., Sato T., Ohkawa M., Maruyama T.

    Proceedings of the IEICE General Conference   2003 ( 1 )   310 - 310   2003.3

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  • Characteristics Shifts of a Semiconductor Laser in a Magnetic Field

    Kondo M., Ohsawa Y., Seto Y., Sato T., Ohkawa M., Maruyama T.

    Proceedings of the IEICE General Conference   2003 ( 1 )   304 - 304   2003.3

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  • Compare optical properties of Rhenium Cluster radiation with Tungsten Cluster radiation

    Hosaka Kazuyuki, Sato Ayumu, Kubo Hiroki, Sekine Seisi, Okawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   20 - 20   2003

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  • Color Discrimination of Digital Camera Picture by Artificial Neural Network

    Sekiya Satoko, Tayagaki Yasuko, Sekine Seishi, Ohkawa Masashi

    27   16 - 17   2003

  • Evaluation of Comfort of Picture by Semantic Differential Method

    Aizaki Tomoyasu, Sekine Seishi, Ohkawa Masashi

    27   102 - 103   2003

  • Measurement of Spectral Radiant Exitance Tungsten Cluster Light Emission

    Kobayashi Tomohiro, Sato Ayumu, Hosaka Kazuyuki, Sekine Seishi, Okawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   35   257 - 257   2002.8

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  • Measurement of Complex Index of Refraction of Metals by Ellipsometry

    Sato Takuya, Sato Ayumu, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   35   259 - 259   2002.8

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  • Frequency stabilization of a semiconductor laser using Rb absorption line and etalon : Construction of highly stable and broad frequency reference

    SASAKI Takeshi, AIBA Tsutomu, HASEBE Keiki, OHSAWA Yasuaki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, TSUBOKAWA Tsuneya

    Technical report of IEICE. LQE   102 ( 117 )   109 - 112   2002.6

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    An atom, such as a Rb, has absolutely stable absorption line at its peculiar frequency. One, therefore, can not select an arbitrary frequency using an atomic absorption line. On the other hand, the transmitted light spectrum of a Fabry-Perot etalon is affected by an environmental temperature, because the cavity length of etalon changes with the temperature variation. So, we constructed highly stable and broad frequency reference using the merits of Rb absorption line and etalon spectrum, and then stabilized the oscillation frequency of a semiconductor laser.

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  • Oscillation frequency stabilization of a semiconductor laser using the Faraday effect of the Rb absorption line : Frequency stabilization using the PEAK method and its evaluation

    ITO Shinichi, NIMONJI Toshiya, SAGA Takashi, SAWAMURA Akihiko, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo

    Technical report of IEICE. LQE   102 ( 117 )   113 - 116   2002.6

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    We have stabilized the oscillation frequency of a semiconductor laser using the Faraday effect of the Rb absorption line. Our method modulates the reference frequency instead of the laser frequency, so the oscillation linewidth is not broadened by our stabilization procedure. We have obtained high stability by using the PEAK method, which we devised. We also improved the frequency stability by making the experimental setup smaller and simpler, and reducing the noise source.

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  • Study for a small variation of a pendulum using semiconductor lasers : Long term observation and its analysis

    MAEHARA Shinya, OHSAWA Yasuaki, SATO Takashi, MARUYAMA Takeo, OHKAWA Masashi, MIZUSHIMA Masataka, TSUBOKAWA Tsuneya

    Technical report of IEICE. LQE   102 ( 62 )   49 - 52   2002.5

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    A kind of small variations of a pendulum is reported as a result of a "gravito-radiative-force", which is one of the gravitational effects derived from the general theory of relativity. The same report also describes the experimental results in which two pendulums moved to the same direction at the same time due to the gravito-radiative-force. This study is planned to confirm this experimental result using the optical measurement system. Our experimental setup is located in a tunnel where we can expect very small level of external noises. We have observed the effects of earthquakes and tidal forces in our measurement.

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  • Preliminary experiments on fundamental waves and inner second harmonic generation waves of semiconductor lasers : Optical feedback conditions and oscillation frequency variation

    SEKI Takeo, SAKAI Masafumi, HOUGA Yusuke, OHSAWA Yasuaki, SATO Takasi, OHKAWA Masasi, MARUYAMA Takeo

    Technical report of IEICE. LQE   102 ( 62 )   45 - 48   2002.5

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    We have studied the oscillation frequency stabilization of semiconductor lasers in a 1.5μm wavelength region using an inner second harmonic generation of 1.56μm laser light by adapting the Rb D_2 absorption line as an external frequency reference. However, the output power of inner SHG is too weak for the frequency stabilization, so we tried to increase it by using an optical feedback method. This method is also effective for decreasing the oscillation width of semiconductor lasers. In this experiment, we survey two DFB lasers with various optical feedback intensity.

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  • Structure of the neural network model for analyzing the information of the visual system

    Nishimura Masakazu, Tayagaki Yasuko, Sekine Seishi, Ohkawa Masashi

    26   18 - 19   2002

  • Generalization and Incandescent Lamps of High Luminous efficacy

    SEKINE Seishi, SATO Ayumu, OHKAWA Masashi

    2001 ( 6 )   1 - 6   2001.10

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  • Estimation of Complex Refraction Index of Tungsten by Ellipsometry

    Sato Ayumu, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   34   280 - 280   2001.9

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  • Estimation of Complex Refraction Index of Tungsten by Ellipsometry

    Sato Ayumu, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   34   53 - 53   2001.9

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  • Experiment of the 24 hours frequency stabilization of a semiconductor laser using the Rb absorption line

    OHSAWA Yasuaki, KATO Takashi, SAGA Takashi, MAEHARA Shin-ya, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, TSUBOKAWA Tsuneya

    Technical report of IEICE. LQE   101 ( 65 )   25 - 30   2001.5

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    We have stabilized an oscillation frequency of a semiconductor laser using the Rb absorption line as an external frequency reference by feeding back the frequency difference between the laser frequency and the external reference frequency. We built up the experimental setup in a very quiet condition of the astronomical observatory site and compared the stability of our experimental setup in a two conditions, i.e., the normal laboratory at the university and the room in a specially designed turnel for the precise measurement.

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  • Oscillation frequency stabilization of a semiconductor laser using the Faraday effect of the Rb absorption line : Examination of a small modulation strength and its application to the PEAK method

    NIMONJI Toshiya, SAGA Takashi, ITO Shin-ichi, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. LQE   101 ( 65 )   31 - 36   2001.5

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    The oscillation frequency stabilization of a semiconductor laser is usually demonstrated by the direct modulation of its injection current, although this method increases its oscillation linewidth. This linewidth broadening, however, must be removed in some application fields. We, therefore, stabilized its oscillation frequency using the Faraday effect of the Rb absorption line. Our method modulates the reference frequency instead of the laser frequency, so the oscillation linewidth is not broadened by this method. We examined the relation between the strength of a small modulation signal for the stabilization and the frequency stability. We also examined the improvement of the frequency stability using the PEAK method, which we devised to obtain the large reproducible control signal for the frequency stabilization.

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  • Neural Networks for Discrimination of Colors : Improvement of Networks

    Nomura Mituyosi, Sekine Seisi, Oukawa Masasi

    25   12 - 13   2001

  • Difference of Phase Sensitivity on Thickness of Diaphragm for Integrated Optic Pressure Sensor

    Nanasawa M., Ohkawa M., Sekine S., Sato T.

    Proceedings of the Society Conference of IEICE   2000 ( 1 )   181 - 181   2000.9

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  • Measurement of Complex Index of Refraction of Tungsten by Ellipsometry

    Sato Ayumu, Kashiwagi Takahito, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   33   39 - 40   2000.8

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  • Improvement on a frequency stabilization method of a semiconductor laser using the Faraday effect of the Rb-D_2 absorption line

    NIMONJI Toshiya, KATO Takashi, HIGASHI Ryouichi, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. LQE   100 ( 73 )   61 - 66   2000.5

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    The oscillation frequency stabilization of a semiconductor laser is usually demonstrated by the direct modulation of its injection current, although this method increases its oscillation width. This broadening of the oscillation width, however, must be removed in some application fields. We, therefore, stabilized the oscillation frequency of a semiconductor laser using the Faraday effect of the Rb-D_2 absorption line and the PEAK method, which we devised to obtain the reproducible and large control signal for the frequency stabilization. Our method modulates the reference frequency of the Rb-D_2 absorption line instead of the laser frequency, so the oscillation spectrum is not broadened by this stabilization method.

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  • Observation System of a Displacement of a Stationary Pendulum Using a Semiconductor Laser

    OHSAWA Y., ICHIBA T., SEKIMOTO T., SATO T., MARUYAMA T., OHKAWA M., MIZUSHIMA M., TSUBOKAWA T.

    Proceedings of the IEICE General Conference   2000 ( 1 )   356 - 356   2000.3

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  • Frequency stabilization without spectrum broadening of a semiconductor laser using Faraday effect of Rb absorption line.

    Kato Takashi, Nimonji Toshiya, Higashi Ryoichi, Sato Takashi, Ohkawa Masashi, Maruyama Takeo, Shimba Minoru

    Proceedings of the IEICE General Conference   2000 ( 1 )   355 - 355   2000.3

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  • Examinations for oscillation characteristic changes of near infrared MQW-semiconductor lasers in a magnetic field

    NAKAGAWA Takayuki, NISHIIE Akinori, OSAWA Yasuaki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    2000 ( 14 )   43 - 48   2000.1

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  • Increase of the inner second-harmonic generation of 1.5μm semiconductor lasers : Effect of the optical feedback

    OKAZAKI Tadashi, SAKAI Masafumi, OHSAWA Yasuaki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    2000 ( 14 )   37 - 42   2000.1

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  • Frequency stabilization of a Semiconductor Laser Using both Etalon and atomic spectra.

    HOSOYA Kuniyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Proceedings of the Society Conference of IEICE   1999 ( 1 )   291 - 292   1999.8

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  • An Integated Optical Accelerometer using Intermodal Interface between TE-like and TM-like modes

    Maruyama A., Nanasawa M., Ohkawa M., Sekine M., Sato T.

    Proceedings of the IEICE General Conference   1999 ( 1 )   227 - 227   1999.3

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  • Fabrication of An Integrated Optical Accelerometer using Mach-Zehnder Interferometer

    Yamashita Y., Ohkawa M., Sekine S., Sato T.

    Proceedings of the IEICE General Conference   1999 ( 1 )   226 - 226   1999.3

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  • Fundamental wave and the inner second-harmonic generation of a semiconductor laser under the optical feedback

    MARUYAMA Shin-ya, OKAZAKI Tadashi, UESUGI Toru, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    1999 ( 1 )   73 - 78   1999.1

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  • Estimation of Light Emitting from Microcavity Radiator

    Kashiwagi Takahito, Sekine Seishi, Ohkawa Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   37 - 38   1999

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  • Estimation of Radiation from Microcavity Radiator

    SEKINE Seishi, KASHIWAGI Takahito, OHKAWA Masashi

    1998 ( 7 )   1 - 6   1998.11

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  • Frequency Stabilization of a Semiconductor Laser under Direct FSK Modulation - Its Modulation Method and Evaluation of Stability -

    WATANABE Hiromichi, AZUMA Hideki, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    The Transactions of the Institute of Electrical Engineers of Japan. C   117 ( 8 )   1119 - 1126   1997.8

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  • Some Oscillation Wavelength Shift Characteristics of a Semiconductor Laser in a Magnetic Field - Observation Using a Beat Note -

    MATSUDA Shinya, SHIBATA Kazunori, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    The Transactions of the Institute of Electrical Engineers of Japan. C   117 ( 4 )   394 - 400   1997.4

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  • Zeeman Effect-Based Control-Signal Improvement for Frequency Stabilization of a Semiconductor Laser

    NAKANO Hiroyuki, WATANABE Naoki, SATO Takashi, OHKAWA Masashi, MARUYAMSA Takeo, SHIMBA Minoru

    The Transactions of the Institute of Electronics,Information and Communication Engineers. C-(0xF9C1)   80 ( 2 )   55 - 63   1997.2

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  • Changes of semiconductor laser characteristics in a magnetic field and consideration of its mechanism

    TOUJOU Shin-ya, SHIBATA Kazunori, NAKANO Hiroyuki, MATSUMOTO Kouichi, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. LQE   97 ( 35 )   91 - 96   1997.2

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    We observed the oscillation-wavelength and optical-output shifts of several semiconductor lasers in a magnetic field. We obtained that a certain thermal effect arising from an applied magnetic field altered the characteristics of infrared semiconductor lasers. It was recently observed, however, that fluctuations in carrier density arising from the aforementioned field also exert considerable influence on the wavelength of a visible semiconductor laser. Also of note, is the fact that multiquantum well lasers displayed characteristics at variance with anything previously encountered. This paper, then, details observations made regarding changes in overall characteristics and discusses the mechanism by which they occur.

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  • Investigation of a laser interferometer for detecing anisotropy of space

    SUNADA Takuya, OHSAWA Yasuaki, ADACHI Masaaki, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. OPE   96 ( 516 )   7 - 12   1997.2

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    A laser interferometer is a measuring system which measures a spatial variation accurately. Therefore, it is used in a variety of precise measurements. The detection of a gravity wave, whose existence is predicted by the theory of relativity, is its remarkable example. On the other hand, anisotropy of space, which is also derived from the theory of relativity as a zero-frequency gravity wave, is reported to be detectable using a plumb line. We, therefore, started to investigate a method detecting the movement of the plumb line using a semiconductor laser. We proposed a laser interferometer, which detect three dimensional movement and discussed its resolving power with the theoretical estimation here.

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  • Pattern Recognition Using Holographic Memory

    SEKIGUCHI Syunji, KOBAYASHI Rieko, HATORI Masaaki, OHKAWA Masashi, TSUCHIDA Keiichi, SEKINE Seishi

    Japanese journal of optics   26 ( 1 )   39 - 46   1997.1

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  • Micro cavity lamps : Simulation of characteristics of radiation

    UENO Masatoshi, SUZUKI Hiraoki, SEKINE Seishi, OHKAWA Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   58 - 59   1997

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  • Micro cavity lamps : Analysis of mode and characteristics of radiation

    SEKINE Seishi, SUZUKI Hiroaki, UENO Masatoshi, OHKAWA Masashi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   56 - 57   1997

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  • Frequency stabilization of a semiconductor laser under direct FSK and improvement of its measuring method

    AZUMA Hideki, TAMURA Kazuto, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. OCS   96 ( 334 )   79 - 84   1996.10

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    We stabilized the oscillation frequency of a semiconductor laser under direct frequency shift keying (FSK) and improved the measuring system of its frequency stability. Semiconductor laser frequency stability is deteriorated under direct FSK when a conventional external frequency reference is employed for the frequency stabilization. Therefore, we devised the control system named "PEAK method", which improves the frequency stability. The accurate measurement of frequency stability requires that the beat note between two stabilized laser beams, the signal and reference laser beams, be measured. The reference laser frequency was adjusted for controlling the beat frequency within the measurable range in this work.

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  • Output power and wavelength shifts in semiconductor lasers oscillating at different wavelength in a magnetic field

    SHIBATA Kazunori, MATSUDA Shinya, TOUJOU Shinya, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. LQE   96 ( 38 )   97 - 102   1996.5

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    We have, during the last decade, examined the mechanisms of oscillation wavelength and light output shifts in six near infrared semiconductor lasers subjected to magnetic fields. In this work, we observed these same shifts of visible wavelength semiconductor lasers and examined the shift mechanisms of lasers oscillating at different wavelengths. The observations were performed, case by case, using a monochromator and a beat note.

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  • Operation of Optical Information Retrieval System Using Spatial Light Modulator

    HATORI Masaaki, SHIOYA Kouhei, TSUCHIDA Keiichi, MITA Motohito, OHKAWA Masashi, SEKINE Seishi

    The Transactions of the Institute of Electronics,Information and Communication Engineers. C-(0xF9C1)   79 ( 1 )   10 - 18   1996.1

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    Other Link: http://hdl.handle.net/10191/9027

  • Feasibility of Integrated Optic Micropressure Sensor Using Ring Resonator

    OHKAWA Masashi, ABE Tetsuharu, SEKINE Seishi, SATO Takashi

    The Transactions of the Institute of Electronics,Information and Communication Engineers. C-(0xF9C1)   79 ( 1 )   1 - 9   1996.1

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    Other Link: http://hdl.handle.net/10191/9026

  • Frequency stabilization of a semiconductor laser by magneto-optical effects and frequency narrowing by optical feedback

    WATANABE Naoki, NAKANO Hiroyuki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    Technical report of IEICE. LQE   95 ( 350 )   37 - 42   1995.11

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    We have reported the oscillation frequency stabilization of a semiconductor laser without a direct modulation. This is because the direct modulation broadens the oscillation frequency. We used the Rb absorption line as a frequency reference and applied a modulated magnetic field to the Rb cell. This method modulates the reference frequency by magneto-optical effects and provides the frequency stabilization without frequency broadening. We also applied the optical feedback techniques for narrowing the oscillation width. The influence of the optical feedback upon the spectrum under the frequency stabilization is confirmed.

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  • Frequency stabilization of a semiconductor laser under direct FSK and its estimation using the beat note

    Azuma H., Watanabe H., Nakano H., Sato T., Maruyama T., Ohkawa M., Shimba M.

    Proceedings of the Society Conference of IEICE   1995 ( 1 )   259 - 259   1995.9

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  • Detection of a second harmonic generation from a semiconductor laser and an effect of an optical feedback

    Yamamoto S., Nokano H., Sato T., Maruyama T., Ohkawa M., Shimba M.

    Proceedings of the Society Conference of IEICE   1995 ( 1 )   262 - 262   1995.9

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  • Some oscillation wavelength shift characteristics of a semiconductor laser in a magnetic field : observation using a beat note

    MATSUDA Shinya, SHIBATA Kazunori, HIRATA Kouichi, YAMAMOTO Shigeki, SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    IEICE technical report. Electron devices   95 ( 156 )   85 - 90   1995.7

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    We have reported the oscillation wavelength shift of semiconductor lasers in a magnetic field at room temperature. The observation method using the monochromator has reading errors and is applicable to measure the oscillation wavelength shift only in a steady state. In this work, we used the beat note between two semiconductor lasers for observing the wavelength shift. This method reduces the reading error to about one tenth of that obtained by the monochromator and enables to observe the time dependence of the wavelength shift. We explain our experimental results and discuss the mechanism of this wavelength shift, here.

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  • Frequency Stabilization of a Semiconductor Laser under Direct FSK Modulation of Different Modulation Conditions

    SATO Takashi, ISHIGURO Makoto, MIZUMOTO Jun'ichi, WATANABE Hiromichi, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    The Transactions of the Institute of Electrical Engineers of Japan. C   115 ( 5 )   728 - 735   1995.4

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  • Reducing the emissivity in the infrared wavelengths

    Shibata Takashi, Sakuraoka Tae, Seki Masahiro, Okawa Masashi, Sekine Seisi

    Proceeding of Annual Conference of The Illuminating Engineering Institute of Japan   47 - 47   1995

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  • Integrated optic pressure sensor with high sensitivity using ring resonator : Theory

    Abe Tetsuharu, Ohkawa Masashi, Sekine Seishi, Sato Takashi

    Technical report of IEICE. OPE   94 ( 397 )   49 - 54   1994.12

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    Integrated optic pressure sensor with high sensitivity and small dimensions is proposed.The sensor is composed of a diaphragm and a ring resonator of which a part is placed on the diaphragm.The diaphragm is deformed by applying pressure.The deformation induced strain in the diaphragm.By the photo-elastic effect,the refractive index changes and then the guided wave propagating on the diaphragm undergoes phase shift.The phase shift is detected from a change in resonant frequency of a ring resonator which is a optical circuit with the highest phase sensitivity.Sensitivity of the sensor depends on shape and dimensions of the diaphragm and finess of the ring resonator.In this report,the relations between the sensitivity and the shape and dimensions are mainly described. According to the theore tical results,the sensor has a potential of sensing low pressure such as acoustic pressure field.

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  • Oscillation wavelength shift measurement of a semiconductor laser in a magnetic field using a beat note

    Yamamoto Shigeki, Matsuda Shinya, Shibata Kazunori, Hirata Kouichi, Sato Takashi, Ohkawa Masashi, Maruyama Takeo, Shinba Minoru

    Technical report of IEICE. LQE   94 ( 395 )   19 - 24   1994.12

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    We have reported the oscillation wavelength shift of semiconductor lasers in a magnetic field at room temperature.The observation method using the monochromator has reading errors and the method using the atomic absorption line has a restrictions in the oscillation wavelength of the semiconductor laser.Both methods can observe the wavelength shift only in a steady state.In this work,we used the beat note between two semiconductor lasers for observing the wavelength shift.This method provides the better resolution and can be applied to observe the time dependence.We explain our experimental results and discuss the mechanism of this wavelength shift,here.

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  • マイクロマシン技術を利用した光集積回路センサー

    大河正志

    光技術コンタクト   32 ( 6 )   300 - 306   1994.6

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  • Frequency stabilization of a semiconductor laser under direct FSK of different modulation conditions

    Ishiguro Makoto, Mizumoto Junichi, Watanabe Hiromichi, Sato Takashi, Ohkawa Masashi, Maruyama Takeo, Shinba Minoru

    Technical report of IEICE. LQE   94 ( 60 )   37 - 42   1994.5

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    The traditional frequency stabilization method of a semiconductor laser using the Rb absorption line as a frequency reference is difficult under direct frequency shift keying(FSK). Moreover,if the signal is modulated by the pulse-duration modulation(PDM)scheme,the frequency stabilily is degraded by the moving frequency-locking point due to the modulation signal.The peak-hold method,which has been devised for improving frequency stability under direct FSK,is clearly demonstrated here for the PDM-FSK scheme and its stability is confirmed unchanged in several modulation conditions.

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  • Frequency stabilization of a semiconductor laser under direct frequency shift keying using the saturated absorption signal and its frequency reference signal

    Mizumoto Junichi, Sato Takashi, Ishiguro Makoto, Ohkawa Masashi, Maruyama Takeo, Shinba Minoru

    IEICE technical report. EMD   93 ( 199 )   13 - 18   1993.8

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    We have stabilized the oscillation frequency of a semiconductor laser under direct frequency shift keying (FSK)using the saturated absorption signal of the Rb atoms.By using the saturated absorption signal,we can obtain the narrow frequency reference signal,which is the Doppler free signal.The frequency stability using the saturated absorption signal is better than that of the normal absorption signal by about one order of magnitude.In this paper,we discuss the better stabilization conditions,by considering the transmitted light intensity under direct FSK using thesaturated absorption signal.

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  • An Information Retrival System using Holograms : The Possibility of The system

    Hatori Masaaki, Shioya Kouhei, Ohkawa Masashi, Sekine Seishi

    IEICE technical report. EMD   93 ( 199 )   1 - 6   1993.8

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    An information retrival system based on the Fourier optics is described.The system enables to pick out required data from a-huge amount of information in parallel using a spatial light modulator(S.L.M).In the system,hologram is used as a storage medium to densely store digital information..We built and tested a experimental system by which nine pieces of information with eighteen bits each could be accessed.The system was influenced by aberration of lenses and performance of S.L.M,for example S, N in detection,the processing time of the system,the number of data in a piece of imformation and so on.The system is expected to be practically used when a higher-performance S.L.M is developed.

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  • Oscillation wavelength shift of a semiconductor laser in a magnetic field and its various characteristics

    Hoshi Tomoya, Sato Takashi, Yamamoto Shigeki, Ohkawa Masashi, Maruyama Takeo, Shinba Minoru

    IEICE technical report. EMD   93 ( 199 )   7 - 12   1993.8

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    We have already reported the oscillation wavelength shift of GaAlAs laser diodes in a magnetic field at room temperature.In this work,we confirmed the reproducibility of the dependence of the wavelength shift on the angle between directions of the magnetic field and the semiconductor laser.In order to investigate the cause of the error observed in the experiment by now,we measured the time dependence of the oscillation wavelength shiftafter we applied the magnetic field.We also measured the output laser power change in a magnetic field.Here,we discuss the mechanism of this wavelength shift by using our experimental results.

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  • Oscillation Wavelength Shift of GaAlAs Laser diodes in a Magnetic Field

    SATO Takashi, KAWASHIMA Hidetoshi, NAKAMURA Toshio, OHKAWA Masashi, MARUYAMA Takeo, SHIMBA Minoru

    The Transactions of the Institute of Electronics,Information and Communication Engineers. C-(0xF9C1)   75 ( 9 )   579 - 586   1992.9

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  • マイクロメカニカル光ICセンサ

    大河正志, 井筒雅之, 末田正

    オプトロニクス   11 ( 9 )   97 - 103   1992.9

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  • 熱伝達現象を利用した光ファイバ風速センサ

    大河 正志, 高橋 敦, 関根 征士, 安東 滋

    レーザー研究   20 ( 3 )   160 - 165   1992

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    DOI: 10.2184/lsj.20.3_160

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  • カンチレバ構造を用いたシリコン基板光集積回路流量センサ

    大河 正志, 井筒 雅之, 末田 正

    レ-ザ-研究   19 ( 6 )   p544 - 550   1991.6

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Awards

  • 照明学会論文賞

    2010.9   照明学会  

    別所誠, 東芝ライテック, 大河正志

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    Award type:Award from Japanese society, conference, symposium, etc.  Country:Japan

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Research Projects

  • 防・減災を目的としたインフラサウンド検出のための光波利用センシングシステムの開発

    Grant number:22K04122

    2022.4 - 2025.3

    System name:科学研究費助成事業

    Research category:基盤研究(C)

    Awarding organization:日本学術振興会

    大河 正志

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    Grant amount:\4030000 ( Direct Cost: \3100000 、 Indirect Cost:\930000 )

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  • Compact and high-sensitive pressure sensors with semi-closed structures for detecting slight pressure fluctuation due to tsunami generation

    Grant number:18K04163

    2018.4 - 2021.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    Ohkawa Masashi

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    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

    Compact and high-sensitive pressure sensors with semi-closed structures were developed for detecting slight pressure fluctuation due to tsunami formation. A key structure is a semi-closed structure with a small hole or a narrow tube, and high-pass filter characteristics of the structure determine sensor performance. In this study, connections between structure dimensions and step response and frequency response were considered, and design guideline of the structure was established. Moreover, guided-wave optical pressure sensors with semi-closed structures were fabricated and demonstrated. Also, their step responses and frequency responses were measured.

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  • Guided-wave optical acoustic emission sensor and its obsevation system

    Grant number:26420302

    2014.4 - 2017.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    Ohkawa Masashi, NIKKUNI Hiroyuki

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    Grant amount:\5070000 ( Direct Cost: \3900000 、 Indirect Cost:\1170000 )

    Our resonance-type guided-wave optical acoustic emission (AE) sensor consists of a diaphragm and a single-mode optical waveguide on the diaphragm. In order to obtain higher resonance frequency, dependences of resonance frequency on diaphragm dimensions were considered. According to experimental results, resonance frequency was found to be proportional to diaphragm thickness, and inversely proportional to square of side length, as theoretically predicted. Regarding to pulse-width characteristics, time constant was several ms. Also, maximum output voltage was found to be proportional to applied sound pressure. Moreover, use of higher-order mode is useful to expand detectable frequency range.
    An AE signal estimation system consisting of noise reduction and AE parameter estimation was built as a Windows application. The system performance was successfully examined using test signals with different amplitude, time duration and noise level.

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  • Fast physical random number generation making use of frequency noise characteristics of a vertical cavity surface emitting lasers

    Grant number:25390093

    2013.4 - 2016.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    Sato Takashi, OHDAIRA Yasuo, OHKAWA Masashi

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    Grant amount:\5070000 ( Direct Cost: \3900000 、 Indirect Cost:\1170000 )

    We generated the physical random number by converting a fluctuation of the semiconductor laser’s frequency into a change of the optical intensity and digitizing it. We compared the generation speeds of random numbers using the Fabry-Perot type laser diode and VCSEL (Vertical Cavity Surface Emitting Laser) and examined the influence of their internal structure. As a result, we generated random number bit strings at 120Gbit/s in VCSEL and at 77Gbit/s in FPLD. The VCSEL’s broad line-width enables us to generate random numbers with the greatest efficiency.
    However, fluctuations in both atmospheric temperature and the injection current to the semiconductor laser affect the laser’s oscillation frequency. Therefore, we improved the stability of generated fast physical random numbers using a semiconductor laser with a stabilized oscillation frequency. We proposed the new Optical Range Finder system used semiconductor laser’s frequency noise and obtained the resolution of 0.5mm.

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  • Oscillation characteristics improvement of a Vertical Cavity Surface Emitting Laser and consideration to its application

    Grant number:22560035

    2010 - 2012

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    SATO Takashi, OHKAWA Masashi, OHDAIRA Yasuo

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    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

    In the present work, we tested the oscillation wavelength shift of a vertical-cavity surface-emitting laser (VCSEL) in a magnetic field, because we expected that the VCSEL would show a shorter wavelength side shift. We also demonstrated a novel method of generating physical random numbers, by means of a diode laser that has an extremely wide-band frequency-noise profile. Fluctuations in the laser frequency affect the intensity of the light transmitted through the optical frequency discriminator, detected thereafter, as random fluctuations. This allows us to simultaneously generate 8 random bit streams, due to the parallel processing of 8-digit binary numbers sampled by an 8-bit analog-to-digital converter (ADC). Finally, we generated physical random numbers at a rate of 40Gb/s.

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  • Development of guided-wave optical sensors with a micromechanical structure and its design support system

    Grant number:22560322

    2010 - 2012

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    OHKAWA Masashi, SATO Takashi, NIKKUNI Hiroyuki

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    Grant amount:\4420000 ( Direct Cost: \3400000 、 Indirect Cost:\1020000 )

    In order to establish design guidelines for guided-wave optical sensors with a micromechanical structure, sensitivity dependences on waveguide position, diaphragm dimensions and so on were determined by theoretical and experimental examinations. Also, regarding an effect of squeeze-film air damping in guided-wave optical microphones, damping ratio was found to increase as air-film thickness decreased, similar to the rough theoretical prediction. Moreover, for guided-wave optical pressure and flow sensors, desktop and web applications to design waveguide and diaphragm were developed, based on our theoretical and experimental results of each sensor.

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  • Development of acoustic input and output devices far MRI scanners and nuclear plants

    Grant number:17360157

    2005 - 2007

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    OHKAWA Masashi, SATO Takashi

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    Grant amount:\14870000 ( Direct Cost: \14300000 、 Indirect Cost:\570000 )

    The guided-wave optical microphone can work even in a hazardous environment, such as a high magnetic field like the MRI, high RFI fields, and other environments that require EMI/RFI immunity.
    The optical microphone consists of a rectangular diaphragm and a straight waveguide on the diaphragm. The sensitivity of the microphone and the resonance frequency of the diaphragm are dependent on the diaphragm dimensions. In this study, the target values for phase sensitivity and resonance frequency were set at 2.5 mrad/Pa and 3.4 kHz, respectively. By design considerations, the diaphragm dimensions were determined to be 20 mm×20 mm×0.15 mm. Measured sensitivity of the fabricated microphone was L3 mrad/Pa, almost a half of the target value. The fabricated microphone detected a sound wave of 1 kHz and 2 Pa, corresponding to 100 dB-SPL (sound pressure level). Moreover from measured frequency characteristics of three fabricated microphones with a 20 mm×20 mm×0.15 mm diaphragm, resonance frequencies were 2.7, 3.3 and 3.7 kHz, similar to the theoretical one.
    Incidentally, silicon is an attractive substrate because of its excellent mechanical properties, which provide the optical microphone with minituarization feasibility. In the last two years, the silicon-based guided-optic microphone has also been developed, and the fabricated optical microphone with a 10 mm×10 mm×40μm diaphragm successfully detected a sound wave of 0.2 Pa (80 dB-SPL) and 1 kHz. Moreover from the frequency characteristic, resonance frequency was experimentally determined to be 5.3 kHz, quite similar to the theoretical one of 5.6 kHz.

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  • Study on High Luminous Efficacy and Long Lifetime Cluster Light Source.

    Grant number:16560241

    2004 - 2005

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    SEKINE Seishi, OHKAWA Masashi

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    Grant amount:\3700000 ( Direct Cost: \3700000 )

    1. Experimental research
    1) We verified that WO_2 and MoO_3 and Re_2O_7 are suitable to make cluster, support material which is optimum for forming the tungsten cluster is NaBr, and NeAr mixed gas is suitable for the electric discharge gas and the filling pressure of 21.3 KPa is optimum.
    2) Using MoO_3 which does not require the support material in the cluster material, we examined how luminescence property of the cluster differs by type of the electric discharge gas. As a result, we obtained the knowledge that the luminous flux of NeAr, Kr, Ar and Xe was high in order.
    3) As a result of examining the metals suitable for formation of the cluster, it was 2 types of molybdenum and rhenium that these cluster emitted light without the halogen which assists the formation of the cluster.
    2. Theoretical research
    Complex index of refraction of the cluster in operating temperatures of 4000 K - 5000 K is necessary in order to theoretically estimate luminescence property of the cluster light sources. In 2004 fiscal year, we measured the complex index of refraction of the bulk tungsten using the ellipsometry equipment which we have constructed. We calculated the complex index of refraction of the tungsten filaments of chandeliers lamps and halogen lamps which emitted light at the operating temperatures of 2000 K - 3000 K by the ellipsometry. The laser beam of the wavelength of 532nm which was second harmonic of the Nd : YAG laser of the wavelength of 1064nm in light source of the ellipsometry was used. As a result of comparing the complex index of refraction calculated by the ellipsometry with the value of the literature, the calculated complex index of refraction verified being a accuracy in which real part and imaginary part are high both.

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  • Development of integrated optic pressure sensors with high sensitivity and high withstanding pressure for tsunami detection

    Grant number:15360186

    2003 - 2004

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    OHKAWA Masashi, SATO Takashi

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    Grant amount:\6000000 ( Direct Cost: \6000000 )

    The proposed sensor is based on a conventional integrated optic pressure sensor using intermodal interference, with an added semi-closed space with a small hole under the bottom side of the diaphragm. By the addition of this semi-closed space, the sensor, unlike conventional sensors, can withstand high static pressure. When there is a sudden change in ambient pressure, pressure within the semi-closed space cannot quickly adjust due to the small hole that restricts fluid flow. So, pressure difference is induced on the diaphragm for a short while. Thus, the sensor shows a response only to changes in pressure, not to static pressure.
    In the first year of this research project, we examined the step response of the sensor, that is, the output characteristics for sudden pressure change. The diaphragm dimensions of the fabricated sensor were 14mm×14mm×0.22mm, and the volume of the semi-closed space was 14mm×14mm×1.8mm. The sectional area of a small rectangular hole was 93μm×25μm. In this experiment, the pressure in a 30cm×28cm×30cm closed box, in which the fabricated sensor was placed, was suddenly increased by 0.78 kPa. Due to the pressure change, the output intensity decreased by approximately 20% of the initial intensity level. Approximately 1.4 sec after the step-like change in pressure, output intensity returned to the initial level.
    In the second year, it was found from the theoretical analysis that the duration of the induced pressure difference is proportional to the V/A ratio between the volume of the semi-closed space and the sectional area of the small hole, and proportional to the square root of the initial pressure difference. So, the relationship between the duration and the sectional area of the small hole was examined experimentally. The radii of the circular holes were 20μm,25μm, and 40μm. The measured duration of the induced pressure difference was approximately 2 sec when the ambient pressure was suddenly changed by 0.7 kPa, although the duration must be dependent on the hole radius according to the theoretical results. It is attributed to pressure leak from the closed box in which the sensor was placed.

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  • 代替コミュニケーション機器、トーキングカードの開発

    Grant number:13878031

    2001 - 2002

    System name:科学研究費助成事業

    Research category:萌芽研究

    Awarding organization:日本学術振興会

    長澤 正樹, 大河 正志

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    Grant amount:\1200000 ( Direct Cost: \1200000 )

    本研究の目的は、ことばに代わるコミュニケーション機器(AAC)及び既製のAAC利用を支援する機器、「トーキングカード」の開発である。
    昨年度作成したプロトタイプの課題は以下の通りであった。(1)評価点が低かった項目の改良(音量・音質、耐久性、大きさ、重量)。(2)障害のある子どもへの臨床実験データの収集。(3)トーキングカードの教育現場への適用。
    そこで今年度は、小型・軽量化と音量の増大を目的とした。小型・軽量化では、市販部品を使う以上、部品の全容積を劇的に減少させることは不可能なので、部品間隔をできるだけ詰めるとともに、厚さを犠牲にして積層構造にし、面積の縮小を実現した。ただし、スイッチパネルは、そこに写真や絵を張って、使用者の認知を促し、操作性も維持するため、当初の目的どおりスイッチの面積をできるだけ大きく保つ設計とした。その結果、今年度のプロトタイプの大きさと重さは100mm×65mm×28mm、103gとなった。また、スイッチの大きさは90mm×55mmであった。音量については、アンプを使用したものを試作し、音量の増大を実現することができたが、電池の消耗が激しく、残念ながら今回のプロトタイプには組み込めなかった。
    今回のプロトタイプを盲学校と知的障害養護学校で使用した。その結果、(1)重度知的障害の児童が機器を使って「先生お願い」という要求が可能になったこと、(2)知的障害と視覚障害を重複する児童の型はめ弁別学習において、トーキングカードの音声が強化子として機能していることが報告された。しかし、教室内では音量が小さくよく聞き取れないという問題点が指摘された。
    今後の課題として、よりいっそうの軽量化(薄型)と音量の増大が残った。

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  • Development of integrated optic pressure sensor to be incorporated into a catheter for blood pressure measurement

    Grant number:12650339

    2000 - 2002

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    OHKAWA Masashi, SATO Takashi

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    Grant amount:\3500000 ( Direct Cost: \3500000 )

    The purpose of this study is to develop an integrated optic pressure sensor that can be inserted into a catheter to measure blood pressure. The sensor consists of a diaphragm as a pressure-sensitive structure and a straight single-mode waveguide across the diaphragm.
    First, we theoretically examined sensor sensitivity with respect to waveguide position and diaphragm dimensions. According to the theoretical results, sensitivity remains constant even if the diaphragm dimensions are reduced as long as both the side length ratio and the characteristic length remain constant. Next, such a scale-reduction rule was experimentally examined using three fabricated sensors with the same side length ratio and the same characteristic length. The exact dimensions of the sensors were 2.0mm×10mm×35μm, 2.5mm×12.5mm×49μm, and 3.0mm×15mm×64μm. The measured sensitivities of the three sensors were quite similar to each other as theoretically predicted.
    Finally, we fabricated the first prototype version using a mimic catheter ten times larger than a 6F catheter. Since the sensor was intended to be inserted into a 20mm-long mimic catheter with a diameter of 20mm, its dimensions were set to be 10mm×20mm×420μm, with the diaphragm dimensions of 1.5mm×7.5mm×23μm. The sensor sensitivity was 81mrad/kPa, which is sufficient to measure blood pressure. Although the fabricated sensor is still quite large, by reducing the diaphragm dimensions based on the scale-reduction rule, the realization of a miniaturized sensor that can be inserted into the catheter can be expected.

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  • Study on incandescent microcavity radiator of high luminous efficacy by reduction of infrared radiation

    Grant number:12650270

    2000 - 2001

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    SEKINE Seishi, OHKAWA Masashi

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    Grant amount:\3700000 ( Direct Cost: \3700000 )

    [1] Using KrF excimer laser, we made a sample of tungsten microcavity radiator that was perforated 640000 cylindrical cavities of diameter 5 μm in 10 μm intervals at central region 8 mm x 8 mm of the quartz glass on which tungsten of thickness 1 μm was deposited. The cutoff wavelength of the cavity of aperture 5 μm is about 9 μm and the temperature of black body at which the radiation of wavelength 9 μm becomes a maximum is about 320 K. Therefore, we measured spectral radiant existances of the sample heated at 300〜700 K. By analyzing measurement results in detail based on a theoretical analysis, we evaluated cutoff characteristics of the sample.
    [2] Complex index of refraction of the tungsten is necessary for design of the tungsten microcavity radiators and evaluation of their luminous efficacy. Therefore, we constructed an ellipsometer in order to measure the complex index of refraction of the tungsten and verified that this ellipsometer measures the complex index of refraction of the tungsten at a high accuracy.

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  • Frequency Stabilization of a Semiconductor Laser in an Optical FSK Communication System

    Grant number:09450151

    1997 - 1999

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    SATO Takashi, OHKAWA Masashi, MARUYAMA Takeo

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    Grant amount:\10400000 ( Direct Cost: \10400000 )

    The current optical communication systems are using the intensity modulation method, but it will be difficult for this method to handle the high speed and large capacity communication needs in the near future. We intended to develop the optical frequency modulation method for the next generation systems. This needs the frequency stabilization of a semiconductor laser. So, we stabilized the oscillation frequency of a semiconductor laser under the direct frequency shift keying (FSK) using the Rb-D2 absorption lines at 780 nm wavelength. The high frequency stability was obtained in the PEAK method, which is the system using the simple envelope detection circuit, under the direct FSK. We, then, investigated the stabilization method applicable to 1.5 μm wavelength for the optical communication systems. We intended to use the inner second harmonic generation (SHG) of the semiconductor laser to get the control signal for the frequency stabilization, because this SHG wavelength is around 780 nm. We also tested how to use two frequency references, I.e., the Rb-D2 absorption line and an etalon, for Stabilizing the 1.5 μm wavelength semiconductor laser, because they have different and supplementary characteristics as a frequency reference. We finally investigated the estimation method of the frequency stability using the beat note between two laser frequency.

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  • 小型のレーザー干渉計を用いた空間の異方性の測定

    Grant number:09874056

    1997 - 1998

    System name:科学研究費助成事業

    Research category:萌芽的研究

    Awarding organization:日本学術振興会

    佐藤 孝, 大河 正志, 丸山 武男

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    Grant amount:\1900000 ( Direct Cost: \1900000 )

    一般相対性理論で予言された重力波の検出には、より高精度化されたマイケルソン-モーレイの干渉計等の干渉計が有望であることが言われるようになり、現在、数kmの長さの巨大な干渉計を用いた重力波天文台の実現を各国が検討している。しかし、その建設費用は膨大なものになるだけではなく、雑音の除去、レーザーの高安定化等解決しなければならない問題は数多い。それに対し、米国コロラド大学の水島教授は、フーコーの振り子や回転する小型のレーザー干渉計を用いた測定で、一般相対性理論から導かれる力を比較的簡単に確認できるとの理論計算を示されている。本研究では、まずフーコーの振り子の実験を行い、水、島教授の理論計算の一般相対性理論から導かれる力によるものと比較検討した。次に、回転する干渉計の製作における問題点を検討した。この時、空間の異方性により干渉計が振動できるような状態のまま回転させると、空間の異方性を10^<-14>程度の精度の実験でも十分観測できるようになると計算されている。この振動可能な干渉計の製作を行うため、この回転する小型のレーザー干渉計に必要なレベルまで発振波長が安定化された半導体レーザーの製作を行った。現在コロラド大学の水島教授等も検討を開始している。我々は水島教授等と共同して、この空間の異方性の測定をこれまでの半導体レーザの波長安定化の実験系と実験技術を用いて始め、理論解析に従いより精度の高い実験を行うための予備的実験を開始した。平成11年4月からは観測装置を国立天文台水沢観測センターに設置して観測を行う予定である。

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  • リング共振器を用いた光集積回路ハイドロホン

    Grant number:05750038

    1993 - 1994

    System name:科学研究費助成事業

    Research category:奨励研究(A)

    Awarding organization:日本学術振興会

    大河 正志

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    Grant amount:\900000 ( Direct Cost: \900000 )

    本研究では、リング共振器を用いた光集積回路ハイドロホンの実現の可能性を確かめるため、理論的考察を行った。ハイドロホンは、感圧部としてのダイアフラムおよび微小音圧による位相変化を検出するリング共振器からなる。測定対象である水中音響は音圧が小さく、センサとして非常に高感度なものが要求される。そこで、特に高感度化を図るために重要となるダイアフラムおよびリング共振器の形状、寸法等について詳しく考察を行った。解析には、以前行ったダイアフラム型光集積回路圧センサの特性解析法を用いた。ここでは、導波路材料として低損失な導波路が形成できるガラスを考えることとした。解析により得られた主な結果を以下に示す。
    1.TMモードの方がTEモードより3倍程度高い感度が期待される。
    2.音圧を検出するために設ける導波路の位置はダイアフラムの端がよいと言える。
    3.ダイアフラムの形状は正方形がよく、感度は辺の長さの3乗に比例する。
    4.導波層の厚さには最適値が存在するが、実用上はカットオフ付近でなければよい。
    5.感度はダイアフラムの厚さの2乗に逆比例する。ただし、厚さは、感度だけでなく、ダイアフラムの耐圧も考慮して決定されるべきである。
    これらの解析結果から、大きさ30mm×30mm、厚さ50mumの正方形ダイアフラムを作成し、センサの構成に工夫を加えれば、これまでに提案されている光ファイバハイドロホンの感度に匹敵するセンサが実現できるものと期待される。

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  • スクイズド状態を用いた光波利用センサの雑音低減に関する基礎研究

    Grant number:03750025

    1991

    System name:科学研究費助成事業

    Research category:奨励研究(A)

    Awarding organization:日本学術振興会

    大河 正志

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    Grant amount:\900000 ( Direct Cost: \900000 )

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Teaching Experience

  • 電気回路

    2022
    Institution name:新潟大学

  • 研究室体験実習

    2021
    -
    2022
    Institution name:新潟大学

  • 総合技術科学演習

    2021
    -
    2022
    Institution name:新潟大学

  • 卒業研修

    2021
    -
    2022
    Institution name:新潟大学

  • 卒業研究

    2021
    -
    2022
    Institution name:新潟大学

  • リメディアル演習

    2021
    Institution name:新潟大学

  • 知能情報システム概論

    2020
    -
    2022
    Institution name:新潟大学

  • 知能情報システム実験I

    2019
    Institution name:新潟大学

  • 知能情報システム実験II

    2019
    Institution name:新潟大学

  • 情報工学実験I

    2019
    -
    2021
    Institution name:新潟大学

  • 基礎電子回路

    2018
    Institution name:新潟大学

  • 工学リテラシー入門(情報電子分野)

    2017
    Institution name:新潟大学

  • 数値計算実習

    2015
    -
    2018
    Institution name:新潟大学

  • 高福祉社会を支える「生活支援工学」入門

    2015
    -
    2016
    Institution name:新潟大学

  • 人間支援科学文献詳読Ⅰ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学セミナーⅠ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学研究発表演習(中間発表)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学セミナーⅡ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学文献詳読Ⅱ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学特定研究Ⅰ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学研究発表(外部発表)

    2013
    -
    2015
    Institution name:新潟大学

  • 人間支援科学特定研究Ⅱ(工業)

    2013
    -
    2015
    Institution name:新潟大学

  • 卒業研修

    2011
    -
    2022
    Institution name:新潟大学

  • 卒業研究

    2011
    -
    2022
    Institution name:新潟大学

  • 論文輪講

    2011
    -
    2019
    Institution name:新潟大学

  • 物理工学特論2

    2011
    Institution name:新潟大学

  • 物理工学特論1

    2011
    Institution name:新潟大学

  • 医用光工学

    2010
    -
    2018
    Institution name:新潟大学

  • 自然科学総論Ⅲ

    2010
    -
    2013
    Institution name:新潟大学

  • 物理工学II

    2009
    -
    2017
    Institution name:新潟大学

  • 工学リテラシー入門(福祉人間工学科)

    2009
    -
    2016
    Institution name:新潟大学

  • 自然科学総論Ⅵ

    2009
    Institution name:新潟大学

  • 電気回路演習

    2009
    Institution name:新潟大学

  • 福祉人間工学実験I

    2008
    -
    2017
    Institution name:新潟大学

  • 数理基礎演習Ⅰ

    2008
    -
    2013
    Institution name:新潟大学

  • スタディスキルズ(福祉人間工学)

    2008
    Institution name:新潟大学

  • センシングデバイス論

    2007
    Institution name:新潟大学

  • 電子デバイス

    2007
    Institution name:新潟大学

  • 環境センシング特論

    2007
    Institution name:新潟大学

  • エレクトロニクスへの招待

    2007
    -
    2016
    Institution name:新潟大学

  • 電気回路II

    2007
    -
    2014
    Institution name:新潟大学

  • レーザ工学

    2007
    -
    2009
    Institution name:新潟大学

  • 数理基礎演習

    2007
    Institution name:新潟大学

  • 福祉人間工学実験II

    2007
    Institution name:新潟大学

  • 電気回路演習II

    2007
    Institution name:新潟大学

▶ display all