記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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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DOI： 10.1117/12.2324692

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DOI： 10.1117/12.2288035

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DOI： 10.1117/12.2288086

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DOI： 10.1117/12.2288160

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DOI： 10.1117/12.2324829

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掲載種別：研究論文（国際会議プロシーディングス）  

© 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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

<p>現在、岐阜県の神岡町では重力波の直接観測を目指し重力波望遠鏡KAGRAが建設されている。試験運転が行われるinisial-KAGRA（iKAGRA）が今年3月から4月にかけて稼働し、続く本格的な観測運転が始まるbaseline-KAGRA（bKAGRA）は2018年度完成予定である。bKAGRAでは200W級という高出力のレーザーを使用するため、レーザー強度の安定化が必要不可欠となる。本研究では音響光学素子（AOM）を用いた強度安定化システムを構築し、レーザー強度の安定化を行っている。</p>

DOI： 10.11316/jpsgaiyo.71.2.0_526

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

DOI： 10.11316/jpsgaiyo.70.2.0_568

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Optical Society of America (OSA)  

Designing a silicon-based guided-wave optical pressure sensor, consisting of a diaphragm and a waveguide across the diaphragm, was considered based on dependences of sensitivity and resonance frequency on diagram dimensions.

DOI： 10.1364/acpc.2014.ath3a.209

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：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.

DOI： 10.1117/12.908016

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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".

DOI： 10.1117/12.908011

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.909622

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.908275

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

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.

DOI： 10.1088/0264-9381/28/9/094011

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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 (&lt;4[T]) magnetic fields, at extremely low temperatures (&lt;80[K]). Not surprisingly, then, in preliminary tests, when we exposed Fabry/Perot-type diode lasers oscillating at 780[nm] to weak magnetic fields (&lt;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.

DOI： 10.1117/12.875851

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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.

DOI： 10.2150/jlve.35.23

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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.

DOI： 10.2150/jlve.35.7

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.875830

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.873660

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

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.

DOI： 10.1088/0264-9381/27/8/084010

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その他リンク： http://orcid.org/0000-0003-1318-2635

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS  

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]

DOI： 10.1117/1.3284784

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.840609

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.841526

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.840626

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.840610

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

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.

DOI： 10.1088/0264-9381/26/9/094019

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その他リンク： http://orcid.org/0000-0003-1318-2635

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS  

The primary objective of the Decihertz Interferometer Gravitational Wave Observatory (DECIGO) mission is to detect and observe black holes&apos; and galactic binaries&apos; 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&apos; 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]

DOI： 10.1117/1.3089887

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2150/jieij.93.814

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.808803

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2150/jieij.93.827

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1541/ieejsmas.129.357

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Optical Society of America (OSA)  

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.

DOI： 10.1364/OE.16.015024

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS  

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.

DOI： 10.1117/1.2909669

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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)&lt;=sigma(2,tau)&lt;= 7.54x10(-10), in averaging time for 0.01s &lt;=tau &lt;= 23s. Furthermore, we heated the Rb cell to up to 313K, in order to enhance the control signal and improve oscillation frequency stability.

DOI： 10.1117/12.761595

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.756222

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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) &lt;=sigma(2,tau)&lt;= 7.54 x 10(-10), in averaging time for 0.01s &lt;=tau &lt;= 23s. By introducing optical feedback, which narrows the laser's linewidth, we obtained improved frequency stability.

DOI： 10.1117/12.756173

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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)&lt;=sigma(2,tau)&lt;= 7.54x10(-10), in averaging time for 0.01s &lt;=tau &lt;= 23s. By introducing an optical feedback, which narrows the laser's linewidth, we obtained improved frequency stability.

DOI： 10.1117/12.788681

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.761598

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.698904

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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) &lt;= sigma(2,tau)&lt;= 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.

DOI： 10.1117/12.698300

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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 &lt; tau &lt; 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.

DOI： 10.1117/12.698306

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.698961

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

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.

DOI： 10.1088/0264-9381/23/8/S17

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.645759

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.685977

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.645913

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.645751

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.645485

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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)&lt;=sigma(2,tau)&lt;= 5.88x10(-11) was achieved, in averaging time for 0.04s &lt;=tau &lt;= 65s.

DOI： 10.1117/12.645726

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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.

DOI： 10.1117/12.645759

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

A satellite-to-satellite laser interferometer is essential for a future gravity-field mission to improve the accuracy and spatial resolution of the Earth&apos;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/&lt;radical&gt;&lt;radicand&gt;Hz&lt;/radicand&gt;&lt;/radical&gt; 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.

DOI： 10.1063/1.2140280

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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.

DOI： 10.1117/12.588457

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPRINGER-VERLAG BERLIN  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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) &lt;= sigma(2,tau) &lt;= 3.72 x 10(-10) was achieved in averaging time for 0.04 &lt;= tau &lt;= 100s.

DOI： 10.1117/12.589743

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.588457

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.588487

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.588487

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.589744

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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) &lt;= sigma &lt;= 1.516 x 10(-10)(24.11kHz &lt;= f &lt;= 58.31kHz) from Is to 39s in the averaging time.

DOI： 10.1117/12.590396

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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.

DOI： 10.1117/12.649176

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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.

DOI： 10.1117/12.588456

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.588456

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2150/jieij.88.281

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Society of Applied Physics  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.474809

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.474348

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.474347

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

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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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.426824

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OPTICAL SOC JAPAN  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OPTICAL SOC AMER  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SCRIPTA TECHNICA-JOHN WILEY & SONS  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.326632

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SCRIPTA TECHNICA-JOHN WILEY & SONS  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SCRIPTA TECHNICA PUBL  

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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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：John Wiley and Sons Inc.  

Optical information retrieval systems based on Fourier optics and using holographic memories of high-density recording capability, which raise the possibility of parallel information processing, have been proposed for a long time. However, the development of spatial light modulators which are the key devices in such systems has been delayed considerably and, so far, there is no report on optical information retrieval systems using spatial light modulators. With this as background, a spatial light modulator (SLM) based on a large-permittivity crystal is fabricated and its operation in a small-size system is verified. First, based on the function of the spatial modulator, the hologram and the detection sections are designed and specifications of the system are decided. Next, the two different schemes of synchronous and direct detection methods are applied to the information retrieval of 18 bits consisting of nine pieces of holograms. As a result, it is understood that retrieval is possible using even the currently available spatial light modulators. The relation between the functions of the SLM and the system also is clarified. However, there are several problems in realization of such systems, a discussion of which is presented in this paper.

DOI： 10.1002/ecjb.4420790802

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN J APPLIED PHYSICS  

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) &gt; sigma(2, tau) &gt; 10(-12) at the averaging time 0.05 s &lt; tau &lt; 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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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPIE - INT SOC OPTICAL ENGINEERING  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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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記述言語：英語   出版者・発行元：INSTITUTE OF PURE AND APPLIED PHYSICS  

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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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

インターネット社会において、暗号技術は必要不可欠なものとなっている。現在多く使われている疑似乱数を用いた暗号は、解読に膨大な時間がかかることを担保に安全性を保っている。しかし、高速処理可能なコンピュータの登場により、解読される危険性がでてきた。一方で、理論上解読不可能な量子暗号通信の研究が進んでおり、物理乱数が大量に必要とされている。本研究では、半導体レーザの周波数雑音を用いて物理乱数の生成を行った。今回は、面発光型レーザ(VCSEL)とファブリ・ペロー型レーザ(FPLD)を用いて乱数生成を行い、VCSELでは120Gb/s、ではFPLDでは40Gb/sで乱数生成できた。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは,低コスト,軽量,低電力,長寿命などの利点から,光距離計測の光源として用いられている.また,半導体レーザは,その発振周波数が変動する周波数雑音を持っており,私たちはそれを用いて物理乱数生成を行ってきた.本研究では,この生成された物理乱数を用いた新しい光距離計測法を考案し計測を行ったので報告する.通常の光距離計測は,パルスなどの変調信号を用いているが,本方式では変調信号の代わりに周波数雑音を用いた.周波数変動は,Rb-D_2吸収線を用いて透過光強度に変換し,距離測定を行った.これにより変調を加えず,0.06mの分解能で,50mまでの距離計測を行うことができた.また,サンプリングレートを変えずに分解能の向上を図る検討を行ったためここに報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振波長は、組成や構造、レーザ温度、注入電流、磁界印加などにより変化することが知られている。本研究では、実用性や応用面から常温(約300K)・比較的弱磁界(〜0.5T)という条件下での半導体レーザの発振特性変化の解析を行っている。これまでの研究では、測定資料にファブリ・ペロー型半導体レーザを用いて、長波長側への波長シフトを観測した。今回は測定資料を面発光型半導体レーザ(VCSEL)とし、磁界による発振波長変化の解析を行った。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザから出力された光は強度及び周波数が変動する高速の雑音特性を持っている。本研究ではその周波数雑音を、周波数弁別器を利用して光強度に変換し、その信号から物理乱数の高速生成を行っている。今回の研究では半導体レーザの発振幅を外部共振器を利用して狭窄化し、そのときの物理乱数とフリーランニング時の物理乱数の比較を行った。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

近年の高度情報化社会の発展に伴い、インターネットなどを通じ情報を交換する機会が増加し、情報の保護という観点から情報の暗号化が日々重要視されている。そこで、解読が困難である「物理乱数」が注目を集めているが、高速に生成することは困難であるとされている。本研究では、「物理乱数」を高速に生成する方法として、半導体レーザが持つ、出力光の周波数が広帯域にかつ不規則に変化する物理現象である「周波数雑音特性」を利用する。Rbの吸収線を利用しレーザ光の周波数の変化を、光強度の変化に変換することで検出し、それをデジタル数値化することで「物理乱数」を高速に生成している。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは,自然放出光の影響による振幅揺らぎとキャリア密度の変動から,屈折率の変動,すなわち発振周波数の変動となる周波数揺らぎを保有している.本研究では,半導体レーザの周波数雑音特性を積極的に利用した新たな応用として,光距離計測が可能か検討した.我々が提案する光距離計測では,周波数雑音の比較により、距離差を求める.それにより,光源の変調を必要とせず,遠距離でも測定精度が変わらないレーザ距離計測が可能と考えられる.ここでは,提案手法により0〜35 mの光距離計測検討を行ったので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは発振周波数が容易に変化するため、発振周波数の安定化が必要となっている。我々は、直接変調を用いた発振周波数の安定化を行い、2つのレーザ光の周波数差の成分を持つビート信号を用いて相対的に安定度の評価を行ってきた。昨今、ビート信号を利用したTHz波の生成が注目されているが、我々はその光源として半導体レーザを用いることにより、安価かつ小型にTHz波生成が実現できるのではないかと考えた。今回はその基礎実験として、GHz帯のビート周波数観測を試みた。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは、自然放出光の影響により、活性層内のキャリア密度の変動がおき、屈折率が変化し、発振周波数が変動する周波数雑音を内在している。我々は、この非周期的で高速な周波数雑音を積極的に用い、物理乱数生成システムを構築してきた。周波数雑音による半導体レーザの発振周波数変動幅は、主に発振幅として表現される。本研究では、フリーランニング半導体レーザと線幅の細い外部共振器半導体レーザを用いて、それぞれ乱数を生成した。生成した各乱数列を暗号用乱数検定FIPS140-2に通し、評価結果を比較し、乱数を生成する半導体レーザの発振幅が乱数性に及ぼす影響を考察した。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザに対する磁界の影響を解析することと磁界の変化する場所や非常に強い磁界のある場所における半導体レーザの使用方法の検討を目的としている。今回は、実用化が容易な"常温・比較的弱磁界(B[T]0.5)"で実験を行い、磁界を加える試料レーザ(面発光型半導体レーザ:VCSEL)と周波数の基準となる端面発光型半導体レーザの周波数差であるビート信号を測定する方法でVCSELの磁界印加時の短波長シフトを観測した。

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは、キャリア密度の変動で利得や屈折率が変動し、単一縦モード発振中でも周波数雑音が発生する。我々はこの半導体レーザの周波数雑音を、周波数弁別器を用いて光強度雑音に変換し、更にA/Dで2進数にすることで、物理乱数の生成を行ってきた。しかし、半導体レーザの発振周波数が大きく変動すると、生成される乱数の乱数性が劣化する可能性がある。そのため、安定化半導体レーザによる物理乱数の乱数検定通過率を測定した。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

大規模シミュレーションや通信の暗号化を行う際に現行では一般的に擬似乱数が用いられている.しかし,近年物理乱数への期待が非常に高まっており,半導体レーザカオスを利用した物理乱数の高速生成も報告されている.そこで本研究では,面発光型半導体レーザの周波数雑音を,Rb原子の吸収線を介して光強度雑音に変換し,A/Dコンバータで2進数列にすることで乱数を生成させ,より高速な物理乱数生成の可能性を検討した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザは発振周波数が容易に変化するため、その発振周波数の安定化が必要となっている。我々は、この周波数安定度を周波数の異なる二つのレーザ光のビート信号の安定度から計測してきた。今回我々は、このビート信号を用いてテラヘルツ波を発生させる方法を検討した。もしこのテラヘルツ光源が半導体レーザを用いた方法で実現できれば、高性能で安価で小型なテラヘルツ光源を作り出すことができ、医療分野や通信分野への応用が期待できる。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振特性は注入電流,温度,磁界などによって変化することが知られている.これまで我々はFabry-Perot型半導体レーザを用いて,その発振周波数特性が常温・比較的弱磁界印可時にどのように変化するかを研究してきた.今回は面発光型半導体レーザ(VCSEL)の磁界印可時の発振特性変化について調べた.その結果,VCSELは出射するレーザ光と平行方向に磁界を印加するとFabry-Perot型半導体レーザとは異なり,その発振周波数が短波長側にシフトした.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

周波数弁別器によって半導体レーザの周波数雑音は簡単に検出することができる.この周波数雑音は広帯域に分布し,高速な物理乱数生成のソースとして有用であると見込まれる.また,周波数雑音を利用した物理乱数生成器は,周波数雑音を検出するための光学系が単純なため,装置の小型化が容易という利点がある.今回,実験的に半導体レーザの周波数雑音を用いて物理乱数生成を生成し,国際標準とされるNIST SP 800-22によって評価した結果を報告する.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

疑似乱数を用いた暗号方式は,高速計算が可能な時代の暗号化としては不十分であると考えられる.そこで,ランダムな自然現象である半導体レーザの強度雑音特性を用いた物理乱数の生成が注目され始めており,Gbpsを超える高速生成が報告されている.本研究では,半導体レーザの強度雑音ではなく,半導体レーザの周波数雑音特性を利用した物理乱数の高速生成を行うことを目的として実験を行い,5Gbpsの生成速度を得たので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

近年,人工衛星搭載型のレーザ干渉計など,特殊な用途でコヒーレンスの高いそしてコンパクトなレーザ光源開発が求められている.半導体レーザもその光源の候補であるが,駆動電流や温度により発振周波数が変化してしまう欠点がある.そこで我々は,半導体レーザの発振周波数を原子の吸収線を外部周波数基準に用いて安定化を行っている.ここでは半導体レーザの発振幅を広げることなく安定化が行える磁気光学効果を用いた発振周波数安定化について述べる.今回は特に,磁界の印加に永久磁石を用いた温度変動の低減による周波数安定度の改善を試みた.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：英語  

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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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

近年,地球重力場の時間的変動を検出することで地球環境を計測するプロジェクトが各国で進められている.その地球重力場の変動は人工衛星で構成される干渉計で計測される.我々は,半導体レーザが小型,軽量,低消費電力,長寿命という特長から,その発振特性を改善することで干渉計の光源に適用できると考えている.これまでの研究では,広帯域かつ高安定な周波数基準の構築を考え,エタロンの透過光スペクトルの1つを絶対的に安定なRb原子の飽和吸収分光法を用いた吸収線に安定化するシステムを構築してきた.今回は更なる安定度改善のために,半導体レーザの温度コントロールの精度を向上させ,光フィードバック法を導入した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

現在,双子衛星を用いて,レーザ干渉計により衛星間の相対速度の変化を観測する事で地球重力場の変動を観測しようという研究がある.宇宙という環境などを考慮すると半導体レーザの持つ,長寿命やメンテナンスフリーなどといった特徴は干渉計用光源として魅力的である.そこで我々は,半導体レーザの発振周波数を外部周波数基準としての原子の吸収線とファブリ・ペローエタロンの特徴,すなわち吸収線の長期における高い安定度をエタロンの短期における高い安定度と広い周波数範囲に渡る調整性と組み合わせて安定化を行っている。安定化に際しては磁界変調を加える事で得られる信号を用いて安定度の向上を目指しており,今回はその雑音の原因について考察を行った.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

最近のFTTH(Fiber To The Home)の普及は,インターネット接続だけでなくケーブルテレビやIP電話などの便利な情報通信サービスを安定でかつ高速に提供している.しかし,近い将来このようなサービスにさらなる高速化が求められるのは必然的である.本研究では外部変調器を必要とする波長多重方式と比較して,高速でありながら安価なVCSELの直接変調方式に注目し,その波長多重の実現を視野に入れた光帰還法によるVCSELの特性改善を行ってきた.その結果,その発振波長の安定度ならびに発振スペクトル幅の狭窄化に多くの改善を確認することができた.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

外部共振器型半導体レーザはコヒーレント光通信や精密な光計測の光源などに注目されている.本研究の安定化の方法は,電気的な制御は行わず,2つの回折格子を使ったダブル光フィードバック法を採用している.この方法には,シングル光フィードバックの時に必要な能動的な共振器の制御素子が不必要になると共に半導体レーザの発振スペクトル幅をシングルの時より更に狭窄化させる働きがあり,より高い安定度を得ることができる.これまでECDLシステムの外部共振器長変動の抑制,小型化を行ってきた.しかし,現在のECDLシステムは未だ雰囲気温度変動が発振周波数変動の原因となっている.そこで,ECDLシステムの雰囲気温度変動による発振周波数変動の軽減を様々な方法で行った.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザはその発振周波数を安定化することで,レーザ干渉計を利用した精密な計測装置や波長多重分割方式を利用した大容量光通信の光源に応用することができる.レーザ干渉計の応用例として,双子衛星間で構成したレーザ干渉計を用いて重力場の変動を衛星間の相対速度の変動として検出し,地球環境を計測することが挙げられる.その干渉計の光源に要求される周波数安定度は10^<-13>以下である.この干渉計の光源に半導体レーザを用いれば装置を小型,軽量,長寿命,低消費電力にできる.そこで我々は,半導体レーザの発振周波数を外部周波数基準としての原子の吸収線とファブリ・ペローエタロンの特徴,すなわち吸収線の長期の安定度とエタロンの短期の安定度と広い周波数範囲に渡る調整性を組み合わせて安定化を行っている.今回の実験では,レーザマウントの温度制御の精度を向上させることで安定度を9×10^<-13>まで向上させることに成功した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

光導波型マイクロホンの感度は,ダイヤフラム厚の2乗に反比例することが理論的に分かっている.また,理論計算によると,感度は,ダイヤフラム辺比1以下では,辺比が大きくなるにつれて高くなっていくが,辺比1以上ではほとんど変化しなくなる.これらの依存性は,光導波型マイクロホンを設計する上で重要であるが,これまで実験的には明らかにされていない.そこで,本研究では,これらの依存性を実験的に考察した.次に,感度のダイヤフラムサイズ依存性を考慮して,ダイヤフラムサイズ20mm×20mm×0.15mmの光マイクロホンを試作し,100dB-SPLの音波検出に成功した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

光導波型マイクロホンの感度は,ダイヤフラム厚の2乗に反比例することが理論的に分かっている.また,理論計算によると,感度は,ダイヤフラム辺比1以下では,辺比が大きくなるにつれて高くなっていくが,辺比1以上ではほとんど変化しなくなる.これらの依存性は,光導波型マイクロホンを設計する上で重要であるが,これまで実験的には明らかにされていない.そこで,本研究では,これらの依存性を実験的に考察した.次に,感度のダイヤフラムサイズ依存性を考慮して,ダイヤフラムサイズ20mm×20mm×0.15mmの光マイクロホンを試作し,100dB-SPLの音波検出に成功した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

乱数には、擬似(算術)乱数と物理乱数がある。擬似乱数は周期性を持つため、高速計算が可能な時代の暗号化としては不十分であると考えられる。一方、物理乱数はランダムな自然現象を用いて生成されるため周期性をもたず、十分なセキュリティが得られると期待されている。そこで本研究では、半導体レーザの雑音特性を利用した物理乱数の高速生成とその暗号化技術への応用の可能性について考察する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

宇宙の様々な極限状態で起こる現象を最も早く人類に届けてくれるものの1つは重力波である.この波は光速で重力の潮汐力が進む波であり,1916年にアインシュタインが一般相対性理論より理論的にその存在を予言した.重力波の存在は連星中性子星PSR1913+16の軌道周期の観測により存在は確かめられているが,直に重力波が検出されたわけではない.この重力波の直接的な存在証明のために高感度なレーザー干渉計の開発が必要である.干渉計のための周波数安定化システムとして,原子分子の吸収線を用いた周波数安定化がある.しかしこの周波数基準は,吸収縮の性質から長期間の周波数安定化の基準としては良好であるが,制御信号の急峻さにおいては良いとは言い難い.そこで我々の研究室で開発されたPEAK方式を採用し制御信号を改善した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

超精密光干渉計や光分析装置に半導体レーザを応用する場合、コスト低減や保守管理などが簡便になる一方、他のレーザに較べてその発振幅が広く周波数安定度が劣るため必然的に分解能が低下する。この欠点を補うべく、既存の半導体レーザの発振周波数安定度と発振幅、並びに各種雑音に対して、外部からの電子的制御無しに改善することを目的とし、二重外部共振器を半導体レーザに付加したことによるその特性の改善を試みた.その結果、発振周波数安定度が向上した。また、システムが環境から受ける影響についても評価・検討を行った.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00052364/

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

重力場計測による大規模な視点から見た地球環境の監視や,重力波検出を目的とした光干渉計には優れた光源が必要である.しかし,2つの衛星によって構成される巨大な光干渉計を実現しようとした場合,光源には低消費電力・長寿命・メンテナンスフリーであることが必要となる.従って,この光源に半導体レーザがその補として挙げられるのだが,既存の半導体レーザの持つ特性のうち,光干渉計にとって最も重要な特性である発振周波数安定度とその発振幅に問題がある.そこで今回,幾つかある半導体レーザの発振周波数安定化法のうち,外部共振器型半導体レーザに注目して実験を行い,その発振周波数安定度の評価を行った.実験では,単一の外部共振器で構成されたECDL (External Cavity Diode Laser)システムに起こる問題を回避すべく,外部共振器を二つ備えたECDLシステムを構築した.また,発振周波数安定度の向上を目指して光学基盤にSuper Invarを採用し,それと同時にECDLシステムの小型化を行った.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザのコヒーレンスを改善して利用する応用を想定し,広帯域かつ高安定な周波数基準の構築を行ってきた.これまでの研究では,広帯域にスペクトルを持つエタロンを絶対的に安定なRb原子の飽和吸収分光法による吸収線を用いて制御することを検討してきた.今回は,更にRb原子の飽和吸収分光法による吸収線を用いた安定度の向上を目指し、安定化の制御信号を得るために加える直接変調信号の変調周波数と変調幅を変えて安定化を行いその影響について検討した.

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00052149/

記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

コヒーレント光通信方式は、次世代の通信として有望である.しかし, 既存の半導体レーザでは, その発振スペクトル幅の狭窄化と, 発振周波数安定化が課題となっている.また, 光共振器を用いた精密レーザ計測においても, 光源の周波数安定度の向上が求められている.今回, 幾つかある半導体レーザの発振周波数安定化法のうち, 光フィードバック法に注目して実験を行い, その発振周波数安定度の評価を行った.実験では, 単一の外部共振器で構成されたECDL (External Cavity Diode Laser)システムに起こる問題を回避すべく, 外部共振器を二つ備えたECDLシステムを構築し, 光学基盤にスーパーインバーを採用した.特に, 新しい手法の提案として, 外部共振器中にRbセルを挿入した, ECDLシステムに飽和吸収分光を取り入れたものは, 一般的なECDLシステムに較べて良好な発振周波数安定度を示した.

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

2台の低軌道衛星を用いたレーザー干渉計方式の地球重力場計測システムが計画されている。衛星間の最大相対速度は0.1m/s程度に達すると予想されており、このとき速度変化を10nm/sの精度で測定することが要求される。このような地球重力場計測システムを実現するために、レーザー干渉計方式の地上シミュレータを構築中である。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザに磁界を印加することで発振周波数がシフトすることは知られている.そこで,本研究室ではこれまで,様々なバルク型の780nm帯半導体レーザに常温(300K)で弱磁界(〜1.4T)を印加して,実験を行ってきた.その結果,周波数が低周波数側にシフトすることを観測した.さらに,780nm帯MQW型半導体レーザに磁界を印加することで,周波数が低周波数側にシフトする結果に加えて,光出力が低出力側に,端子間電庄が高電圧側にシフトするという結果を得た.これらの測定から,諸特性の変化が半導体内部の温度上昇と縦磁気抵抗効果の両方が原因となるというシフトメカニズムを仮定し,検討したので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

本研究では光の周波数や位相を利用する様々な分野への半導体レーザの応用を想定し,広帯域かつ高安定な周波数基準の構築を行ってきた.これまでの研究で,広帯域にスペクトルを持つエタロンを絶対句に安定なRb吸収線を用いて制御することを検討してきた.今回は,更なる安定度の向上を目的とし,エタロンに本研究室で考案したPEAK方式を適用して,Rb吸収線の飽和吸収分光信号をエタロンの制御信号として用い,実験を行った.

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

人工衛星を用い地球重力場の精密観測により,氷床量変動や陸水分布変動などのグローバルな環境変化を長期的に監視する研究が進められている.このシステムでは,周波数の安定したレーザ光源による光干渉計を用いて2つの衛星間の相対速度変化を平均化時間1〜100[s]において10nm/sの精度で測定することが必要である.そこで本研究では,これまで行ってきた半導体レーザの周波数安定化技術を用いてアラン分散の平方根値で10^<-12>より良い周波数安定度を持った光源の開発を目的としている.今回の実験では,1つの半導体レーザに2つの光フィードバック系による発振幅制御と共に,電気的制御を施した2つの安定化されたレーザ光のビート信号による相対的な周波数安定度について検討を行う.

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051666/

記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051613/

記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々はRb原子の吸収線に磁気光学効果を用いる安定化法に,我々が考案したPEAK方式を採用することで基準信号を得て,半導体レーザの発振周波数安定化を行ってきた.また近年,フェムト秒パルスモード同期レーザによる光周波数コムが光周波数の新たな基準として注目されている.そこで本研究ではPEAK方式を用いて安定化したレーザの周波数安定度を,光コムジェネレータを用いて測定した.さらに安定度の改善と発振スペクトル幅の狭窄化を目的として,1つの半導体レーザに2つの光フィードバック(ダブル光フィードバック)を施した状態で発振周波数を安定化することについて検討した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々は,現在光通信に用いられている1.5μm帯半導体レーザの内在的二次高調波(SHG)を用いて半導体レーザの発振周波数を安定化させる方法を検討してきた.我々の安定化法は,1.56μm半導体レーザのSHG出力とRb原子のD_2吸収線(780.02nm)を外部波長基準として用いる事で1.5μm帯半導体レーザの波長安定化が行えるが,SHG出力は安定化の制御信号として用いるには小さすぎるので増大させる必要がある.そこで,光フィードバック法によるSHG出力の増大を試みてきた.また,光フィードバック法には半導体レーザの発振スペクトル幅を狭窄化させる働きもあり,より高い安定度を得る事が期待できる.今回の実験では,光フィードバック法による半導体レーザの基本波スペクトルの狭窄化について実験を行い,光フィードバック法による半導体レーザの波長安定化について考察した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々は,近赤外および可視光で発振するいくつかの構造の異なる半導体レーザに磁界を印加し,その時に生じる光出力,発振波長の変化を測定してきた。初期の結果から当初は,特性変化は内部の温度上昇によるものと考えていた。しかし,発振波長帯および内部構造の異なる半導体レーザにおいて,温度の効果だけでは説明の出来ない結果を得た。そこで我々は内部のキャリア密度の変化もシフトに影響すると考え,その効果を加えた新たなシフト理論を考案した。今回は特性のシフト機構を更に詳しく見て行くための実験を行ったので,その結果と検討について報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051400/

記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051443/

記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

Rb等の原子の吸収線は固有のスペクトル線を持ち絶対的な安定性を持っているが,任意の周波数を選ぶ事は困難である.一方,エタロンの透過光スペクトルは雰囲気温度の変化等により共振器長が変化してしまうことで共振周波数,すなわち透過光スペクトルが変動してしまうが,スペクトルのピーク周波数をシフトさせることが可能である.そこで,本研究ではこれら2つの周波数基準の特徴を利用することで高安定かつ広帯域な周波数基準を構築し,半導体レーザの発振周波数の安定化への応用を検討した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々はRb原子の吸収線にファラデー効果を用いて安定化のための基準信号を得て,半導体レーザの発振周波数安定化を行ってきた.この方法では直接半導体レーザに変調を加えないため発振周波数幅を広げずに安定化が行える.さらに独自に開発したPEAK方式を用い,より高い周波数安定度を得てきた.本研究ではPEAK方式の光学系及び実験系を簡単なものにすることで実験系を小型化し,雑音源を削減することにより安定度の向上を実現した.

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記述言語：英語   出版者・発行元：一般社団法人電子情報通信学会  

一般相対性理論から導出された天の川銀河の重力場が地球に及ぼす影響に関する報告があり,振り子の変位を観測することで,天の川銀河系の中心核の影響により地球が受ける力を検出することが可能であり,2種類の振り子の観測を行い,周時刻に同一方向への変位が見られたと報告されている.本報告では,この実験結果の検証を目的とし,半導体レーザーを用いた振り子の変位の光計測システムを構築し,外部雑音の影響が非常に少ない国立天文台の観測所のトンネルで観測を行っている.これまでの観測では,地震による影響が観測されており,今回は潮汐力による影響について検討し,重力放射力の検証の基礎実験を行ったので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

1.5μm帯半導体レーザーの内在的二次高調波(SHG)を用いて半導体レーザーの発振周波数を安定化させる方法を検討している.本方法ではRbのD_2吸収線(780.02nm)を外部波長基準として用いることで1.56μmの波長に安定化されるが,SHGは基本波に比べ非常に小さいため増大させる必要がある.そこで光フィードバック法により基本波を増大させることによりSHGを増大させることを試みている.光フィードバック法には基本波スペクトルを狭窄化させる働きもある.今回の実験では2つのDFBレーザーに光フィードバックを施し戻り光の強さの影響を観測し比較検討を行った.

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051221/

記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

我々は, Rb原子の吸収線を外部周波数基準として, その基準周波数とレーザの発振周波数との差を駆動電流にフィードバックすることにより, 半導体レーザの発振周波数安定化を行っている. しかしながら, その安定度は雰囲気温度の変動等の外部雑音により制限されている. 今回, これまでの実験環境である通常の大学の実験室とは異なり, 外部雑音の影響が非常に少なく設計された天文台の観測基地のトンネルにおいて, 長時間の安定化を行い, 通常の実験において安定度を劣化させる雰囲気温度等の原因について検討を加えたので報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振周波数安定化を行う場合、発振スペクトル幅は広がるが半導体レーザの注入電流に直後微小変調を加える方法が一般に用いられてきた。しかし、わずかな発振幅の広がりも応用分野によっては取り除く必要がある。そこで、我々はRb吸収線のファラデー効果を用いて基準周波数に微小変調を加えることで、レーザの発振スペクトル幅を広げることなく安定化する方法を検討してきた。今回は、その微小変調の大きさと発振周波数の安定度の関係を調べ、我々が考案した"PEAK方式"へ応用することを検討したので報告する。

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記述言語：日本語   出版者・発行元：日本色彩学会  

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その他リンク： http://id.nii.ac.jp/1141/00051036/

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振周波数安定化を行う場合, 発振スペクトル幅は広がるが半導体レーザの注入電流に直接微小変調を加える方法が一般に用いられてきた。しかし, わずかな発振幅の広がりも応用分野によっては取り除く必要がある。そこで, 我々はRb吸収線のファラデー効果を用いて基準周波数に変調を加えることで、レーザの発振スペクトル幅を広げることなく安定化する方法を検討してきた。今回は、本研究室で考案した"PEAK方式"をこれまでの方法より工夫を加えた光学系に対して適用し、これまで問題となっていた制御信号の再現性を改善し、高い安定度が期待できる方法を開発し安定化を行ったので報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：電気学会  

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記述言語：日本語   出版者・発行元：電気学会  

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記述言語：日本語   出版者・発行元：電子情報通信学会  

我々はこれまで，Rb原子のD_2吸収線を用い，780nm帯の半導体レーザの発振周波数の安定化を行ってきた．吸収線は自然幅やドップラー幅などの広がりをもちこれが安定度を制限している．そこでこれまでに，吸収線の広がりを抑えるため，飽和吸収分光法によりドップラーフリーの自然幅程度の広がりをもつ吸収線を得て安定化を行ってきた．しかし，光学系の工夫だけではこれ以上狭い吸収線を得ることはできない．本論文では，Rb原子の吸収線のゼーマン効果および新たに提案したPEAK方式，BOTTOM方式を用い，更に広がりの少ない基準信号を得て周波数弁別曲線の幅を狭くすることで，基準周波数に対するレーザ発振周波数の追随度を改善した．更に，この周波数弁別曲線の掃引が可能であることを確認した．

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その他リンク： http://hdl.handle.net/10191/8849

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

幾つかの種類の半導体レーザに磁界を印加した時の発振波長シフトと光出力シフトを観測した。近赤外光で発振する半導体レーザでは、これまで温度変化による影響が大きいと考えられる結果が得られていたが、最近計測した可視光半導体レーザでは、磁界によるキャリア密度の変化の影響と思われる結果が得られた。また、多重量子井戸構造の半導体レーザでは、これまでとは異なる特性が観測された。今回は、実験結果を示すとともに、この磁界による半導体レーザの特性変化の機構について検討を加えたので報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

レーザ干渉計は、非常に精度良く空間的変位を測定することができる計測系である。その為、様々な精密測定の分野で用いられつつあり、例えば相対性理論から導かれる重力波の検出への応用が試みられている。一方、同じ相対性理論から導かれる周波数が零の重力波に相当する空間の異方性は、振り子の変動から重力波よりも低い測定精度(数μm程度)で測定可能だという報告がある。そこで、我々は振り子の動きを半導体レーザを用いたレーザ干渉計で観測する方法の検討を始めた。今回は、3次元的な振り子の動きを検出するためのレーザ干渉計測系を考案し、計算から導かれる測定精度を実現できるかを検討したので報告する。

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記述言語：日本語   出版者・発行元：応用物理学会分科会日本光学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

コヒーレント光通信の送信システムを想定し, 半導体レーザの直接FSK変調時における周波数安定化とその安定度測定法の改善を行った. 原子の吸収線を周波数基準として用いた安定化法では, 直接FSK変調時には変調に伴うサイドバンドと周波数チャーピングのため安定度が低下する. そこで, PEAK方式を考案して安定度を改善してきた. 安定度の評価法としては, ロックインアンプの同期検波出力を用いた方法及び被測定レーザと基準レーザとのビート信号を用いた方法の検討を行った. ビート信号の測定では, 測定機器の周波数範囲に制限がある. そこで今回, 基準レーザの発振周波数を制御して測定する方法を導入した.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々は、近赤外光で発振するいくつかの半導体レーザに磁界を印加したときに生じる、半導体レーザの発振波長および光出力等の特性の変化を観測し、その変化の機構を検討してきた。今回、可視光で発振する半導体レーザを用いて同様の観測を行い、これらの結果を比較する事で磁界による特性変化の材料による相違について検討したので報告する。測定方法には、モノクロメータを用いた方法とレーザ光間のビート信号を用いてそれぞれの特徴を生かした観測を行った。

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記述言語：日本語   出版者・発行元：電子情報通信学会  

並列光情報処理を実行するフーリエ光学系と高密度記録の可能なホログラフィックメモリを組み合わせた光情報検索システムが以前より提案されている．しかし，システムのキーデバイスである空間光変調器の開発の遅れから，現在まで空間光変調器を利用した光情報検索システムについて報告はされていない．そこで本研究では，強誘電性結晶を用いた空間光変調器を使用して小形の動作実証用システムを構成し，その動作確認を行った．まず，使用した空間光変調器の性能をもとに，ホログラムと光検出部の設計を行い，試作システムの仕様を決定した．ついで，光検出部での光検出法として同期検波と直接検波の二つの方法を用い，各々が18ビットの情報からなる9個のホログラムを使って情報検索を行った．その結果，既存の空間光変調器の性能でも検索が可能であることがわかり，変調器の性能とシステム性能の関係についても明らかとなった．しかし，本システムが実用化されるに至ってはまだ数々の問題を抱えており，これらの問題点については最後に言及した．

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その他リンク： http://hdl.handle.net/10191/9027

記述言語：日本語   出版者・発行元：電子情報通信学会  

光集積回路圧力センサの高感度化について考察を行い，考察結果をもとに，その実現性および問題点を明らかにした．センサは高感度化を図るために多重干渉光回路であるリング共振器とダイヤフラムから構成される．センサに圧力が加わるとダイヤフラムがひずみ，屈折率がわずかに変化して，ダイヤフラム上を伝搬する導波光に位相変化が生じる．この変化によって引き起こされる共振周波数変化から印加圧力の大きさを検出する．今回，ダイヤフラムの形状とセンサ感度の関係に重点を置き，考察を行った．解析結果より，ダイヤフラムの形状を正方形とし，ダイヤフラムの端に導波路を設け，導波モードとしてTM-likeモードを利用するのが，高感度なセンサを構成するうえで適していると言える．更に，最小検出可能圧力の評価を行った結果，水中音響のような微小圧力に対しても感度を有する光集積回路圧力センサを実現できるものと期待される．

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その他リンク： http://hdl.handle.net/10191/9026

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの周波数安定化では,微少変調信号を半導体レーザの注入電流に直接印加する方法が良く採用されている.しかしこの方法では安定化しようとしている周波数に変調を加えている為,半導体レーザの発振幅が広がり,スペクトル幅の狭いレーザ光が必要な場合には問題となる.そこで我々は,Rb原子の吸収線の磁気光学効果を用いて吸収線を変調することで,半導体レーザには直接変調を加えない周波数安定化の方法を検討してきた.今回は,光フィードバックを用いて更なる狭スペクトル化を試み,磁気光学効果を用いて安定化を行っている状態で,光フィードバックの影響を確認することができたので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザを用いてコヒーレント光通信を行う場合、発振周波数の安定化が問題となる。本研究ではRb原子の吸収線(波長780.02nm)を外部周波数基準とし、電流によるフィードバック制御により安定化を行っている。さらに、我々が提案してきたPEAK方式を用いることで、直接変調時において一桁程度の安定度の向上を確認できている。今回は2つのレーザ間のビート信号から安定度の評価を行ったので報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

これまで我々は、Rb原子の吸収線(780.02nm)を用いることにより、半導体レーザの周波数安定化を行ってきた。しかし、実際に光通信を行う上で光ファイバケーブルの減衰が一番小さい周波数は1.5μm〜1.6μmとなっている。そこで、レーザは1.56μmのものを用い、その二次高調波(SHG)を観測することでRb原子を用いた周波数安定化をすることが必要である。本研究では、半導体レーザのSHGと基本波の関係を詳しく調べることを目的としているので、レーザは取り扱い易い780nm帯のものを用い、その結果を報告する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

我々は,室温・弱磁界の条件下で,磁界による半導体レーザの発振波長シフトの研究を行ってきた.これまでは,モノクロメータを用いて実験を行ってきた.今回は,実験の精度の向上と過渡状態の発振波長のシフトの観測を目的として考案したビート信号を用いる実験方法を採用し実験を行った.その結果,実験の測定誤差がモノクロメータを用いた方法に比べて1/10程度に軽減させるとともに,過渡状態の時間変化についても観測を行えた.ここではこれらの実験結果と共に,発振波長シフトの理論について考察する.

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記述言語：日本語   出版者・発行元：電気学会  

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記述言語：日本語   出版者・発行元：一般社団法人照明学会  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

光集積回路構成を用いた小型で高感度な圧力センサを提案する。センサは高感度化を図るために多重干渉光回路であるリング共振器とダイアフラム(加圧部)から構成されている。センサに圧力が加わるとダイアフラムがたわみ、リング共振器の一部分にひずみが生じる。このひずみにより起こる共振周波数変化から印加された圧力を検出する。今回、ダイアフラムの形状とセンサ感度の関係に重点をおき、考察を行った。解析結果から、ダイアフラムを正方形とし、ダイアフラムの端に導波路を位置させることが、高感度なセンサを構成する上で適していると言える。また、このような構成とすることで、水中音響のような微小圧力に対しても感度をもつ光集積回路圧力センサを実現できるものと期待される。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振波長は磁界を印加することによってシフトする。我々は、室温、比較的弱磁界の条件において磁界による発振波長シフトの観測を行ってきた。しかし、これまでのモノクロメータを用いた実験では読取り誤差が大きく、原子の吸収線を用いた実験では用いる半導体レーザの波長の制約が厳しかった。また、両者とも磁界印加時の定常状態の波長シフトしか観測できなかった。今回は、独立した二つの半導体レーザを用いて、ビート信号による発振波長シフトの観測を行った。このビート信号を用いた測定では、モノクロメータを用いた場合と比べて誤差が1, 10となり、過渡状態の観測も可能となった。ここではこれらの実験結果を示すと共に、波長シフトの機構について検討する。

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振周波数の安定化を,直接FSK変調時に外部基準周波数にRb原子の吸収線を用いて行う時,従来の方式では安定度が低下する.また,光通信の送信システムを想定し,変調パルス信号のデューティレシオを変化させた条件で安定化を行うと,デュティレシオの変化と共に安定化点も動くためさらに安定度が低下する.直接FSK変調時用に考案されたピークホールド方式を用いると,デューティレシオに左右されず,常に無変調時よりも高い安定度が得られることが実験的に確認されたので報告する.

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

本研究では、飽和吸収分光信号を用いて直接周波数変調時における半導体レーザの発振周波数の安定化を行った。飽和吸収分光信号は、吸収線のドップラー広がりの影響を受けないスペクトル幅の狭い周波数基準信号を与える。そのため直接周波数変調時においても、通常の吸収分光信号を用いた場合の周波数安定度と比較すると、1けた以上の安定度の改善が得られた。ここでは、直接周波数変調時の飽和吸収分光信号波形を検討することで、更なる発振周波数の安定度の向上のための条件を検討する。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

ホログラムを光メモリに応用すると、大量のディジタル情報を高密度に記録でき、これを情報検索に活用すれば大量情報の同時並列処理が可能になる。そこで、本研究では実際にフーリエ光学系を用いた情報検索システムを設計し、この設計に基づく予備実験系の試作を行った。その結果、光学系はレンズの収差の影響を受け易く、検索時のS, N比,システムの応答速度,さらには検索項目等はデータマスクである空間光変調器に依存するところが多く、システムの実用化にあたっては特に高性能な空間光変調器の開発は不可欠と考えられる。

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

半導体レーザの発振波長は,磁界を印加することによりシフトする.我々は,室温,比較的弱磁界の条件下でこの磁界による発振波長シフトの研究を行ってきた.今回は,この波長シフトが磁界の方向とレーザの方向との関係に依存することを角度依存性として観測し,その再現性を確認した.また,磁界印加後の波長シフトの時間変化を測定し,これまでの実験で観測された誤差原因の究明と実験結果の再現性の確認を行った.更に,磁界を印加することで生じる光出力パワーの低下を測定した.ここでは,これらの実験結果を示すと共に,波長シフトの機構について検討している.

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記述言語：日本語   出版者・発行元：電子情報通信学会  

半導体レーザの発振波長が，磁界を印加することでシフトすることは半導体レーザの開発当初から知られている．しかしそのほとんどは，極低温・強磁界の下での研究であった．そこで，近年開発されてきた室温で連続発振するいくつかの半導体レーザを用いて実験を行ったところ，半導体レーザの内部構造により波長シフトの特性が大きく異なることが明らかになり，また磁界の方向によって発振波長がシフトする場合としない場合があることがわかった．従来の極低温・強磁界の実験条件では，主としてランダウ準位によりその波長シフトは説明されてきたが，今回我々が用いた室温・比較的弱磁界の条件においてはランダウ準位は形成されず，従来の理論では今回の波長シフトは説明できない．ここでは，現在までに得られた各種構造のGaAlAsレーザダイオードによる実験結果について述べると共に，波長シフトの機構とこの波長シフトを用いた波長制御について検討している．

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その他リンク： http://hdl.handle.net/10191/9028

記述言語：日本語   掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）  

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記述言語：日本語   出版者・発行元：レ-ザ-学会  

DOI： 10.2184/lsj.20.3_160

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記述言語：日本語   出版者・発行元：レ-ザ-学会  

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