2021/10/20 更新

写真a

クマノ ヒデカズ
熊野 英和
KUMANO Hidekazu
所属
教育研究院 自然科学系 情報電子工学系列 教授
創生学部 創生学修課程 教授
職名
教授
外部リンク

学位

  • 博士(工学) ( 2004年3月   北海道大学 )

研究キーワード

  • 量子光学

  • 教育工学

  • 物性物理学

  • 科学教育

研究分野

  • 人文・社会 / 教育工学  / 教育工学(文理融合教育、ICT利活用、情報リテラシー など)

  • ナノテク・材料 / ナノ構造物理  / 量子物理(量子物性、量子情報科学 など)

経歴(researchmap)

  • 新潟大学   創生学部 創生学修課程   教授

    2017年4月 - 現在

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  • 北海道大学   電子科学研究所   准教授

    2007年4月 - 2017年3月

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経歴

  • 新潟大学   創生学部 創生学修課程   教授

    2017年4月 - 現在

所属学協会

委員歴

  • 応用物理学会   教育企画委員会 副委員長  

    2016年4月 - 2017年3月   

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論文

  • Fiber-coupled pillar array as a highly pure and stable single-photon source 査読

    S. Odashima, H. Sasakura, H. Nakajima, H. Kumano

    Journal of Applied Physics   122 ( 22 )   223104 - 223104   2017年12月

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    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Publishing  

    DOI: 10.1063/1.4995225

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  • Optical control of spectral diffusion with single InAs quantum dots in a silver-embedded nanocone 査読

    Xiangming Liu, Hideaki Nakajima, Yulong Li, Satoru Odashima, Ikuo Suemune, Hidekazu Kumano

    OPTICS EXPRESS   25 ( 7 )   8073 - 8084   2017年4月

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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  

    We study the spectral diffusion in a single epitaxial InAs quantum dot placed in a silver-embedded nanocone structure. Making use of a series of stroboscopic detection of optical transitions, we demonstrate the temporal fluctuations in peak energy of photoluminescence. In particular, the photoluminescence fluctuations can be effectively suppressed by strong illumination. By analyzing the photon statistics, we find that the dot emission exhibits stable non-classical nature with the strong anti-bunching behavior after this stabilization. (C) 2017 Optical Society of America

    DOI: 10.1364/OE.25.008073

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  • Stable and efficient collection of single photons emitted from a semiconductor quantum dot into a single-mode optical fiber 査読

    Hidekazu Kumano, Takumi Harada, Ikuo Suemune, Hideaki Nakajima, Takashi Kuroda, Takaaki Mano, Kazuaki Sakoda, Satoru Odashima, Hirotaka Sasakura

    APPLIED PHYSICS EXPRESS   9 ( 3 )   2016年3月

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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 study stable and efficient coupling of single photons generated from a quantum dot (QD) into a single-mode fiber (SMF) prepared in a fiber couple module (FCM). We propose a method to focus the objective lens to a sample surface without imaging with the help of laser reflection. By assembling all the constituents, i.e., a pair of lenses, the SMF, and the optical alignment to the QD source, we demonstrate stable single-photon count rate and a high collection efficiency of 43.5% of the photons emitted in air from the QD into the collection lens in the FCM. (C) 2016 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.9.032801

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  • Highly pure and stable single photon source directly coupled to a fiber 査読

    Satoru Odashima, Hirotaka Sasakura, Hideaki Nakajima, Hidekazu Kumano

    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS)   2016年

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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  

    Highly pure and stable single photon source is established. Well-prepared pillar array which involve InAs QDs is directly contacted to a fiber end-surface, and cooled in a liquid He bath. Auto-correlation measurement shows that it works as a highly pure single photon source providing g((2))(0) <0.1 not only in the weak excitation case but also in the moderately strong excitation one. This photon source is quite rigid against the external disturbance such as cooling-heating cycle and vibration, with a long term stability. Such a pure and stable single photon source is quite promising to build up fiber-based quantum information technology to the actual stage.

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  • Ultrahigh quality factor in a metal-embedded semiconductor microdisk cavity 査読

    Hiroyuki Kurosawa, Hidekazu Kumano, Ikuo Suemune

    OPTICS LETTERS   40 ( 24 )   5766 - 5769   2015年12月

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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  

    We numerically and theoretically investigate electrodynamics of a metal-embedded semiconductor microdisk cavity. The electrodynamics of a cavity mode is discussed from the viewpoint of quantum mechanics, which clarifies the condition for high Q factor. Using numerical calculations, we optimize the cavity structure and show that the Q factor can be increased up to 1,700,000. Our study suggests that the metal-embedded cavity is a promising candidate for cavity quantum electrodynamics (QED) devices. (C) 2015 Optical Society of America

    DOI: 10.1364/OL.40.005766

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  • Single photon interference between bidirectionally extracted photons originating from semiconductor quantum dots 査読

    Hirotaka Sasakura, Shunichi Muto, Hidekazu Kumano

    APPLIED PHYSICS EXPRESS   8 ( 11 )   2015年11月

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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 report the experimental demonstration of the single-photon interference of bidirectionally extracted photons from epitaxially grown semiconductor quantum dots. The quantum dots were directly connected to single-mode optical fibers. Single-photon nature between transmission and reflection directions was confirmed through detection of antibunching in second-order photon correlation measurements. A Mach-Zehnder interferometer that was naturally formed by introducing the two outputs into a 2 x 2-fiber coupler was used to perform first-order photon correlation measurements. (C) 2015 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.8.112002

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  • Superconducting Light-Emitting Diodes 査読

    Sinthia Shabnam Mou, Hiroshi Irie, Yasuhiro Asano, Kouichi Akahane, Hiroyuki Kurosawa, Hideaki Nakajima, Hidekazu Kumano, Masahide Sasaki, Ikuo Suemune

    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS   21 ( 2 )   2015年3月

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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:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    Cooper pairs form spin singlet states and are regarded as entangled electron pairs. Extracting entangled electrons has been actively studied by the use of superconductor-normal metal junctions. We have proposed to convert Cooper pairs to entangled photon pairs via interband radiative recombination of Cooper pairs penetrated into a semiconductor by the proximity effect. We fabricated a superconducting (SC) light emitting diode, where a superconductor is used for the n-type electrode. We observed light output enhancement and recombination lifetime shortening below the SC critical temperature. Our observations were very well explained with an analysis based on a time-dependent perturbation theory of the radiative recombination. Superconductivity was included via the Bogoliubov transformation. We present our measurements on the Cooper-pair-enhanced luminescence from InAs quantum dots. We demonstrate the observation of sharp edge in the luminescence spectra that reflects the SC density of states.

    DOI: 10.1109/JSTQE.2014.2346617

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  • Subwavelength metallic cavities with high-Q resonance modes 査読

    Nagisa Ishihara, Hiroyuki Kurosawa, Ryo Takemoto, Nahid A. Jahan, Hideaki Nakajima, Hidekazu Kumano, Ikuo Suemune

    NANOTECHNOLOGY   26 ( 8 )   2015年2月

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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  

    Metallic cavities have been extensively studied to realize small-volume nanocavities and nanolasers. However cavity-resonance quality (Q) factors of nanolasers observed up to now remain low (up to similar to 500) due to metal optical absorption. In this paper, we report the observation of highest Q factors of 9000 at low temperature and similar to 6000 near room temperature in a metallic cavity with a probe of sub-bandgap emission of Si-doped GaAs. We analyze the temperature dependence of cavity-mode resonance wavelengths and show that the refractive-index term dominates the measured temperature dependence. We also show that this refractive-index term is cavity-mode dependent and the fitting procedure offers a new method to identify cavity modes. We simulate the metallic cavity with finite-element method and attribute the high-Q cavity mode to a whispering gallery optical mode. This mode is shown to have isotropic polarization dependence of the output emission, which is preferable for quantum information applications.

    DOI: 10.1088/0957-4484/26/8/085201

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  • Time-resolved measurements of Cooper-pair radiative recombination in InAs quantum dots 査読

    S. Mou, H. Irie, Y. Asano, K. Akahane, H. Nakajima, H. Kumano, M. Sasaki, A. Murayama, I. Suemune

    Journal of applied physics   118 ( 7 )   073102(1) - 073102(7)   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.4928621

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  • Nonlocal biphoton generation in a Werner state from a single semiconductor quantum dot 査読

    Kumano H, Nakajima H, Kuroda T, Mano T, Sakoda K, Suemune I

    Physical Review B   91 ( 20 )   NA   2015年

  • Optical Observation of Superconducting Density of States in Luminescence Spectra of InAs Quantum Dots 査読

    S. Mou, H. Irie, Y. Asano, K. Akahane, H. Nakajima, H. Kumano, M. Sasaki, A. Murayama, I. Suemune

    Phys Rev B Condens Matter Mater Phys   92 ( 3 )   035308(1) - 035308(9)   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.92.035308

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  • Vanishing fine-structure splittings in telecommunication-wavelength quantum dots grown on (111)A surfaces by droplet epitaxy 査読

    Xiangming Liu, Neul Ha, Hideaki Nakajima, Takaaki Mano, Takashi Kuroda, Bernhard Urbaszek, Hidekazu Kumano, Ikuo Suemune, Yoshiki Sakuma, Kazuaki Sakoda

    Physical Review B - Condensed Matter and Materials Physics   90 ( 8 )   2014年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The emission cascade of a single quantum dot is a promising source of entangled photons. A prerequisite for this source is the use of a symmetric dot analogous to an atom in a vacuum, but the simultaneous achievement of structural symmetry and emission in a telecom band poses a challenge. Here we report the growth and characterization of highly symmetric InAs/InAlAs quantum dots self-assembled on C3v symmetric InP(111)A. The broad emission spectra cover the O (λ∼1.3 μm), C (λ∼1.55 μm), and L (λ∼1.6 μm) telecom bands. The distribution of the fine-structure splittings is considerably smaller than those reported in previous works on dots at similar wavelengths. The presence of dots with degenerate exciton lines is further confirmed by the optical orientation technique. Thus, our dot systems are expected to serve as efficient entangled photon emitters for long-distance fiber-based quantum key distribution. © 2014 American Physical Society.

    DOI: 10.1103/PhysRevB.90.081301

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  • Vanishing fine-structure splittings in telecommunication-wavelength quantum dots grown on (111)A surfaces by droplet epitaxy 査読

    Xiangming Liu, Neul Ha, Hideaki Nakajima, Takaaki Mano, Takashi Kuroda, Bernhard Urbaszek, Hidekazu Kumano, Ikuo Suemune, Yoshiki Sakuma, Kazuaki Sakoda

    PHYSICAL REVIEW B   90 ( 8 )   2014年8月

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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 PHYSICAL SOC  

    The emission cascade of a single quantum dot is a promising source of entangled photons. A prerequisite for this source is the use of a symmetric dot analogous to an atom in a vacuum, but the simultaneous achievement of structural symmetry and emission in a telecom band poses a challenge. Here we report the growth and characterization of highly symmetric InAs/InAlAs quantum dots self-assembled on C-3 upsilon symmetric InP(111)A. The broad emission spectra cover the O (lambda similar to 1.3 mu m), C (lambda similar to 1.55 mu m), and L (lambda similar to 1.6 mu m) telecom bands. The distribution of the fine-structure splittings is considerably smaller than those reported in previous works on dots at similar wavelengths. The presence of dots with degenerate exciton lines is further confirmed by the optical orientation technique. Thus, our dot systems are expected to serve as efficient entangled photon emitters for long-distance fiber-based quantum key distribution.

    DOI: 10.1103/PhysRevB.90.081301

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  • Two-photon interference and coherent control of single InAs quantum dot emissions in an Ag-embedded structure 査読

    X. Liu, H. Kumano, H. Nakajima, S. Odashima, T. Asano, T. Kuroda, I. Suemune

    JOURNAL OF APPLIED PHYSICS   116 ( 4 )   2014年7月

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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  

    We have recently reported the successful fabrication of bright single-photon sources based on Ag-embedded nanocone structures that incorporate InAs quantum dots. The source had a photon collection efficiency as high as 24.6%. Here, we show the results of various types of photonic characterizations of the Ag-embedded nanocone structures that confirm their versatility as regards a broad range of quantum optical applications. We measure the first-order autocorrelation function to evaluate the coherence time of emitted photons, and the second-order correlation function, which reveals the strong suppression of multiple photon generation. The high indistinguishability of emitted photons is shown by the Hong-Ou-Mandel-type two-photon interference. With quasi-resonant excitation, coherent population flopping is demonstrated through Rabi oscillations. Extremely high single-photon purity with a g((2))(0) value of 0.008 is achieved with pi-pulse quasi-resonant excitation. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4891224

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  • 7pAD-7 一般化された光線方程式と磁気カイラルメタマテリアルにおける光のローレンツ力(7pAD フォトニック結晶,領域5(光物性))

    黒澤 裕之, 澤田 桂, 熊野 英和, 末宗 幾夫

    日本物理学会講演概要集   69 ( 0 )   2014年

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

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  • Metal-coated semiconductor nanostructures and simulation of photon extraction and coupling to optical fibers for a solid-state single-photon source 査読

    Ikuo Suemune, Hideaki Nakajima, Xiangming Liu, Satoru Odashima, Tomoya Asano, Hitoshi Iijima, Jae-Hoon Huh, Yasuhiro Idutsu, Hirotaka Sasakura, Hidekazu Kumano

    NANOTECHNOLOGY   24 ( 45 )   2013年11月

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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 have realized metal-coated semiconductor nanostructures for a stable and efficient single-photon source (SPS) and demonstrated improved single-photon extraction efficiency by the selection of metals and nanostructures. We demonstrate with finite-difference time-domain (FDTD) simulations that inclination of a pillar sidewall, which changes the structure to a nanocone, is effective in improving the photon extraction efficiency. We demonstrate how such nanocone structures with inclined sidewalls are fabricated with reactive ion etching. With the optimized design, a photon extraction efficiency to outer airside as high as similar to 97% generated from a quantum dot in a nanocone structure is simulated, which is the important step in realizing SPS on-demand operations. We have also examined the direct contact of such a metal-embedded nanocone structure with a single-mode fiber facet as a simple and practical method for preparing fiber-coupled SPS and demonstrated practical coupling efficiencies of similar to 16% with FDTD simulation.

    DOI: 10.1088/0957-4484/24/45/455205

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  • Metal-coated semiconductor nanostructures and simulation of photon extraction and coupling to optical fibers for a solid-state single-photon source 査読

    Ikuo Suemune, Hideaki Nakajima, Xiangming Liu, Satoru Odashima, Tomoya Asano, Hitoshi Iijima, Jae-Hoon Huh, Yasuhiro Idutsu, Hirotaka Sasakura, Hidekazu Kumano

    NANOTECHNOLOGY   24 ( 45 )   2013年11月

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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 have realized metal-coated semiconductor nanostructures for a stable and efficient single-photon source (SPS) and demonstrated improved single-photon extraction efficiency by the selection of metals and nanostructures. We demonstrate with finite-difference time-domain (FDTD) simulations that inclination of a pillar sidewall, which changes the structure to a nanocone, is effective in improving the photon extraction efficiency. We demonstrate how such nanocone structures with inclined sidewalls are fabricated with reactive ion etching. With the optimized design, a photon extraction efficiency to outer airside as high as similar to 97% generated from a quantum dot in a nanocone structure is simulated, which is the important step in realizing SPS on-demand operations. We have also examined the direct contact of such a metal-embedded nanocone structure with a single-mode fiber facet as a simple and practical method for preparing fiber-coupled SPS and demonstrated practical coupling efficiencies of similar to 16% with FDTD simulation.

    DOI: 10.1088/0957-4484/24/45/455205

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  • Metal-coated semiconductor nanostructures and simulation of photon extraction and coupling to optical fibers for a solid-state single-photon source 査読

    Ikuo Suemune, Hideaki Nakajima, Xiangming Liu, Satoru Odashima, Tomoya Asano, Hitoshi Iijima, Jae-Hoon Huh, Yasuhiro Idutsu, Hirotaka Sasakura, Hidekazu Kumano

    NANOTECHNOLOGY   24 ( 45 )   2013年11月

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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 have realized metal-coated semiconductor nanostructures for a stable and efficient single-photon source (SPS) and demonstrated improved single-photon extraction efficiency by the selection of metals and nanostructures. We demonstrate with finite-difference time-domain (FDTD) simulations that inclination of a pillar sidewall, which changes the structure to a nanocone, is effective in improving the photon extraction efficiency. We demonstrate how such nanocone structures with inclined sidewalls are fabricated with reactive ion etching. With the optimized design, a photon extraction efficiency to outer airside as high as similar to 97% generated from a quantum dot in a nanocone structure is simulated, which is the important step in realizing SPS on-demand operations. We have also examined the direct contact of such a metal-embedded nanocone structure with a single-mode fiber facet as a simple and practical method for preparing fiber-coupled SPS and demonstrated practical coupling efficiencies of similar to 16% with FDTD simulation.

    DOI: 10.1088/0957-4484/24/45/455205

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  • High-Q resonance modes observed in a metallic nanocavity 査読

    R. Takemoto, N. Ishihara, H. Kurosawa, N. A. Jahan, T. Asano, X. Liu, H. Nakajima, H. Kumano, I. Suemune

    APPLIED PHYSICS LETTERS   103 ( 19 )   2013年11月

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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  

    Metallic nanocavities have been actively studied for realizing nanolasers with low threshold. Presence of resonance modes with high cavity Q values is the indication of low internal loss that leads to low threshold lasing. However, cavity Q values observed in metallic nanocavities below lasing threshold remain low at present on the order of 100 to 500. We study the possibility to realize higher resonance Q values with a metallic nanocavity. For probing purpose of cavity modes we propose to employ broad mid-gap-state optical emission of n-type GaAs. With this method we report the observation of a resonance mode with the high Q value of 3800 at room temperature with the metallic nanocavity. The cavity mode is identified as a whispering-gallery mode with finite-element- method simulation. (c) 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4828351

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  • High-Q resonance modes observed in a metallic nanocavity 査読

    R. Takemoto, N. Ishihara, H. Kurosawa, N. A. Jahan, T. Asano, X. Liu, H. Nakajima, H. Kumano, I. Suemune

    APPLIED PHYSICS LETTERS   103 ( 19 )   2013年11月

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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  

    Metallic nanocavities have been actively studied for realizing nanolasers with low threshold. Presence of resonance modes with high cavity Q values is the indication of low internal loss that leads to low threshold lasing. However, cavity Q values observed in metallic nanocavities below lasing threshold remain low at present on the order of 100 to 500. We study the possibility to realize higher resonance Q values with a metallic nanocavity. For probing purpose of cavity modes we propose to employ broad mid-gap-state optical emission of n-type GaAs. With this method we report the observation of a resonance mode with the high Q value of 3800 at room temperature with the metallic nanocavity. The cavity mode is identified as a whispering-gallery mode with finite-element- method simulation. (c) 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4828351

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  • Single-photon emission in telecommunication band from an InAs quantum dot grown on InP with molecular-beam epitaxy 査読

    X. Liu, K. Akahane, N. A. Jahan, N. Kobayashi, M. Sasaki, H. Kumano, I. Suemune

    Applied Physics Letters   103 ( 6 )   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the experimental demonstration of a single-photon source based on an InAs quantum dot (QD) on InP grown by molecular-beam epitaxy emitting in the telecommunication band. We develop a method to reduce the QD density to prevent inter-dot coupling via tunneling through coupled excited states. A single InAs QD embedded in an as-etched pillar structure exhibits intense and narrow emission lines. Photon antibunching is clearly observed using superconducting single-photon detectors with high sensitivity, and further improvement of the generated single-photon purity is demonstrated with below-barrier-bandgap excitation. © 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4817940

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  • Single-photon emission in telecommunication band from an InAs quantum dot grown on InP with molecular-beam epitaxy 査読

    X. Liu, K. Akahane, N. A. Jahan, N. Kobayashi, M. Sasaki, H. Kumano, I. Suemune

    Applied Physics Letters   103 ( 6 )   061114-1 - 4   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the experimental demonstration of a single-photon source based on an InAs quantum dot (QD) on InP grown by molecular-beam epitaxy emitting in the telecommunication band. We develop a method to reduce the QD density to prevent inter-dot coupling via tunneling through coupled excited states. A single InAs QD embedded in an as-etched pillar structure exhibits intense and narrow emission lines. Photon antibunching is clearly observed using superconducting single-photon detectors with high sensitivity, and further improvement of the generated single-photon purity is demonstrated with below-barrier-bandgap excitation. © 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4817940

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  • Single-photon emission in telecommunication band from an InAs quantum dot grown on InP with molecular-beam epitaxy 査読

    X. Liu, K. Akahane, N. A. Jahan, N. Kobayashi, M. Sasaki, H. Kumano, I. Suemune

    Applied Physics Letters   103 ( 6 )   061114-1 - 4   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the experimental demonstration of a single-photon source based on an InAs quantum dot (QD) on InP grown by molecular-beam epitaxy emitting in the telecommunication band. We develop a method to reduce the QD density to prevent inter-dot coupling via tunneling through coupled excited states. A single InAs QD embedded in an as-etched pillar structure exhibits intense and narrow emission lines. Photon antibunching is clearly observed using superconducting single-photon detectors with high sensitivity, and further improvement of the generated single-photon purity is demonstrated with below-barrier-bandgap excitation. © 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4817940

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  • Symmetric quantum dots as efficient sources of highly entangled photons: Violation of Bell's inequality without spectral and temporal filtering 査読

    Takashi Kuroda, Takaaki Mano, Neul Ha, Hideaki Nakajima, Hidekazu Kumano, Bernhard Urbaszek, Masafumi Jo, Marco Abbarchi, Yoshiki Sakuma, Kazuaki Sakoda, Ikuo Suemune, Xavier Marie, Thierry Amand

    PHYSICAL REVIEW B   88 ( 4 )   041306-1 - 5   2013年7月

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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 PHYSICAL SOC  

    An ideal emitter of entangled photon pairs combines the perfect symmetry of an atom with the convenient electrical trigger of light sources based on semiconductor quantum dots. Our source consists of strain-free GaAs dots self-assembled on a triangular symmetric (111)A surface. The emitted photons reveal a fidelity to the Bell state as high as 86(+/- 2)% without postselection. We show a violation of Bell's inequality by more than five times the standard deviation, a prerequisite to test a quantum cryptography channel for eavesdropping. Due to the strict nonlocal nature the source can be used for real quantum processing without any postprocessing. The remaining decoherence channel of the photon source is ascribed to random charge and nuclear spin fluctuations in and near the dot.

    DOI: 10.1103/PhysRevB.88.041306

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  • Creating Highly Entangled Photons Using a Symmetric Quantum Dot Cascade 査読

    T. Kuroda, T. Mano, N. Ha, H. Nakajima, H. Kumano, B. Urbaszek, M. Jo, M. Abbarachi, Y. Sakuma, K. Sakoda, I. Suemune, X. Marie, T. Amand

    Phys. Rev. B   88   041306(R)   2013年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.88.041306

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  • Symmetric quantum dots as efficient sources of highly entangled photons: Violation of Bell's inequality without spectral and temporal filtering 査読

    Takashi Kuroda, Takaaki Mano, Neul Ha, Hideaki Nakajima, Hidekazu Kumano, Bernhard Urbaszek, Masafumi Jo, Marco Abbarchi, Yoshiki Sakuma, Kazuaki Sakoda, Ikuo Suemune, Xavier Marie, Thierry Amand

    PHYSICAL REVIEW B   88 ( 4 )   2013年7月

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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 PHYSICAL SOC  

    An ideal emitter of entangled photon pairs combines the perfect symmetry of an atom with the convenient electrical trigger of light sources based on semiconductor quantum dots. Our source consists of strain-free GaAs dots self-assembled on a triangular symmetric (111)A surface. The emitted photons reveal a fidelity to the Bell state as high as 86(+/- 2)% without postselection. We show a violation of Bell's inequality by more than five times the standard deviation, a prerequisite to test a quantum cryptography channel for eavesdropping. Due to the strict nonlocal nature the source can be used for real quantum processing without any postprocessing. The remaining decoherence channel of the photon source is ascribed to random charge and nuclear spin fluctuations in and near the dot.

    DOI: 10.1103/PhysRevB.88.041306

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  • Symmetric quantum dots as efficient sources of highly entangled photons: Violation of Bell's inequality without spectral and temporal filtering 査読

    Takashi Kuroda, Takaaki Mano, Neul Ha, Hideaki Nakajima, Hidekazu Kumano, Bernhard Urbaszek, Masafumi Jo, Marco Abbarchi, Yoshiki Sakuma, Kazuaki Sakoda, Ikuo Suemune, Xavier Marie, Thierry Amand

    PHYSICAL REVIEW B   88 ( 4 )   041306-1 - 5   2013年7月

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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 PHYSICAL SOC  

    An ideal emitter of entangled photon pairs combines the perfect symmetry of an atom with the convenient electrical trigger of light sources based on semiconductor quantum dots. Our source consists of strain-free GaAs dots self-assembled on a triangular symmetric (111)A surface. The emitted photons reveal a fidelity to the Bell state as high as 86(+/- 2)% without postselection. We show a violation of Bell's inequality by more than five times the standard deviation, a prerequisite to test a quantum cryptography channel for eavesdropping. Due to the strict nonlocal nature the source can be used for real quantum processing without any postprocessing. The remaining decoherence channel of the photon source is ascribed to random charge and nuclear spin fluctuations in and near the dot.

    DOI: 10.1103/PhysRevB.88.041306

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  • Carrier-transfer dynamics between neutral and charged excitonic states in a single quantum dot probed with second-order photon correlation measurements 査読

    H. Nakajima, H. Kumano, H. Iijima, S. Odashima, I. Suemune

    PHYSICAL REVIEW B   88 ( 4 )   2013年7月

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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 PHYSICAL SOC  

    We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.

    DOI: 10.1103/PhysRevB.88.045324

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  • Carrier-transfer dynamics between neutral and charged excitonic states in a single quantum dot probed with second-order photon correlation measurements 査読

    H. Nakajima, H. Kumano, H. Iijima, S. Odashima, I. Suemune

    PHYSICAL REVIEW B   88 ( 4 )   2013年7月

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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 PHYSICAL SOC  

    We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.

    DOI: 10.1103/PhysRevB.88.045324

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  • Carrier-transfer dynamics between neutral and charged excitonic states in a single quantum dot probed with second-order photon correlation measurements 査読

    H. Nakajima, H. Kumano, H. Iijima, S. Odashima, I. Suemune

    PHYSICAL REVIEW B   88 ( 4 )   2013年7月

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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 PHYSICAL SOC  

    We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.

    DOI: 10.1103/PhysRevB.88.045324

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  • Fiber-Based Bidirectional Solid-State Single-Photon Emitter Based on Semiconductor Quantum Dot 査読

    Hirotaka Sasakura, Xiangming Liu, Satoru Odashima, Hidekazu Kumano, Shunichi Muto, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   065203-1 - 3   2013年6月

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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  

    Fiber-based bidirectional photon detection from nanoscale emitters and photon antibunching behavior between two outputs of two single-mode fibers (SMFs) are experimentally demonstrated. Flakes containing the epitaxially grown quantum dots (QDs) are mechanically fixed by both sides with the edge faces of the SMF patch cables. The emitting photons from a single QD are directly taken out of both sides through the SMFs. Single-photon emission between two SMF outputs is confirmed by detecting nonclassical antibunching in second-order photon correlation measurements. This simple optomechanical alignment-free single-photon emitter is advantageous because of its robust stability of more than three months and low-cost fabrication. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.065203

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  • Enhanced Photon Extraction from a Quantum Dot Induced by a Silver Microcolumnar Photon Reflector 査読

    Hidekazu Kumano, Hideaki Nakajima, Hitoshi Iijima, Satoru Odashima, Yasuhiro Matsuo, Kuniharu Ijiro, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   2013年6月

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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 have fabricated silver microcolumnar photon reflectors to enhance the photon extraction efficiency from a quantum dot. The mechanically robust planar structure is favorable to couple to optical fibers for stable and efficient single-photon sources. A high photon extraction efficiency of up to 18% is achieved. Furthermore, strong suppression of multiphoton generation is confirmed. The proposed structure is quite promising toward the implementation of practical quantum key distribution systems with dot-fiber-coupled photon sources. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.062801

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  • Enhanced Photon Extraction from a Quantum Dot Induced by a Silver Microcolumnar Photon Reflector 査読

    Hidekazu Kumano, Hideaki Nakajima, Hitoshi Iijima, Satoru Odashima, Yasuhiro Matsuo, Kuniharu Ijiro, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   062801-1 - 4   2013年6月

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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 have fabricated silver microcolumnar photon reflectors to enhance the photon extraction efficiency from a quantum dot. The mechanically robust planar structure is favorable to couple to optical fibers for stable and efficient single-photon sources. A high photon extraction efficiency of up to 18% is achieved. Furthermore, strong suppression of multiphoton generation is confirmed. The proposed structure is quite promising toward the implementation of practical quantum key distribution systems with dot-fiber-coupled photon sources. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.062801

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  • Enhanced Photon Extraction from a Quantum Dot Induced by a Silver Microcolumnar Photon Reflector 査読

    Hidekazu Kumano, Hideaki Nakajima, Hitoshi Iijima, Satoru Odashima, Yasuhiro Matsuo, Kuniharu Ijiro, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   062801-1 - 4   2013年6月

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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 have fabricated silver microcolumnar photon reflectors to enhance the photon extraction efficiency from a quantum dot. The mechanically robust planar structure is favorable to couple to optical fibers for stable and efficient single-photon sources. A high photon extraction efficiency of up to 18% is achieved. Furthermore, strong suppression of multiphoton generation is confirmed. The proposed structure is quite promising toward the implementation of practical quantum key distribution systems with dot-fiber-coupled photon sources. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.062801

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  • Fiber-Based Bidirectional Solid-State Single-Photon Emitter Based on Semiconductor Quantum Dot 査読

    Hirotaka Sasakura, Xiangming Liu, Satoru Odashima, Hidekazu Kumano, Shunichi Muto, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   2013年6月

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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 SOC APPLIED PHYSICS  

    Fiber-based bidirectional photon detection from nanoscale emitters and photon antibunching behavior between two outputs of two single-mode fibers (SMFs) are experimentally demonstrated. Flakes containing the epitaxially grown quantum dots (QDs) are mechanically fixed by both sides with the edge faces of the SMF patch cables. The emitting photons from a single QD are directly taken out of both sides through the SMFs. Single-photon emission between two SMF outputs is confirmed by detecting nonclassical antibunching in second-order photon correlation measurements. This simple optomechanical alignment-free single-photon emitter is advantageous because of its robust stability of more than three months and low-cost fabrication. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.6.065203

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  • Fiber-Based Bidirectional Solid-State Single-Photon Emitter Based on Semiconductor Quantum Dot 査読

    Hirotaka Sasakura, Xiangming Liu, Satoru Odashima, Hidekazu Kumano, Shunichi Muto, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   6 ( 6 )   065203-1 - 3   2013年6月

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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 SOC APPLIED PHYSICS  

    Fiber-based bidirectional photon detection from nanoscale emitters and photon antibunching behavior between two outputs of two single-mode fibers (SMFs) are experimentally demonstrated. Flakes containing the epitaxially grown quantum dots (QDs) are mechanically fixed by both sides with the edge faces of the SMF patch cables. The emitting photons from a single QD are directly taken out of both sides through the SMFs. Single-photon emission between two SMF outputs is confirmed by detecting nonclassical antibunching in second-order photon correlation measurements. This simple optomechanical alignment-free single-photon emitter is advantageous because of its robust stability of more than three months and low-cost fabrication. (C) 2013 The Japan Society of Applied Physics

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  • 招待講演 半導体量子ドットを用いた量子もつれ光子対の発生 (レーザ・量子エレクトロニクス)

    黒田 隆, 間野 高明, 迫田 和彰, 中島 秀朗, 熊野 英和, 末宗 幾夫

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報   113 ( 49 )   35 - 40   2013年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    半導体量子ドットのカスケード遷移を用いて、もつれた光子対を発生することができる.提案は10年以上前に遡るが、量子ドットに内在する、わずかな形状異方性のために、実現は困難だった.これまで様々の超絶技巧で光学等方性を回復し、もつれあい光子対を検証する実験はあったが、いずれも拡張性に乏しい.我々は、液滴エピタキシー成長法を用いて、対称性の高いGaAs/AlGaAs量子ドットの自己形成に成功した.鍵は、成長基板面としてGaAs(111)A面を用いたことである.その結果、高いもつれあい度の光子対発生を観測できたので報告する.

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  • Bright single-photon source based on an InAs quantum dot in a silver-embedded nanocone structure 査読

    X. Liu, T. Asano, S. Odashima, H. Nakajima, H. Kumano, I. Suemune

    APPLIED PHYSICS LETTERS   102 ( 13 )   2013年4月

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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  

    High photon-extraction efficiency is strongly required for a practical single-photon source. We succeed in fabricating metal (sliver)-embedded nanocone structure incorporating an InAs quantum dot. Efficient photon emission of similar to 200 000 photons per second is detected and single-photon emission is demonstrated using autocorrelation measurements. The photon-extraction efficiency as high as 24.6% is obtained from the structure. (C) 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4801334]

    DOI: 10.1063/1.4801334

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  • Bright single-photon source based on an InAs quantum dot in a silver-embedded nanocone structure 査読

    X. Liu, T. Asano, S. Odashima, H. Nakajima, H. Kumano, I. Suemune

    APPLIED PHYSICS LETTERS   102 ( 13 )   131114-1 - 3   2013年4月

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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  

    High photon-extraction efficiency is strongly required for a practical single-photon source. We succeed in fabricating metal (sliver)-embedded nanocone structure incorporating an InAs quantum dot. Efficient photon emission of similar to 200 000 photons per second is detected and single-photon emission is demonstrated using autocorrelation measurements. The photon-extraction efficiency as high as 24.6% is obtained from the structure. (C) 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4801334]

    DOI: 10.1063/1.4801334

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  • Bright single-photon source based on an InAs quantum dot in a silver-embedded nanocone structure 査読

    X. Liu, T. Asano, S. Odashima, H. Nakajima, H. Kumano, I. Suemune

    APPLIED PHYSICS LETTERS   102 ( 13 )   131114-1 - 3   2013年4月

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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  

    High photon-extraction efficiency is strongly required for a practical single-photon source. We succeed in fabricating metal (sliver)-embedded nanocone structure incorporating an InAs quantum dot. Efficient photon emission of similar to 200 000 photons per second is detected and single-photon emission is demonstrated using autocorrelation measurements. The photon-extraction efficiency as high as 24.6% is obtained from the structure. (C) 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4801334]

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  • Carrier dynamics and photoluminescence quenching mechanism of strained InGaSb/AlGaSb quantum wells 査読

    Nahid A. Jahan, Claus Hermannstädter, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Hidekazu Kumano, Ikuo Suemune

    Journal of Applied Physics   113 ( 5 )   053505-1 - 7   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    GaSb based quantum wells (QWs) show promising optical properties in near-infrared spectral range. In this paper, we present photoluminescence (PL) spectroscopies of InxGa1-xSb/AlyGa 1-ySb QWs and discuss the possible thermal quenching and non-radiative carrier recombination mechanisms of the QW structures. The In and Al concentrations as well as the QW thicknesses were precisely determined with the X-ray diffraction measurements. Temperature dependent time-integrated and time-resolved PL spectroscopies resulted in the thermal activation energies of ∼45 meV, and the overall self-consistent calculation of the band parameters based on the measured physical values confirmed that the activation energies are due to the hole escape from the QW to the barriers. The relation of the present single carrier escape mechanism with the other escape mechanisms reported with other material systems was discussed based on the estimated band offset. The relation of the present thermal hole escape to the Auger recombination was also discussed. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4789374

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  • Carrier dynamics and photoluminescence quenching mechanism of strained InGaSb/AlGaSb quantum wells 査読

    Nahid A. Jahan, Claus Hermannstädter, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Hidekazu Kumano, Ikuo Suemune

    Journal of Applied Physics   113 ( 5 )   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    GaSb based quantum wells (QWs) show promising optical properties in near-infrared spectral range. In this paper, we present photoluminescence (PL) spectroscopies of InxGa1-xSb/AlyGa 1-ySb QWs and discuss the possible thermal quenching and non-radiative carrier recombination mechanisms of the QW structures. The In and Al concentrations as well as the QW thicknesses were precisely determined with the X-ray diffraction measurements. Temperature dependent time-integrated and time-resolved PL spectroscopies resulted in the thermal activation energies of ∼45 meV, and the overall self-consistent calculation of the band parameters based on the measured physical values confirmed that the activation energies are due to the hole escape from the QW to the barriers. The relation of the present single carrier escape mechanism with the other escape mechanisms reported with other material systems was discussed based on the estimated band offset. The relation of the present thermal hole escape to the Auger recombination was also discussed. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4789374

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  • Carrier dynamics and photoluminescence quenching mechanism of strained InGaSb/AlGaSb quantum wells 査読

    Nahid A. Jahan, Claus Hermannstädter, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Hidekazu Kumano, Ikuo Suemune

    Journal of Applied Physics   113 ( 5 )   053505-1 - 7   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    GaSb based quantum wells (QWs) show promising optical properties in near-infrared spectral range. In this paper, we present photoluminescence (PL) spectroscopies of InxGa1-xSb/AlyGa 1-ySb QWs and discuss the possible thermal quenching and non-radiative carrier recombination mechanisms of the QW structures. The In and Al concentrations as well as the QW thicknesses were precisely determined with the X-ray diffraction measurements. Temperature dependent time-integrated and time-resolved PL spectroscopies resulted in the thermal activation energies of ∼45 meV, and the overall self-consistent calculation of the band parameters based on the measured physical values confirmed that the activation energies are due to the hole escape from the QW to the barriers. The relation of the present single carrier escape mechanism with the other escape mechanisms reported with other material systems was discussed based on the estimated band offset. The relation of the present thermal hole escape to the Auger recombination was also discussed. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4789374

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  • Spectral and Transient Luminescence Measurements on GaSb/AlGaSb Quantum Wells Grown on GaSb/GaAs Heterojunctions with and without Interfacial Misfit Arrays 査読

    Jahan Nahid A., Ahirwar Pankaj, Rotter Thomas J., Balakrishnan Ganesh, Kumano Hidekazu, Suemune Ikuo

    Japanese journal of applied physics : JJAP   52 ( 2 )   22101 - 1-7   2013年2月

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    記述言語:英語   出版者・発行元:The Japan Society of Applied Physics  

    DOI: 10.7567/JJAP.52.022101

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    その他リンク: http://hdl.handle.net/2115/52473

  • Spectral and Transient Luminescence Measurements on GaSb/AlGaSb Quantum Wells Grown on GaSb/GaAs Heterojunctions with and without Interfacial Misfit Arrays 査読

    Nahid A. Jahan, Pankaj Ahirwar, Thomas J. Rotter, Ganesh Balakrishnan, Hidekazu Kumano, Ikuo Suemune

    JAPANESE JOURNAL OF APPLIED PHYSICS   52 ( 2 )   022101-1 - 7   2013年2月

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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 SOC APPLIED PHYSICS  

    Growth of 90 degrees interfacial-misfit-dislocation (IMF) array at heterointerfaces offers low dislocation densities in highly mismatched heterostructures such as GaSb/GaAs. We investigated time-integrated and time-resolved photoluminescence (PL) properties of a GaSb/AlGaSb quantum well (QW) structure grown on (001) GaAs substrate with and without IMF array at the GaSb-buffer/GaAs interface. Our observation reveals that the low-temperature PL from the QW with IMF is twice more intense than that of the QW without IMF, indicating higher quantum efficiency with IMF. The QW with IMF also exhibited the band filling effect at higher excitation power revealed from the spectrally resolved PL decay measurements. These results are the indication of subdued dislocation density with the IMF growth mode. Our PL measurement results along with supportive band-structure calculation of the GaSb/AlGaSb QW show that the luminescence efficiency of the present QW structure is limited by the hole leakage at elevated temperature. Therefore the IMF effect will be more clearly demonstrated by replacing the heterostructure with the one with higher band-offsets. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.52.022101

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  • Spectral and Transient Luminescence Measurements on GaSb/AlGaSb Quantum Wells Grown on GaSb/GaAs Heterojunctions with and without Interfacial Misfit Arrays 査読

    Nahid A. Jahan, Pankaj Ahirwar, Thomas J. Rotter, Ganesh Balakrishnan, Hidekazu Kumano, Ikuo Suemune

    JAPANESE JOURNAL OF APPLIED PHYSICS   52 ( 2 )   2013年2月

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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 SOC APPLIED PHYSICS  

    Growth of 90 degrees interfacial-misfit-dislocation (IMF) array at heterointerfaces offers low dislocation densities in highly mismatched heterostructures such as GaSb/GaAs. We investigated time-integrated and time-resolved photoluminescence (PL) properties of a GaSb/AlGaSb quantum well (QW) structure grown on (001) GaAs substrate with and without IMF array at the GaSb-buffer/GaAs interface. Our observation reveals that the low-temperature PL from the QW with IMF is twice more intense than that of the QW without IMF, indicating higher quantum efficiency with IMF. The QW with IMF also exhibited the band filling effect at higher excitation power revealed from the spectrally resolved PL decay measurements. These results are the indication of subdued dislocation density with the IMF growth mode. Our PL measurement results along with supportive band-structure calculation of the GaSb/AlGaSb QW show that the luminescence efficiency of the present QW structure is limited by the hole leakage at elevated temperature. Therefore the IMF effect will be more clearly demonstrated by replacing the heterostructure with the one with higher band-offsets. (C) 2013 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.52.022101

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  • Temperature dependent carrier dynamics in telecommunication band InAs quantum dots and dashes grown on InP substrates 査読

    Nahid A. Jahan, Claus Hermannstaedter, Jae-Hoon Huh, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Kouichi Akahane, Masahide Sasaki, Hidekazu Kumano, Ikuo Suemune

    JOURNAL OF APPLIED PHYSICS   113 ( 3 )   033506-1 - 11   2013年1月

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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  

    InAs quantum dots (QDs) grown on InP substrates can be used as light emitters in the telecommunication bands. In this paper, we present optical characterization of high-density circular quantum dots (QDots) grown on InP(311)B substrates and elongated dots (QDashes) grown on InP(001) substrates. We study the charge carrier transfer and luminescence thermal quenching mechanisms of the QDots and QDashes by investigating the temperature dependence of their time-integrated and time-resolved photoluminescence properties. This results in two different contributions of the thermal activation energies. The larger activation energies are attributed to the carrier escape to the barrier layer and the wetting layer (WL) from QDots and QDashes, respectively. The smaller activation energies are found to be originated from inter-dot/dash carrier transfer via coupled excited states. The variation of the average oscillator strength associated with the carrier re-distribution is discussed. The relation of the two activation energies is also quantitatively studied with the measurements of excited-state and ground-state energy separations. Finally, we show an approach to isolate individual quantum dots or dashes in a suitable nanostructure. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775768]

    DOI: 10.1063/1.4775768

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  • Temperature dependent carrier dynamics in telecommunication band InAs quantum dots and dashes grown on InP substrates 査読

    Nahid A. Jahan, Claus Hermannstaedter, Jae-Hoon Huh, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Kouichi Akahane, Masahide Sasaki, Hidekazu Kumano, Ikuo Suemune

    JOURNAL OF APPLIED PHYSICS   113 ( 3 )   033506-1 - 11   2013年1月

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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  

    InAs quantum dots (QDs) grown on InP substrates can be used as light emitters in the telecommunication bands. In this paper, we present optical characterization of high-density circular quantum dots (QDots) grown on InP(311)B substrates and elongated dots (QDashes) grown on InP(001) substrates. We study the charge carrier transfer and luminescence thermal quenching mechanisms of the QDots and QDashes by investigating the temperature dependence of their time-integrated and time-resolved photoluminescence properties. This results in two different contributions of the thermal activation energies. The larger activation energies are attributed to the carrier escape to the barrier layer and the wetting layer (WL) from QDots and QDashes, respectively. The smaller activation energies are found to be originated from inter-dot/dash carrier transfer via coupled excited states. The variation of the average oscillator strength associated with the carrier re-distribution is discussed. The relation of the two activation energies is also quantitatively studied with the measurements of excited-state and ground-state energy separations. Finally, we show an approach to isolate individual quantum dots or dashes in a suitable nanostructure. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775768]

    DOI: 10.1063/1.4775768

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  • Temperature dependent carrier dynamics in telecommunication band InAs quantum dots and dashes grown on InP substrates 査読

    Nahid A. Jahan, Claus Hermannstaedter, Jae-Hoon Huh, Hirotaka Sasakura, Thomas J. Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Kouichi Akahane, Masahide Sasaki, Hidekazu Kumano, Ikuo Suemune

    JOURNAL OF APPLIED PHYSICS   113 ( 3 )   2013年1月

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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  

    InAs quantum dots (QDs) grown on InP substrates can be used as light emitters in the telecommunication bands. In this paper, we present optical characterization of high-density circular quantum dots (QDots) grown on InP(311)B substrates and elongated dots (QDashes) grown on InP(001) substrates. We study the charge carrier transfer and luminescence thermal quenching mechanisms of the QDots and QDashes by investigating the temperature dependence of their time-integrated and time-resolved photoluminescence properties. This results in two different contributions of the thermal activation energies. The larger activation energies are attributed to the carrier escape to the barrier layer and the wetting layer (WL) from QDots and QDashes, respectively. The smaller activation energies are found to be originated from inter-dot/dash carrier transfer via coupled excited states. The variation of the average oscillator strength associated with the carrier re-distribution is discussed. The relation of the two activation energies is also quantitatively studied with the measurements of excited-state and ground-state energy separations. Finally, we show an approach to isolate individual quantum dots or dashes in a suitable nanostructure. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775768]

    DOI: 10.1063/1.4775768

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  • Single-Photon Emission in Telecommunication Band from an InAs Quantum Dot in a Pillar Structure 査読

    X. Liu, N. Kobayashi, K. Akahane, M. Sasaki, H. Kumano, I. Suemune

    2013 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM)   2013年

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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 report on the experimental demonstration of single-photon source based on a single InAs quantum dot emitting in the telecommunication band. The low-density quantum dots grown by epitaxial method are embedded in an as-etched pillar structure. Photoluminescence spectrum of a single InAs quantum dot exhibits intense and narrow emission lines. Photon antibunching behavior is clearly observed using superconducting single-photon detectors with high sensitivity, which indicates the single-photon emission.

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  • 単一光子光源評価のための強度自己相関関数の一般化 : 量子2準位系における分布相関の効果

    熊野 英和, 中島 秀朗, 末宗 幾夫

    量子情報技術研究会資料   27   69 - 72   2012年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:量子情報技術時限研究専門委員会  

    CiNii Article

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  • Anomalous dip observed in intensity autocorrelation function as an inherent nature of single-photon emitters 査読

    H. Nakajima, H. Kumano, H. Iijima, I. Suemune

    APPLIED PHYSICS LETTERS   101 ( 16 )   161107-1 - 4   2012年10月

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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  

    We report the observation of an anomalous antibunching dip in intensity autocorrelation function with photon correlation measurements on a single-photon emitter (SPE). We show that the anomalous dip observed is a manifestation of quantum nature of SPEs. Taking population dynamics in a quantum two-level system into account correctly, we redefine intensity autocorrelation function. This is of primary importance for precisely evaluating the lowest-level probability of multiphoton generation in SPEs toward realizing versatile pure SPEs for quantum information and communication. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4760222]

    DOI: 10.1063/1.4760222

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  • Anomalous dip observed in intensity autocorrelation function as an inherent nature of single-photon emitters 査読

    H. Nakajima, H. Kumano, H. Iijima, I. Suemune

    APPLIED PHYSICS LETTERS   101 ( 16 )   161107-1 - 4   2012年10月

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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  

    We report the observation of an anomalous antibunching dip in intensity autocorrelation function with photon correlation measurements on a single-photon emitter (SPE). We show that the anomalous dip observed is a manifestation of quantum nature of SPEs. Taking population dynamics in a quantum two-level system into account correctly, we redefine intensity autocorrelation function. This is of primary importance for precisely evaluating the lowest-level probability of multiphoton generation in SPEs toward realizing versatile pure SPEs for quantum information and communication. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4760222]

    DOI: 10.1063/1.4760222

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  • Anomalous dip observed in intensity autocorrelation function as an inherent nature of single-photon emitters 査読

    Hideaki Nakajima, Hidekazu Kumano, Hitoshi Iijima, Ikuo Suemune

    APPLIED PHYSICS LETTERS   101 ( 16 )   2012年7月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    We report the observation of an anomalous antibunching dip in intensity
    autocorrelation function with photon correlation measurements on a
    single-photon emitter (SPE). We show that the anomalous dip observed is a
    manifestation of quantum nature of SPEs. Taking population dynamics in a
    quantum two-level system into account correctly, we redefine intensity
    autocorrelation function. This is of primary importance for precisely
    evaluating the lowest-level probability of multiphoton generation in SPEs
    toward realizing versatile pure SPEs for quantum information and communication.

    DOI: 10.1063/1.4760222

    Web of Science

    arXiv

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    その他リンク: http://arxiv.org/pdf/1207.6472v1

  • Longitudinal and transverse exciton-spin relaxation in a single InAsP quantum dot embedded inside a standing InP nanowire using photoluminescence spectroscopy 査読

    H. Sasakura, C. Hermannstädter, S. N. Dorenbos, N. Akopian, M. P. Van Kouwen, J. Motohisa, Y. Kobayashi, H. Kumano, K. Kondo, K. Tomioka, T. Fukui, I. Suemune, V. Zwiller

    Physical Review B - Condensed Matter and Materials Physics   85 ( 7 )   2012年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated the optical properties of a single InAsP quantum dot embedded in a standing InP nanowire. Elongation of the transverse exciton-spin relaxation time of the exciton state with decreasing excitation power was observed by first-order photon correlation measurements. This behavior is well explained by the motional narrowing mechanism induced by Gaussian fluctuations of environmental charges in the nanowire. The longitudinal exciton-spin relaxation time is evaluated by the degree of the random polarization of emission originating from exciton states confined in a single-nanowire quantum dot by using Mueller calculus based on Stokes parameters representation. The reduction in the random polarization component with decreasing excitation power is caused by suppression of the exchange interaction of electron and hole due to an optically induced internal electric field by the dipoles at the wurtzite and zinc-blende heterointerfaces in the InP nanowire. © 2012 American Physical Society.

    DOI: 10.1103/PhysRevB.85.075324

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  • Longitudinal and transverse exciton-spin relaxation in a single InAsP quantum dot embedded inside a standing InP nanowire using photoluminescence spectroscopy 査読

    H. Sasakura, C. Hermannstaedter, S. N. Dorenbos, N. Akopian, M. P. van Kouwen, J. Motohisa, Y. Kobayashi, H. Kumano, K. Kondo, K. Tomioka, T. Fukui, I. Suemune, V. Zwiller

    PHYSICAL REVIEW B   85 ( 7 )   075324   2012年2月

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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 PHYSICAL SOC  

    We have investigated the optical properties of a single InAsP quantum dot embedded in a standing InP nanowire. Elongation of the transverse exciton-spin relaxation time of the exciton state with decreasing excitation power was observed by first-order photon correlation measurements. This behavior is well explained by the motional narrowing mechanism induced by Gaussian fluctuations of environmental charges in the nanowire. The longitudinal exciton-spin relaxation time is evaluated by the degree of the random polarization of emission originating from exciton states confined in a single-nanowire quantum dot by using Mueller calculus based on Stokes parameters representation. The reduction in the random polarization component with decreasing excitation power is caused by suppression of the exchange interaction of electron and hole due to an optically induced internal electric field by the dipoles at the wurtzite and zinc-blende heterointerfaces in the InP nanowire.

    DOI: 10.1103/PhysRevB.85.075324

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  • Longitudinal and Transverse Exciton Spin Relaxation in Single InP/InAsP/InP Nanowire Quantum Dots 査読

    H. Sasakura, C. Hermannstädter, S. N. Dorenbos, N. Akopian, M. P. van Kouwen, J. Motohisa, Y. Kobayashi, H. Kumano, K. Kondo, K. Tomioka, T. Fukui, I. Suemune, V. Zwiller

    Phys. Rev. B   85   075324   2012年2月

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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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  • Longitudinal and transverse exciton-spin relaxation in a single InAsP quantum dot embedded inside a standing InP nanowire using photoluminescence spectroscopy 査読

    H. Sasakura, C. Hermannstaedter, S. N. Dorenbos, N. Akopian, M. P. van Kouwen, J. Motohisa, Y. Kobayashi, H. Kumano, K. Kondo, K. Tomioka, T. Fukui, I. Suemune, V. Zwiller

    PHYSICAL REVIEW B   85 ( 7 )   075324   2012年2月

     詳細を見る

    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 PHYSICAL SOC  

    We have investigated the optical properties of a single InAsP quantum dot embedded in a standing InP nanowire. Elongation of the transverse exciton-spin relaxation time of the exciton state with decreasing excitation power was observed by first-order photon correlation measurements. This behavior is well explained by the motional narrowing mechanism induced by Gaussian fluctuations of environmental charges in the nanowire. The longitudinal exciton-spin relaxation time is evaluated by the degree of the random polarization of emission originating from exciton states confined in a single-nanowire quantum dot by using Mueller calculus based on Stokes parameters representation. The reduction in the random polarization component with decreasing excitation power is caused by suppression of the exchange interaction of electron and hole due to an optically induced internal electric field by the dipoles at the wurtzite and zinc-blende heterointerfaces in the InP nanowire.

    DOI: 10.1103/PhysRevB.85.075324

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  • Cooper-Pair Radiative Recombination in Semiconductor Heterostructures: Impact on Quantum Optics and Optoelectronics 査読

    Ikuo Suemune, Hirotaka Sasakura, Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Yasuhiro Asano, Ryotaro Inoue, Hideaki Takayanagi, Eiichi Hanamura, Jae-Hoon Huh, Claus Hermannstaedter, Satoru Odashima, Hidekazu Kumano

    JAPANESE JOURNAL OF APPLIED PHYSICS   51 ( 1 )   2012年1月

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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 injection of Cooper pairs into a normal medium such as a semiconductor is known as the proximity effect at the superconductor/normal interface. We confirm this injection as well as the contribution of Cooper pairs to a drastic enhancement of inter-band optical transitions in semiconductor heterostructures. In this paper we investigate and clarify the relation of internal quantum efficiencies and radiative lifetimes in Cooper-pair light emitting diodes (CP-LEDs). A quantitative description of the dynamic photon generation processes is given, and the contribution of the Cooper-pair recombination relative to normal-electron recombination in CP-LEDs is discussed in detail. (C) 2012 The Japan Society of Applied Physics

    DOI: 10.1143/JJAP.51.010114

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  • Photon-pair generation based on superconductivity 査読

    Ikuo Suemune, Hirotaka Sasakura, Yasuhiro Asano, Hidekazu Kumano, Ryotaro Inoue, Kazunori Tanaka, Tatsushi Akazaki, Hideaki Takayanagi

    IEICE ELECTRONICS EXPRESS   9 ( 14 )   1184 - 1200   2012年

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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:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    Superconductivity and optoelectronics have developed almost independently and had very rare interactions with each other in science and technologies. However recent interdisciplinary research opens up the potential for developing new optoelectronic devices. This review paper presents our recent theoretical and experimental demonstrations that superconductivity significantly modifies and accelerates photon generation processes. We have prepared superconducting light emitting diodes (LEDs) emitting at similar to 1.6-mu m optical-fiber communication band for the experimental demonstrations. This new-type LED operation is based on a unique physics related to Cooper-pair interband transition in a semiconductor, and further research leads to the solid-state simultaneously generated photon-pair sources for the potential application in quantum information and communication.

    DOI: 10.1587/elex.9.1184

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  • Photon-pair generation based on superconductivity 査読

    Ikuo Suemune, Hirotaka Sasakura, Yasuhiro Asano, Hidekazu Kumano, Ryotaro Inoue, Kazunori Tanaka, Tatsushi Akazaki, Hideaki Takayanagi

    IEICE ELECTRONICS EXPRESS   9 ( 14 )   1184 - 1200   2012年

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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:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    Superconductivity and optoelectronics have developed almost independently and had very rare interactions with each other in science and technologies. However recent interdisciplinary research opens up the potential for developing new optoelectronic devices. This review paper presents our recent theoretical and experimental demonstrations that superconductivity significantly modifies and accelerates photon generation processes. We have prepared superconducting light emitting diodes (LEDs) emitting at similar to 1.6-mu m optical-fiber communication band for the experimental demonstrations. This new-type LED operation is based on a unique physics related to Cooper-pair interband transition in a semiconductor, and further research leads to the solid-state simultaneously generated photon-pair sources for the potential application in quantum information and communication.

    DOI: 10.1587/elex.9.1184

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  • Photon-pair generation based on superconductivity 査読

    Ikuo Suemune, Hirotaka Sasakura, Yasuhiro Asano, Hidekazu Kumano, Ryotaro Inoue, Kazunori Tanaka, Tatsushi Akazaki, Hideaki Takayanagi

    IEICE ELECTRONICS EXPRESS   9 ( 14 )   1184 - 1200   2012年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    Superconductivity and optoelectronics have developed almost independently and had very rare interactions with each other in science and technologies. However recent interdisciplinary research opens up the potential for developing new optoelectronic devices. This review paper presents our recent theoretical and experimental demonstrations that superconductivity significantly modifies and accelerates photon generation processes. We have prepared superconducting light emitting diodes (LEDs) emitting at similar to 1.6-mu m optical-fiber communication band for the experimental demonstrations. This new-type LED operation is based on a unique physics related to Cooper-pair interband transition in a semiconductor, and further research leads to the solid-state simultaneously generated photon-pair sources for the potential application in quantum information and communication.

    DOI: 10.1587/elex.9.1184

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  • Cooper-pair Radiative Recombination in Semiconductors and Its Superconductivity Impact on Optoelectronics and Quantum Optics 査読

    I. Suemune, H. Sasakura, Y. Hayashi, K. Tanaka, T. Akazaki, Y. Asano, R. Inoue, H. Takayanagi, E. Hanamura, J.-H. Huh, C. Hermannstädter, S. Odashima, H. Kumano

    Jpn. J. App. Phys.   51   010114   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JJAP.51.010114

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  • 超伝導による量子もつれ光子対源の可能性とその展望

    末宗幾夫, 笹倉弘理, 浅野泰寛, 熊野英和

    応用物理   81 ( 12 )   1029 - 1033   2012年

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    記述言語:日本語   出版者・発行元:応用物理学会  

    CiNii Article

    J-GLOBAL

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  • Origin of the blueshift of photoluminescence in a type-II heterostructure 査読

    Masafumi Jo, Mitsuru Sato, Souta Miyamura, Hirotaka Sasakura, Hidekazu Kumano, Ikuo Suemune

    Nanoscale Research Letters   7   654   2012年

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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:1  

    Blueshifts of luminescence observed in type-II heterostructures are quantitatively examined in terms of a self-consistent approach including excitonic effects. This analysis shows that the main contribution to the blueshift originates from the well region rather than the variation of triangular potentials formed in the barrier region. The power law for the blueshift, ΔEPL ∝ Plaserm, from m = 1/2 for lower excitation Plaser to m = 1/4 for higher excitation, is obtained from the calculated results combined with a rate equation analysis, which also covers the previously believed m = 1/3 power law within a limited excitation range. The present power law is consistent with the blueshift observed in a GaAsSb/GaAs quantum well. © 2012 Jo et al.

    DOI: 10.1186/1556-276X-7-654

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    PubMed

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  • Cooper-pair Radiative Recombination in Semiconductors and Its Superconductivity Impact on Optoelectronics and Quantum Optics 査読

    I. Suemune, H. Sasakura, Y. Hayashi, K. Tanaka, T. Akazaki, Y. Asano, R. Inoue, H. Takayanagi, E. Hanamura, J.-H. Huh, C. Hermannstädter, S. Odashima, H. Kumano

    Jpn. J. App. Phys.   51   010114   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JJAP.51.010114

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  • Enhanced Photon Generation in a Nb/n - InGaAs/p - InP Superconductor/Semiconductor-Diode Light Emitting Device 査読

    H. Sasakura, S. Kuramitsu, Y. Hayashi, K. Tanaka, T. Akazaki, E. Hanamura, R. Inoue, H. Takayanagi, Y. Asano, C. Hermannstaedter, H. Kumano, I. Suemune

    PHYSICAL REVIEW LETTERS   107 ( 15 )   157403-1 - 5   2011年10月

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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 PHYSICAL SOC  

    We experimentally demonstrate Cooper pairs' drastic enhancement of the band-to-band radiative recombination rate in a semiconductor. Electron Cooper pairs injected from a superconducting electrode into an active layer by the proximity effect recombine with holes injected from a p-type electrode. The recombination of a Cooper pair with p-type carriers dramatically increases the photon generation probability of a light-emitting diode in the optical-fiber communication band. The measured radiative decay time rapidly decreases with decreasing temperature below the superconducting transition temperature of the niobium electrodes. Our results indicate the possibility to open up new interdisciplinary fields between superconductivity and optoelectronics.

    DOI: 10.1103/PhysRevLett.107.157403

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  • Enhanced Photon Generation in a Nb/n - InGaAs/p - InP Superconductor/Semiconductor-Diode Light Emitting Device 査読

    H. Sasakura, S. Kuramitsu, Y. Hayashi, K. Tanaka, T. Akazaki, E. Hanamura, R. Inoue, H. Takayanagi, Y. Asano, C. Hermannstaedter, H. Kumano, I. Suemune

    PHYSICAL REVIEW LETTERS   107 ( 15 )   157403-1 - 5   2011年10月

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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 PHYSICAL SOC  

    We experimentally demonstrate Cooper pairs' drastic enhancement of the band-to-band radiative recombination rate in a semiconductor. Electron Cooper pairs injected from a superconducting electrode into an active layer by the proximity effect recombine with holes injected from a p-type electrode. The recombination of a Cooper pair with p-type carriers dramatically increases the photon generation probability of a light-emitting diode in the optical-fiber communication band. The measured radiative decay time rapidly decreases with decreasing temperature below the superconducting transition temperature of the niobium electrodes. Our results indicate the possibility to open up new interdisciplinary fields between superconductivity and optoelectronics.

    DOI: 10.1103/PhysRevLett.107.157403

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  • Enhanced Photon Generation in a Nb/n - InGaAs/p - InP Superconductor/Semiconductor-Diode Light Emitting Device 査読

    H. Sasakura, S. Kuramitsu, Y. Hayashi, K. Tanaka, T. Akazaki, E. Hanamura, R. Inoue, H. Takayanagi, Y. Asano, C. Hermannstaedter, H. Kumano, I. Suemune

    PHYSICAL REVIEW LETTERS   107 ( 15 )   157403-1 - 5   2011年10月

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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 PHYSICAL SOC  

    We experimentally demonstrate Cooper pairs' drastic enhancement of the band-to-band radiative recombination rate in a semiconductor. Electron Cooper pairs injected from a superconducting electrode into an active layer by the proximity effect recombine with holes injected from a p-type electrode. The recombination of a Cooper pair with p-type carriers dramatically increases the photon generation probability of a light-emitting diode in the optical-fiber communication band. The measured radiative decay time rapidly decreases with decreasing temperature below the superconducting transition temperature of the niobium electrodes. Our results indicate the possibility to open up new interdisciplinary fields between superconductivity and optoelectronics.

    DOI: 10.1103/PhysRevLett.107.157403

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  • Enhanced Photon Generation in a Nb/n - InGaAs/p - InP Superconductor/Semiconductor-Diode Light Emitting Device 査読

    H. Sasakura, S. Kuramitsu, Y. Hayashi, K. Tanaka, T. Akazaki, E. Hanamura, R. Inoue, H. Takayanagi, Y. Asano, C. Hermannstaedter, H. Kumano, I. Suemune

    PHYSICAL REVIEW LETTERS   107 ( 15 )   2011年10月

     詳細を見る

    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 PHYSICAL SOC  

    We experimentally demonstrate Cooper pairs' drastic enhancement of the band-to-band radiative recombination rate in a semiconductor. Electron Cooper pairs injected from a superconducting electrode into an active layer by the proximity effect recombine with holes injected from a p-type electrode. The recombination of a Cooper pair with p-type carriers dramatically increases the photon generation probability of a light-emitting diode in the optical-fiber communication band. The measured radiative decay time rapidly decreases with decreasing temperature below the superconducting transition temperature of the niobium electrodes. Our results indicate the possibility to open up new interdisciplinary fields between superconductivity and optoelectronics.

    DOI: 10.1103/PhysRevLett.107.157403

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  • 量子情報通信のための単一光子・量子もつれ光子対光源

    末宗 幾夫, 熊野 英和, 笹倉 弘理

    光学   40 ( 9 )   472 - 477   2011年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:応用物理学会分科会日本光学会  

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  • Characterization of two-photon polarization mixed states generated from entangled-classical hybrid photon source 査読

    H. Kumano, K. Matsuda, S. Ekuni, H. Sasakura, I. Suemune

    OPTICS EXPRESS   19 ( 15 )   14249 - 14259   2011年7月

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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  

    We experimentally prepare bi-photon mixed states in polarization employing an entangled-classical hybrid photon emitter which can properly model solid-state entangled photon sources with uncorrelated background photons. Polarization-uncorrelated photon pairs in totally mixed (TM) states are embodied with classical thermal radiation, while the polarization-entangled ones in a Bell state are generated by conventional parametric down conversion. The bi-photon states generated from the hybrid photon emitter are characterized in terms of a linear entropy-tangle plane, which reveals the formation of two-qubit Werner states. We also propose a direct way for evaluating the Werner states by means of minimal coincidence counts measurements. This simple method can be widely applicable in examining the bi-photon states from solid-state entangled photon sources, in which the polarization-entangled photon pairs have temporal correlation while the background photons in the TM states do not. (C)2011 Optical Society of America

    DOI: 10.1364/OE.19.014249

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  • Characterization of two-photon polarization mixed states generated from entangled-classical hybrid photon source 査読

    H. Kumano, K. Matsuda, S. Ekuni, H. Sasakura, I. Suemune

    OPTICS EXPRESS   19 ( 15 )   14249 - 14259   2011年7月

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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  

    We experimentally prepare bi-photon mixed states in polarization employing an entangled-classical hybrid photon emitter which can properly model solid-state entangled photon sources with uncorrelated background photons. Polarization-uncorrelated photon pairs in totally mixed (TM) states are embodied with classical thermal radiation, while the polarization-entangled ones in a Bell state are generated by conventional parametric down conversion. The bi-photon states generated from the hybrid photon emitter are characterized in terms of a linear entropy-tangle plane, which reveals the formation of two-qubit Werner states. We also propose a direct way for evaluating the Werner states by means of minimal coincidence counts measurements. This simple method can be widely applicable in examining the bi-photon states from solid-state entangled photon sources, in which the polarization-entangled photon pairs have temporal correlation while the background photons in the TM states do not. (C)2011 Optical Society of America

    DOI: 10.1364/OE.19.014249

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  • H. Kumano, K. Matsuda, S. Ekuni, H. Sasakura, and I. Suemune 査読

    Characterization of, wo-photon, polarization mixe, states generated, from entangled-classical hybrid photon source

    Opt. Express   19   14249 - 14259   2011年

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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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  • Drastic enhancement of interband optical transition probability with electron pairing in semiconductors 査読

    I. Suemune, H. Sasakura, C. Hermannstädter, J. H. Huh, Y. Asano, K. Tanaka, T. Akazaki, H. Kumano

    2011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf.   1119 - 1120   2011年

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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)  

    Interband optical transition probability (usually given as the B coefficient) is normally fixed for a given semiconductor structure. Here we will show the B coefficient can be drastically enhanced effectively with electron injection in paired states. © 2011 IEEE.

    DOI: 10.1109/IQEC-CLEO.2011.6193687

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  • InP/InAsP/InPナノワイヤー量子ドットの局在励起子発光の偏光状態

    笹倉弘理, DORENBOS S. N., VAN KOUWEN M. P., AKOPIAN N., ZWILLER V., 小林靖典, 本久順一, 冨岡克広, 福井孝志, HERMANNSTAEDTER C., 熊野英和, 末宗幾夫

    日本物理学会講演概要集   66 ( 2 )   2011年

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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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  • H. Kumano, K. Matsuda, S. Ekuni, H. Sasakura, and I. Suemune 査読

    Characterization of, wo-photon, polarization mixe, states generated, from entangled-classical hybrid photon source

    Opt. Express   19   14249 - 14259   2011年

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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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  • Strongly suppressed multi-photon generation from a single quantum dot in a metal-embedded structure

    Hideaki Nakajima, Shingo Ekuni, Hidekazu Kumano, Yasuhiro Idutsu, Souta Miyamura, Daimotsu Kato, Sotaro Ida, Hirotaka Sasakura, Ikuo Suemune

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2   8 ( 2 )   337 - 339   2011年

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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:WILEY-V C H VERLAG GMBH  

    We introduce a novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for practical use, single-photon purity with g(2)(0) as low as 0.015 has been measured. The extremely small semiconductor volume of the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation from a single quantum dot at a rate of up to 6.4 million per second has been achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201000519

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  • Strongly suppressed multi-photon generation from a single quantum dot in a metal-embedded structure

    Hideaki Nakajima, Shingo Ekuni, Hidekazu Kumano, Yasuhiro Idutsu, Souta Miyamura, Daimotsu Kato, Sotaro Ida, Hirotaka Sasakura, Ikuo Suemune

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2   8 ( 2 )   337 - 339   2011年

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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:WILEY-V C H VERLAG GMBH  

    We introduce a novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for practical use, single-photon purity with g(2)(0) as low as 0.015 has been measured. The extremely small semiconductor volume of the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation from a single quantum dot at a rate of up to 6.4 million per second has been achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201000519

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  • Strongly suppressed multi-photon generation from a single quantum dot in a metal-embedded structure 査読

    Hideaki Nakajima, Shingo Ekuni, Hidekazu Kumano, Yasuhiro Idutsu, Souta Miyamura, Daimotsu Kato, Sotaro Ida, Hirotaka Sasakura, Ikuo Suemune

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2   8 ( 2 )   337 - 339   2011年

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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:WILEY-V C H VERLAG GMBH  

    We introduce a novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for practical use, single-photon purity with g(2)(0) as low as 0.015 has been measured. The extremely small semiconductor volume of the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation from a single quantum dot at a rate of up to 6.4 million per second has been achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201000519

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  • Strongly suppressed multi-photon generation from a single quantum dot in a metal-embedded structure 査読

    Hideaki Nakajima, Shingo Ekuni, Hidekazu Kumano, Yasuhiro Idutsu, Souta Miyamura, Daimotsu Kato, Sotaro Ida, Hirotaka Sasakura, Ikuo Suemune

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2   8 ( 2 )   337 - 339   2011年

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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:WILEY-V C H VERLAG GMBH  

    We introduce a novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for practical use, single-photon purity with g(2)(0) as low as 0.015 has been measured. The extremely small semiconductor volume of the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation from a single quantum dot at a rate of up to 6.4 million per second has been achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201000519

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  • 超伝導発光ダイオードにおける電子クーパー対の寄与

    笹倉 弘理, 田中 和典, 許 載勲, 赤崎 達志, 熊野 英和, 末宗 幾夫

    電子情報通信学会技術研究報告. LQE, レーザ・量子エレクトロニクス   110 ( 353 )   39 - 42   2010年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    超伝導電極を付加した通信波長帯の光子を放出する発光ダイオード構造を作製し,電子クーパー対の発光再結合過程への寄与を調べた.本構造を低電流で駆動させ,発光再結合寿命の温度依存性を測定したところ,超伝導転移温度以下で顕著な短縮効果を確認した.これは超伝導体から半導体へ近接効果により侵入した電子クーパー対が振動子強度を増強したことによるものである.

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  • Position controlled nanowires for infrared single photon emission 査読

    S. N. Dorenbos, H. Sasakura, M. P. van Kouwen, N. Akopian, S. Adachi, N. Namekata, M. Jo, J. Motohisa, Y. Kobayashi, K. Tomioka, T. Fukui, S. Inoue, H. Kumano, C. M. Natarajan, R. H. Hadfield, T. Zijlstra, T. M. Klapwijk, V. Zwiller, I. Suemune

    APPLIED PHYSICS LETTERS   97 ( 17 )   2010年10月

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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  

    We report the experimental demonstration of single-photon and cascaded photon pair emission in the infrared, originating from a single InAsP quantum dot embedded in a standing InP nanowire. A regular array of nanowires is fabricated by epitaxial growth on an electron-beam patterned substrate. Photoluminescence spectra taken on single quantum dots show narrow emission lines. Superconducting single photon detectors, which have a higher sensitivity than avalanche photodiodes in the infrared, enable us to measure auto and cross correlations. Clear antibunching is observed [g((2))(0) = 0.12] and we show a biexciton-exciton cascade, which can be used to create entangled photon pairs. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506499]

    DOI: 10.1063/1.3506499

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  • First-order photon interference of a single photon from a single quantum dot 査読

    S. Ekuni, H. Nakajima, H. Sasakura, I. Suemune, H. Kumano

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   42 ( 10 )   2536 - 2539   2010年9月

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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:ELSEVIER SCIENCE BV  

    Photon interference indicating wave-like nature of a single photon emitted from a single quantum dot is demonstrated. Photon state as a superposition of two orthogonal linear polarization modes is prepared inside a solid-state single photon source, which causes the first-order interference analogous to the Young&apos;s double slit experiment. The lack of which-mode information is essential for observing the single photon interference. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physe.2009.11.029

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  • First-order photon interference of a single photon from a single quantum dot

    S. Ekuni, H. Nakajima, H. Sasakura, I. Suemune, H. Kumano

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   42 ( 10 )   2536 - 2539   2010年9月

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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:ELSEVIER SCIENCE BV  

    Photon interference indicating wave-like nature of a single photon emitted from a single quantum dot is demonstrated. Photon state as a superposition of two orthogonal linear polarization modes is prepared inside a solid-state single photon source, which causes the first-order interference analogous to the Young&apos;s double slit experiment. The lack of which-mode information is essential for observing the single photon interference. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physe.2009.11.029

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  • First-order photon interference of a single photon from a single quantum dot

    S. Ekuni, H. Nakajima, H. Sasakura, I. Suemune, H. Kumano

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   42 ( 10 )   2536 - 2539   2010年9月

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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:ELSEVIER SCIENCE BV  

    Photon interference indicating wave-like nature of a single photon emitted from a single quantum dot is demonstrated. Photon state as a superposition of two orthogonal linear polarization modes is prepared inside a solid-state single photon source, which causes the first-order interference analogous to the Young&apos;s double slit experiment. The lack of which-mode information is essential for observing the single photon interference. (C) 2009 Elsevier B.V. All rights reserved.

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  • 金属埋め込みInAs量子ドットからの高効率単一光子発生

    中島 秀朗, 江国 晋吾, 熊野 英和, 井筒 康洋, 飯島 仁史, 笹倉 弘理, 末宗 幾夫

    電子情報通信学会技術研究報告. LQE, レーザ・量子エレクトロニクス   110 ( 103 )   11 - 14   2010年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    量子情報分野への応用に向けた量子ドットの研究において、量子ドットを含む半導体ピラー構造を金属層中に埋め込む金属埋め込み構造を新規に提案し、その作製を行い、単一光子発生に関して単一光子純度(多光子発生の抑制)・光子取り出し効率の2つの観点から評価を行った。金属埋め込み構造による非共鳴励起下での高純度な単一光子発生、光子取出し効率の向上について報告する。

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  • 金属埋め込みInAs量子ドットからの高効率単一光子発生

    中島 秀朗, 江国 晋吾, 熊野 英和, 井筒 康洋, 飯島 仁史, 笹倉 弘理, 末宗 幾夫

    電子情報通信学会技術研究報告. OPE, 光エレクトロニクス   110 ( 102 )   11 - 14   2010年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    量子情報分野への応用に向けた量子ドットの研究において、量子ドットを含む半導体ピラー構造を金属層中に埋め込む金属埋め込み構造を新規に提案し、その作製を行い、単一光子発生に関して単一光子純度(多光子発生の抑制)・光子取り出し効率の2つの観点から評価を行った。金属埋め込み構造による非共鳴励起下での高純度な単一光子発生、光子取出し効率の向上について報告する。

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  • A Cooper-Pair Light-Emitting Diode: Temperature Dependence of Both Quantum Efficiency and Radiative Recombination Lifetime 査読

    Ikuo Suemune, Yujiro Hayashi, Shuhei Kuramitsu, Kazunori Tanaka, Tatsushi Akazaki, Hirotaka Sasakura, Ryotaro Inoue, Hideaki Takayanagi, Yasuhiro Asano, Eiichi Hanamura, Satoru Odashima, Hidekazu Kumano

    APPLIED PHYSICS EXPRESS   3 ( 5 )   2010年

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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 SOC APPLIED PHYSICS  

    A light-emitting diode (LED) in the optical-fiber communication band showed special features after replacing the n-type electrode with niobium (Nb) superconducting metal. Nb electrodes prepared on an InGaAs-based semiconductor surface formed a superconductor/semiconductor/superconductor junction, and the current-voltage characteristics exhibited both DC and AC Josephson junction properties. This was a result of the injection of electron Cooper-pairs into the n-InGaAs active layer of an LED. The drastic enhancement of the electroluminescence output observed below the Nb superconducting critical temperature, T(c), demonstrates the active role of electron Cooper-pairs in radiative recombination. Lifetime measurements of this LED and accurate evaluation of the luminescence output made it possible to estimate the radiative recombination lifetimes. A theoretical formula derived for the Cooper-pair radiative recombination accurately describes both the measured steep reduction of the radiative recombination lifetime and the observed enhancement of the internal quantum efficiency below Tc. This work will assist the development of interdisciplinary physics and new applications in superconductivity and optoelectronics. (C) 2010 The Japan Society of Applied Physics

    DOI: 10.1143/APEX.3.054001

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  • Quantum-Dot-Based Photon Emission and Media Conversion for Quantum Information Applications 査読

    H. Kumano, H. Nakajima, S. Ekuni, Y. Idutsu, H. Sasakura, I. Suemune

    ADVANCES IN MATHEMATICAL PHYSICS   2010年

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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:HINDAWI PUBLISHING CORPORATION  

    Single-photon as well as polarization-correlated photon pair emission from a single semiconductor quantum dots is demonstrated. Single photon generation and single photon-pair generation with little uncorrelated multiphoton emission and the feasibility of media conversion of the quantum states between photon polarization and electron spin are fundamental functions for quantum information applications. Mutual media conversion for the angular momentum between photon polarization and electron spin is also achieved with high fidelity via positively charged exciton state without external magnetic field. This is a clear indication that the coupling of photon polarizations and electron spins keeps secured during whole processes before photon emission. Possibility of a metal-embedded structure is demonstrated with the observation of drastic enhancement of excitation and/or collection efficiency of luminescence as well as clear antibunching of photons generated from a quantum dot.

    DOI: 10.1155/2010/391607

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  • Quantum-Dot-Based Photon Emission and Media Conversion for Quantum Information Applications

    H. Kumano, H. Nakajima, S. Ekuni, Y. Idutsu, H. Sasakura, I. Suemune

    ADVANCES IN MATHEMATICAL PHYSICS   2010   391607-1-14   2010年

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    記述言語:英語   出版者・発行元:HINDAWI PUBLISHING CORPORATION  

    Single-photon as well as polarization-correlated photon pair emission from a single semiconductor quantum dots is demonstrated. Single photon generation and single photon-pair generation with little uncorrelated multiphoton emission and the feasibility of media conversion of the quantum states between photon polarization and electron spin are fundamental functions for quantum information applications. Mutual media conversion for the angular momentum between photon polarization and electron spin is also achieved with high fidelity via positively charged exciton state without external magnetic field. This is a clear indication that the coupling of photon polarizations and electron spins keeps secured during whole processes before photon emission. Possibility of a metal-embedded structure is demonstrated with the observation of drastic enhancement of excitation and/or collection efficiency of luminescence as well as clear antibunching of photons generated from a quantum dot.

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  • Quantum-Dot-Based Photon Emission and Media Conversion for Quantum Information Applications

    H. Kumano, H. Nakajima, S. Ekuni, Y. Idutsu, H. Sasakura, I. Suemune

    ADVANCES IN MATHEMATICAL PHYSICS   2010   391607-1-14   2010年

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    記述言語:英語   出版者・発行元:HINDAWI PUBLISHING CORPORATION  

    Single-photon as well as polarization-correlated photon pair emission from a single semiconductor quantum dots is demonstrated. Single photon generation and single photon-pair generation with little uncorrelated multiphoton emission and the feasibility of media conversion of the quantum states between photon polarization and electron spin are fundamental functions for quantum information applications. Mutual media conversion for the angular momentum between photon polarization and electron spin is also achieved with high fidelity via positively charged exciton state without external magnetic field. This is a clear indication that the coupling of photon polarizations and electron spins keeps secured during whole processes before photon emission. Possibility of a metal-embedded structure is demonstrated with the observation of drastic enhancement of excitation and/or collection efficiency of luminescence as well as clear antibunching of photons generated from a quantum dot.

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  • Electron-Cooper-pair Operated Long-wavelength Light Emitting Diodes 査読

    H. Sasakura, K. Tanaka, J. -H. Huh, T. Akazaki, H. Kumano, I. Suemune

    22ND IEEE INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE   203 - +   2010年

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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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  • Spin-flip quenching in trion state mediated by optical phonons in a single quantum dot 査読

    H. Kumano, S. Ekuni, H. Kobayashi, H. Sasakura, I. Suemune, S. Adachi, S. Muto

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   246 ( 4 )   775 - 778   2009年4月

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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:WILEY-V C H VERLAG GMBH  

    High degree of preservation of spin states mediated by optical phonons is demonstrated with a positive trion state in a single quantum dot. At the optical phonon resonance suppression of spin relaxation is clearly identified as a dip structures in photoluminescence excitation spectra under cross-circularly polarize detection with respect to a pumping. As a result, distinguishably high degree of circular polarization up to similar to 0.85 is achieved in the absence of external magnetic field, which is no the case for neutral excitons with finite fine structure splitting. The absence of continuum states plays a crucial role for this observation. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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  • Spin-flip quenching in trion state mediated by optical phonons in a single quantum dot

    H. Kumano, S. Ekuni, H. Kobayashi, H. Sasakura, I. Suemune, S. Adachi, S. Muto

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   246 ( 4 )   775 - 778   2009年4月

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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:WILEY-V C H VERLAG GMBH  

    High degree of preservation of spin states mediated by optical phonons is demonstrated with a positive trion state in a single quantum dot. At the optical phonon resonance suppression of spin relaxation is clearly identified as a dip structures in photoluminescence excitation spectra under cross-circularly polarize detection with respect to a pumping. As a result, distinguishably high degree of circular polarization up to similar to 0.85 is achieved in the absence of external magnetic field, which is no the case for neutral excitons with finite fine structure splitting. The absence of continuum states plays a crucial role for this observation. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssb.200880619

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  • Spin-flip quenching in trion state mediated by optical phonons in a single quantum dot

    H. Kumano, S. Ekuni, H. Kobayashi, H. Sasakura, I. Suemune, S. Adachi, S. Muto

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   246 ( 4 )   775 - 778   2009年4月

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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:WILEY-V C H VERLAG GMBH  

    High degree of preservation of spin states mediated by optical phonons is demonstrated with a positive trion state in a single quantum dot. At the optical phonon resonance suppression of spin relaxation is clearly identified as a dip structures in photoluminescence excitation spectra under cross-circularly polarize detection with respect to a pumping. As a result, distinguishably high degree of circular polarization up to similar to 0.85 is achieved in the absence of external magnetic field, which is no the case for neutral excitons with finite fine structure splitting. The absence of continuum states plays a crucial role for this observation. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssb.200880619

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  • High photon extraction efficiency from GaAs pillar with InAs quantum dots embedded in Niobium 査読

    Daimotsu Kato, Yasuhiro Idutsu, Makoto Takada, Saki Ito, Hiroyasu Sato, Jae-Hoon Huh, Sotaro Ida, Hirotaka Sasakura, Hidekazu Kumano, Ikuo Suemune

    Proceedings of SPIE - The International Society for Optical Engineering   7393   2009年

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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)  

    We studied the novel structure for improving the emission properties of semiconductor light sources both theoretically and experimentally. The proposed structure is a semiconductor pillar buried in a metal except for one end surface of the pillar. Photons are extracted only from the air-exposed surface. The structure consists of the GaAs nanopillar structures embedded in metal and is analyzed by the finite-difference-time-domain method. InAs quantum dots buried in a GaAs pillar are assumed to be the photon emitters. Simulations are performed on GaAs pillars with different diameters buried in Niobium. Consequently, the simulation showed 75% light extraction efficiency from the pillar to air with the optimization of the structure. In addition, we experimentally measured photoluminescence intensities of up to 40 times enhancement in embedded structures compared to normal pillar structure. These are promising for future applications to overcome single photon sources. © 2009 SPIE.

    DOI: 10.1117/12.828183

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  • Exciton coherence in clean single InP/InAsP/InP nanowire quantum dots emitting in infra-red measured by Fourier spectroscopy

    H. Sasakura, H. Kumano, I. Suemune, J. Motohisa, Y. Kobayashi, M. van Kouwen, K. Tomioka, T. Fukui, N. Akopian, V. Zwiller

    16TH INTERNATIONAL CONFERENCE ON ELECTRON DYNAMICS IN SEMICONDUCTORS, OPTOELECTRONICS AND NANOSTRUCTURES (EDISON 16)   193   012132-1-4   2009年

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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:IOP PUBLISHING LTD  

    We report optical properties of InP/InAsP/InP nanowire quantum dots and single-photon Fourier spectroscopy of an exciton in a single InAsP quantum dot embedded in an InP nanowire. The coherent length of the time-averaged emission originating from the single InAsP QD was measured by a Mach-Zehnder interferometer inserted in the photoluminescence path. Effects of fluctuations in surrounding excess charges trapped in the InP nanowire were investigated by excitation power and energy dependencies.

    DOI: 10.1088/1742-6596/193/1/012132

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  • Exciton coherence in clean single InP/InAsP/InP nanowire quantum dots emitting in infra-red measured by Fourier spectroscopy

    H. Sasakura, H. Kumano, I. Suemune, J. Motohisa, Y. Kobayashi, M. van Kouwen, K. Tomioka, T. Fukui, N. Akopian, V. Zwiller

    16TH INTERNATIONAL CONFERENCE ON ELECTRON DYNAMICS IN SEMICONDUCTORS, OPTOELECTRONICS AND NANOSTRUCTURES (EDISON 16)   193   012132-1-4   2009年

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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:IOP PUBLISHING LTD  

    We report optical properties of InP/InAsP/InP nanowire quantum dots and single-photon Fourier spectroscopy of an exciton in a single InAsP quantum dot embedded in an InP nanowire. The coherent length of the time-averaged emission originating from the single InAsP QD was measured by a Mach-Zehnder interferometer inserted in the photoluminescence path. Effects of fluctuations in surrounding excess charges trapped in the InP nanowire were investigated by excitation power and energy dependencies.

    DOI: 10.1088/1742-6596/193/1/012132

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  • Observation of enhanced luminescence emitted from InAs quantum dots with direct contact to superconducting niobium stripe

    Yasuhiro Idutsu, Makoto Takada, Yujiro Hayashi, Tatsushi Akazaki, Hidekazu Kumano, Ikuo Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, NO 4   6 ( 4 )   849 - +   2009年

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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:WILEY-V C H VERLAG GMBH  

    Observation of drastically enhanced luminescence emitted from InAs quantum dots (QDs) which were in direct contact to superconducting Niobium (Nb) is reported. Although the PL intensity was essentially temperature independent without Nb stripe, drastic temperature dependence was observed with the presence of the Nb stripe. PL intensity was substantially increased below the Nb superconducting critical temperature (T-c). About 3-times enhancement was observed below T-c. This phenomenon is attributed to the Cooper pairs penetrated from the superconducting Nb stripe to adjacent InAs QDs by the proximity effect. This is the first experimental demonstration that the Cooper pairs enhance radiative recombination through QDs. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.200880669

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  • Observation of enhanced luminescence emitted from InAs quantum dots with direct contact to superconducting niobium stripe

    Yasuhiro Idutsu, Makoto Takada, Yujiro Hayashi, Tatsushi Akazaki, Hidekazu Kumano, Ikuo Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, NO 4   6 ( 4 )   849 - +   2009年

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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:WILEY-V C H VERLAG GMBH  

    Observation of drastically enhanced luminescence emitted from InAs quantum dots (QDs) which were in direct contact to superconducting Niobium (Nb) is reported. Although the PL intensity was essentially temperature independent without Nb stripe, drastic temperature dependence was observed with the presence of the Nb stripe. PL intensity was substantially increased below the Nb superconducting critical temperature (T-c). About 3-times enhancement was observed below T-c. This phenomenon is attributed to the Cooper pairs penetrated from the superconducting Nb stripe to adjacent InAs QDs by the proximity effect. This is the first experimental demonstration that the Cooper pairs enhance radiative recombination through QDs. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.200880669

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  • Excitonic spin-state preservation mediated by optical-phonon resonant excitation in a single quantum dot

    H. Kumano, H. Kobayashi, S. Ekuni, Y. Hayashi, M. Jo, H. Sasakura, S. Adachi, S. Muto, I. Suemune

    PHYSICAL REVIEW B   78 ( 8 )   081306-1-4 (R)   2008年8月

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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 PHYSICAL SOC  

    High degree of excitonic spin-state preservation during energy relaxation is demonstrated in a single quantum dot. Optical-phonon resonances and corresponding suppression of spin relaxation are clearly identified as dip structures in photoluminescence excitation spectra probed by the positive trion emission. Consequently, under the longitudinal optical-phonon resonant excitation, a distinguishably high degree of circular polarization up to similar to 0.85 is achieved. Extended spin-relaxation time in the positive trion ground state compared to that in neutral exciton ground state is also revealed.

    DOI: 10.1103/PhysRevB.78.081306

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  • Excitonic spin-state preservation mediated by optical-phonon resonant excitation in a single quantum dot

    H. Kumano, H. Kobayashi, S. Ekuni, Y. Hayashi, M. Jo, H. Sasakura, S. Adachi, S. Muto, I. Suemune

    PHYSICAL REVIEW B   78 ( 8 )   081306-1-4 (R)   2008年8月

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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 PHYSICAL SOC  

    High degree of excitonic spin-state preservation during energy relaxation is demonstrated in a single quantum dot. Optical-phonon resonances and corresponding suppression of spin relaxation are clearly identified as dip structures in photoluminescence excitation spectra probed by the positive trion emission. Consequently, under the longitudinal optical-phonon resonant excitation, a distinguishably high degree of circular polarization up to similar to 0.85 is achieved. Extended spin-relaxation time in the positive trion ground state compared to that in neutral exciton ground state is also revealed.

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  • Excitonic spin-state preservation mediated by optical-phonon resonant excitation in a single quantum dot 査読

    H. Kumano, H. Kobayashi, S. Ekuni, Y. Hayashi, M. Jo, H. Sasakura, S. Adachi, S. Muto, I. Suemune

    PHYSICAL REVIEW B   78 ( 8 )   2008年8月

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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 PHYSICAL SOC  

    High degree of excitonic spin-state preservation during energy relaxation is demonstrated in a single quantum dot. Optical-phonon resonances and corresponding suppression of spin relaxation are clearly identified as dip structures in photoluminescence excitation spectra probed by the positive trion emission. Consequently, under the longitudinal optical-phonon resonant excitation, a distinguishably high degree of circular polarization up to similar to 0.85 is achieved. Extended spin-relaxation time in the positive trion ground state compared to that in neutral exciton ground state is also revealed.

    DOI: 10.1103/PhysRevB.78.081306

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  • Exciton-phonon interactions observed in blue emission band in Te-delta-doped ZnSe 査読

    M. Jo, Y. Hayashi, H. Kumano, I. Suemune

    JOURNAL OF APPLIED PHYSICS   104 ( 3 )   2008年8月

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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  

    Photoluminescence (PL) in the blue wavelength region originating from a no-phonon (NP) transition at 2.734 eV and longitudinal optical (LO) phonon sidebands of Te isoelectronic centers (ICs) were clearly resolved after thermal annealing by delta-doping of Te in ZnSe layers. Broad luminescence (conventionally called the S1 band) had been previously observed in this region (i.e., around 2.65 eV). The PL intensities of the NP line and the phonon replicas followed a Poisson distribution with a mean phonon number (Huang-Rhys factor) of S similar to 1.1. This indicates that the broadening of the 2.65 eV emission band is due to the superposition of the NP lines and their LO phonon replicas originating from the Te ICs with slight variations in their transition energies. The origin of the luminescence is discussed in relation to linearly polarized PL measurements. (C) 2008 American Institute of Physics.

    DOI: 10.1063/1.2966697

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  • Single photon emission with high degree of circular polarization from a single quantum dot under zero magnetic field 査読

    H. Kumano, H. Kobayashi, Y. Hayashi, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   40 ( 6 )   1824 - 1827   2008年4月

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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:ELSEVIER SCIENCE BV  

    Single photon emission with high degree of circular polarization (DCP) from a positively charged exciton (trion) state in a single quantum dot (QD) is demonstrated under zero magnetic field. Obtained high DCP as large as 0.6 is a clear manifestation of highly effective mutual polarization conversion between single photon and single electron spin. This finding also reveals that the spin relaxation is strongly suppressed during capture and thermalization processes and also in trion ground states in a QD. Moreover, exciton charging state control is shown to be possible by modifying the electron capture probability through the excitation energy tuning, which leads to an exclusive formation of the positive trion in a QD. (c) 2007 Published by Elsevier B.V.

    DOI: 10.1016/j.physe.2007.10.041

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  • Single photon emission with high degree of circular polarization from a single quantum dot under zero magnetic field

    H. Kumano, H. Kobayashi, Y. Hayashi, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   40 ( 6 )   1824 - 1827   2008年4月

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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:ELSEVIER SCIENCE BV  

    Single photon emission with high degree of circular polarization (DCP) from a positively charged exciton (trion) state in a single quantum dot (QD) is demonstrated under zero magnetic field. Obtained high DCP as large as 0.6 is a clear manifestation of highly effective mutual polarization conversion between single photon and single electron spin. This finding also reveals that the spin relaxation is strongly suppressed during capture and thermalization processes and also in trion ground states in a QD. Moreover, exciton charging state control is shown to be possible by modifying the electron capture probability through the excitation energy tuning, which leads to an exclusive formation of the positive trion in a QD. (c) 2007 Published by Elsevier B.V.

    DOI: 10.1016/j.physe.2007.10.041

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  • Single photon emission with high degree of circular polarization from a single quantum dot under zero magnetic field

    H. Kumano, H. Kobayashi, Y. Hayashi, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   40 ( 6 )   1824 - 1827   2008年4月

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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:ELSEVIER SCIENCE BV  

    Single photon emission with high degree of circular polarization (DCP) from a positively charged exciton (trion) state in a single quantum dot (QD) is demonstrated under zero magnetic field. Obtained high DCP as large as 0.6 is a clear manifestation of highly effective mutual polarization conversion between single photon and single electron spin. This finding also reveals that the spin relaxation is strongly suppressed during capture and thermalization processes and also in trion ground states in a QD. Moreover, exciton charging state control is shown to be possible by modifying the electron capture probability through the excitation energy tuning, which leads to an exclusive formation of the positive trion in a QD. (c) 2007 Published by Elsevier B.V.

    DOI: 10.1016/j.physe.2007.10.041

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  • Highly circular-polarized single photon generation from a single quantum dot at zero magnetic field 査読

    H. Kobayashi, H. Kumano, M. Endo, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   327 - 330   2008年3月

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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:ELSEVIER SCI LTD  

    Origin of sharp photoluminescence lines observed from an InAlAs quantum dot was identified with the measurements of excitation-power dependences and polarization correlations, together with photon correlation measurements. Single photon emission with high degree of circular polarization (DCP) up to 60% was observed from a positively charged exciton (trion) state in the single quantum dot under non-resonant excitation at zero magnetic field. (C) 2007 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.mejo.2007.07.098

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  • Role of Cooper pairs for the generation of entangled photon pairs from single quantum dots

    I. Suemune, T. Akazaki, K. Tanaka, M. Jo, K. Uesugi, M. Endo, H. Kumano, E. Hanamura

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   344 - 347   2008年3月

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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:ELSEVIER SCI LTD  

    Generation of entangled photon pairs from semiconductor quantum dots (QDs) is highly desirable for realizing practical solid-state photon sources for quantum information processing and quantum cryptography. However, the energy splitting of exciton states in QDs almost prevent the generation of entangled photon pairs. This paper discusses the new possibility with the injection of electron as well as hole Cooper pairs into QDs. (C) 2007 Published by Elsevier Ltd.

    DOI: 10.1016/j.mejo.2007.07.009

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  • Role of Cooper pairs for the generation of entangled photon pairs from single quantum dots

    I. Suemune, T. Akazaki, K. Tanaka, M. Jo, K. Uesugi, M. Endo, H. Kumano, E. Hanamura

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   344 - 347   2008年3月

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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:ELSEVIER SCI LTD  

    Generation of entangled photon pairs from semiconductor quantum dots (QDs) is highly desirable for realizing practical solid-state photon sources for quantum information processing and quantum cryptography. However, the energy splitting of exciton states in QDs almost prevent the generation of entangled photon pairs. This paper discusses the new possibility with the injection of electron as well as hole Cooper pairs into QDs. (C) 2007 Published by Elsevier Ltd.

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  • Role of Cooper pairs for the generation of entangled photon pairs from single quantum dots 査読

    I. Suemune, T. Akazaki, K. Tanaka, M. Jo, K. Uesugi, M. Endo, H. Kumano, E. Hanamura

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   344 - 347   2008年3月

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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:ELSEVIER SCI LTD  

    Generation of entangled photon pairs from semiconductor quantum dots (QDs) is highly desirable for realizing practical solid-state photon sources for quantum information processing and quantum cryptography. However, the energy splitting of exciton states in QDs almost prevent the generation of entangled photon pairs. This paper discusses the new possibility with the injection of electron as well as hole Cooper pairs into QDs. (C) 2007 Published by Elsevier Ltd.

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  • Highly circular-polarized single photon generation from a single quantum dot at zero magnetic field

    H. Kobayashi, H. Kumano, M. Endo, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   327 - 330   2008年3月

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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:ELSEVIER SCI LTD  

    Origin of sharp photoluminescence lines observed from an InAlAs quantum dot was identified with the measurements of excitation-power dependences and polarization correlations, together with photon correlation measurements. Single photon emission with high degree of circular polarization (DCP) up to 60% was observed from a positively charged exciton (trion) state in the single quantum dot under non-resonant excitation at zero magnetic field. (C) 2007 Elsevier Ltd. All rights reserved.

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  • Highly circular-polarized single photon generation from a single quantum dot at zero magnetic field

    H. Kobayashi, H. Kumano, M. Endo, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto

    MICROELECTRONICS JOURNAL   39 ( 3-4 )   327 - 330   2008年3月

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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:ELSEVIER SCI LTD  

    Origin of sharp photoluminescence lines observed from an InAlAs quantum dot was identified with the measurements of excitation-power dependences and polarization correlations, together with photon correlation measurements. Single photon emission with high degree of circular polarization (DCP) up to 60% was observed from a positively charged exciton (trion) state in the single quantum dot under non-resonant excitation at zero magnetic field. (C) 2007 Elsevier Ltd. All rights reserved.

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  • Superconductor-based light emitting diode: Demonstration of role of cooper pairs in radiative recombination processes

    Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Masafumi Jo, Hidekazu Kumano, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   1 ( 1 )   011701   2008年1月

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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 SOC APPLIED PHYSICS  

    A light emitting diode with superconducting Nb electrodes was fabricated to investigate the contribution of cooper pairs to radiative recombination in a semiconductor. Electroluminescence observed from the active layer in which electron cooper pairs and normal holes are injected was drastically enhanced at the temperature lower than the superconducting transition temperature of the Nb electrodes. This is the first experimental evidence that cooper pairs enhance radiative recombinations by the superradiance effect. (c) 2008 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.1.011701

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  • Superconductor-based light emitting diode: Demonstration of role of cooper pairs in radiative recombination processes 査読

    Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Masafumi Jo, Hidekazu Kumano, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   1 ( 1 )   2008年1月

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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 SOC APPLIED PHYSICS  

    A light emitting diode with superconducting Nb electrodes was fabricated to investigate the contribution of cooper pairs to radiative recombination in a semiconductor. Electroluminescence observed from the active layer in which electron cooper pairs and normal holes are injected was drastically enhanced at the temperature lower than the superconducting transition temperature of the Nb electrodes. This is the first experimental evidence that cooper pairs enhance radiative recombinations by the superradiance effect. (c) 2008 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.1.011701

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  • Superconductor-based light emitting diode: Demonstration of role of cooper pairs in radiative recombination processes

    Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Masafumi Jo, Hidekazu Kumano, Ikuo Suemune

    APPLIED PHYSICS EXPRESS   1 ( 1 )   011701   2008年1月

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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 SOC APPLIED PHYSICS  

    A light emitting diode with superconducting Nb electrodes was fabricated to investigate the contribution of cooper pairs to radiative recombination in a semiconductor. Electroluminescence observed from the active layer in which electron cooper pairs and normal holes are injected was drastically enhanced at the temperature lower than the superconducting transition temperature of the Nb electrodes. This is the first experimental evidence that cooper pairs enhance radiative recombinations by the superradiance effect. (c) 2008 The Japan Society of Applied Physics.

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  • Fourier spectroscopy of decoherence of exciton and their complexes in single InAlAs quantum dots

    S. Adachi, H. Sasakura, N. Yatsu, R. Kaji, K. Yamada, S. Muto, H. Kumano, I. Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 1   5 ( 1 )   351 - +   2008年

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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:WILEY-V C H VERLAG GMBH  

    We report the photon-correlation Fourier spectroscopy of exciton and exciton complexes in single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dots. A Michelson interferometer inserted in the photoluminescence path was used to measure the coherent length of the time-averaged emission of neutral exciton, biexciton, and positive trion. As comparing with their coherence time and their excitation energy dependence, the effects of the exchange interaction and the fluctuation of the surrounding excess charge are discussed.

    DOI: 10.1002/pssc.200776553

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  • Fourier spectroscopy of decoherence of exciton and their complexes in single InAlAs quantum dots

    S. Adachi, H. Sasakura, N. Yatsu, R. Kaji, K. Yamada, S. Muto, H. Kumano, I. Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 1   5 ( 1 )   351 - +   2008年

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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:WILEY-V C H VERLAG GMBH  

    We report the photon-correlation Fourier spectroscopy of exciton and exciton complexes in single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dots. A Michelson interferometer inserted in the photoluminescence path was used to measure the coherent length of the time-averaged emission of neutral exciton, biexciton, and positive trion. As comparing with their coherence time and their excitation energy dependence, the effects of the exchange interaction and the fluctuation of the surrounding excess charge are discussed.

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  • Luminescence observed from a junction field-effect transistor with Nb/n-InGaAs/Nb junction

    Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Masafumi Jo, Hidekazu Kumano, Ikuo Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 9   5 ( 9 )   2816 - +   2008年

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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:WILEY-V C H VERLAG GMBH  

    To investigate the contribution of Cooper pairs to radiative recombination in a semiconductor, a junction field-effect transistor (FET) with a Nb/n-InGaAs/Nb junction was fabricated. Electroluminescence was observed from a 11.0nm-wide gap between the source and drain Nb electrodes in addition to the confirmation of the FET operation. Micro-photoluminescence observed from the gap in the Nb electrodes was drastically enhanced at the temperature lower than the superconducting critical value of similar to 8K. This new finding is discussed based on the proximity effect at the super-normal junction. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssc.200779278

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  • Luminescence observed from a junction field-effect transistor with Nb/n-InGaAs/Nb junction

    Yujiro Hayashi, Kazunori Tanaka, Tatsushi Akazaki, Masafumi Jo, Hidekazu Kumano, Ikuo Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 9   5 ( 9 )   2816 - +   2008年

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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:WILEY-V C H VERLAG GMBH  

    To investigate the contribution of Cooper pairs to radiative recombination in a semiconductor, a junction field-effect transistor (FET) with a Nb/n-InGaAs/Nb junction was fabricated. Electroluminescence was observed from a 11.0nm-wide gap between the source and drain Nb electrodes in addition to the confirmation of the FET operation. Micro-photoluminescence observed from the gap in the Nb electrodes was drastically enhanced at the temperature lower than the superconducting critical value of similar to 8K. This new finding is discussed based on the proximity effect at the super-normal junction. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssc.200779278

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  • Superconducting effect on radiative recombinations in long-wavelength light emitting diode 査読

    H. Sasakura, Y. Hayashi, K. Tanaka, T. Akazaki, S. Kuramitsu, H. Kumano, I. Suemune

    Device Research Conference - Conference Digest, DRC   303 - 304   2008年

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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)  

    DOI: 10.1109/DRC.2008.4800850

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  • Superconducting photonics and development of light emitting diodes based on new concept 査読

    I. Suemune, Y. Hayashi, K. Tanaka, T. Akazaki, H. Sasakura, H. Kumano

    Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS   567 - 568   2008年

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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)  

    DOI: 10.1109/LEOS.2008.4688744

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  • LUMINESCENCE OF n-InGaAs/p-InP LIGHT EMITTING DIODE WITH SUPERCONDUCTING Nb ELECTRODE 査読

    Y. Hayashi, M. Jo, H. Kumano, I. Suemune, K. Tanaka

    2008 IEEE 20TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM)   528 - +   2008年

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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  

    To demonstrate the contribution of Cooper pairs to radiative recombination in a semiconductor, a n-InGaAs/p-InP light emitting diode with superconducting Nb electrodes was fabricated. Electroluminescence as well as photoluminescence from the n-InGaAs into which electron Cooper pairs were expected to penetrate from the superconducting Nb electrodes by the proximity effect was drastically enhanced at the temperature lower than the superconducting transition temperature. This is the experimental evidence that Cooper pairs enhance radiative recombinations by the superradiance effect.

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  • Toward regulated photon from semiconductor quantum dots generations and their applications 査読

    I. Suemune, H. Kumano, Y. Hayashi, K. Tanaka, T. Akazaki, M. Jo, Y. Idutsu

    QUANTUM SENSING AND NANOPHOTONIC DEVICES V   6900   2008年

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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  

    Quantum information processing and quantum cryptography are expected to realize highly secure future information networks. How to control photon qubits will be one of the major issues for this direction, but the technologies related to generations and detections of individual photons are still being developed. Semiconductor quantum dots (QDs) have been expected to play major role for on-demand generations of single photons as well as entangled photon pairs. In this talk, photon generation processes from a single QD will be studied for the control of the quantum states of generated photons. Generation of entangled photon pairs from QDs based on biexciton-exciton cascade recombination processes is presently in a difficult situation due to exciton states energy splitting related to growth-related issues. An approach to open new paradigm will be discussed with preliminary results.

    DOI: 10.1117/12.764104

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  • Detailed measurements of nuclear spin polarizations in a single InAlAs quantum dot through overhauser shift of photoluminescence

    R. Kaji, S. Adachi, H. Sasakura, S. Muto, H. Kumano, I. Suemune

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM   20 ( 6 )   447 - 451   2007年8月

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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:SPRINGER  

    We investigated optical pumping of nuclear spin polarizations in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The nuclear spin polarization exhibits the abrupt jump and hysteresis in the excitation power dependence at a particular excitation polarization. Measurement of circular polarization rate of the photoluminescence reveals that the abrupt change of the nuclear spin polarization is created mainly by the spin flip-flop process between nuclei and an electron of a positive charged exciton in this single quantum dot. Model calculation explains well the experimentally observed bistable behavior in InAlAs quantum dot. By using this abrupt change, the sign and magnitude of electron and hole g-factors in z-direction are verified.

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  • Detailed measurements of nuclear spin polarizations in a single InAlAs quantum dot through overhauser shift of photoluminescence 査読

    R. Kaji, S. Adachi, H. Sasakura, S. Muto, H. Kumano, I. Suemune

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM   20 ( 6 )   447 - 451   2007年8月

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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:SPRINGER  

    We investigated optical pumping of nuclear spin polarizations in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The nuclear spin polarization exhibits the abrupt jump and hysteresis in the excitation power dependence at a particular excitation polarization. Measurement of circular polarization rate of the photoluminescence reveals that the abrupt change of the nuclear spin polarization is created mainly by the spin flip-flop process between nuclei and an electron of a positive charged exciton in this single quantum dot. Model calculation explains well the experimentally observed bistable behavior in InAlAs quantum dot. By using this abrupt change, the sign and magnitude of electron and hole g-factors in z-direction are verified.

    DOI: 10.1007/s10948-007-0240-9

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  • Detailed measurements of nuclear spin polarizations in a single InAlAs quantum dot through overhauser shift of photoluminescence

    R. Kaji, S. Adachi, H. Sasakura, S. Muto, H. Kumano, I. Suemune

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM   20 ( 6 )   447 - 451   2007年8月

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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:SPRINGER  

    We investigated optical pumping of nuclear spin polarizations in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The nuclear spin polarization exhibits the abrupt jump and hysteresis in the excitation power dependence at a particular excitation polarization. Measurement of circular polarization rate of the photoluminescence reveals that the abrupt change of the nuclear spin polarization is created mainly by the spin flip-flop process between nuclei and an electron of a positive charged exciton in this single quantum dot. Model calculation explains well the experimentally observed bistable behavior in InAlAs quantum dot. By using this abrupt change, the sign and magnitude of electron and hole g-factors in z-direction are verified.

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  • Luminescence study on evolution from Te isoelectronic centers to type-II ZnTe quantum dots grown by metalorganic molecular-beam epitaxy 査読

    M. Jo, M. Endo, H. Kumano, I. Suemune

    JOURNAL OF CRYSTAL GROWTH   301   277 - 280   2007年4月

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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:ELSEVIER SCIENCE BV  

    Isoelectronically substitutional material systems are proposed as offering a unique possibility to study the physics of different regimes from single isoelectronic centers (ICs) to self-assembled quantum dots (QDs) within the same material combinations. Luminescence evolution of ZnSe:Te system were investigated as such isoelectronically substitutional system. A successive change in the spectral dominance of luminescence with increasing ZnTe layer thickness indicates the evolution from ICs to QDs in ZnSe:Te system. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2006.11.292

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  • Luminescence study on evolution from Te isoelectronic centers to type-II ZnTe quantum dots grown by metalorganic molecular-beam epitaxy

    M. Jo, M. Endo, H. Kumano, I. Suemune

    JOURNAL OF CRYSTAL GROWTH   301 ( 301 )   277 - 280   2007年4月

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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:ELSEVIER SCIENCE BV  

    Isoelectronically substitutional material systems are proposed as offering a unique possibility to study the physics of different regimes from single isoelectronic centers (ICs) to self-assembled quantum dots (QDs) within the same material combinations. Luminescence evolution of ZnSe:Te system were investigated as such isoelectronically substitutional system. A successive change in the spectral dominance of luminescence with increasing ZnTe layer thickness indicates the evolution from ICs to QDs in ZnSe:Te system. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2006.11.292

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  • Luminescence study on evolution from Te isoelectronic centers to type-II ZnTe quantum dots grown by metalorganic molecular-beam epitaxy

    M. Jo, M. Endo, H. Kumano, I. Suemune

    JOURNAL OF CRYSTAL GROWTH   301 ( 301 )   277 - 280   2007年4月

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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:ELSEVIER SCIENCE BV  

    Isoelectronically substitutional material systems are proposed as offering a unique possibility to study the physics of different regimes from single isoelectronic centers (ICs) to self-assembled quantum dots (QDs) within the same material combinations. Luminescence evolution of ZnSe:Te system were investigated as such isoelectronically substitutional system. A successive change in the spectral dominance of luminescence with increasing ZnTe layer thickness indicates the evolution from ICs to QDs in ZnSe:Te system. (c) 2007 Elsevier B.V. All rights reserved.

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  • Room temperature ultraviolet lasing action in high-quality ZnO thin films 査読

    X. Q. Zhang, Ikuo Suemune, H. Kumano, Z. G. Yao, S. H. Huang

    JOURNAL OF LUMINESCENCE   122   828 - 830   2007年1月

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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:ELSEVIER SCIENCE BV  

    High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. In the edge emission geometry, lasing action has been demonstrated in ZnO thin films. The physical origin responsible for lasing action is discussed. The well-defined longitudinal modes could be observed, the mode spacing of 0.9 nm corresponds to a cavity of around 17.5 mu m, and result from accidentally or naturally formed cavities. The lasing threshold was measured as a function of temperature, and the threshold was found to show weak temperature dependence. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jlumin.2006.01.300

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  • Room temperature ultraviolet lasing action in high-quality ZnO thin films

    X. Q. Zhang, Ikuo Suemune, H. Kumano, Z. G. Yao, S. H. Huang

    JOURNAL OF LUMINESCENCE   122   828 - 830   2007年1月

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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:ELSEVIER SCIENCE BV  

    High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. In the edge emission geometry, lasing action has been demonstrated in ZnO thin films. The physical origin responsible for lasing action is discussed. The well-defined longitudinal modes could be observed, the mode spacing of 0.9 nm corresponds to a cavity of around 17.5 mu m, and result from accidentally or naturally formed cavities. The lasing threshold was measured as a function of temperature, and the threshold was found to show weak temperature dependence. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jlumin.2006.01.300

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  • Room temperature ultraviolet lasing action in high-quality ZnO thin films

    X. Q. Zhang, Ikuo Suemune, H. Kumano, Z. G. Yao, S. H. Huang

    JOURNAL OF LUMINESCENCE   122   828 - 830   2007年1月

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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:ELSEVIER SCIENCE BV  

    High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. In the edge emission geometry, lasing action has been demonstrated in ZnO thin films. The physical origin responsible for lasing action is discussed. The well-defined longitudinal modes could be observed, the mode spacing of 0.9 nm corresponds to a cavity of around 17.5 mu m, and result from accidentally or naturally formed cavities. The lasing threshold was measured as a function of temperature, and the threshold was found to show weak temperature dependence. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jlumin.2006.01.300

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  • Superconductor-Based Quantum-Dot Light-Emitting Diodes: Role of Cooper Pairs in Generating Entangled Photon Pairs 査読

    Suemune Ikuo, Akazaki Tatsushi, Tanaka Kazunori, Jo Masafumi, Uesugi Katsuhiro, Endo Michiaki, Kumano Hidekazu, Hanamura Eiichi, Takayanagi Hideaki, Yamanishi Masamichi, Kan Hirofumi

    Japanese journal of applied physics Pt. 1 Regular papers, brief communications & review papers   45 ( 12 )   9264 - 9271   2006年12月

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    記述言語:英語   出版者・発行元:Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics  

    DOI: 10.1143/jjap.45.9264

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    その他リンク: http://hdl.handle.net/2115/33907

  • Role of Nitrogen Precursor Supplies on InAs Quantum Dot Surfaces in Their Emission Wavelengths

    Suemune Ikuo, Sasikala Ganapathy, Kumano Hidekazu, UESUGI Katsuhiro, NABETANI Yoichi, MATSUMOTO Takashi, MAENG J.-T., SEONG Tae Yeon

    Japanese journal of applied physics. Pt. 2, Letters   45 ( 20 )   L529 - L532   2006年6月

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    記述言語:英語   出版者・発行元:Japan Society of Applied Physics  

    DOI: 10.1143/JJAP.45.L529

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    その他リンク: http://hdl.handle.net/2115/33910

  • Role of nitrogen precursor supplies on InAs quantum dot surfaces in their emission wavelengths 査読

    Ikuo Suemune, Ganapathy Sasikala, Hidekazu Kumano, Katsuhiro Uesugi, Yoichi Nabetani, Takashi Matsumoto, J. -T. Maeng, Tae Yeon Seong

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   45 ( 20-23 )   L529 - L532   2006年6月

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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 SOC APPLIED PHYSICS  

    The role of nitrogen (N) in emission wavelengths from InAs quantum dots (QDs) was studied with intentional supplies of a N precursor (monomethylhydrazine) to InAs dot surfaces just before burying them with GaAs capping layers by metalorganic molecular-beam epitaxy. Luminescence from the InAs QDs showed a red shift with the N-precursor supplies on the dot surfaces, and more clear separations of the luminescence sub peaks originating from QD excited-state transitions were observed. The increase in the N precursor supplies on the dot surfaces however changed the relative variation in the emission wavelengths from the red shift to the blue shift. Additional observations of the dot sizes, as well as the model calculations of the emission peaks and of the energy separations of the lowest and QD excited-state transitions showed that the red shift is due to the reduced Ga inclusion in the InAs QDs and that the blue shift is due to the reduced dot sizes.

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  • Role of nitrogen precursor supplies on InAs quantum dot surfaces in their emission wavelengths

    Ikuo Suemune, Ganapathy Sasikala, Hidekazu Kumano, Katsuhiro Uesugi, Yoichi Nabetani, Takashi Matsumoto, J. -T. Maeng, Tae Yeon Seong

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   45 ( 20-23 )   L529 - L532   2006年6月

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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 SOC APPLIED PHYSICS  

    The role of nitrogen (N) in emission wavelengths from InAs quantum dots (QDs) was studied with intentional supplies of a N precursor (monomethylhydrazine) to InAs dot surfaces just before burying them with GaAs capping layers by metalorganic molecular-beam epitaxy. Luminescence from the InAs QDs showed a red shift with the N-precursor supplies on the dot surfaces, and more clear separations of the luminescence sub peaks originating from QD excited-state transitions were observed. The increase in the N precursor supplies on the dot surfaces however changed the relative variation in the emission wavelengths from the red shift to the blue shift. Additional observations of the dot sizes, as well as the model calculations of the emission peaks and of the energy separations of the lowest and QD excited-state transitions showed that the red shift is due to the reduced Ga inclusion in the InAs QDs and that the blue shift is due to the reduced dot sizes.

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  • Triggered single-photon emission and cross-correlation properties in InAlAs quantum dot 査読

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Ikuo Suemune, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Hai Zhi Song, Shinichi Hirose, Tatsuya Usuki

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   32 ( 1-2 )   144 - 147   2006年5月

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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:ELSEVIER SCIENCE BV  

    Triggered single-photon generation from InAlAs quantum dot (QD) was demonstrated for the first time. Emitted photon energy coincides with high detection efficiency range of Si single-photon detectors, which is highly suitable for free-space communication. Single-QD spectroscopy and crossed photon correlation measurements unambiguously revealed that several emitting lines observed in a single mesa structure originated from the identical QD, and two temporary competing decay processes associated with neutral states and charged states were identified. Presence of the competing process is also inferred from an analysis of steady-state photoluminescence intensities. Formation process of charged exciton in QD is also discussed. (c) 2006 Elsevier B.V. All rights reserved.

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  • Triggered single-photon emission and cross-correlation properties in InAlAs quantum dot

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Ikuo Suemune, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Hai Zhi Song, Shinichi Hirose, Tatsuya Usuki

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   32 ( 1-2 )   144 - 147   2006年5月

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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:ELSEVIER SCIENCE BV  

    Triggered single-photon generation from InAlAs quantum dot (QD) was demonstrated for the first time. Emitted photon energy coincides with high detection efficiency range of Si single-photon detectors, which is highly suitable for free-space communication. Single-QD spectroscopy and crossed photon correlation measurements unambiguously revealed that several emitting lines observed in a single mesa structure originated from the identical QD, and two temporary competing decay processes associated with neutral states and charged states were identified. Presence of the competing process is also inferred from an analysis of steady-state photoluminescence intensities. Formation process of charged exciton in QD is also discussed. (c) 2006 Elsevier B.V. All rights reserved.

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  • Triggered single-photon emission and cross-correlation properties in InAlAs quantum dot

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Ikuo Suemune, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Hai Zhi Song, Shinichi Hirose, Tatsuya Usuki

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   32 ( 1-2 )   144 - 147   2006年5月

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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:ELSEVIER SCIENCE BV  

    Triggered single-photon generation from InAlAs quantum dot (QD) was demonstrated for the first time. Emitted photon energy coincides with high detection efficiency range of Si single-photon detectors, which is highly suitable for free-space communication. Single-QD spectroscopy and crossed photon correlation measurements unambiguously revealed that several emitting lines observed in a single mesa structure originated from the identical QD, and two temporary competing decay processes associated with neutral states and charged states were identified. Presence of the competing process is also inferred from an analysis of steady-state photoluminescence intensities. Formation process of charged exciton in QD is also discussed. (c) 2006 Elsevier B.V. All rights reserved.

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  • Deterministic single-photon and polarization-correlated photon pair generations from a single InAlAs quantum dot 査読

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Ikuo Suemune

    JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS   1 ( 1 )   39 - 51   2006年4月

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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 SCIENTIFIC PUBLISHERS  

    Photon emission with nonclassical photon statistics is discussed with a single InAlAs quantum dot. The deterministic single-photon generation in which the emitted photon wavelength matches well to the highly sensitive wavelength region of highly efficient, low-noise Si-single-photon detectors and also to an atmospheric transmission window is demonstrated. Competing transition processes between neutral and charged exciton species originating from an exclusive formation in the same single quantum dot are clarified. It was found that suppressing the charged exciton formation is possible by a quasi-resonant excitation for a deterministic monochromatic single-photon generation. Polarization-dependent photoluminescence spectroscopy clearly indicates the preservation of photon polarizations between photons emitted by biexciton/exciton recombinations. Furthermore, the deterministic polarization-correlated photon pair generation with biexciton-exciton cascaded transition occurring in a single quantum dot is directly confirmed by the polarized second-order photon correlation measurements. This indicates a longer polarization flip time than the exciton lifetime, which is an essential requirement for the deterministic Einstein-Podolsky-Rosen photon pair generation under the present biexciton-exciton cascaded transition scheme.

    DOI: 10.1166/jno.2006.003

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  • Deterministic single-photon and polarization-correlated photon pair generations from a single InAlAs quantum dot

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Ikuo Suemune

    JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS   1 ( 1 )   39 - 51   2006年4月

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    記述言語:英語   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    Photon emission with nonclassical photon statistics is discussed with a single InAlAs quantum dot. The deterministic single-photon generation in which the emitted photon wavelength matches well to the highly sensitive wavelength region of highly efficient, low-noise Si-single-photon detectors and also to an atmospheric transmission window is demonstrated. Competing transition processes between neutral and charged exciton species originating from an exclusive formation in the same single quantum dot are clarified. It was found that suppressing the charged exciton formation is possible by a quasi-resonant excitation for a deterministic monochromatic single-photon generation. Polarization-dependent photoluminescence spectroscopy clearly indicates the preservation of photon polarizations between photons emitted by biexciton/exciton recombinations. Furthermore, the deterministic polarization-correlated photon pair generation with biexciton-exciton cascaded transition occurring in a single quantum dot is directly confirmed by the polarized second-order photon correlation measurements. This indicates a longer polarization flip time than the exciton lifetime, which is an essential requirement for the deterministic Einstein-Podolsky-Rosen photon pair generation under the present biexciton-exciton cascaded transition scheme.

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  • Deterministic single-photon and polarization-correlated photon pair generations from a single InAlAs quantum dot

    Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Ikuo Suemune

    JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS   1 ( 1 )   39 - 51   2006年4月

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    記述言語:英語   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    Photon emission with nonclassical photon statistics is discussed with a single InAlAs quantum dot. The deterministic single-photon generation in which the emitted photon wavelength matches well to the highly sensitive wavelength region of highly efficient, low-noise Si-single-photon detectors and also to an atmospheric transmission window is demonstrated. Competing transition processes between neutral and charged exciton species originating from an exclusive formation in the same single quantum dot are clarified. It was found that suppressing the charged exciton formation is possible by a quasi-resonant excitation for a deterministic monochromatic single-photon generation. Polarization-dependent photoluminescence spectroscopy clearly indicates the preservation of photon polarizations between photons emitted by biexciton/exciton recombinations. Furthermore, the deterministic polarization-correlated photon pair generation with biexciton-exciton cascaded transition occurring in a single quantum dot is directly confirmed by the polarized second-order photon correlation measurements. This indicates a longer polarization flip time than the exciton lifetime, which is an essential requirement for the deterministic Einstein-Podolsky-Rosen photon pair generation under the present biexciton-exciton cascaded transition scheme.

    DOI: 10.1166/jno.2006.003

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  • Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates 査読

    XQ Zhang, ZG Yao, SH Huang, Suemune, I, H Kumano

    JOURNAL OF APPLIED PHYSICS   99 ( 6 )   2006年3月

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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  

    High-quality ZnO thin films have been grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Free-exciton absorption and exciton-LO phonon absorption peaks are observed in the films at room temperature, indicating that the exciton states are stable even at room temperature. Three excitonic transitions associated with valence bands A, B, and C are clearly revealed in the reflectance spectrum measured at low temperatures. This result indicates that the ZnO thin films have a perfect wurtzite crystal structure. Biexciton emission is observed in the photoluminescence spectra at low temperatures, from which the biexciton binding energy is estimated to be 14.5 meV, in good agreement with previous results. Exciton-LO (Ex-LO) and exciton-2LO (Ex-2LO) photon emission peaks are observed at low temperature. The energy difference between the Ex-LO and Ex-2LO bands is about 72.5 meV, which coincides with previously reported values of the LO phonon energy for ZnO thin films. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2183354

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  • Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates

    XQ Zhang, ZG Yao, SH Huang, Suemune, I, H Kumano

    JOURNAL OF APPLIED PHYSICS   99 ( 6 )   063709-063709   2006年3月

     詳細を見る

    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  

    High-quality ZnO thin films have been grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Free-exciton absorption and exciton-LO phonon absorption peaks are observed in the films at room temperature, indicating that the exciton states are stable even at room temperature. Three excitonic transitions associated with valence bands A, B, and C are clearly revealed in the reflectance spectrum measured at low temperatures. This result indicates that the ZnO thin films have a perfect wurtzite crystal structure. Biexciton emission is observed in the photoluminescence spectra at low temperatures, from which the biexciton binding energy is estimated to be 14.5 meV, in good agreement with previous results. Exciton-LO (Ex-LO) and exciton-2LO (Ex-2LO) photon emission peaks are observed at low temperature. The energy difference between the Ex-LO and Ex-2LO bands is about 72.5 meV, which coincides with previously reported values of the LO phonon energy for ZnO thin films. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2183354

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  • Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates

    XQ Zhang, ZG Yao, SH Huang, Suemune, I, H Kumano

    JOURNAL OF APPLIED PHYSICS   99 ( 6 )   063709-063709   2006年3月

     詳細を見る

    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  

    High-quality ZnO thin films have been grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Free-exciton absorption and exciton-LO phonon absorption peaks are observed in the films at room temperature, indicating that the exciton states are stable even at room temperature. Three excitonic transitions associated with valence bands A, B, and C are clearly revealed in the reflectance spectrum measured at low temperatures. This result indicates that the ZnO thin films have a perfect wurtzite crystal structure. Biexciton emission is observed in the photoluminescence spectra at low temperatures, from which the biexciton binding energy is estimated to be 14.5 meV, in good agreement with previous results. Exciton-LO (Ex-LO) and exciton-2LO (Ex-2LO) photon emission peaks are observed at low temperature. The energy difference between the Ex-LO and Ex-2LO bands is about 72.5 meV, which coincides with previously reported values of the LO phonon energy for ZnO thin films. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2183354

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  • Origin of asymmetric splitting of a neutral exciton in a single semiconductor quantum dot

    I. Suemune, H. Kumano, S. Kimura, H. Sasakura, S. Adachi, S. Muto, H. Z. Song, S. Hirose, T. Usui

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 11   3 ( 11 )   3908 - +   2006年

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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:WILEY-V C H VERLAG GMBH  

    It is well-recognized that exciton-state energy splitting makes it difficult to generate entangled photon pairs (EPP) from a single quantum dot (QD). It will be shown that the splitting of the exciton states originates from not only QD anisotropy but also ionization of residual impurities. This result shows that the growth of highly pure barrier layers will be necessary for the generation of EPP. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssc.200671611

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  • Overhauser shift in photoluminescence of excitons with fine structure from a single self-assembled InAlAs quantum dot

    T. Mukumoto, R. Kaji, H. Sasakura, S. Adachi, H. Kumano, S. Muto, I. Suemune

    Physica Status Solidi (C) Current Topics in Solid State Physics   3 ( 12 )   4372 - 4375   2006年

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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)  

    We report optical pumping of nuclear spin polarization in a single self-assembled In0.75 Al0.25 As/Al0.3Ga 0.7As quantum dot where the exciton has a fine structure. Through the change of state mixing that is induced by the anisotropic exchange interaction and the applied magnetic field, the relationship between the magnitude of the Overhauser shift and the optically injected electron spin polarization is discussed. © 2006 WILEY-VCH Verlag GmbH &amp
    Co. KGaA.

    DOI: 10.1002/pssc.200672810

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  • Overhauser shift in photoluminescence of excitons with fine structure from a single self-assembled InAlAs quantum dot

    T. Mukumoto, R. Kaji, H. Sasakura, S. Adachi, H. Kumano, S. Muto, I. Suemune

    Physica Status Solidi (C) Current Topics in Solid State Physics   3 ( 12 )   4372 - 4375   2006年

     詳細を見る

    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)  

    We report optical pumping of nuclear spin polarization in a single self-assembled In0.75 Al0.25 As/Al0.3Ga 0.7As quantum dot where the exciton has a fine structure. Through the change of state mixing that is induced by the anisotropic exchange interaction and the applied magnetic field, the relationship between the magnitude of the Overhauser shift and the optically injected electron spin polarization is discussed. © 2006 WILEY-VCH Verlag GmbH &amp
    Co. KGaA.

    DOI: 10.1002/pssc.200672810

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  • Overhauser shift in photoluminescence of excitons with fine structure from a single self-assembled InAlAs quantum dot

    T. Mukumoto, R. Kaji, H. Sasakura, S. Adachi, H. Kumano, S. Muto, I. Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 12   3 ( 12 )   4372 - 4375   2006年

     詳細を見る

    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:WILEY-V C H VERLAG GMBH  

    We report optical pumping of nuclear spin polarization in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot where the exciton has a fine structure. Through the change of state mixing that is induced by the anisotropic exchange interaction and the applied magnetic field, the relationship between the magnitude of the Overhauser shift and the optically injected electron spin polarization is discussed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.200672810

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  • Overhauser shift in photoluminescence of excitons with fine structure from a single self-assembled InAlAs quantum dot

    T. Mukumoto, R. Kaji, H. Sasakura, S. Adachi, H. Kumano, S. Muto, I. Suemune

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 12   3 ( 12 )   4372 - 4375   2006年

     詳細を見る

    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:WILEY-V C H VERLAG GMBH  

    We report optical pumping of nuclear spin polarization in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot where the exciton has a fine structure. Through the change of state mixing that is induced by the anisotropic exchange interaction and the applied magnetic field, the relationship between the magnitude of the Overhauser shift and the optically injected electron spin polarization is discussed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.200672810

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  • Origin of asymmetric splitting of a neutral exciton in a single semiconductor quantum dot

    I. Suemune, H. Kumano, S. Kimura, H. Sasakura, S. Adachi, S. Muto, H. Z. Song, S. Hirose, T. Usui

    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 11   3 ( 11 )   3908 - +   2006年

     詳細を見る

    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:WILEY-V C H VERLAG GMBH  

    It is well-recognized that exciton-state energy splitting makes it difficult to generate entangled photon pairs (EPP) from a single quantum dot (QD). It will be shown that the splitting of the exciton states originates from not only QD anisotropy but also ionization of residual impurities. This result shows that the growth of highly pure barrier layers will be necessary for the generation of EPP. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssc.200671611

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  • 高効率量子鍵配送に向けた半導体単一光子光源の作製

    熊野 英和, 木村 聡, 末宗 幾夫

    電子情報通信学会技術研究報告. LQE, レーザ・量子エレクトロニクス   105 ( 251 )   55 - 60   2005年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    単一光子の不可分性に基づく極めて高い秘匿性を持つ高効率量子鍵配送の実現に向け、シリコン単一光子検出器の検出感度が高い波長での光子生成が可能な半導体量子ドットを形成し、単一の励起子遷移による高純度の単一の光子数状態にある光子発生を確認した。応用上、複数光子の同時発生を抑制する必要があるが、多励起子状態の関与が単一光子発生動作に大きな影響を与えることを、光子同時計数確率の励起光強度依存性の検討により明らかにした。さらに、励起子分子-励起子の時系列的遷移過程による光子対発生の検証についても実施した。

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  • 高効率量子鍵配送に向けた半導体単一光子光源の作製

    熊野 英和, 木村 聡, 末宗 幾夫

    電子情報通信学会技術研究報告. CPM, 電子部品・材料   105 ( 247 )   55 - 60   2005年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    単一光子の不可分性に基づく極めて高い秘匿性を持つ高効率量子鍵配送の実現に向け、シリコン単一光子検出器の検出感度が高い波長での光子生成が可能な半導体量子ドットを形成し、単一の励起子遷移による高純度の単一の光子数状態にある光子発生を確認した。応用上、複数光子の同時発生を抑制する必要があるが、多励起子状態の関与が単一光子発生動作に大きな影響を与えることを、光子同時計数確率の励起光強度依存性の検討により明らかにした。さらに、励起子分子-励起子の時系列的遷移過程による光子対発生の検証についても実施した。

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  • 高効率量子鍵配送に向けた半導体単一光子光源の作製

    熊野 英和, 木村 聡, 末宗 幾夫

    電子情報通信学会技術研究報告. EMD, 機構デバイス   105 ( 245 )   55 - 59   2005年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    単一光子の不可分性に基づく極めて高い秘匿性を持つ高効率量子鍵配送の実現に向け、シリコン単一光子検出器の検出感度が高い波長での光子生成が可能な半導体量子ドットを形成し、単一の励起子遷移による高純度の単一の光子数状態にある光子発生を確認した。応用上、複数光子の同時発生を抑制する必要があるが、多励起子状態の関与が単一光子発生動作に大きな影響を与えることを、光子同時計数確率の励起光強度依存性の検討により明らかにした。さらに、励起子分子-励起子の時系列的遷移過程による光子対発生の検証についても実施した。

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  • 高効率量子鍵配送に向けた半導体単一光子光源の作製

    熊野 英和, 木村 聡, 末宗 幾夫

    電子情報通信学会技術研究報告. OPE, 光エレクトロニクス   105 ( 249 )   55 - 60   2005年8月

     詳細を見る

    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人電子情報通信学会  

    単一光子の不可分性に基づく極めて高い秘匿性を持つ高効率量子鍵配送の実現に向け、シリコン単一光子検出器の検出感度が高い波長での光子生成が可能な半導体量子ドットを形成し、単一の励起子遷移による高純度の単一の光子数状態にある光子発生を確認した。応用上、複数光子の同時発生を抑制する必要があるが、多励起子状態の関与が単一光子発生動作に大きな影響を与えることを、光子同時計数確率の励起光強度依存性の検討により明らかにした。さらに、励起子分子-励起子の時系列的遷移過程による光子対発生の検証についても実施した。

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  • Cerebral glucose metabolism associated with a fear network in panic disorder 査読

    Y Sakai, H Kumano, M Nishikawa, Y Sakano, H Kaiya, E Imabayashi, T Ohnishi, H Matsuda, A Yasuda, A Sato, M Diksic, T Kuboki

    NEUROREPORT   16 ( 9 )   927 - 931   2005年6月

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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:LIPPINCOTT WILLIAMS & WILKINS  

    The present study was performed to assess cerebral glucose metabolism in patients with panic disorder using positron emission tomography. F-18-fluorodeoxyglucose positron emission tomography with voxel-based analysis was used to compare regional brain glucose utilization in 12 nonmedicated panic disorder patients, without their experiencing panic attacks during positron emission tomography acquisition, with that in 22 healthy controls. Panic disorder patients showed appreciably high state anxiety before scanning, and exhibited significantly higher levels of glucose uptake in the bilateral amygdala, hippocampus, and thalamus, and in the midbrain, caudal pons, medulla, and cerebellum than controls. These results provided the first functional neuroimaging support in human patients for the neuroanatomical hypothesis of panic disorder focusing on the amygdala-based fear network. NeuroReport 16:927-931 (c) 2005 Lippincott Williams & Wilkins.

    DOI: 10.1097/00001756-200506210-00010

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  • Photon antibunching observed from an InAlAs single quantum dot 査読

    S Kimura, H Kumano, M Endo, Suemune, I, T Yokoi, H Sasakura, S Adachi, S Muto, HZ Song, S Hirose, T Usuki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   44 ( 24-27 )   L793 - L796   2005年

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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:INST PURE APPLIED PHYSICS  

    Single-photon emitters and detectors are key devices to realize secure communications with single-photon-based quantum cryptography and single-photon-based quantum computing. InAlAs quantum dots (QDs) cover the wavelength range with high quantum efficiencies of Si-based single-photon detectors. Clear photon antibunching was observed from an InAlAs single QD under weak excitations. To realize single-photon emitters on demand, complete population of the QD energy states before the photon emission events is necessary, but the measured antibunching properties were dependent substantially on the photo-excitation powers. The physical origin of this problem is discussed. The criterion to distinguish the real deviation from the photon antibunching condition and the artifact of the measurements is clarified. The capability of single-photon emissions on demand will be demonstrated with photon antibunching under pulsed operations.

    DOI: 10.1143/jjap.44.L793

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  • Single-photon generation from InAlAs single quantum dot 査読

    S. Kimura, H. Kumano, M. Endo, I. Suemune, T. Yokoi, H. Sasakura, S. Adachi, S. Muto, H. Z. Song, S. Hirose, T. Usuki

    physica status solidi (c)   2   3833 - 3837   2005年

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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)  

    DOI: 10.1002/pssc.200562027

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  • Dynamic nuclear polarization in a self-assembled InAlAs quantum dot 査読

    S. Adachi, T. Yokoi, H. Sasakura, S. Muto, H. Kumano, I. Suemune

    physica status solidi (c)   2   3838 - 3842   2005年

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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)  

    DOI: 10.1002/pssc.200562032

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  • Structural and luminescence properties of InAs quantum dots: Effect of nitrogen exposure on dot surfaces 査読

    G Sasikala, Suemune, I, P Thilakan, H Kumano, K Uesugi, Y Nabetani, T Matsumoto, H Machida

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   44 ( 50-52 )   L1512 - L1515   2005年

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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:INST PURE APPLIED PHYSICS  

    The role of nitrogen (N) in InAs quantum dots (QDs) surfaces was studied by supplying a nitrogen (N) precursor to InAs QDs surfaces just before burying them under GaAs capping layers. Monomethylhydrazine was used as the N precursor. InAs QDs treated by such N exposure of their upper surfaces showed the following distinct improvements in their uniformity and efficiency: the peaks of histograms showing QD size distributions observed by atomic-force microscopy became narrower. Photoluminescence (PL) subpeaks originating from QD energy states showed clearer structures. The full widths at half maximum of the PL linewidths were reduced to 20 meV at room temperature, which is among the lowest reported. In addition to these observations of higher QD uniformities, the thermal activation energy for the temperature dependence of integrated PL intensity increased from 150 to 310 meV and also the PL efficiency increased similar to 6-folds with the N-exposure of the InAs QD surfaces. The role of N in these marked improvements in characteristics was discussed on the basis of valence-force field model calculations.

    DOI: 10.1143/JJAP.44.L1512

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  • Surface-emitting stimulated emission in high-quality ZnO thin films 査読

    XQ Zhang, Suemune, I, H Kumano, J Wang, SH Huang

    JOURNAL OF APPLIED PHYSICS   96 ( 7 )   3733 - 3736   2004年10月

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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  

    High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Three excitonic transitions associated with the valence bands A, B, and C were clearly revealed in the reflectance spectrum measured at 33 K. This result indicates that the ZnO thin films have the wurtzite crystalline structure. The emission spectra were measured with backscattering geometry at room temperature. When the excitation exceeded a certain value, linewidth narrowing, nonlinear rise of emission intensity, and the shortening of the carrier lifetime were clearly observed and these demonstrate the onset of stimulated emission. Together with the ZnO thickness dependence, we conclude that the observation of a stimulated emission in a direction perpendicular to the film surface is predominantly due to scattering of the in-plane stimulated emission by slightly remaining surface undulations in the ZnO films. (C) 2004 American Institute of Physics.

    DOI: 10.1063/1.1778216

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  • Study on enhanced excitonic effects in wide-gap semiconductor quantum structures and formation of atom-like discrete levels 査読

    Hidekazu Kumano

    2004年3月

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    記述言語:英語   掲載種別:学位論文(博士)  

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  • Dynamical properties of atom-like emissions from single localized states in ZnCdS ternary mesa-shaped structures 査読

    H Kumano, Y Hitaka, Suemune, I

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   241 ( 3 )   503 - 506   2004年3月

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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:WILEY-V C H VERLAG GMBH  

    Dynamical properties of exciton localization into spatially isolated localized states with atom-like density of states caused by alloy potential fluctuations were examined. Submicron-sized mesa-shaped structures were prepared to resolve the contribution of single localized states to the optical spectra, which makes it possible to observe atom-like emission lines and to discuss the dynamical properties of exciton energy relaxations by employing micro-time-resolved PL measurements. It will be shown that in the samples with high exciton energy transfer efficiency, photogenerated excitons can relax into the spatially isolated localized centers with strong zero-dimensional nature, which leads to the limited number of atom-like emission lines. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssb.200304270

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  • Formation of ohmic contacts to p-type ZnO 査読

    M Kurimoto, ABMA Ashrafi, M Ebihara, K Uesugi, H Kumano, Suemune, I

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   241 ( 3 )   635 - 639   2004年3月

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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:WILEY-V C H VERLAG GMBH  

    Formation of ohmic contacts to p-type zinc oxide (ZnO) was studied. The p-type ZnO samples were grown by metalorgarric molecular-beam epitaxy with diethylzinc, deionized water vapor and monomethythidrazine and were annealed under oxygen gas ambient at 650 degreesC or 700 degreesC for 20 min to activate doped nitrogen acceptors. Although the current-voltage characteristics measured through gold p-contacts were not perfectly ohmic, they showed perfectly ohmic properties after rapid thermal annealing (RTA) in the temperature range of 300 to 520 degreesC for 2 min. The ohmic contact resistivity was measured with the transmission-line measurement method and it was decreased to approximately 1/64 with increasing the RTA temperature. The minimum contact resistivity of 3.15 x 10(-3) Ohm cm(2) was observed with RTA at 520 degreesC for 2 min. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssb.200304286

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  • Epitaxial ZnO growth and p-type doping with MOMBE 査読

    Suemune, I, ABMA Ashrafi, M Ebihara, M Kurimoto, H Kumano, TY Seong, BJ Kim, YW Ok

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   241 ( 3 )   640 - 647   2004年3月

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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:WILEY-V C H VERLAG GMBH  

    Control of ZnO and CdO crystalline structures and p-type doping in ZnO were studied. Formation of zincblende ZnO layers as well as zincblende CdO/ZnO short-period superlattices (SPSL) are demonstrated and bright luminescence was observed even at room temperature from the CdO/ZnO SPSL. p-Type conductivity observed in N-doped ZnO is studied and the relation to the photoluminescence peaks is discussed. (C) 2004 WILEY-VCH Vertag GmbH & Co. KGaA, Weinheim.

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  • Pyramidal-shaped optical microcavities and preparation of atom-like states(半導体レーザ及び光パッシブコンポネント, 及び一般)

    熊野 英和, 末宗 幾夫

    電子情報通信学会技術研究報告   103 ( 528 )   41 - 44   2003年12月

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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:一般社団法人電子情報通信学会  

    最近の量子情報科学の著しい進展に伴い、量子暗号通信用光振として用いられる単一光子光源や、量子演算の中核を担う単一量子ゲート等々,種々の新規な単一量子デバイスの展開が急となっている。絶対的に安全な秘匿情報通信を可能とする単一光子光源の実現のためには、現在の減衰コヒーレント光に代わり光子数揺らぎのない非古典光の発生が必須である。我々はピラミッド型半導体三次元微小光共振器と、半導体中に形成される原子様の単一量子状態の結合により非古典的単一光子光源を実現することを提案し、その作製技術及び光学物性の検討を行っている。本講演では,大きな振動子強度のためより効率的な光子発生が期待されるII-VI族広禁制帯半導体を用いて形成したピラミッド型三次元微小光共振器の作製及び共振特性と、混晶半導体中に形成される局在準位を利用した原子様単一量子準位の形成に関して報告する。

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  • [招待講演]Pyramidal-shaped optical microcavities and preparation of atom-like states(半導体レーザ及び光パッシブコンポネント, 及び一般)

    熊野 英和, 末宗 幾夫

    電子情報通信学会技術研究報告   103 ( 525 )   41 - 44   2003年12月

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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:一般社団法人電子情報通信学会  

    最近の量子情報科学の著しい進展に伴い、量子暗号通信用光振として用いられる単一光子光源や、量子演算の中核を担う単一量子ゲート等々,種々の新規な単一量子デバイスの展開が急となっている。絶対的に安全な秘匿情報通信を可能とする単一光子光源の実現のためには、現在の減衰コヒーレント光に代わり光子数揺らぎのない非古典光の発生が必須である。我々はピラミッド型半導体三次元微小光共振器と、半導体中に形成される原子様の単一量子状態の結合により非古典的単一光子光源を実現することを提案し、その作製技術及び光学物性の検討を行っている。本講演では,大きな振動子強度のためより効率的な光子発生が期待されるII-VI族広禁制帯半導体を用いて形成したピラミッド型三次元微小光共振器の作製及び共振特性と、混晶半導体中に形成される局在準位を利用した原子様単一量子準位の形成に関して報告する。

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  • Improvement of InAs quantum-dot optical properties by strain compensation with GaNAs capping layers 査読

    XQ Zhang, S Ganapathy, Suemune, I, H Kumano, K Uesugi, Y Nabetani, T Matsumoto

    APPLIED PHYSICS LETTERS   83 ( 22 )   4524 - 4526   2003年12月

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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  

    Two kinds of self-assembled InAs quantum dots (QDs) grown on GaAs (001) substrates were studied. One is capped with GaAs layers and the other with GaNAs strain-compensating layers. Photoluminescence (PL) measurements on the two kinds of InAs QDs showed distinct dependence on the selection of the capping layers. The homogeneity and luminescence efficiency of the InAs QDs were much improved when the net strain was reduced with GaNAs layers. These results demonstrate the importance of net strain compensation for the improved optical quality of InAs QDs. (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1629803

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  • GaNAs as Strain Compensating Layer for 1.55 μm Light Emission from InAs Quantum Dots 査読

    Ganapathy Sasikala, Zhang Xi Qing, Suemune Ikuo, UESUGI Katsuhiro, KUMANO Hidekazu, KIM B. J., SEONG Tae-Yeon

    Japanese journal of applied physics. Pt. 1, Regular papers & short notes   42 ( 9 )   5598 - 5601   2003年9月

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    記述言語:英語   出版者・発行元:Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics  

    GaNAs strain-compensating layers (SCLs) are applied to bury InAs quantum dots (QDs) grown on GaAs substrates. The main idea is the compensation of the compressive strain induced by InAs QDs with the tensile strain in the GaNAs SCLs to keep the total strain of the system minimum. The application of the GaNAs SCLs resulted in a systematic shift of photoluminescence (PL) peaks of the InAs QDs toward the longer wavelengths with the increase of the nitrogen (N) composition in GaNAs, and luminescence at a wavelength of 1.55 &mu;m has been achieved from the InAs QDs for the N composition of 2.7% in the GaNAs SCL. This result is promising for the application of GaNAs SCL for InAs-QDs-based long-wavelength light sources for optical-fiber communication systems.

    DOI: 10.1143/jjap.42.5598

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  • Emissions from single localized states observed in ZnCdS ternary alloy mesa structures 査読

    H Kumano, Y Hitaka, Suemune, I

    APPLIED PHYSICS LETTERS   82 ( 24 )   4277 - 4279   2003年6月

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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  

    Sharp and discrete emission lines from single localized states in ZnCdS ternary alloys were clearly observed from selectively grown mesa structures. This is a demonstration that compound semiconductor alloy systems, which usually show broad emission spectra due to alloy fluctuations, are able to exhibit emissions from discrete energy levels with quasi-zero-dimensional density of states in limited mesa areas where limited number of deeper localized states will contribute. Introduction of ZnCdS/MgS short-period superlattices is found to play a significant role for the exciton migration enhancement from shallower to deeper localized states, which makes the observation of the emission lines from the single localized states possible in the ZnCdS alloy layers. (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1583859

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  • Structural properties of CdO layers grown on GaAs (001) substrates by metalorganic molecular beam epitaxy 査読

    BJ Kim, YW Ok, TY Seong, ABMA Ashrafi, H Kumano, Suemune, I

    JOURNAL OF CRYSTAL GROWTH   252 ( 1-3 )   219 - 225   2003年5月

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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:ELSEVIER SCIENCE BV  

    Transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made to investigate the microstructural behaviour of rock-salt CdO layers grown on (0 0 1) GaAs substrates with two different buffer layers of ZnS and ZnO/ZnS. It is shown that the CdO layer grown on the ZnS buffer layer has epitaxial relationship to the GaAs substrate, even though a low density of CdO nano-crystallites (18-25 nm across) are formed at the CdO/ZnS interface region. TEM and TED results show that the CdO layer grown on the ZnO/ZnS buffer layer is polycrystalline. TED results also show that the ZnO buffer layer is polycrystalline with a mixture of wurtzite and zinc-blende phases, which results in the formation of polycrystalline CdO layers. (C) 2003 Published by Elsevier Science B.V.

    DOI: 10.1016/S0022-0248(02)02521-6

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  • II-VI quantum dots grown by MOVPE 査読

    Suemune, I, K Yoshida, H Kumano, T Tawara, A Ueta, S Tanaka

    JOURNAL OF CRYSTAL GROWTH   248   301 - 309   2003年2月

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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:ELSEVIER SCIENCE BV  

    II-VI quantum dots (QDs) have been Linder debate on their ripening properties for some time, and a unified understanding of this phenomenon will be given in this paper. Improvement of QD size uniformity is the main concern for practical applications. Scaling of the dot size distributions on some II-VI QDs will be discussed for the better understanding of the size distributions and for the improvement of the dot size uniformity. QD size distributions also tend to smear out the special features of QDs which are expected to modulate electron-photon interactions in optical microcavities coupled with QDs. Study of energy relaxation processes in QDs reveals the possibility of selectively exciting QDs which are in resonance with longitudinal optical (LO)-phonon emission processes. This scheme will be applied to the study of the strong coupling regime of optical microcavities coupled with QDs. CdS/ZnS QDs embedded in pyramidal three-dimensional microcavities are also examined to study the capability to observe enhanced spontaneous emissions by the coupling with cavity modes in pyramidal microcavities. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0022-0248(02)01862-6

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  • Photoluminescence study of InAs quantum dots embedded in GaNAs strain compensating layer grown by metalorganic-molecular-beam epitaxy 査読

    XQ Zhang, S Ganapathy, H Kumano, K Uesugi, Suemune, I

    JOURNAL OF APPLIED PHYSICS   92 ( 11 )   6813 - 6818   2002年12月

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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  

    Self-assembled InAs quantum dots (QDs) embedded in GaN0.007As0.993 strain compensating layers have been grown by metalorganic-molecular-beam epitaxy on a GaAs (001) substrate with a high density of 1x10(11) cm(-2). The photoluminescence properties have been studied for two periods of InAs quantum dots layers embedded in GaN0.007As0.993 strain compensating layers. Four well-resolved excited-state peaks in the photoluminescence spectra have been observed from these highly packed InAs QDs embedded in the GaN0.007As0.993 strain compensating layers. This indicates that the InAs QDs are uniformly formed and that the excited states in QDs due to the quantum confinement effect are well defined. This is explained by tensile strain in GaNAs layers instead of the usual GaAs layers to relieve the compressive strain formed in InAs QDs to keep the total strain of the system at a minimum. (C) 2002 American Institute of Physics.

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  • Nitrogen-doped p-type ZnO layers prepared with H2O vapor-assisted metalorganic molecular-beam epitaxy 査読

    ABMA Ashrafi, Suemune, I, H Kumano, S Tanaka

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   41 ( 11B )   L1281 - L1284   2002年11月

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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:INST PURE APPLIED PHYSICS  

    Nitrogen (N) doping in ZnO is studied to realize reproducible p-type conductivity. Undoped ZnO layers prepared on a-face of sapphire substrates with H2O vapor-assisted growth showed n-type conductivity. However, N-doped ZnO (ZnO:N) layers grown in the similar manner showed the type conversion to p-type conductivity. As-grown p-type ZnO:N layers showed low net acceptor concentrations (N-A-N-D) of similar to10(14) cm(-3), but thermal annealing of the N-doped ZnO samples as well as the optimization of growth parameters increased the N-A-N-D up to similar to5 x 10(16) cm(-3). Photoluminescence measurements showed consistent spectra with the electrical properties by a clear conversion from neutral donor-bound exciton emission in n-ZnO to neutral acceptor-bound exciton emission in the p-ZnO layers.

    DOI: 10.1143/JJAP.41.L1281

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  • Longitudinal-optical-phonon-assisted energy relaxation in self-assembled CdS quantum dots embedded in ZnSe 査読

    H Kumano, H Yoshida, T Tawara, Suemune, I

    JOURNAL OF APPLIED PHYSICS   92 ( 7 )   3573 - 3578   2002年10月

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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  

    The energy relaxation processes of CdS self-assembled quantum dots (QDs) embedded in ZnSe were investigated. Longitudinal-optical (LO)-phonon resonant structures were discerned in the photoluminescence spectra under the CdS selective excitation, especially under nearly resonant excitation conditions. Strong energy selectivity among the Gaussian distributed energy levels of the QDs are observed in energy relaxation processes, in which excitons are dominantly injected into the QDs whose ground state energies with respect to the excitation energy are equal to the multi-LO-phonon energy of ZnSe. Detection-energy dependent photoluminescence excitation (PLE) measurements also suggest that the coupling strength between the excitons and LO phonons is strongly size-dependent, i.e., coupling is strongly enhanced in smaller QDs. In addition, type-II band alignment of the CdS/ZnSe heterostructure is experimentally confirmed directly by PLE measurements. (C) 2002 American Institute of Physics.

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  • Growth activation of ZnO layers with H2O vapor on a-face of sapphire substrate by metalorganic molecular-beam epitaxy 査読

    A. B M A Ashrafi, I. Suemune, H. Kumano, K. Uesugi

    Physica Status Solidi (A) Applied Research   192 ( 1 )   224 - 229   2002年7月

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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)  

    H2O vapor-activated ZnO layers have been grown on the a-face of sapphire substrates. The grown ZnO layers revealed a crystalline orientation of c-face ZnO ∥ a-face sapphire. For the II/VI flux ratio of 14, the ZnO layers showed a bandedge luminescence with the emission energy of 3.376 and 3.304 eV at 17 K and room temperature, respectively. The amount of the blue-shifted energy in the Zn-rich ZnO is estimated to be ∼30 meV in comparison to the donor-bound exciton emission reported previously. The energy shifting towards the higher level could be attributed to the drastic reduction of carrier concentration in the order of ∼1017 cm-3 for the II/VI flux ratio of 14. With this growth condition, electron mobility is recorded typically to be ∼90 cm2/Vs which is considerably higher for the same carrier concentrations reported previously with plasma as oxygen source.

    DOI: 10.1002/1521-396X(200207)192:1<224::AID-PSSA224>3.0.CO;2-#

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  • H2O-vapor-activated ZnO growth on a-face sapphire substrates by metalorganic molecular-beam epitaxy 査読

    ABMA Ashrafi, Suemune, I, H Kumano

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS   41 ( 5A )   2851 - 2854   2002年5月

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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:INST PURE APPLIED PHYSICS  

    ZnO layers have been grown on a-face sapphire substrates using H2O vapor and O-2 plasma as oxygen sources. The growth rate of HO-vapor-assisted growth of ZnO (v-ZnO) is similar to3 times higher than that of plasma-assisted growth of ZnO (p-ZnO) for the same DEZn flux. This report addresses the higher growth activation of ZnO layers with H2O vapor than with O-2 plasma at the same substrate temperature. A sharp and intense photoluminescence (PL) spectrum is observed in v-ZnO at the neutral donor-bound exciton energy of 3.368eV at 16K. The PL excitation spectrum measurement revealed A and B free exciton energies of 3.382 and 3.388eV, respectively. On the other hand, the p-ZnO showed the band-edge emission energy of 3.373eV but with a very weak PL intensity and broader half width, The PL intensity from v-ZnO was similar to10(4) times brighter than that of p-ZnO and the integrated PL intensity measured at room temperature was kept to similar to1/8 of that measured at 16 K.

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  • CdO epitaxial layers grown on (001) GaAs surfaces by metalorganic molecular-beam epitaxy 査読

    ABMA Ashrafi, H Kumano, Suemune, I, YW Ok, TY Seong

    JOURNAL OF CRYSTAL GROWTH   237   518 - 522   2002年4月

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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:ELSEVIER SCIENCE BV  

    DOI: 10.1016/S0022-0248(01)01956-X

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  • Erbium-doped GaP grown by MOMBE and their optical properties 査読

    Suemune, I, K Uesugi, T Shimozawa, H Kumano, H Machida, N Shimoyama

    JOURNAL OF CRYSTAL GROWTH   237   1423 - 1427   2002年4月

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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:ELSEVIER SCIENCE BV  

    Er doping in GaP was studied with metalorganic molecular-beam epitaxy employing a Knudsen cell for Er doping. Coherent growth of the Er-doped Gap layer was observed with relatively smooth surfaces up to Er concentration as high as similar to0.5%. Sharp 1.54-mum luminescence from Er3+ 4f-4f intra-shell transitions showed a weak temperature dependence and was observed up to room temperature. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Modified spontaneous emission properties of Cds quantum dots embedded in novel three-dimensional microcavities 査読

    H Kumano, A Ueta, Suemune, I

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   13 ( 2-4 )   441 - 445   2002年3月

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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:ELSEVIER SCIENCE BV  

    Modified spontaneous emission properties in the presence of confined photon modes inside the three-dimensional (3-D) optical microcavities are demonstrated, Self-formed pyramidal-shaped semiconductor structures fabricated by selective-area growth technique are utilized as an optical microcavity in which discrete photon modes are generated. Noticeable modification of spontaneous emission from active layers embedded in microcavity structures is clearly observed in mu-PL spectra at room temperature, Almost perfect coincidence between enhanced photoluminescence peak wavelengths and the resonance modes inside microcavity is observed. Furthermore. Purcell factors calculated from the obtained Q values reach similar to9, which is inaccessible in the planar microcavitics with only one-dimensional photon confinement normal to the layers. These results indicate that the effective coupling between electronic system and 3-D confined optical fields is realized by the achievement of present low-loss 3-D microcavities with small cavity volume V-c whose dimension is comparable with lambda(3). (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Strong coupling of US quantum dots to confined photonic modes in ZnSe-based microcavities 査読

    T Tawara, Suemune, I, H Kumano

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   13 ( 2-4 )   403 - 407   2002年3月

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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:ELSEVIER SCIENCE BV  

    Microcavities in the visible wavelength region were fabricated based on ZnSe-based distributed Bragg reflectors and US quantum dots were inserted in the cavities. Strong coupling of photonic fields with the US quantum dots in the II-VI semiconductor microcavities was studied, and the Rabi vacuum-field splitting of similar to3 meV was observed. The rationality of observing the strong coupling with the quantum dots is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S1386-9477(02)00152-2

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  • Longitudinal-optical-phonon-assisted resonant excitations of US quantum dots embedded in ZnSe/(ZnSe-MgS superlattice) microcavities 査読

    Suemune, I, T Tawara, H Kumano, H Yoshida

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   229 ( 2 )   961 - 969   2002年1月

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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:WILEY-V C H VERLAG GMBH  

    CdS quantum dots (QDs) embedded in ZnSe-based microcavities were studied. The distributed Bragg reflectors (DBRs) consisted of quarter-wavelength-thick ZnSe, and ZnSe-MgS superlattices were grown, which exhibited a high reflectivity of 92% with just five periods. Microcavities with ZnSe lambda cavities were sandwiched with the DBRs and clear cavity resonance modes were observed. The US QDs were embedded at the antinode position of the ZnSe lambda cavity and were selectively excited by longitudinal-optical (LO) phonon-assisted energy relaxation to the QDs coupled to the cavity modes. This scheme made it possible to observe vacuum-field Rabi splitting with a coupling with QDs for the first time.

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  • Study of resonance wavelengths in II-VI semiconductor photonic dots: Pyramidal size dependences and luminescence properties 査読

    A Ueta, H Kumano, T Shimozawa, Suemune, I

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   229 ( 2 )   971 - 976   2002年1月

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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:WILEY-V C H VERLAG GMBH  

    Optical cavity properties of selectively grown ZnS pyramidal structures were studied. The resonance wavelengths were shifted with the pyramidal size, and pyramidal size dependence of the resonance wavelength was reasonably interpreted by an approximate calculation. Luminescence properties of the ZnS pyramidal photonic dot structures with embedded CdS active layers were studied and a clear modulation of the spontaneous emission was observed at room temperature. Modulated luminescence peaks showed very little temperature dependence of their peaks and their half-line width, which was 2.1 x 10(-4) nm/K and about 4.4 x 10(-3) meV/K, respectively. These properties will demonstrate the possibility of the future application to the temperature-stabilized light emitters with pyramidal photonic dot structures.

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  • Single-crystalline rocksalt CdO layers grown on GaAs(001) substrates by metalorganic molecular-beam epitaxy 査読

    ABMA Ashrafi, H Kumano, Suemune, I, YW Ok, TY Seong

    APPLIED PHYSICS LETTERS   79 ( 4 )   470 - 472   2001年7月

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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  

    In this letter, we report the growth of single-crystalline rocksalt CdO layers on (001) GaAs substrates using ZnS buffer layers. The growth processes of CdO layers were studied by reflection high-energy electron diffraction (RHEED), and the grown CdO layers were evaluated with atomic force microscopy (AFM), and x-ray diffraction (XRD) measurements. After an initial growth delay, the formation of polycrystalline CdO was observed in RHEED measurements during the initial growth of very thin CdO layers. With the increase of the CdO layer thicknesses, streaky RHEED patterns were observed, which indicate the formation of single-crystalline cubic-phase CdO layers. Surface morphology of the CdO layers observed by AFM was atomically flat with root-mean-square roughness of similar to1 nm. The crystalline structures were elucidated from XRD measurements by the determination of the lattice constant to be 4.686 +/-0.001 Angstrom, indicating the single-phase rocksalt CdO structure. (C) 2001 American Institute of Physics.

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  • Role of ZnS buffer layers in growth of zincblende ZnO on GaAs substrates by metalorganic molecular-beam epitaxy 査読

    AA Ashrafi, A Ueta, H Kumano, Suemune, I

    JOURNAL OF CRYSTAL GROWTH   221   435 - 439   2000年12月

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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:ELSEVIER SCIENCE BV  

    ZnS buffer layers were used to grow ZnO films on GaAs(001) substrates. The role of ZnS buffer layers in the growth of zincblende ZnO films on GaAs(001) substrates was investigated by atomic force microscopy. X-ray diffraction, and photoluminescence (PL) measurements. The optimization of the ZnS buffer layer thickness resulted in improvements of the surface morphology and crystalline quality of ZnO films by homogeneous nucleation. With the optimized ZnS buffer layer thickness of similar to 72 nm the surface root-mean-square roughness of the grown ZnO film was minimized to similar to 14 nm and the deep-level PL intensity was reduced to 1/76 of the near-band edge PL intensity at room temperature. (C) 2000 Elsevier Science B.V. All rights reserved.

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  • Origin of size distributions in ZnSe self-organized quantum dots grown on ZnS layers 査読

    T Tawara, S Tanaka, H Kumano, Suemune, I

    JOURNAL OF ELECTRONIC MATERIALS   29 ( 5 )   515 - 519   2000年5月

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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:MINERALS METALS MATERIALS SOC  

    Main factors which determine the size, the standard deviations which show the degree of the size fluctuations for the average dot height and diameter, and density in ZnSe self-organized quantum dots (QDs) grown on ZnS layers were studied. By lowering the growth temperature the QDs average size and its standard deviation decreased and the density increased due to the slower surface migration. With the application of the scaling theory, it was revealed that the normalized size distributions were uniquely determined by the nucleation process although the apparent standard deviations of the QD sizes were dependent on the growth temperature. The influence of surface roughness of the underneath layer on the formation of the relations of the dot height and diameter was also examined. It was shown that the fluctuation of the surface potential contributes significantly to the apparent standard deviations of ZnSe self-organized QDs sizes.

    DOI: 10.1007/s11664-000-0037-0

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  • Growth and characterization of hypothetical zinc-blende ZnO films on GaAs(001) substrates with ZnS buffer layers 査読

    ABMA Ashrafi, A Ueta, A Avramescu, H Kumano, Suemune, I, YW Ok, TY Seong

    APPLIED PHYSICS LETTERS   76 ( 5 )   550 - 552   2000年1月

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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 stable wurtzite phase of ZnO is commonly observed. In this letter, we report the growth and characterization of zinc-blende ZnO on GaAs(001) substrates. The ZnO films grown on GaAs(001) substrates using microwave-plasma-assisted metalorganic molecular-beam epitaxy were characterized by reflection high-energy electron diffraction, x-ray diffraction, transmission electron microscope, and atomic force microscope measurements. The use of a ZnS buffer layer was found to lead to the growth of the zinc-blende ZnO films. Although the zinc-blende ZnO films were polycrystalline with columnar structures, they showed bright band-edge luminescence at room temperature. (C) 2000 American Institute of Physics. [S0003-6951(00)01005-6].

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  • Growth and luminescence properties of self-organized ZnSe quantum dots 査読

    T Tawara, S Tanaka, H Kumano, Suemune, I

    APPLIED PHYSICS LETTERS   75 ( 2 )   235 - 237   1999年7月

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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  

    Self-organized ZnSe quantum dots (QDs) were grown on (100) ZnS/GaAs surfaces to study the relation of the size dispersion and luminescence. The exact dot sizes were obtained by measurements of atomic force microscope with its tip calibration and transmission electron microscope. The average dot size was 2.0 nm high and 11 nm in its diameter and the density was 1 x 10(10) cm(-2). Transition energies of ZnSe QDs were calculated using these measured dot sizes. These calculated peaks were in reasonable agreement with measured photoluminescence (PL) peaks. It was also revealed that the broadening of the PL spectra from ZnSe QDs were consistently explained by the dot size distribution. (C) 1999 American Institute of Physics. [S0003-6951(99)03928-5].

    DOI: 10.1063/1.124333

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  • Semiconductor photonic dots: Visible wavelength-sized optical resonators 査読

    Suemune, I, A Ueta, A Avramescu, S Tanaka, H Kumano, K Uesugi

    APPLIED PHYSICS LETTERS   74 ( 14 )   1963 - 1965   1999年4月

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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  

    Here we describe a strategy toward constructing semiconductor photonic dots in the ultraviolet to blue region. An array of ZnS dots was grown on a GaAs substrate with a selective growth method. The ZnS dots have a pyramidal structure with the base plane of 800 nm square and the height of 300 nm. The {034} crystallographic planes form the sidewalls of the pyramids. Therefore, the size of the pyramidal dots is uniquely determined by the mask patterning. The optical reflection spectra showed clear resonance peaks which are reasonably assigned by the calculation of the resonance modes. Each resonance showed the Q values on the order of 160-300, a reasonable value to observe the modification of the total spontaneous emission rate in this kind of photonic dots. (C) 1999 American Institute of Physics. [S0003-6951(99)03614-1].

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  • Excitonic luminescence up to room temperature in a ZnSe/MgS superlattice 査読

    Hiroyuki Nashiki, Ikuo Suemune, Hidekazu Kumano, Hideki Suzuki, Toshio Obinata, Katsuhiro Uesugi, JuN'Ichiro Nakahara

    Applied Physics Letters   70 ( 18 )   2350 - 2352   1997年5月

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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:American Institute of Physics Inc.  

    Optical properties of a ZnSe/MgS superlattice (SL) were studied by reflection and photoluminescence (PL) spectroscopies. Excitonic structures were clearly observed in the reflection spectra up to room temperature, and the exciton absorption peak energy and linewidth were well coincident with the PL peak energy and linewidth. The origin of the lowest luminescence peak was indicated to be C1-HH1 exciton up to room temperature. The lineshape broadening due to longitudinal-optical-phonon scattering of excitons is much decreased in this SL compared to bulk ZnSe. © 1997 American Institute of Physics.

    DOI: 10.1063/1.118867

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  • Excitonic properties of zinc-blende ZnSe/MgS superlattices studied by reflection spectroscopy 査読

    Hidekazu Kumano, Hiroyuki Nashiki, Ikuo Suemune, Munetaka Arita, Toshio Obinata, Hideki Suzuki, Katsuhiro Uesugi

    Physical Review B - Condensed Matter and Materials Physics   55 ( 7 )   4449 - 4455   1997年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Excitonic properties of newly developed zinc-blende ZnSe/MgS superlattices (SLșs) were measured by reflection spectroscopy. The modification of the excitonic peaks by the multiple reflection in the SL films was treated theoretically and a fitting method to estimate the exciton absorption peak positions and exciton linewidths was developed. Although zinc-blende MgS did not exist before, excellent optical properties were observed in the ZnSe/MgS SL"s. Excitonic structures were clearly observed from 13 K up to the measured room temperature. In spite of strong ionicity of MgS barrier layers in the ZnSe/MgS SLșs, the reduction of exciton-LO-phonon coupling was clearly observed in narrower wells. This indicates that the quantum confinement effect on excitons is large due to the large band offsets and it overcomes the enhancement of exciton-LO-phonon scattering due to high ionicity in barrier layers. © 1997 The American Physical Society.

    DOI: 10.1103/PhysRevB.55.4449

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  • Epitaxial growth of zinc-blende ZnSe/MgS superlattices on (001) GaAs 査読

    Katsuhiro Uesugi, Toshio Obinata, Ikuo Suemune, Hidekazu Kumano, Jun'ichiro Nakahara

    Applied Physics Letters   68 ( 6 )   844 - 846   1996年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report the growth of zinc-blende ZnSe/MgS superlattices (SLs) on GaAs (001) substrates. The SLs were grown with metalorganic vapor phase epitaxy by selecting appropriate precursors for Mg and S. MgS naturally forms rocksalt structures, but zinc-blende MgS layers were grown. The lattice constant of MgS was estimated to be 5.59 Å. X-ray diffraction measurements show that the ZnSe/MgS SLs are grown coherently to the GaAs substrates up to the total thicknesses of ∼3000 Å. © 1996 American Institute of Physics.

    DOI: 10.1063/1.116552

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▶ 全件表示

書籍等出版物

  • 創生ジャーナル(2018年度第2巻)

    ( 担当: 分担執筆 ,  範囲: 高大連携の取り組み-酒田東高校との協働 -人工知能・ロボットは人を幸せにするか?-)

    2018年10月 

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  • Wide Bandgap Semiconductors–Fundamental Properties and Modern Photonic and Electronic Devices

    T. Kiyoshi, Y. Akihiko, S. Adarsh( 担当: 共著 ,  範囲: 5.1.1節 (Single photon devices))

    Springer  2007年  ( ISBN:9783540472346

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    総ページ数:460   担当ページ:281-287   記述言語:英語 著書種別:学術書

    ノーベル物理学賞を受賞した青色LEDで有名になったワイドバンドギャップ半導体について、様々な半導体の結晶成長からプロセス、電気・光学特性等の知見を幅広く網羅した専門書。5.1.1節 (Single photon devices(単一光子デバイス) の執筆を担当。

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MISC

  • 大学文理混合クラスにおけるPython導入方法の検討

    熊野英和, 田中一裕, 鳴海敬倫

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   67th   2020年

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  • 大学2年次文理混合クラスでの「AIって使える」への意識転換

    熊野英和, 田中一裕, 鳴海敬倫

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   80th   ROMBUNNO.21a‐PA1‐2   2019年9月

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    記述言語:日本語  

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  • 大学1・2年次文理混合クラスにおけるプログラミング学修

    熊野英和, 鳴海敬倫

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   66th   ROMBUNNO.11p‐PA7‐15   2019年2月

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  • ピラー型微細形状を有するQDinFアレイを用いた光子数状態の生成

    笹倉弘理, 小田島聡, 大宮寛太, 熊野英和

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   65th   ROMBUNNO.18a‐P8‐4   2018年

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  • ピラー型微細形状を有するQDinFにおける相互相関信号による励起子複合体の推定

    笹倉弘理, 小田島聡, 熊野英和

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   64th   ROMBUNNO.15p‐E205‐12   2017年

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  • ピラー型微細形状を有するQDinFを用いた高純度単一光子状態の生成

    村上大輔, 小田島聡, 中島秀朗, 熊野英和, 笹倉弘理

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   63rd   ROMBUNNO.21P-S621-9   2016年

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    記述言語:日本語  

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  • 半導体量子ドットによる単一光子および量子もつれ光源

    熊野英和, 中島秀朗, 末宗幾夫

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   62nd   ROMBUNNO.11P-B4-5   2015年2月

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  • (111)A面上量子ドットにおける励起子微細構造分裂の高精度評価

    中島秀朗, 熊野英和, LIU X, 間野高明, 黒田隆, 末宗幾夫

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   62nd   ROMBUNNO.12A-A10-5   2015年2月

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  • 微細構造分裂の抑制された量子ドット中性励起子状態を介した単一スピンの読み出し

    中島秀朗, LIU X., HA N., 竹本亮, 黒澤裕之, 間野高明, 黒田隆, 迫田和彰, 末宗幾夫, 熊野英和

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   76th   ROMBUNNO.15P-2C-12   2015年

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    記述言語:日本語  

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  • InP(311)B基板上InAs量子ドットからの単一光子発生とその温度特性

    細井響子, 高熊亨, 黒澤裕之, 中島秀朗, 赤羽浩一, 熊野英和, 末宗幾夫, 早瀬潤子

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   62nd   ROMBUNNO.12A-A10-4   2015年

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  • 長期安定性に優れたプレーナ型高輝度単一光子光源の開発

    熊野英和

    村田学術振興財団年報   ( 28 )   428 - 436   2014年12月

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    記述言語:日本語  

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  • 2波長励起による量子ドット荷電状態制御とその励起ダイナミクスの考察

    中島秀朗, 原田拓弥, 熊野英和, 小田島聡, 末宗幾夫

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   75th   ROMBUNNO.18P-A27-16   2014年9月

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  • Telecommunication band InAs quantum dots and dashes embedded in different barrier materials

    Nahid A Jahan, Claus Hermannstädter, Jae-Hoon Huh, Hirotaka Sasakura, Thomas J Rotter, Pankaj Ahirwar, Ganesh Balakrishnan, Kouichi Akahane, Masahide Sasaki, Hidekazu Kumano, Ikuo Suemune

    2012年2月

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    掲載種別:機関テクニカルレポート,技術報告書,プレプリント等  

    We investigate the long wavelength (1.2 to 1.55 micro-m) photoluminescence of
    high-density InAs quantum dots and dashes, which were grown on InP substrates.
    We analyze the temperature dependence of the recombination and carrier
    distribution on the alloy composition of the barrier materials, InGaAlAs, and
    on the existence of a wetting layer. Carrier escape and transfer are discussed
    based on temperature dependent photoluminescence measurements and theoretical
    considerations about the heterostructures' confinement energies and band
    structure. We propose two different contributions to the thermal quenching,
    which can explain the observations for both the quantum dot and dash samples.
    Among these one is a unique phenomenon for high density quantum dot/dash
    ensembles which is related to significant inter-dot/dash coupling. With the
    goal ahead to use these dots and dashes for quantum optical applications on the
    single-dot/dash level in the telecommunication C band as well as at elevated
    temperatures we present first steps towards the realization of such devices.

    arXiv

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    その他リンク: http://arxiv.org/pdf/1202.1360v1

  • Ag埋め込み半導体ピラー構造を用いた高効率光子発生源の作製と発光特性評価

    飯島仁史, 中島秀朗, 中島秀朗, 小田島聡, 小田島聡, 熊野英和, 西尾崇, 松尾保孝, 居城邦治, 末宗幾夫

    応用物理学会学術講演会講演予稿集(CD−ROM)   72nd   ROMBUNNO.31A-A-5   2011年8月

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  • 剥離層を用いたAg埋め込み半導体ピラー構造の作製と発光特性評価

    飯島仁史, 和田雅樹, 中島秀朗, 井田惣太郎, 小田島聡, 小田島聡, 熊野英和, 熊野英和, 西尾崇, 松尾保孝, 居城邦治, 末宗幾夫, 末宗幾夫

    応用物理学関係連合講演会講演予稿集(CD−ROM)   58th   ROMBUNNO.24A-KS-1   2011年3月

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  • 剥離層を用いた金属埋め込み半導体ピラー構造の作製と光学評価

    飯島仁史, 和田雅樹, 中島秀朗, 井田惣太郎, 小田島聡, 小田島聡, 熊野英和, 熊野英和, 西尾崇, 松尾保孝, 居城邦治, 末宗幾夫, 末宗幾夫

    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集   46th-7th   32   2011年1月

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  • 特集半導体光源の最前線:量子情報通信のための単一光子・量子もつれ光子対光源 招待

    末宗幾夫, 熊野英和, 笹倉弘理

    光学   40 ( 9 )   472 - 477   2011年

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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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  • Exploring Spontaneous Simultaneous Photon-pair Generation in Semiconductors

    SUEMUNE I, SUEMUNE I, ASANO Y, TANAKA K, TANAKA K, INOUE R, INOUE R, TAKAYANAGI H, TAKAYANAGI H, SASAKURA H, SASAKURA H, AKAZAKI T, AKAZAKI T, KUMANO H, KUMANO H

    AIP Conf Proc   1399 Pt.A   411-412   2011年

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    記述言語:英語  

    DOI: 10.1063/1.3666428

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  • 剥離層を用いた金属埋め込み半導体ピラー構造の作製

    飯島仁史, 宮村壮太, 中島秀朗, 井田惣太郎, 小田島聡, 熊野英和, 熊野英和, 西尾崇, 松尾保孝, 居城邦治, 末宗幾夫, 末宗幾夫

    応用物理学会学術講演会講演予稿集(CD−ROM)   71st   ROMBUNNO.17A-P13-12   2010年8月

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  • AlGaAs犠牲層を用いた金属埋め込み半導体ピラー構造の作製

    宮村壮太, 飯島仁史, 定昌史, 加藤大望, 井田惣太郎, 中島秀朗, 江國晋吾, 熊野英和, 熊野英和, 末宗幾夫, 末宗幾夫

    応用物理学関係連合講演会講演予稿集(CD-ROM)   57th   2010年

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  • 金属埋め込み量子ドットによる高効率単一光子源の検討

    中島秀朗, 江国晋吾, 熊野英和, 熊野英和, 宮村壮太, 加藤大望, 井田惣太郎, 笹倉弘理, 笹倉弘理, 末宗幾夫, 末宗幾夫

    応用物理学関係連合講演会講演予稿集(CD-ROM)   57th   2010年

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  • マグネタイトからInGaAs/AlGaAs量子井戸へのスピン注入効率の測定

    江尻剛士, 熊野英和, 鈴木健司, BABU J.Bubesh, 陽完治

    応用物理学会学術講演会講演予稿集   70th ( 2 )   2009年

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  • 超伝導Nb電極によるn-InGaAs発光再結合寿命の短縮

    倉光周平, 笹倉弘理, 田中和典, 田中和典, 赤崎達志, 赤崎達志, 熊野英和, 熊野英和, 末宗幾夫, 末宗幾夫

    応用物理学会学術講演会講演予稿集   69th ( 3 )   2008年

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  • GaAsSb/GaAsヘテロ構造の発光特性と伝導帯制御

    佐藤充, 井筒康平, 定昌史, 定昌史, 熊野英和, 末宗幾夫, 末宗幾夫

    応用物理学会北海道支部・日本光学会北海道支部合同学術講演会講演予稿集   43rd-4th   2008年

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  • Nb/n-InGaAs/p-InP超伝導発光ダイオードの発光特性

    林雄二郎, 田中和典, 田中和典, 赤崎達志, 赤崎達志, 倉光周平, 定昌史, 熊野英和, 熊野英和, 末宗幾夫, 末宗幾夫

    応用物理学関係連合講演会講演予稿集   55th ( 3 )   2008年

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  • 超伝導Nb/n-InGaAs接合におけるフォトルミネセンス増大効果

    倉光周平, 林雄二郎, 田中和典, 田中和典, 赤崎達志, 赤崎達志, 定昌史, 熊野英和, 熊野英和, 末宗幾夫, 末宗幾夫

    応用物理学関係連合講演会講演予稿集   55th ( 3 )   2008年

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  • InAs/GaAs量子リングにおける励起子微細構造分裂の抑制

    定昌史, SURAPRAPAPICH S., TU C.W., 林雄二郎, 笹倉弘理, 熊野英和, 末宗幾夫, 末宗幾夫, 足立智, 足立智, 武藤俊一, 武藤俊一

    応用物理学関係連合講演会講演予稿集   55th ( 3 )   2008年

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  • 顕微TRPLによるZnCdS混晶中離散化局在中心への励起子分布

    熊野英和, 飛高功明, 末宗幾夫

    応用物理学関係連合講演会講演予稿集   51st ( 1 )   2004年

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  • 分布ブラッグ反射鏡とZnSピラミッド形構造の光学的な結合の最適化についての研究

    中屋大佑, 飛高功明, 熊野英和, 末宗幾夫

    応用物理学会学術講演会講演予稿集   64th ( 1 )   2003年

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  • 次世代材料・デバイス調査報告書

    熊野英和

    日本学術振興会光電相互変換第125委員会   2001年3月

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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)   出版者・発行元:日本学術振興会光電相互変換第125委員会  

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講演・口頭発表等

  • Semiconductor quantum dot nano-array as a single-photon source directly coupled to a fiber

    S. Odashima, H. Sasakura, H. Kumano, H. Nakajima

    European Advanced Materials Congress (EAMC 2018)  2018年8月 

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    開催年月日: 2018年8月

    会議種別:口頭発表(招待・特別)  

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  • Discrimination of exciton complexes in quantum-dot-in-fiber by photon correlations 国際会議

    H. Sasakura

    International conference on optics of excitons in confined systems  2017年9月 

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    記述言語:英語   会議種別:口頭発表(一般)  

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  • Highly pure and stable single photon source directly coupled to a fiber 国際会議

    S. Odashima

    The 43rd International Symposium on Compound Semiconductors  2016年6月 

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    記述言語:英語   会議種別:口頭発表(一般)  

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  • Quantum photon-pair generation from an isotropic quantum dot grown by droplet epitaxy 招待 国際会議

    H. Kumano

    III International Workshop on Metal Droplet Epitaxy of Semiconductor Nanostructures  2016年5月 

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    記述言語:英語   会議種別:口頭発表(招待・特別)  

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  • 微細構造分裂の抑制された量子ドット中性励起子状態を介した単一スピンの読み出し

    中島秀朗

    第76回応用物理学会秋期学術講演会  2015年11月 

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    記述言語:日本語   会議種別:口頭発表(一般)  

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  • Tolerance of Photon Entanglement in a Droplet Epitaxial Quantum Dot Grown on (111)A Surface 国際会議

    H. Nakajima

    2015 International Conference on Solid State Devices and Materials  2015年9月 

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    記述言語:英語   会議種別:口頭発表(一般)  

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  • Semiconductor quantum-dot-based quantum photon sources 招待 国際会議

    H. Kumano

    Physical Science Symposia-2015-Boston  2015年9月 

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    記述言語:英語   会議種別:口頭発表(招待・特別)  

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  • Quantum tomographic analysis of the time-evolved nonlocal biphoton states from a semiconductor quantum dot 国際会議

    H. Kumano

    The 17th International Conference on Modulated Semiconductor Structures  2015年7月 

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    記述言語:英語   会議種別:口頭発表(一般)  

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  • Effect of exciton dephasing on the generated entangled biphoton states from a single quantum dot 招待 国際会議

    H. Kumano

    Japan, Vietnam, Bulgaria and Taiwan Joint Workshop  2015年7月 

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    記述言語:英語   会議種別:口頭発表(招待・特別)  

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  • Single and entangled biphoton generation from semiconductor quantum dot for secure cryptographic telecommunication 招待 国際会議

    H. Kumano

    Collaborative Conference on 3D & Materials Research  2015年6月 

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    記述言語:英語   会議種別:口頭発表(招待・特別)  

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  • Entangled and nonlocal biphoton generation from a semiconductor quantum dot 招待 国際会議

    H. Kumano

    Energy Materials Nanotechnology  2015年5月 

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    記述言語:英語   会議種別:口頭発表(招待・特別)  

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  • 量子情報応用に向けた半導体量子ナノ構造物性と生成光子状態の評価

    熊野英和

    附置研究所間アライアンスによるナノとマクロをつなぐ物質・デバイス・ システム創成戦略プロジェクト 平成26年度成果報告会  2015年4月 

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    記述言語:日本語   会議種別:口頭発表(一般)  

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  • InP(311)B基板上InAs量子ドットからの単一光子発生とその温度特性

    細井響子

    第62回応用物理学会春季学術講演会  2015年3月 

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    記述言語:日本語   会議種別:口頭発表(一般)  

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  • 半導体量子ドットによる単一光子および量子もつれ光源 招待

    熊野英和

    第62回応用物理学会春季学術講演会  2015年3月 

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    記述言語:日本語   会議種別:口頭発表(招待・特別)  

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  • (111)A面上量子ドットにおける励起子微細構造分裂の高精度評価

    中島秀朗

    第62回応用物理学会春季学術講演会  2015年3月 

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    記述言語:日本語   会議種別:口頭発表(一般)  

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  • Entangled photon emission at temperatures up to 60 K from droplet epitaxial quantum dots

    X. Liu

    第62回応用物理学会春季学術講演会  2015年3月 

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    記述言語:日本語   会議種別:口頭発表(一般)  

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産業財産権

  • 量子もつれ光子対発生素子および量子もつれ光子対発生方法

    赤崎 達志, 末宗 幾夫, 笹倉 弘理, 熊野 英和

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    出願人:日本電信電話株式会社, 国立大学法人北海道大学

    出願番号:特願2013-099881  出願日:2013年5月

    公開番号:特開2014-219612  公開日:2014年11月

    特許番号/登録番号:特許第6057373号  発行日:2016年12月

    J-GLOBAL

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  • 量子もつれ光子対発生素子および量子もつれ光子対発生方法

    赤崎 達志, 末宗 幾夫, 笹倉 弘理, 熊野 英和

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    出願人:日本電信電話株式会社, 国立大学法人北海道大学

    出願番号:特願2013-099881  出願日:2013年5月

    公開番号:特開2014-219612  公開日:2014年11月

    J-GLOBAL

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受賞

  • 応用物理学会 優秀論文賞受賞

    2010年7月   応用物理学会  

    末宗幾夫

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    受賞区分:学会誌・学術雑誌による顕彰  受賞国:日本国

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共同研究・競争的資金等の研究

  • 単一光子エンタングルメントを介したスピン間制御

    研究課題/領域番号:20H02555  2020年4月 - 2024年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    笹倉 弘理, 足立 智, 小田島 聡, 鍜治 怜奈, 熊野 英和

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    配分額:17550000円 ( 直接経費:13500000円 、 間接経費:4050000円 )

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  • 量子ドット内蔵光ファイバーを用いた光子を介する遠隔電子スピン間制御

    研究課題/領域番号:16H03817  2016年4月 - 2020年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    笹倉 弘理, 近藤 憲治, 熊野 英和

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    資金種別:競争的資金

    配分額:18980000円 ( 直接経費:14600000円 、 間接経費:4380000円 )

    本申請研究の目的として掲げた光子を中継媒体とした遠隔スピンネットワークの創成に向け, 離散化した内部エネルギーを取っている半導体量子ドット(QD)成長膜をナノピラーアレイ化し, 単一モード光ファイバー(SMF)に直接接合させたデバイス(Quantum Dot in Fiber: QDinF)を作製し, 量子通信の実現に必要不可欠な単一光子状態の高純度発生及び, 長時間耐久性・安定性を実証した. 更にQD中の局在電子スピンを量子ビットに見立てたネットワーク形成に向けて, 12芯SMFアレイモジュールを用いた並列化に着手し, 二次の光子相関信号の取得により, 単一光子状態の並列動作を実証した.

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  • 高秘匿通信のための量子ドット偏光相関2光子源:生成機構の解明と通信波長帯展開

    研究課題/領域番号:16H03816  2016年4月 - 2019年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    熊野 英和

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    配分額:19240000円 ( 直接経費:14800000円 、 間接経費:4440000円 )

    通信網の恒久的な安全性の確保を目指し、物理原理的に盗聴不可能な暗号通信を高度化するための基幹的デバイスである、量子ドットを用いた単一光子/量子もつれ光子対源の開発を行った。
    安全性と安定動作の両立のため、環境系と量子ドットとの相互作用のために生じる、発光の明滅現象および遷移エネルギーシフトのメカニズムを明らかにした。また温度変化や振動などの外乱に対し強固で長期間安定な光子(対)生成を実現するとともに、光源の並列化や光子の量子的性格を左右する励起子状態の物理モデルの構築により光源高度化の指針を得た。更に、光ファイバーとの親和性が最大限利用できる通信波長帯への展開等、光源の高次機能化を実施した。

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  • 高秘匿通信のための量子ドット偏光相関2光子源:生成機構の解明と通信波長帯展開

    2016年4月 - 2018年3月

    科学研究費補助金 

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    資金種別:競争的資金

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  • 高秘匿通信のための量子ドット偏光相関2光子源:生成機構の解明と通信波長帯展開

    2016年4月 - 2018年3月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    熊野英和

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    担当区分:研究代表者  資金種別:競争的資金

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  • 長期安定性に優れたプレーナ型高輝度単一光子光源の開発

    2013年4月 - 2014年3月

    民間学術研究振興費補助金 

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    資金種別:競争的資金

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  • 固体光源から発生する光子対の量子もつれに関する研究とその量子情報応用

    研究課題/領域番号:24226007  2012年5月 - 2017年3月

    日本学術振興会  科学研究費助成事業 基盤研究(S)  基盤研究(S)

    末宗 幾夫, 赤羽 浩一, 熊野 英和, 笹倉 弘理

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    配分額:85800000円 ( 直接経費:66000000円 、 間接経費:19800000円 )

    本研究では、これまで進めてきた金属埋め込み構造による単一光子発生と単一光子純度の向上、光子取り出し効率の増大量子もつれ光子対の同時生成に関する研究とその量子情報応用に関する検討を進める。
    本年度は特に長距離の量子情報通信で重要な単一光子発生純度の向上に向けて、これまで用いられてきた理論的な評価方法に根本的な問題点があることを指摘し、新たな評価方法を提示した。これによって、単一光子純度を示す2次の相関関数の値g(2)(τ=0)の値として、発光波長950nm帯のInAs/GaAs系量子ドットを使って世界最低レベルの0.003を実現した。さらにこれをナノコーン構造に加工して金属(銀)に埋め込むことにより、ごく最近光子取り出し効率として24%と高い量子効率を実現した。また発光波長1550nm帯のInAs/InP系量子ドットを銀の中に埋め込み,30倍以上の発光増強を確認し、現在その光子取り出し量子効率の絶対値の見積もりを進めている。
    超伝導体から電子クーパー対を半導体量子ドットへ注入し、電子対の同時再結合により量子もつれ光子対の同時発生を目指す研究は、これまで量子井戸構造の評価にとどまっていた。本年,一度に一対の光子対を生成するのに欠かせない量子ドット構造を含むn型ドープ半導体構造に電子クーパー対を注入し、超伝導体に近接するバリア層において電子クーパー対の発光再結合による発光増強の再現に成功した。現在量子ドットへの電子クーパー対注入の確認実験を進めている。
    量子ドットから光子対を同時生成するもう一つの方法として、微小光共振器を用いる方法が提案されている。我々の提案する金属埋め込み構造は、発生した光子対を同じ確率で表面から取り出すことができ量子情報に応用しやすい特長を持つ。本年度,金属埋め込み構造としては世界最高の共振Q値7000を観測し,現在さらに検討を進めつつある。

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  • 固体光源から発生する光子対の量子もつれに関する研究とその量子情報応用

    2012年4月 - 2017年3月

    日本学術振興会  科学研究費助成事業  基盤研究(S)

    末宗幾夫

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    資金種別:競争的資金

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  • 半導体ナノ構造中2準位系の共鳴エネルギー変動の研究

    研究課題/領域番号:24310084  2012年4月 - 2015年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    熊野 英和

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    配分額:20280000円 ( 直接経費:15600000円 、 間接経費:4680000円 )

    単一のInAs量子ドット構造を用いて強固な秘匿通信を可能とする単一光子光源構造を作製し、生成光子状態の動的変動を理解するためドット構造内部の荷電状態変動の検討を行った。独自開発した金属微小鏡筒構造により、通常の平面構造では1%程度の光子取り出し効率について18%迄の向上に成功、詳細な状態解析を可能とした。
    光子相関法に基づき高い時間分解能で観測した状態揺動を、単一量子ドット内に形成される荷電状態を5準位系でモデル化し、ある初期条件の下での分布の時間変動シミュレーションにより解析した結果、高い精度で実測結果を再現することに成功、量子光源を特徴付ける動的荷電状態変動の制御に向けて重要な知見を得た。

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  • 半導体ナノ構造中2準位系の共鳴エネルギー変動の研究

    2012年4月 - 2014年3月

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    熊野英和

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    担当区分:研究代表者  資金種別:競争的資金

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  • 金属―半導体界面を応用した950nm帯1550nm帯光子生成プロセス制御の研究

    研究課題/領域番号:24246051  2012年

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    末宗 幾夫, 熊野 英和, 笹倉 弘理

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    配分額:9880000円 ( 直接経費:7600000円 、 間接経費:2280000円 )

    本研究では、(1)量子ドットの金属埋め込み構造による光子取り出し効率のさらなる増大を目指して、埋め込み構造の形状最適化、金属半導体界面の絶縁膜の最適化を、FDTDシミュレーションとその実験的検証により進める,(2)金属埋め込み微小共振器構造における共振モードによるパーセル効果の検討を進める,(3)金属-半導体界面で発生する表面プラズモンポラリトン(SPP)について、その光吸収による損失を低減する観点、ならびにその局在化した光場による光学双極子遷移確率を増大させる観点の双方から検討を進める,(4)InAs/GaAs系量子ドットによる950nm帯、InAs/lnP系量子ドットによる1300nm帯と1550nm帯における単一光子発生効率と単一光子純度の向上、ならびに遷移確率の増大による発光寿命の短縮を検討する,(5)金属埋め込み微小光共振器を用いた量子もつれ光子対の同時発生に関する新たな試みを進める,等を目指して4月,5月と研究を進めていた。しかし6月により高度な量子もつれに関する基盤S研究「固体光源から発生する光子対の量子もつれに関する研究とその量子情報応用」の内定をいただき,そちらに研究をシフトさせることとした。その間2ヶ月と短期間であったために,大きな進展は無い。しかし量子ドットの金属埋め込み構造の新たな製作方法に取り組み,光子取り出し部分の半導体表面を平坦化する新たな作製方法を検討して,現在その見通しがたちつつある。これは光子取り出し効率を増大するためには重要な成果であり,今後基盤Sの研究推進の礎ともなる。

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  • 金属微小光共振器埋め込み量子ドットにおける電子ー光子状態変換に関する研究

    2009年4月 - 2011年3月

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    末宗幾夫

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    資金種別:競争的資金

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  • 金属微小光共振器埋め込み量子ドットにおける電子.光子状態変換に関する研究

    研究課題/領域番号:21246048  2009年 - 2011年

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    末宗 幾夫, 熊野 英和, 笹倉 弘理, 植杉 克弘

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    配分額:43940000円 ( 直接経費:33800000円 、 間接経費:10140000円 )

    InAs量子ドットを内部に含んだGaAs円柱構造を金属に埋め込み、当初チタンに埋め込み、外部のNA=0.4のレンズに光子を取り出す効率として8%を得た。さらに金属を銀に変えることによって取り出し効率18%を観測した。また単一光子発生純度を表す2次光子相関関数の零遅延での値、g(2)(0)として、非共鳴励起で0.02と世界で報告されている最も低い値と同程度の特性を得、さらに準共鳴励起により0.007の低い良好な特性を得た。

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  • 形状揺らぎ許容度の高いもつれ合い光子対発生源の作製に関する研究

    研究課題/領域番号:21681020  2009年 - 2011年

    日本学術振興会  科学研究費助成事業 若手研究(A)  若手研究(A)

    熊野 英和

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:24960000円 ( 直接経費:19200000円 、 間接経費:5760000円 )

    ガリウムひ素部分埋め込みによる異方性の抑制とインジウムフラッシュ法による量子ディスク形状化による形状制御を用いて微細構造分裂(FSS)の低減を行った。低温・低速条件によって異方性を抑制、更にインジウムフラッシュ条件を最適化して作製した量子ディスク構造により、大幅なFSS低減が可能となった。典型値として、100μeV程度のFSSを持つ量子ドットに対して最適な部分埋め込み・インジウムフラッシュを実施することにより、30μeV程度以下までの低減が見られた。更に量子リング構造とすることで、5μeV程度までFSSを抑えられる可能性が示された。

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  • 高効率量子ドット量子光源の作製と空間伝送量子暗号通信への応用に関する研究

    研究課題/領域番号:18681025  2006年 - 2008年

    日本学術振興会  科学研究費助成事業 若手研究(A)  若手研究(A)

    熊野 英和

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:28860000円 ( 直接経費:22200000円 、 間接経費:6660000円 )

    将来の量子鍵配送システム全体として考えた場合、ファイバー系と相補的な役割が期待される空間伝送量子鍵配送に向け、大気の透過率が高くかつSi 単一光子検出器の検出感度とマッチングの良いナノ構造として単一In0.75Al0.25As 量子ドットを形成し、励起エネルギー選択による純度の高い単一光子発生を実現した。さらに、後段での暗号化の際の偏光変調のため高い円偏光度を持つ単一光子の発生を実現した。すなわち、発光エネルギーに対して光学フォノンのエネルギー分高い準位を共鳴的に励起した場合、零磁場中にもかかわらず0.85 と著しい円偏光度の上昇が観測され、電子スピンと光子偏光の間での高効率での状態変換が可能であることが示された。レート方程式解析の結果、InAs LO フォノン共鳴励起下ではスピン反転確率が7.5%以下に抑制され、また荷電励起子基底状態におけるスピン緩和時間は発光再結合寿命の11 倍程度であることが判った。この値は中性励起子のスピン反転時間の約3 倍であり、交換相互作用の無い荷電励起子におけるスピン状態の安定化という、応用に向けて重要な特徴が顕在化された結果と考えられる。これらの成果は、波長短波化した量子ドットによる空間伝送量子暗号通信への展開を展望する上で、非常に大きな意義を持つ。

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  • 光ファイバー通信波長帯量子ドットを用いた高次機能光子源の研究

    2005年4月 - 2008年3月

    文部科学省  科学研究費助成事業  特定領域研究

    末宗幾夫

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    資金種別:競争的資金

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  • 光ファイバー通信波長帯量子ドットを用いた高次機能光子源の研究

    研究課題/領域番号:17068001  2005年 - 2008年

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    末宗 幾夫, 井上 修一郎, 植杉 克弘, 熊野 英和

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    配分額:69500000円 ( 直接経費:69500000円 )

    量子情報通信では、量子情報を伝送する光子状態とこれを量子情報処理することが期待されている電子スピン状態の量子情報変換が重要である。これまでに励起子状態を準共鳴励起することにより、入射円偏光状態を92.100%の量子効率で電子スピン状態に変換し、再度電子スピンから同じ円偏光状態に変換することを試みた。その結果、全体としての量子効率として92%という高い値を達成した。これは量子情報変換を実現する基礎となる。
    光子の検出に関しては、InGaAs APD を正弦波変調することにより、アフターパルスなどの雑音発生を防ぎ、単一光子検出器の動作を800MHz まで高速化したが,この高速光子検出器を使ってNTT と共同で量子鍵配送実験を行った。これによって、15km の通信距離では鍵生成率1.5Mビット/秒、ビットエラー率2.3%の高性能を実現した。

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  • ピラミッド微小光共振器を用いた量子ドット励起子状態のコヒーレント制御に関する研究

    研究課題/領域番号:16106005  2004年 - 2008年

    日本学術振興会  科学研究費助成事業 基盤研究(S)  基盤研究(S)

    末宗 幾夫, 熊野 英和, 植杉 克弘, 植杉 克弘

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    資金種別:競争的資金

    配分額:110110000円 ( 直接経費:84700000円 、 間接経費:25410000円 )

    微小光共振器中で量子ドットの励起子と光子の結合を強め、励起子状態をコヒーレントに制御することを目指して研究し、発光寿命より10倍長いスピンフリップ時間、磁場印可無しで光子円偏光-電子スピンー光子円偏光へ効率92%の高い量子状態変換,金属共振器の開発とこれによる量子ドット励起×光子取り出し効率の40倍改善などの成果を得た。

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  • 自己形成メサ上に作製した単一量子ドット中の多重励起子からの相関光子発生

    2003年4月 - 2004年3月

    日本学術振興会  科学研究費助成事業  若手研究(B)

    熊野英和

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    担当区分:研究代表者  資金種別:競争的資金

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  • 自己形成メサ上に作製した単一量子ドット中の多重励起子からの相関光子対発生

    研究課題/領域番号:15710100  2003年 - 2004年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    熊野 英和

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    配分額:3700000円 ( 直接経費:3700000円 )

    現在、通信の秘匿性の重要性が増し、量子力学の原理に基づいて安全が保証される量子暗号通信の実現が強く求められている。量子暗号通信用の光源として、現在は減衰させたレーザー光が利用されているが、光子数の揺らぎのためビットレートを高くできない問題がある。そこで、光子数状態と呼ばれる光子数揺らぎのない半導体光源の作製を検討した。光子数状態の発生には、離散的状態密度の存在が必要であり、安定性、加工精度、集積性の観点から最適であると判断した半導体零次元系を用いて研究を行った。半導体材料としてはSi-APD単一光子検出器との波長整合の観点からInAlAsを選択し、自己組織化量子ドットを成長後、微細加工技術によりメサ加工を施した。メサ領域に存在する量子ドットからの発光を顕微光学系に入射させたところ、単一量子ドットに起因する半値全幅約200μeV程度の鋭いピークが観測され、その起源を時間分解分光による強度減衰、また励起光強度依存性により検討したところ、単一量子ドット内に存在する励起子、あるいは励起子分子起源の発光線であると確認した。
    この内の一本の発光線、例えば励起子発光による光子数状態光の発生、更には単一光子発生の検証実験を、HBT setupと呼ばれる強度の二次相関関数を測定する光学系を用いて行った。結果として、励起子発光がアンチバンチングと呼ばれる状態を示すことを確認した。これは、単一量子ドットから生成した光子が光子数状態と呼ばれる光子数の確定した状態にあり、かつその光子数が1であることを示しており、本研究により盗聴の対象となる光子の複数個発生が強く抑制されていることが示された。また、引き続き励起子分子発光線と励起子発光線を用いて光子相関測定を行った。結果、単一量子ドット内の励起子分子発光→励起子発光→基底状態という連続的な発光再結合プロセスによる相関光子対の発生が明瞭に示された。

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  • 半導体3次元微小光共振器を用いた単一光子による量子位相変調の研究

    研究課題/領域番号:15656077  2003年 - 2004年

    日本学術振興会  科学研究費助成事業 萌芽研究  萌芽研究

    末宗 幾夫, 植杉 克弘, 熊野 英和

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    配分額:3500000円 ( 直接経費:3500000円 )

    現在の計算機で数10億年もかかる因数分解が数分で解けてしまう可能性があるとの衝撃的なアナウンスメントから,量子計算が脚光を浴びている。その動作には制御ノット操作が必要であるが,制御光子1つが存在したときのみ,信号光子の位相が180度変化するような「量子位相ゲート」を構築できればこの動作が可能である。これまで研究代表者らは(001)GaAs基板上に成長したZnSピラミッドによって3次元微小光共振器の研究を進めてきた。
    これまでのピラミッド共振器はGaAs基板上に成長したZnSピラミッドからなっていたが,共振波長の400nm付近ではGaAsが吸収媒質となることから,これを透明媒質からなる分布反射ミラーとすることによって特性の向上が図れないか検討を加えた。その結果,分布反射ミラーが95%くらいの高い反射率を有していても,ZnSピラミッドとの反射位相が適当な条件にならないと,位相関係によって反射率が低下する課題が生じた。この問題を理論的に検討したところ,分布反射ミラーの周期を20〜30周期に増して,反射率もさらに増大すれば,位相関係によらず高い反射率を維持し,ピラミッド共振器の特性が向上することがわかった。また別の方法として,GaAs基板を選択的にエッチングして除去し,ZnSよりも低い屈折率を持つ誘電体薄膜に置き換える方法を開発し,共振モードを確認している。
    このような微小共振器に単一の光子を導入する準備として,単一量子ドットから発生する光子が一つずつ発生していることを,いわゆるHBT相関測定系を用いた2次の光子相関測定におけるアンチバンチング特性から確認した。この測定系を用い,昨年度から検討を進めているソリッドイマルジョンレンズによるピラミッドに入射する光との結合効率の向上をはかった。これらを組み合わせて,ピラミッド内部に挿入した量子ドットによる反射スペクトル測定に成功した。今後単一光子の吸収飽和を利用した量子位相変化の検討を進めていく。

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  • 原子レベル表面状態制御による低欠陥窒化物半導体のヘテロエピタキシー

    研究課題/領域番号:14205001  2002年 - 2004年

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    田中 悟, 熊野 英和, 青柳 克信, 坂口 春典

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    配分額:46930000円 ( 直接経費:36100000円 、 間接経費:10830000円 )

    窒化物半導体の高品質化のためには,主たる構造欠陥である貫通転位の低減が課題である.現状ではGaNホモエピ基板が欠如しているため.ヘテロエピを余儀なくされている.ヘテロエピ用の基板として本研究では,汎用基板であるサファイア・SiCを取り上げ原子レベル表面状態制御という立揚から高品質化を目指している.初年度は.まずSiC基板の表面平坦化のために,高温HC1/H2ガスエッチング装置を開発し,種々のSiC基板(ポリタイプ・微傾斜特性)に関して原子レベルの平坦化を試みた.実験パラメータ(エッチング温度,プロセス,流量,ガス本圧)および基板パラメータ(ポリタイプ,傾斜角度,面極性,傾斜方向)について総合的な検討を行い,基板表面構造の制御に成功した.最適化実験パラメータにより,傾斜基板には特有な周期化ナノファセット構造が誘起されるとを見出した.この構造は表面の自己組織化と考えられ,エネルギー・速度論的な立場から検討を加えた.このようなナノ周期構造表面はナノ表面として定義・提案することができ,今後ヘテロ系材料への展開を試みる基礎となった.更に,上述の原子レベルで平坦化した基板表面上への窒化物(GaN)半導体のヘテロ結晶成長を分子線エピタキシー法により行った.特に,成長初期過程である核発生・核め融合に注目し成長モードのパラメータ依存性を検討した.また,欠陥生成過程に関するモデリングも行い,微傾斜基板では構造に異方性を生じることを明らかにした.更にGaの吸着脱離状態を制御することによりナノオーダーの選択成長が可能であること見出し,世界で初めてGaN量子細線の作製に成功した.
    また,同様な手法でAINを成長し,AIN表面に規則化したステップバンチングが生じることを見出し,Stranski-Krastanov成長モードによりGaN量子ドットを作製,ドットの1次元規則配列を達成した.これらのドットは規則配列により光学特性が改善されることがわかった.

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  • 3次元微小光共振器における巨大プーセル効果の検証

    研究課題/領域番号:14350154  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    末宗 幾夫, 熊野 英和, 植杉 克弘

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    配分額:14400000円 ( 直接経費:14400000円 )

    経済分野など信頼性が最も重要な領域にまでインターネットが普及するのに伴い,通信の信頼性を高めることが大きな課題となりつつある。その最有力な方法が量子暗号通信である。量子暗号の特徴は,光子一つ一つに偏光情報などをのせると光子一粒だけの測定では不確定性原理により情報を読みとれないことを利用することであり,暗号化する乱数表を盗聴されることなく送受信者が共有できる。このためには,光パルスあたりの光子数を確実に1以下にする必要がある。このような問題点を解決し高速の単一光子源を実現するには,微小共振器により真空場のモード数を低減するとともに共振器内にただ一つの量子ドットを埋め込み,量子ドットの基底状態に関与した励起子を一つの共振モードに強く結合させ,単一光子を発生させることが有力である。
    当該研究では,単一光子源を実現するためにピラミッド共振器を提案し,ピラミッド共振Q値〜5000を実験的に観測するとともに,ピラミッド微小共振器内部にCdS発光層を導入し,自然放出光が共振モードによって増大(遷移確率の増大)を示すことを確認した。単一光子を発生するためのZnCdS混晶ポテンシャル揺らぎによって生じた単一局在準位からの鋭いスペクトルを持った発光を観測した。さらに時間行きでもプーセル効果を確認するためにストリークカメラの感度増強を行い,単一エネルギー準位からの発光を時間分解することに成功した。この成果を今後単一光子源の実現に生かしていく。

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  • 可視・赤外波長域での多波長同時発光デバイスとその集積化の研究

    研究課題/領域番号:14041201  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    末宗 幾夫, 熊野 英和, 植杉 克弘

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    配分額:7200000円 ( 直接経費:7200000円 )

    近年波長多重通信の進展など,波長軸上で多くの光波を利用することの重要性,情報の秘匿性を高めるニーズも高まっている。これらのニーズに対応するには,波長多重通信など多数の波長を同時に発生,制御する技術,またこれらを集積する技術を開拓して扱える情報量を高めるとともに,単一光子を発生・検出する技術を研究開発して量子暗号通信など秘匿性の高い通信システムの研究を進める必要がある。
    当該研究では,III-V-N窒化物混晶半導体による新しい波長多重通信用光源を目指した研究を進めるとともに,ピラミッド型微小光共振器による自然放出波長の制御,波長集積とともに単一光子発生の可能性に関する検討を進め,両者を同じ基板の上に集積する研究を進めている。今年度は,III-V-N窒化物混晶半導体を応用した新しい長波長系発光材料の研究成果として,(1)GaInNAs/GaAs系超格子を用いて,これまで困難であった1.55μm長波長発光の観測の観測に成功,(2)InAs量子ドットに起因する圧縮ひずみを補償するGaNAsひずみ補償(SCL)層を適用し,1.55μmの長波長発光の観測とともに発光効率も大幅に改善することを見いだしたが,この主要因としてひずみの補償が光学特性に寄与していることを示した。一方同じGaAs基板を用いたZnCdS混晶系についても,混晶中の単一局在準位発光を時間分解測定することに成功し,局在準位での発光が観測できる機構について検討を進めた。

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  • 半導体微小共振器中の励起子ポラリトンのエネルギー緩和過程の研究

    研究課題/領域番号:13750263  2001年 - 2002年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    熊野 英和

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    配分額:2000000円 ( 直接経費:2000000円 )

    フレーリッヒ相互作用による縦光学フォノンとの相互作用が大きなII-VI族半導体の量子ドット構造上のエネルギー緩和過程を連続光場中で検討を行った。更に、光波長程度のサイズを持つ微小な共振器構造を導入することで光場を離散化し、その内部での励起子と光場の相互作用の研究を行った。連続場中においては、ZnSe上にMOVPE法により形成した平均ドット高さ1.7ML〜6.6ML(密度約2x10^9cm^<-2>)のCdS自己組織化量子ドット構造を用いて発光及び励起スペクトルを測定した結果、発光スペクトルの励起波長依存性より、エネルギー的にフォノンと結合可能な準位を持つドットにフォノン放出過程による高速な励起子の分布が生じること、また、励起スペクトルにより検出するエネルギー(ドット集団の中から特定のサイズを持つドットを選択することに対応)をチューニングして緩和効率を検討した結果、励起子とLOフォノンに結合強度はドットサイズに強く依存し、より小さなドットの場合に高効率なエネルギー緩和が生じることが判った。更に、CdS自己組織化量子ドットをDBRミラーを含めた全構成要素をII-VI族半導体で形成した微小共振器構造の電場振幅の最大部分に埋め込んだ構造を形成し、その発光スペクトルを共振器モードとドット発光との離調度の関数として測定及び解析した結果、約3meVのRabi分裂を明瞭に観測した。これは量子ドットと共振モードとの間の強い結合を示す初めての成果であり、II-VI族半導体における振動子強度がIII-V族半導体に比べて約200倍増大するとの理論的予見に基づき実現されたと解釈される。これらの成果は、キャビティポラリトンを利用して無閾値VCSELへ道を拓くものであり、今後更なる高性能化を図るべくより励起子-光場相互作用を増進出来る3次元的な光場の閉じ込めが可能な高Q値を有するピラミッド型微小共振器への移行を目指していく。

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  • III族窒化物半導体量子ドットLED・レーザの開発研究

    研究課題/領域番号:13555083  2001年 - 2002年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    田中 悟, 坂口 春典, 只友 一行, 熊野 英和

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    配分額:14000000円 ( 直接経費:14000000円 )

    紫外線域の発光デバイスの実現のために,紫外線の広い領域で発光可能なIII族窒化物系半導体による量子ドット発光ダイオード(LED)或いはレーザーを作製することを最終目的とした.初年度においては,量子ドット作製手法として我々が提案している窒化物表面の原子レベル構造改質法である「アンチサーファクタント法」を用い,SiC基板や汎用基板であるサファイア上でのGaN(InGaN)量子ドットの構造制御(サイズ・密度等)を試みた.下地であるAlGaN表面の原子レベルでの構造制御(ステップ構造)は均一なサイズ,配列のためには非常に重要であることがわかった.最終年度は,量子ドットの発光特性の改善のために下地AlGaN層の更なる原子レベル平坦化やアンチサーファクタント供給条件の最適化を行った.下地AlGaN層の表面平坦性は,基板表面によって大きな影響を受けることから,AlGaN薄膜品質(表面も含む)の基板であるSiC表面のステップ・テラス構造依存性も明らかにした.更にデバイス構造実現のためにp-AlGaN,p-GaNを含んだドーピング制御及びドット埋め込み条件およびデバイス構造の最適化(膜厚やAlGaNのAl組成比等),積層量子ドット構造の可能性等に関する知見を得た.最終的にGaN量子ドットを含む発光ダイオード構造を作製し,電流注入(室温・連続注入)によって紫外線領域(〜359nm)からの発光を得た.実用化のためには更なる発光効率の改善が必要であるが,量子ドットが短波長発光デバイスに有効であることが示され,今後の展開が期待される.

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  • 可視・赤外波長域での多波長同時発光デバイスとその集積化の研究

    研究課題/領域番号:13026201  2001年

    日本学術振興会  科学研究費助成事業 特定領域研究(A)  特定領域研究(A)

    末宗 幾夫, 熊野 英和, 植杉 克弘

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    配分額:4200000円 ( 直接経費:4200000円 )

    近年波長多重通信の進展など,波長軸上で多くの光波を利用することの重要性,情報の秘匿性を高めるニーズも高まっている。これらのニーズに対応するには,波長多重通信など多数の波長を同時に発生,制御する技術,またこれらを集積する技術を開拓して扱える情報量を高めるとともに,単一光子を発生・検出する技術を研究開発して量子暗号通信など秘匿性の高い通信システムの研究を進める必要がある。
    当該研究では,GaAs, GaPなどの半導体基板上に格子整合した可視波長域発光デバイスと赤外波長域発光デバイスの同時集積の可能性を開くとともに,我々が開発したピラミッド型微小光共振器による自然放出光制御を用いて,任意に波長集積の波長設定が行える特徴を持つ集積可能な多波長面発光デバイスの研究,さらに単一光子発生の可能性に関する検討を進めている。今年度は特にピラミッド型の微小3次元光共振器に関する研究を進めた。その結果,共振Q値が5000近くと大きな鋭い共振特性が得られた。これはピラミッド下部のGaAs基盤が光吸収層であるにもかかわらず,大きな屈折率差によってこのような良好な特性が得られたと理解された。しかしこの方法では共振の得られる波長域が限られるために,任意の波長域で共振特性を実現できる分布反射ミラーとの組み合わせを検討した。さらに発光層としてのCdS量子ドット層を組み込み,共振モードによって強く変調された自然放出光の室温での観測に成功した。この変調された自然放出光の発光波長ならびにその半値幅は非常に小さな温度依存性を示し,その特性が共振器によって決定されていることを確認した。

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  • 選択成長した半導体フォトニックドットによる自然放出光制御の研究

    研究課題/領域番号:12450118  2000年 - 2001年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    末宗 幾夫, 熊野 英和, 植杉 克弘, 田中 悟

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    配分額:14500000円 ( 直接経費:14500000円 )

    現在光を用いた空間並列多重通信とこれを用いた光インターコネクション,光並列情報処理が是非とも必要であるとの認識が高まり,その光源として面発光レーザとその集積化の研究が活発に進められている。しかしレーザの光出力は発振しきい値に敏感なため,大規模(>100)に集積化するにはレーザ特性の均一性が要求され,各レーザの光出力をそろえるという観点から集積度が増すにつれyield(良品率)に関する困難が増大する。この点,将来的には"しきい値の無いレーザ"ができれば理想的である。本研究では当該研究者らがフォトニック・ドットと呼ぶ3次元フォトニック量子構造を作製し,強い励起子フォトン結合に基づく顕著な自然放出の増大(Purcell効果)・抑制に関する検討を目指している。
    昨年度GaAs基板上に作製したZnSピラミッドにおいて共振Q値が5000近くと大きな鋭い共振特性が得られた。これはピラミッド下部のGaAs基板が光吸収層であるにもかかわらず,大きな屈折率差によってこのような良好な特性が得られたと理解された。しかしこの方法では共振の得られる波長域が限られるために,任意の波長域で共振特性を実現できる分布反射ミラーとの組み合わせを検討した。さらに発光層としてのCdS量子ドット層を組み込み,共振モードによって強く変調された自然放出光の室温での観測に成功した。通常半導体からの発光波長はエネルギーギャップの温度変化に伴い比較的大きな変化を示し,その発光半値幅もキャリアの熱分布を反映して温度の上昇とともに広がってしまうが,この変調された自然放出光の発光波長ならびにその半値幅は非常に小さな温度依存性を示し,その特性が共振器によって決定されていることを確認した。

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