Updated on 2023/05/28

写真a

 
HARAYAMA, Takahisa
 
Scopus Paper Info  
Paper Count: 143  Citation Count: 2401  h-index: 28

Click to view the Scopus page. The data was downloaded from Scopus API in May 27, 2023, via http://api.elsevier.com and http://www.scopus.com .

Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor
Degree
博士
 

Papers

  • Universal single-mode lasing in fully chaotic two-dimensional microcavity lasers under continuous-wave operation with large pumping power [Invited]

    Takahisa Harayama, Satoshi Sunada, Susumu Shinohara

    PHOTONICS RESEARCH   5 ( 6 ) B39 - B46  2017.12  [Refereed]

     View Summary

    For a fully chaotic two-dimensional (2D) microcavity laser, we present a theory that guarantees both the existence of a stable single-mode lasing state and the nonexistence of a stable multimode lasing state, under the assumptions that the cavity size is much larger than the wavelength and the external pumping power is sufficiently large. It is theoretically shown that these universal spectral characteristics arise from the synergistic effect of two different kinds of nonlinearities: deformation of the cavity shape and mode interaction due to a lasing medium. Our theory is based on the linear stability analysis of stationary states for the Maxwell-Bloch equations and accounts for single-mode lasing phenomena observed in real and numerical experiments of fully chaotic 2D microcavity lasers. (C) 2017 Chinese Laser Press

    DOI

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    8
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  • Self-adjustment of a nonlinear lasing mode to a pumped area in a two-dimensional microcavity [Invited]

    Yuta Kawashima, Susumu Shinohara, Satoshi Sunada, Takahisa Harayama

    PHOTONICS RESEARCH   5 ( 6 ) B47 - B53  2017.12  [Refereed]

     View Summary

    We numerically performed wave dynamical simulations based on the Maxwell-Bloch (MB) model for a quadrupole-deformed microcavity laser with spatially selective pumping. We demonstrate the appearance of an asymmetric lasing mode whose spatial pattern violates both the x-and y-axes mirror symmetries of the cavity. Dynamical simulations revealed that a lasing mode consisting of a clockwise or counterclockwise rotating-wave component is a stable stationary solution of the MB model. From the results of a passive-cavity mode analysis, we interpret these asymmetric rotating-wave lasing modes by the locking of four nearly degenerate passive-cavity modes. For comparison, we carried out simulations for a uniform pumping case and found a different locking rule for the nearly degenerate modes. Our results demonstrate a nonlinear dynamical mechanism for the formation of a lasing mode that adjusts its pattern to a pumped area. (C) 2017 Chinese Laser Press

    DOI

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    5
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    (Scopus)
  • Random Number Generation from Intermittent Optical Chaos

    Andreas Karsaklian Dal Bosco, Naoki Sato, Yuta Terashima, Shoma Ohara, Atsushi Uchida, Takahisa Harayama, Masanobu Inubushi

    IEEE Journal of Selected Topics in Quantum Electronics   23 ( 6 )  2017.11

     View Summary

    We propose a method to generate physical random numbers based on intermittent optical chaos. Intermittent chaotic output is produced in a semiconductor laser subjected to optical feedback embedded in a photonic integrated circuit. This dynamics is characterized by a temporal waveform organized in a succession of laminar regions of low amplitude and bursts of high amplitude. The temporal randomness ruling the alternation of successive laminar regions and bursts is used as an entropy source to generate sequences of random bits. We compare the performances of the exclusive OR and reverse methods implemented in the bit generation process and evaluate the quality of the random bits with the Rabbit test of TestU01 for different bit sequences lengths.

    DOI

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    19
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  • Dynamics-dependent synchronization in on-chip coupled semiconductor lasers

    Shoma Ohara, Andreas Karsaklian Dal Bosco, Kazusa Ugajin, Atsushi Uchida, Takahisa Harayama, Masanobu Inubushi

    PHYSICAL REVIEW E   96 ( 3 )  2017.09  [Refereed]

     View Summary

    Synchronization properties of chaotic dynamics in two mutually coupled semiconductor lasers with optical feedback embedded in a photonic integrated circuit are investigated from the point of view of their dynamical content. A phenomenon in which the two lasers can show qualitatively different synchronization properties according to the frequency range of investigation and their nonlinear dynamics is identified and termed dynamics-dependent synchronization. In-phase synchronization is observed for original signals and antiphase synchronization is observed for low-pass filtered signals in the case where one of the lasers shows chaotic oscillations while the other laser exhibits low-frequency fluctuations dynamics. The experimental conditions causing the synchronization states to vary according to the considered frequency interval are studied and the key roles of asymmetric coupling strength and injection currents are clarified.

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    7
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  • Dynamics Versus Feedback Delay Time in Photonic Integrated Circuits: Mapping the Short Cavity Regime

    Andreas Karsaklian Dal Bosco, Shoma Ohara, Naoki Sato, Yasuhiro Akizawa, Atsushi Uchida, Takahisa Harayama, Masanobu Inubushi

    IEEE PHOTONICS JOURNAL   9 ( 2 )  2017.04  [Refereed]

     View Summary

    We report a comprehensive experimental investigation of the nonlinear dynamics yielded in five photonic integrated circuits, each consisting of a semiconductor laser with optical feedback from a short external cavity. The external cavity lengths are different for each laser and range from 1.3 to 10.3 mm, allowing analysis of the dependence of the dynamical scenario on the feedback delay time. We draw two-dimensional bifurcation diagrams and study the relative predominance of the different dynamics exhibited in each laser when the feedback strength and the laser injection current are varied. We identify that, in the commonly termed short cavity regime, small variations of the external cavity length can result in totally different dynamical distributions, suggesting the possibility to use the feedback delay time as a means to control laser behaviors.

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    11
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  • Chaotic laser based physical random bit streaming system with a computer application interface

    Susumu Shinohara, Kenichi Arai, Peter Davis, Satoshi Sunada, Takahisa Harayama

    OPTICS EXPRESS   25 ( 6 ) 6461 - 6474  2017.03  [Refereed]

     View Summary

    We demonstrate a random bit streaming system that uses a chaotic laser as its physical entropy source. By performing real-time bit manipulation for bias reduction, we were able to provide the memory of a personal computer with a constant supply of ready-to-use physical random bits at a throughput of up to 4 Gbps. We pay special attention to the end-toend entropy source model describing how the entropy from physical sources is converted into bit entropy. We confirmed the statistical quality of the generated random bits by revealing the pass rate of the NIST SP800-22 test suite to be 65 % to 75 %, which is commonly considered acceptable for a reliable random bit generator. We also confirmed the stable operation of our random bit steaming system with long-term bias monitoring.

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    20
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  • Real-time fast physical random number generator with a photonic integrated circuit

    Kazusa Ugajin, Yuta Terashima, Kento Iwakawa, Atsushi Uchida, Takahisa Harayama, Kazuyuki Yoshimura, Masanobu Inubushi

    OPTICS EXPRESS   25 ( 6 ) 6511 - 6523  2017.03  [Refereed]

     View Summary

    Random number generators are essential for applications in information security and numerical simulations. Most optical-chaos-based random number generators produce random bit sequences by offline post-processing with large optical components. We demonstrate a real-time hardware implementation of a fast physical random number generator with a photonic integrated circuit and a field programmable gate array (FPGA) electronic board. We generate 1-Tbit random bit sequences and evaluate their statistical randomness using NIST Special Publication 800-22 and TestU01. All of the BigCrush tests in TestU01 are passed using 410-Gbit random bit sequences. A maximum real-time generation rate of 21.1 Gb/s is achieved for random bit sequences in binary format stored in a computer, which can be directly used for applications involving secret keys in cryptography and random seeds in large-scale numerical simulations.

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    60
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  • One-port ring refractive index sensor with attached sub-ring

    H. Okayama, H. Takahisa, M. Tsutsui, M. Mendez-Astudillo, H. Nakajima

    OPTICAL REVIEW   24 ( 1 ) 11 - 16  2017.02  [Refereed]

     View Summary

    In this report, we propose a ring resonator with one port for surface normal input/output attached with another ring resonator. A resonance generated by one of the ring resonators is used for sensing and that by the other as a reference. The device characteristics were examined using the FDTD simulation.

    DOI

  • Photonic integrated circuits unveil crisis-induced intermittency

    Andreas Karsaklian Dal Bosco, Yasuhiro Akizawa, Kazutaka Kanno, Atsushi Uchida, Takahisa Harayama, Kazuyuki Yoshimura

    OPTICS EXPRESS   24 ( 19 ) 22198 - 22209  2016.09  [Refereed]

     View Summary

    We experimentally investigate an intermittent route to chaos in a photonic integrated circuit consisting of a semiconductor laser with time-delayed optical feedback from a short external cavity. The transition from a period-doubling dynamics to a fully-developed chaos reveals a stage intermittently exhibiting these two dynamics. We unveil the bifurcation mechanism underlying this route to chaos by using the Lang-Kobayashi model and demonstrate that the process is based on a phenomenon of attractor expansion initiated by a particular distribution of the local Lyapunov exponents. We emphasize on the crucial importance of the distribution of the steady-state solutions introduced by the time-delayed feedback on the existence of this intermittent dynamics. (C) 2016 Optical Society of America

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    23
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  • Photonic integrated circuits unveil crisis-induced intermittency

    Andreas Karsaklian Dal Bosco, Yasuhiro Akizawa, Kazutaka Kanno, Atsushi Uchida, Takahisa Harayama, Kazuyuki Yoshimura

    OPTICS EXPRESS   24 ( 19 ) 22198 - 22209  2016.09  [Refereed]

     View Summary

    We experimentally investigate an intermittent route to chaos in a photonic integrated circuit consisting of a semiconductor laser with time-delayed optical feedback from a short external cavity. The transition from a period-doubling dynamics to a fully-developed chaos reveals a stage intermittently exhibiting these two dynamics. We unveil the bifurcation mechanism underlying this route to chaos by using the Lang-Kobayashi model and demonstrate that the process is based on a phenomenon of attractor expansion initiated by a particular distribution of the local Lyapunov exponents. We emphasize on the crucial importance of the distribution of the steady-state solutions introduced by the time-delayed feedback on the existence of this intermittent dynamics. (C) 2016 Optical Society of America

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    23
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  • Long-path formation in a deformed microdisk laser

    Shinohara, Susumu, Fukushima, Takehiro, Sunada, Satoshi, Harayama, Takahisa, Arai, Kenichi

    Physical Review A - Atomic, Molecular, and Optical Physics   94 ( 1 )  2016.07

     View Summary

    © 2016 American Physical Society.An asymmetric resonant cavity can be used to form a path that is much longer than the cavity size. We demonstrate this capability for a deformed microdisk equipped with two linear waveguides, by constructing a multiply reflected periodic orbit that is confined by total internal reflection within the deformed microdisk and outcoupled by the two linear waveguides. Resonant mode analysis reveals that the modes corresponding to the periodic orbit are characterized by high-quality factors. From measured spectral and far-field data, we confirm that the fabricated devices can form a path about 9.3 times longer than the average diameter of the deformed microdisk.

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  • Signature of Wave Chaos in Spectral Characteristics of Microcavity Lasers

    Satoshi Sunada, Susumu Shinohara, Takehiro Fukushima, Takahisa Harayama

    PHYSICAL REVIEW LETTERS   116 ( 20 )  2016.05  [Refereed]

     View Summary

    We report an experimental investigation on the spectra of fully chaotic and nonchaotic microcavity lasers under continuous-wave operating conditions. It is found that fully chaotic microcavity lasers operate in single mode, whereas nonchaotic microcavity lasers operate in multimode. The suppression of multimode lasing for fully chaotic microcavity lasers is explained by large spatial overlaps of the resonance wave functions that spread throughout the two-dimensional cavity due to the ergodicity of chaotic ray orbits.

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    24
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  • N-1-20 Intermittent route to chaos in a photonic integrated circuit

    Karsaklian Dal, Bosco Andreas, Akizawa Yasuhiro, Kanno Kazutaka, Uchida Atsushi, Harayama Takahisa, Yoshimura Kazuyuki

    Proceedings of the IEICE Engineering Sciences Society/NOLTA Society Conference   2016   358 - 358  2016.03

    CiNii

  • Cycles of self-pulsations in a photonic integrated circuit

    Andreas Karsaklian Dal Bosco, Kazutaka Kanno, Atsushi Uchida, Marc Sciamanna, Takahisa Harayama, Kazuyuki Yoshimura

    PHYSICAL REVIEW E   92 ( 6 )  2015.12  [Refereed]

     View Summary

    We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

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    10
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  • Secret-Key Distribution Based on Bounded Observability

    Jun Muramatsu, Kazuyuki Yoshimura, Peter Davis, Atsushi Uchida, Takahisa Harayama

    PROCEEDINGS OF THE IEEE   103 ( 10 ) 1762 - 1780  2015.10  [Refereed]

     View Summary

    This paper reviews an approach to secret-key distribution based on the bounded observability (BO) model. First, the information-theoretic framework of secret-key agreement from a correlated random source is reviewed. Next, the BO model is introduced. In the context of this model, the BO condition is presented as a necessary and sufficient condition for the possibility of secret-key distribution. This condition describes limits on the information obtained by observation of a random object, and models the practical difficulty of completely observing random physical phenomena. Finally, an implementation of secret-key distribution based on BO in an optical fiber system is described.

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    13
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  • Secret-Key Distribution Based on Bounded Observability

    Jun Muramatsu, Kazuyuki Yoshimura, Peter Davis, Atsushi Uchida, Takahisa Harayama

    PROCEEDINGS OF THE IEEE   103 ( 10 ) 1762 - 1780  2015.10  [Refereed]

     View Summary

    This paper reviews an approach to secret-key distribution based on the bounded observability (BO) model. First, the information-theoretic framework of secret-key agreement from a correlated random source is reviewed. Next, the BO model is introduced. In the context of this model, the BO condition is presented as a necessary and sufficient condition for the possibility of secret-key distribution. This condition describes limits on the information obtained by observation of a random object, and models the practical difficulty of completely observing random physical phenomena. Finally, an implementation of secret-key distribution based on BO in an optical fiber system is described.

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    13
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  • Ray-wave correspondence in chaotic dielectric billiards

    Takahisa Harayama, Susumu Shinohara

    PHYSICAL REVIEW E   92 ( 4 )  2015.10  [Refereed]

     View Summary

    Based on the reformulation of the boundary integral equations recently derived by Creagh, Hamdin, and Tanner [J. Phys. A: Math. Theor. 46, 435203 (2013)] together with semiclassical (short wavelength) approximation, we theoretically show that low-loss resonances of a fully chaotic dielectric billiard can be related with ray dynamical orbits whose intensities are weighted by the Fresnel reflection and transmission coefficients. In addition, it is revealed that intensity localization spots observed in the phase-space representation of an individual resonance wave function are ray-dynamically correlated.

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    18
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  • A-2-17 Self-pulsations and dynamics in photonic integrated circuit

    Andreas Karsaklian, Dal Bosco, Ugajin Kazusa, Kanno Kazutaka, Harayama Takahisa, Yoshimura Kazuyuki, Uchida Atsushi

    Proceedings of the IEICE General Conference   2015   48 - 48  2015.02

    CiNii

  • A-2-15 Frequency dependence on chaos synchronization in photonic integrated circuit with mutually-coupled semiconductor lasers

    Ohara Shoma, Ugajin Kazusa, Takahashi Rie, Harayama Takahisa, Yoshimura Kazuyuki, Uchida Atsushi

    Proceedings of the IEICE General Conference   2015   46 - 46  2015.02

    CiNii

  • Efficient optical path folding by using multiple total internal reflections in a microcavity

    Susumu Shinohara, Satoshi Sunada, Takehiro Fukushima, Takahisa Harayama, Kenichi Arai, Kazuyuki Yoshimura

    APPLIED PHYSICS LETTERS   105 ( 15 )  2014.10  [Refereed]

     View Summary

    We propose using an asymmetric resonant microcavity for the efficient generation of an optical path that is much longer than the diameter of the cavity. The path is formed along a star polygonal periodic orbit within the cavity, which is stable and confined by total internal reflection. We fabricated a semiconductor device based on this idea with an average diameter of 0.3 mm and achieved a path length of 2.79 mm experimentally. (C) 2014 AIP Publishing LLC.

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    2
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Research Projects

  • 光の波動カオス現象に基づく情報処理と動的深層学習

    Project Year :

    2020.04
    -
    2023.03
     

     View Summary

    脳のような高度で柔軟な情報処理システムの構築には,外部からの刺激に対して多様に応答し,並列分散的に処理する機構が不可欠である。本研究では,そのような多様で並列的な処理機能を“波動カオス”と呼ばれる光の物理現象に担わせることで,分類・予測処理を高効率かつ高速に実行する光情報処理系を創出する。更に,深層学習と動的システムの最適制御との類似性に基づき,”動的深層学習”という新しい概念を導入する。この概念に基づき,光の動的システムを制御することで,深層学習を光の物理現象によって実行させるような処理機能を実現する

  • Characteristics of weak chaos in view of large deviation analysis and infinite ergodicity

    Project Year :

    2013.04
    -
    2016.03
     

     View Summary

    There still remain many unsolved problems in the nonstationary regime of chaotic or turbulent phenomena; for instance, anomalous diffusion in hamiltonian systems, intermittency, and infinite ergodicity, et cetera. In this research, we studied several nonlinear dynamical models, such as the hamiltonian dynamics of lattice vibrations, mushroom billiards with clear boundaries between chaos and torus, antlion models with dissipative infinite measure ergodicity, nonchaotic strange attractors in periodically driven systems, wave turbulence in Bloch equation, etc., and succeeded to elucidate the diversity of the nonstationary chaos and its universal aspects in statistical behaviors. Furthermore, we studied a new method for the numerical analysis of chaotic intermittent time series by using the real data of interoccurrence time statistics of earthquakes, and succeeded to obtain some new statistical laws of magnitude correlations in the shock sequences

  • The origin of 1/f spectrum fluctuation in the hamiltonian dynamics for lattice systems.

     View Summary

    The classical and quantum mechanical aspects of hamiltonian chaos have been studied in relation to the 1/f spectral fluctuations in the long time behaviors. The recent results are the followings :1.The spectral structure of the most stable KAM torus was determined under the nontwist condition.2.The universality of the 1/f^<mu> spectrum (1<less than or equal>mu<less than or equal>2) was obtained by the computer simulations for the symplectic map in 4 dimensional3.The relaxation mechanisms of resonace states were theoretically elucidated by the geodesics representation and the subdynamics method.4.The level statistics for the l/f quantum billiard was obtained by computer simulations, but the mechanism of level repulsions has not yet been elucidated completely.The preliminary results have been already reported in severeal journals

  • Ergodic and Kinetic Properties of Hamiltonian Dynamical Systems

     View Summary

    In order to elucidate the universal laws of Hamiltonian dynamical systems, we studied ergodic and kinetic properties of trajectories generated by complex phase space structures. For various Hamiltonian systems, phase space phenomena such as breakup of invariant tori and bifurcations of periodic trajectories were thoroughly studied with particular interest in their effects on the long-term behavior of trajectories for classical systems and on the energy level statistics for quantum systems. In particular, for many particle systems, we developed a kinetic theory of complex phenomena such as clustering motions, relaxation processes and anomoulous diffusion. In addition, we pursued the possibility to apply our theoretical results to real experiments in the optical laser systems, where Hamiltonian dynamical theory can be applicable.Main results are summarized as follows :(1) Fractal structures and phase transition phenomena in mixed Hamiltonian systemsUniversal scaling laws are revealed in the transition regime between tori and chaos. It is shown that many particle systems exhibit statistical distributions such as Weibull distribution and Log-Weibull distribution, which are consistent with the Arnold diffusion theory.(2)Universal properties of Hamiltonian systems violating the KAM conditionA new method is proposed to systematically investigate the phase space of Hamiltonian systems violating the KAM condition. Using this method, we succeed in analyzing the reconnection phenomena and accurately determining the critical threshold for global chaos. It is shown that the set of critical threshold constitutes a fractal.3) Quantum signatures of classical phase space phenomenaWe establish a systematic method to determine the Berry-Robnik parameter of energy level statistics for non-integrable billiard systems. On the basis of this method, we demonstrate that the classical bifurcation phenomena clearly effect the level statistics properties of the corresponding quantum systems

 

Syllabus

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Sub-affiliation

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Research Institute

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

Internal Special Research Projects

  • 2次元マイクロキャビティレーザーを用いたリザバーコンピューティング

    2022  

     View Summary

    リザバーコンピューティングとは、人工ニューラルネットワークを利用した機械学習の一つであり、学習が著しく速いことが特徴である。本研究では、リカレントネット部分を、複雑なダイナミクスを呈するスタジアム形状の2次元マイクロキャビティ内の光の伝搬で代用する。スタジアムキャビティの端面の複数の点で出射光強度を測定し、それらに結合の重みを付けて和を取ったものを最終的な出力とし、この出力がターゲットとできるだけ近くなるように結合の重みを調整することによって学習が行われる。これにより、蔵本・シバシンスキー方程式に従う化学乱流を数値的に求めたものを入力・ターゲット信号として用いて、複雑な振る舞いをする時系列であっても予測可能であることを示した。

  • 2次元微小光共振器における共鳴波動関数のオーバーラップの普遍性に関する研究

    2021  

     View Summary

    2次元微小光共振器を用いたレーザーは2次元全方位に光を出射することのできる新しいタイプのレーザーで、形状を工夫することで出射方向を調整でき、様々な応用が提案・期待されている。また、共振器形状によっては光線軌道がカオスを示す。本研究では、光線軌道が完全カオスを示すような共振器形状として、スタジアム形、D形、および、カージオイド形を用いて、多数の共鳴波動関数を数値的に求め、共鳴波動関数同士の類似度を調べる指標であるオーバーラップの値が0.77を中心に正規分布することを明らかにした。異なる共振器形状で同じオーバーラップの値分布となることにより、これが普遍則であることを示した。

  • カオティックビリヤードレーザーにおけるシングルモード発振の解明

    2020  

     View Summary

    幾何光学として完全カオスであることが数学的に厳密に証明されているカージオイド形状、Bunimovichのスタジアム形状、およびD形状という異なる形状を用いて、完全カオス2次元マイクロキャビティレーザー(カオティックビリヤードレーザー)では、共振器サイズが発振波長よりも十分に大きく、利得媒質への注入エネルギーが十分に大きくなると、1つの共鳴波動関数だけがレーザー発振するシングルモード発振が普遍的に生じる現象であることを明らかにした。さらに、この普遍的シングルモード発振が光線軌道の完全カオスの波動光学的性質としての顕在化であり、共鳴波動関数の量子エルゴード性に起因していることを解明した。

  • 非対称2次元微小光共振器における光線・波動対応

    2019  

     View Summary

    2次元形状を有する微小光共振器は、従来の1次元形状のものにはない全く新しいレーザーとしての機能が期待されており、さらに、波動カオスという基礎物理学研究の舞台としても注目されている。本研究課題では、波動カオスにおけるカイラリティについての研究を推進した。完全に非対称な微小光共振器の固有状態の一種である共鳴の波動関数は、一方向の回転成分を多く含むカイラリティという性質がある。完全カオスであることが数学的に厳密に証明されている2種類の2次元形状の微小光共振器の共鳴を境界要素法を用いて数値的に多数求め、光線動力学の不変分布と比較し、波動・光線対応を解明し、光線動力学でもカイラリティが生じることを明らかにした。

  • 完全カオスビリヤードレーザーにおける発振モードの非線形ダイナミクスの研究

    2018   篠原晋

     View Summary

    対称性を全く持たない完全非対称なリマソン型マイクロキャビティについて研究し、発振モードの候補となる共鳴には、近縮退するものがカイラルモードペアとして2つ組で存在し、それらが共に時計回りの回転波を主成分とすることを解明した。さらに、この共振器を用いたレーザー発振を数値的に研究し、発振時には、カイラルモードペアがロックすることを解明した。そして、2つの共鳴波動関数の位相の関係により、時計回りだけでなく、反時計回りのモードが発振することも可能であることを明らかにした。

  • 2次元マイクロキャビティレーザーの波動・光線カオスと非線形ダイナミクスの研究

    2018   篠原晋

     View Summary

    完全カオスを示す2次元マイクロキャビティレーザーとして、D型およびスタジアム型マイクロキャビティレーザーを数値的に詳しく研究し、両者に共通するレーザー発振特性として、注入電流が十分に大きくなると単一モード発振となることを解明した。また、完全可積分系である楕円型マイクロキャビティレーザーに関しても同様に研究し、注入電流が大きくなっても複数のモードが発振することを解明した。これらの数値的な研究と理論研究によって、単一モード発振が完全カオス型2次元マイクロキャビティレーザーの普遍則であることを明らかにした。

  • 2次元マイクロキャビティレーザーの波動・光線カオスと非線形ダイナミクスの研究

    2017   篠原晋

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    2次元マイクロキャビテイレーザーの光線軌道のエルゴード性が共鳴波動関数およびレーザー発振に及ぼす効果を解明した。光線軌道の定常確率分布と共鳴波動関数の分布を比較し、Q値の高い多数の共鳴波動関数の平均が光線軌道の定常確率分布と一致することを明らかにした。また、光線軌道がカオスを示す場合には、カオスでない場合よりも、共鳴波動関数の重なりが非常に大きくなることを明らかにした。さらに、レーザー発振に関して、光線軌道がカオスを示す場合にはシングルモード発振となり、そうでない場合はマルチモード発振となることを解明した。

  • カオティックビリヤードレーザーに関する波動・光線対応の研究

    2016   鈴木慎, 関口峻矢, 小山廣英, 川嶋悠太, 折原眞児, 外崎真広, 中村友彦, 鈴木裕一郎, 吉川真生

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    カオティックビリヤードレーザーを舞台に、乱流状の複雑な共鳴波動関数と予測不可能な光線軌道の対応を研究した。光線軌道が完全カオスとなるような微小光共振器の場合、光線軌道のエルゴード性を反映して、すべての共鳴波動関数の重なりが大きいことを明らかにした。これに対して、光線軌道が予測可能な可積分微小光共振器では、共鳴波動関数は局在するため、重なりが小さいことを明らかにした。共鳴波動関数はレーザー媒質を通じて相互作用を及ぼすが、その大きさは重なりによって決定される。このため、可積分微小光共振器では、共鳴波動関数は別々の場所に局在し、レーザー発振モードはマルチモードとなる。これに対して、完全カオスビリヤードレーザーでは単一モード発振となることが明らかとなった。

  • 2次元マイクロキャビティレーザーにおける光線と波動の対応

    2014  

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    規則的な光線軌道とカオティックな光線軌道の両方が混在するような2次元マイクロキャビティを外部キャビティとして用い、入力レーザー光をそのカオティックビリヤードキャビティ内部で多重反射させることで長い光路を伝搬遅延した後、レーザーに戻すことで、レーザー光源を不安定化させ、レーザー出力光のカオティックな変動を実現した。この場合のカオティックビリヤードキャビティは、光線波動対応確認のために細長い形状を用いた。この方法が機能することを実験で確認できたため、さらに、円形に近い形状を用い、全反射の利用により反射損失を低減し、戻り光レーザーカオスに必要な長い光路が可能となるように改良した。

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