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

2011 Fiscal Year Annual Research Report

• Project/Area Number: 21246048
• Research Institution: Hokkaido University
• Principal Investigator: 末宗 幾夫 北海道大学, 電子科学研究所, 教授 (00112178)
• Co-Investigator(Kenkyū-buntansha): 熊野 英和 北海道大学, 電子科学研究所, 准教授 (70292042) ; 笹倉 弘理 北海道大学, 電子科学研究所, 助教 (90374595)
• Keywords: 半導体量子ドット / 金属埋め込み / 単一光子光源 / 2次相関関数 / 光子相関測定 / 荷電励起子 / オンデマンド / FDTD

Research Abstract

量子ドットにおける電子一光子状態変換を効率的に行ためには、両者を効率よく結合させる「環境」を準備する必要がある。本研究ではその第一ステップとして、半導体量子ドットを金属に埋め込んで金属微小光共振器を作製し、量子ドットから発生した光子を外部へ効率よく取り出す研究を進めた。これまでに、量子ドットを含む半導体ピラー構造を作製し、これをチタン金属に埋め込み、30倍以上の発光増強を観測し、単一光子発生条件を用いて光子の外部取り出し効率の絶対値を見積もる手法を確立して、量子効率8%を見積もった。本年度はより反射率の高い銀に埋め込む方法を開発し、光子取り出し効率として18%を観測した。同時に研究を進めたFDTD法による金属微小光共振器内の電磁界シミュレーションでは、埋め込む半導体を円錐に近い構造にし、集光するレンズの開口数(NA)を0.8程度とすることによって、光子取り出し効率80%が見込めることが示された。今年度の実験ではNAが0.4のレンズを用いており、NAの高いレンズによる光子取り出しも含めてさらに検討を継続中である。量子ドットとしては、従来のGaAs系による波長950nm帯に加え、ファイバー結合を目指して、InP系による波長1300nm,1550nmで発光する単一量子ドットも実現した。一方量子ドットから発生する光子は、量子準位に関するパウリの排他律により原理的には一つの電子状態から一つの光子が発生する。しかし現実には欠陥準位からの発光や、発光後にすぐ準位を埋めるRe-fillingの効果により、背景光子が発生してしまう。このような単一光子発生の純度は、発生光子の2次相関関数g(2)(τ=0)によって評価できる。昨年度g(2)(τ=0)として、0.02の低い値を観測したが、本年は量子ドットの準位より1光学フォノンエネルギーだけ高いエネルギー位置を準共鳴励起することにより、パルス励起ごとに光子が発生する飽和励起条件で0.007、低い励起レベルでは0.0035と世界最小値を観測した。

Research Products

• [Journal Article] Cooper-pair Raidative Recombination in Semiconductor Heterostructures : Impact on Quantum Optics and Optoelectronics (2012)
  • Author(s): I.Suemune, H.Sasakura, Y.Hayashi, K.Tanaka, T.Akazaki, Y.Asano, R.Inoue, H.Takayanagi, E.Hanamura, J.-H.Huh, C.Hemannstaedter, S.Odashima, H. Kumano
  • Journal Title: Japan.J.App.Phys. Volume: Vol.51 Pages: 10114-1-10114-10
  • DOI: 10.1143/JJAP.51.010114
  • Peer Reviewed
• [Journal Article] Inter-dot Coupling and Excitation Transfer Mechanisms of Telecommunication Band InAs Quantum Dots at Elevated Temperatures (2012)
  • Author(s): C.Hermannst adter, N.A.Jahan, J.-H.Huh, H.Sasakura, K.Akahane, M.Sasaki, I.Suemune
  • Journal Title: New J.Phys. Volume: Vol.14 Pages: 023037-1-023037-19
  • DOI: 10.1088/1367-2630/14/2/023037
  • Peer Reviewed
• [Journal Article] Characterization of Two-photon Polarization Mixed States Generated from Entangled-classical Hybrid Photon Source (2011)
  • Author(s): H.Kumano,K.Matsuda,S.Ekuni, H.Sasakura, I.Suemune
  • Journal Title: Opt.Express Volume: 19 Pages: 14249-14259
  • DOI: 10.1364/OE.19.014249
  • Peer Reviewed
• [Journal Article] Conversion of Light Propagation Direction for Highly Efficient Solar Cells (2011)
  • Author(s): I.Suemune
  • Journal Title: Appl.Phys.Express Volume: 4 Pages: 102301-1-102301-3
  • DOI: 10.1143/APEX.4.102301
  • Peer Reviewed
• [Journal Article] Enhanced Photon Generation in a Nb/n-InGaAs/p-InP Superconductor/Semiconductor-diode Light Emitting Device (2011)
  • Author(s): H.Sasakura, S.Kuramitsu, Y.Hayashi, K.Tanaka, T.Akazaki, E.Hanamura, R.Inoue, H.Takayanagi, Y.Asano, H.Kumano, I.Suemune
  • Journal Title: Phys.Rev.Lett. Volume: Vol.107 Pages: 157403-1-157403-5
  • DOI: 10.1103/PhysRevLett.107.157403
  • Peer Reviewed
• [Presentation] Two-photon Emission Process with Cooper-pair Injection into Semiconductor (2012)
  • Author(s): H.Sasakura, C.Hermannsdadter, H.Kumano, I.Suemune
  • Organizer: Photonic West (Invited)
  • Place of Presentation: The Moscone Center, San Franscisco (USA)
  • Year and Date: 20120121-20120126
• [Presentation] Photon Generation and Absorption Processes in Semiconductor Nanostructures (2011)
  • Author(s): I.Suemune
  • Organizer: 12th RIES-Hokudai International Symposium (Invited)
  • Place of Presentation: 札幌・シャトレーゼガトーキングダム
  • Year and Date: 20111121-20111122
• [Presentation] Transformation from InAs Quantum Dots to Disks for Reduced Exction-State Splitting (2011)
  • Author(s): S.Sakurai, S.Odashima, H.Iijima, I.Suemune
  • Organizer: 24th International Microprocesses and Nanotechnology Conference (MNC 2011)
  • Place of Presentation: 京都・全日空ホテル
  • Year and Date: 20111024-20111027
• [Presentation] Size Control of Tapered Cones for High Density Quantum Dots as 1.55μm Emitters (2011)
  • Author(s): J.-H.Huh, C.Hemannstadter, K.Akahane, N.A Jahan, H.Sasakura, H.Sasaki, I.Suemune
  • Organizer: 24th International Microprocesses and Nanotechnology Conference (MNC 2011)
  • Place of Presentation: 京都・全日空ホテル
  • Year and Date: 20111024-20111027
• [Presentation] n-ZnO/InAs QDs/p-GaAs Pillar structure Prepared as a Single Photon Emitter (2011)
  • Author(s): H.Iijima, S.Odashima, I.Suemune
  • Organizer: 24th International Microprocesses and Nanotechnology Conference (MNC 2011)
  • Place of Presentation: 京都・全日空ホテル
  • Year and Date: 20111024-20111027
• [Presentation] Exciton Polarization in A Single Nanowire Quantum Dot (2011)
  • Author(s): H.Sasakura, S.N.Dorenbos, M.P.van Kouwen, N.Akopian, V.Zwiller, J.Motohisa, T.Fukui, C.Hermannstadter, H.Kumano, I.Suemune
  • Organizer: 12th International Conference on Optics of Excitons in Confined Systems (OECS12)
  • Place of Presentation: Cite Internationale Universitaire, Paris (France)
  • Year and Date: 20110912-20110916
• [Presentation] Characterization of Two-photon Mixed states Employed with Polarization Entangled-classical Hybrid Photon Source (2011)
  • Author(s): K.Matsuda, H.Kumano, S.Ekuni, H.Sasakura, I.Suemune
  • Organizer: International Conference on Quantum Information Processing and Communication (QIPC 2011)
  • Place of Presentation: ETH Zurich (Switzerland)
  • Year and Date: 20110905-20110909
• [Presentation] Drastic Enahancement of Interband Optical Transition Probability with Electron Pairing in Semiconductors (2011)
  • Author(s): I.Suemune, H.Sasakura, C.Hermannstadter, J.-H.Huh, Y.Asano, K.Tanaka, T.Akazaki, H.Kumano
  • Organizer: IQEC/CLEO Pacific Rim 2011
  • Place of Presentation: Sydney Convention and Exhibition Center (Australia)
  • Year and Date: 20110828-20110901
• [Presentation] Radiative Recombination Processes based on Electron Cooper Pairs in Doped Semiconductors : Quantitative Evaluation of Roles of Cooper Pairs and Normal Electrons (2011)
  • Author(s): I.Suemune, H.Sasakura, C.Hermannstadter, J.-H.Huh, Y.Asano, K.Tanaka, T.Akazaki, H.Kumano
  • Organizer: The 15th Conference on Modulated Semiconductor structures (MSS15)
  • Place of Presentation: Turnbill Conference Center, Tallahassee, Florida (USA)
  • Year and Date: 20110725-20110729
• [Presentation] High extraction efficiency of photons emitted from a single quantumdot in a pillar structure embedded in Silver (2011)
  • Author(s): H.Iijima, M.Wada, H.Nakajima, S.Odashina, T.Nishio, Y.Matsuo, K.Ijiro, H.Kumano, I.Suemune
  • Organizer: The 15th Conference on Modulated Semiconductor Structures (MSS15)
  • Place of Presentation: Turnbill Conference Center, Tallahassee, Florida (USA)
  • Year and Date: 20110725-20110729
• [Presentation] Highly Pure Single-Photon Emission from a Metal-embedded Single Quantum Dot under Quasi-resonant Excitation (2011)
  • Author(s): H.Nakajima, H.Kumano, H.Iijima, I.Suemune
  • Organizer: The 15th Co nference on Modulated Semiconductor structures (MSS15)
  • Place of Presentation: Turnbill Conference Center, Tallahassee, Florida (USA)
  • Year and Date: 20110725-20110729
• [Presentation] Band Structure and Thermal Escape Processesof strained InGaSb/AlGaSb Quantum Wells (2011)
  • Author(s): N.A.Jahan, H.Iijima, C.Hemannstadter, P.Ahirwar, T.J.Rotter, G.Balakrishnan, H.Kumano, I.Suemune
  • Organizer: Electronic Materials Conference 2011
  • Place of Presentation: Univ.of California, Santa Barbara, CA (USA)
  • Year and Date: 20110622-20110624
• [Presentation] Temperature Dependent Photoluminescence of Ensemble and Single InAs/InGaAlAs Quantum Dots (2011)
  • Author(s): N.A.Jahan, C.Hermannstadter, J.-H.Huh, H.Sasakura, K.Akahane, M.Sasaki, P.Ahirwar, T.J.Rotter, G.Balakrishnan, H.Kumano, I.Suemune
  • Organizer: Electronic Materials Conference 2011
  • Place of Presentation: Univ.of California, Santa Barbara, CA (USA)
  • Year and Date: 20110622-20110624
• [Presentation] Long Wavelength Emission from Nano-cone Structures with Embedded Single InAs/InGaAlAs Quantum Dots Grown on InP Substrates (2011)
  • Author(s): C.Hermannstadter, J.-H. Huh, N.A.Jahan, H.Sasakura, I.Suemune
  • Organizer: 23rd International Conference on InP and Related Materials (IPRM2011)
  • Place of Presentation: Maritim proArte Hotel, Berlin (Germany)
  • Year and Date: 20110522-20110526
• [Presentation] Control of Photon Emission Processes in Semiconductor Nanostructures (2011)
  • Author(s): I.Suemune
  • Organizer: Villa Conference on Interactions Among Nanostructures (Invited)
  • Place of Presentation: Red Rock Casino, Las Vegas, Nevada (USA)
  • Year and Date: 20110421-20110425