K. Tomioka

Publications (5)0 Total impact

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

  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
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  ABSTRACT: 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.
  Phys. Rev. B. 02/2012; 85(7).
• Source

  Available from: Hidekazu Kumano

  Article: Longitudinal and transverse exciton spin relaxation times in single InP/InAsP/InP nanowire quantum dots

  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
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  ABSTRACT: We have investigated the optical properties of a single InAsP quantum dot embedded in a standing InP nanowire. A regular array of nanowires was fabricated by epitaxial growth and electron-beam patterning. The elongation of 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 InP nanowire. The longitudinal exciton spin relaxation time was evaluated by the degree of the random polarization of emission originating from exciton state confined in a single nanowire quantum dots by using Mueller Calculus based on Stokes parameters representation.
  09/2011;
• Conference Proceeding: Selective-area MOVPE growth and optical properties of single InAsP quantum dots embedded in InP NWs

  Y. Kobayashi, J. Motohisa, K. Tomioka, S. Hara, K. Hiruma, T. Fukui
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  ABSTRACT: We grew InAsP and InP/InAsP/InP heterostructure NWs (NWs) by selective-area MOVPE and carried out micro-photoluminescence (μ-PL) measurement. We investigated growth conditions for InAsP NWs and that embedded in InP NWs, and obtained exciton and biexciton emissions from InAsP QDs at optimized growth conditions. Negative binding energy of biexciton was observed due to the strong Coulomb interaction between the holes in the QDs.
  Indium Phosphide & Related Materials (IPRM), 2010 International Conference on; 07/2010
• Source

  Available from: V. Zwiller

  Article: 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
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  ABSTRACT: 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.
  Journal of Physics Conference Series 11/2009; 193(1):012132.
• Source

  Available from: Hidekazu Kumano

  Article: Position controlled nanowires for infrared single photon emission

  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
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  ABSTRACT: 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.