H Nakano

NTT DATA Corporation, Edo, Tōkyō, Japan

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Publications (50)56.82 Total impact

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    ABSTRACT: We have used a femtosecond time-resolved core-level surface PES system based on the 92-eV harmonic source to study the surface carrier dynamics that induces the transient SPV on semiconductor surfaces. We clarified the temporal evolution of the transient SPV characterized by the time of the photo-generated carrier separation and recombination. This result demonstrates the potential of this technique for clarifying the initial stage of the surface carrier dynamics after photoexcitation.
    The European Physical Journal Conferences 03/2013; 41:04017-. DOI:10.1051/epjconf/20134104017
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    ABSTRACT: Proposed is an approach to achieving a carrier-envelope-offset (CEO)-locked frequency comb with 25 GHz mode spacing in the telecommunications wavelength region. To achieve the approach, a 250 fs laser pulse train at a 25 GHz repetition rate was developed by intensity- and phase-modulating a seed light emitted from a continuous-wave laser diode and propagating it through a dispersive fibre. Using the authors developed tellurite photonics crystal fibre with a high-nonlinear coefficient, octave-spanning supercontinuum generation in the 1.5 m band from a 250 MHz gated pulse train for CEO frequency detection was demonstrated.
    Electronics Letters 10/2010; DOI:10.1049/el.2010.2228 · 1.07 Impact Factor
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    ABSTRACT: We propose an approach to achieving a carrier-envelope phase-locked frequency comb with 25-GHz mode spacing at 1.5 µm. We demonstrate octave-spanning supercontinuum generation with the widest mode spacing ever achieved using a CW laser diode.
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    ABSTRACT: Ultrashort laser pulses allow us to do the real-time observation of carrier and phonon dynamics. Under the resonant excitation, the strong coupling between carriers and coherent phonons in Si is observed in time-domain. By using photon below the direct band gap (-3.4 eV), Si is excited non-resonantly from the valence band and the conduction band p- and n-type Si, respectively. An opposite effect between p- and n-type doping on the dephasing dynamics of coherent phonons is observed.
    Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
  • H. Nakano, A. Ishizawa, K. Oguri
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    ABSTRACT: The authors investigate the dependence of the properties of an EUV emission driven by a sub-10- fs laser pulse on the carrier envelope phase (CEP). The results indicated that a complicated fine structure appeared near the highest edge of the "plateau," which might be interference between the regular harmonics and the modulated spectral components in the cut-off region.
    Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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    ABSTRACT: We investigated the magneto-optical properties of charge-tunable GaAs quantum dots (QDs). Photoluminescence (PL) spectra change greatly with charge states of the QDs, and the PL lines of excited trions show complex magnetic field dependencies, which are quite different from that of the lowest radiative trion. A simulation using the configuration-interaction method supports the assignment of the PL emissions, and the effects of electron-electron and electron-hole interactions on shell and spin configurations of excited trions are discussed.
    Physical review. B, Condensed matter 03/2009; 79(12). DOI:10.1103/PhysRevB.79.121303 · 3.66 Impact Factor
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    ABSTRACT: We demonstrate a carrier-envelope-offset (CEO)-locked frequency comb with 230-pJ fiber coupling pulse energy by using a passive-modelocked Er-fiber amplifier laser. We succeeded in CEO stabilization at telecommunications wavelengths using the lowest fiber coupling pulse energy.
    Lasers and Electro-Optics, 2008 and 2008 Conference on Quantum Electronics and Laser Science. CLEO/QELS 2008. Conference on; 06/2008
  • K. Tateno, G. Zhang, H. Nakano
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    ABSTRACT: Two types of InP growth in GaP-based nanowires have been reported. The nanowires were grown by the vapor–liquid–solid method using Au particles of around 20-nm diameter as catalysts. For GaP/InP/GaP nanowire growth, InP egg-like structures were formed when the InP growth temperature was higher than the GaP growth one. Successively, the second GaP nanowire could be grown on these InP structures. Transmission electron microscopy and energy dispersive X-ray spectroscopy analyses indicated that these InP nanostructures were grown in both the axial and radial directions and that the edge of the first GaP nanowires was partly covered with InP, which formed a core-shell structure. For InP capping growth, which was performed after the growth of two-times-alternated GaP/GaAs on GaP nanowires, selective InP growth on the two GaAs parts was confirmed.
    Journal of Crystal Growth 06/2008; 310(12):2966–2969. DOI:10.1016/j.jcrysgro.2008.03.001 · 1.69 Impact Factor
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    ABSTRACT: One-dimensional periodically polarity-inverted (PPI) structures of ZnO for nonlinear optical devices are fabricated on c-plane Al2O3 substrates. To do so, corrugated MgO buffer layers are fabricated by etching after patterning, which is followed by the growth of ZnO layers by plasma-assisted molecular beam epitaxy. The polarity-inverted structures are confirmed by scanning piezoresponse microscopy and atomic-force microscopy. PPI structures with submicron periodicity are fabricated to satisfy the quasiphase matching condition for second harmonic generation of light.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 05/2008; 26(3). DOI:10.1116/1.2905244 · 1.36 Impact Factor
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    ABSTRACT: The integration of III-V semiconductor materials with Si technology is of great interest for optoelectronic integration circuits. We have studied the growth and structural aspects of GaP nanowires (NWs) grown on Si substrate in a metalorganic vapor phase epitaxy system. Au colloid particles dispersed on Si substrate were used as catalysts to conduct the NW growth. The growth temperature considerably affected the growth rate and shape of GaP NWs. The growth rate showed a maximum value of 14.69 nm/s at 480 °C. When growth temperature increased the radial growth on NW sides was enhanced and the NWs therefore exhibited a tapering shape. GaP NWs with a uniform diameter could be grown at a growth temperature as low as 420 °C using a two-temperature process. The NW diameter could be well controlled by using size-selective Au colloid particles. The growth rate dependence showed that the thin NWs grew more slowly than thick ones and the V/III source ratio had a significant effect on the growth rate dependence. An analysis of the GaP/Si interface by transmission electron microscopy indicated that the NWs were epitaxially grown on the Si(111) substrate. Based on these experimental results, the growth mechanism of the GaP NWs on Si was discussed.
    Journal of Applied Physics 01/2008; 103(1). DOI:10.1063/1.2828165 · 2.19 Impact Factor
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    ABSTRACT: We have systematically evaluated quality (Q) factor in quantum-dot (QD) photonic-crystal nanocavities. The measured Q factor was very sensitive to the detuning energy of the cavity mode to QD inhomogeneous broadening due to the re-absorption effect of the uncoupled QDs within the nanocavity. We achieved a high Q factor of over 10,000 and an ultra-low threshold lasing by the detuning of the cavity mode and the suppression of this effect.
    Indium Phosphide & Related Materials, 2007. IPRM '07. IEEE 19th International Conference on; 06/2007
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    ABSTRACT: The growth of GaP and AlAs/GaAs/GaP heterostructure nanowires on Si using Au colloids as catalysts was investigated. For GaP nanowire growth, we found an epitaxial relationship between the GaP nanowires and Si substrate. The AlAs/GaAs/GaP heterostructure nanowires were found to grow vertically on Si. Structural analysis indicates that the hetero-interfaces are within several atomic layers in thickness and that the GaAs and AlAs segments have very few dislocations.
    Indium Phosphide & Related Materials, 2007. IPRM '07. IEEE 19th International Conference on; 06/2007
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    ABSTRACT: We report on narrow photoluminescence (PL) spectra obtained from spatially localized excitons in InGaN quantum wells (QW). These PL lines (less than 1 meV wide) are clearly detected in QWs on several buffer structures and substrates with the micro-PL technique in low temperature regions. A narrow PL spectrum is one of the characteristics of an exciton confined in a quantum dot (QD). Our results directly confirm that QD-like nano-objects exist in InGaN QWs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 06/2007; 4(7):2350-2353. DOI:10.1002/pssc.200674756
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    ABSTRACT: Temperature insensitive ultra low threshold lasing up to 90 K is observed in quantum dots in photonic crystal nanocavities, due to the fast radiative recombination of excitons and the suppression of the phonon scattering probability.
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    ABSTRACT: The authors report the effects of nonradiative recombination on the properties of spatially localized excitons in InGaN quantum well structures studied using a microphotoluminescence (PL) technique. Sharp PL lines (linewidth of less than 1 meV) are clearly obtained by combining the PL and nanolithographic techniques. The PL originates from localized excitons induced by quantum-dot-like local potential minima where indium is accumulated. A systematic study with various kinds of samples reveals that suppressing the density of the nonradiative centers is crucially important in terms of observing the exciton localization effects rather than increasing the effects of indium accumulation.
    Applied Physics Letters 11/2006; 89(22):222110-222110-3. DOI:10.1063/1.2399347 · 3.52 Impact Factor
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    Y Tokura, H. Nakano, T Kubo
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    ABSTRACT: We discuss the effect of quantum interference on transport through a quantum dot system. We introduce an indirect coherent coupling parameter alpha, which provides constructive/destructive interference in the transport current depending on its phase and the magnetic flux. We estimate the current through the quantum dot system using the non-equilibrium Green's function method as well as the master equation method in the sequential tunneling regime. The visibility of the Aharonov-Bohm oscillation is evaluated. For a large inter-dot Coulomb interaction, the current is strongly suppressed by the quantum interference effect, while the current is restored by applying an oscillating resonance field with the frequency of twice the inter-dot tunneling energy. Comment: 10 pages, 3 figures
    New Journal of Physics 11/2006; DOI:10.1088/1367-2630/9/5/113 · 3.67 Impact Factor
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    ABSTRACT: We report vertical GaP nanowires self-arranged in lines formed from Au islands that were initially arranged at single-layer steps on Si(111) substrates. These Au islands are spontaneously arranged by controlling the deposition. There are three aspects to the growth of vertical GaP wires: the cosupply of TMGa and PH3, two growths at different temperatures, and a low PH3 flow rate. The grown wires are quite ordered in lines of several micrometers. Electrical measurement confirmed selective current flow at the wires and we confirmed photoluminescence from the wires. This bottom-up technique is promising for nano-hetero-device integration on Si circuits.
    Applied Physics Letters 07/2006; 89(3):033114-033114-3. DOI:10.1063/1.2227800 · 3.52 Impact Factor
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    ABSTRACT: Spatially localized excitons are observed in InGaN quantum well structures at 4K by using a micro-photoluminescence (PL) technique. By combining PL and nano-lithographic techniques, we are able to detect PL signals with a 0.2μm spatial resolution. A sharp PL line (linewidth of
    Solid State Communications 06/2006; 138(12):590-593. DOI:10.1016/j.ssc.2006.04.006 · 1.70 Impact Factor
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    ABSTRACT: We have studied the emission properties of individual InAs quantum dots (QDs) grown in an InGaAsP matrix on InP(100) by metal-organic vapor-phase epitaxy. Low-temperature microphotoluminescence spectroscopy shows emission from single QDs around 1550 nm with characteristic exciton-biexciton behavior, and a biexciton antibinding energy of more than 2 meV. Temperature-dependent measurements reveal negligible optical-phonon induced broadening of the exciton line up to 50 K, and emission from the exciton state clearly persists above 70 K. Furthermore, we find no measurable polarized fine structure splitting of the exciton state within the experimental precision. These results are encouraging for the development of a controllable photon source for fiber-based quantum information and cryptography systems. Comment: 3 pages, 4 figures, submitted APL
    Applied Physics Letters 03/2006; 89(18). DOI:10.1063/1.2378403 · 3.52 Impact Factor
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    ABSTRACT: We present a detailed investigation into the optical characteristics of individual InAs quantum dots (QDs) grown by metalorganic chemical vapor deposition, with low temperature emission in the telecoms window around 1300nm . Using microphotoluminescence (PL) spectroscopy we have identified neutral, positively charged, and negatively charged exciton and biexciton states. Temperature-dependent measurements reveal dot-charging effects due to differences in carrier diffusivity. We observe a pronounced linearly polarized splitting of the neutral exciton and biexciton lines (˜250mueV) resulting from asymmetry in the QD structure. This asymmetry also causes a mixing of the excited trion states which is manifested in the fine structure and polarization of the charged biexciton emission; from this data we obtain values for the ratio between the anisotropic and isotropic electron-hole exchange energies of Delta˜1/Delta˜0≈0.2-0.5 . Magneto-PL spectroscopy has been used to investigate the diamagnetic response and Zeeman splitting of the various exciton complexes. We find a significant variation in g factor between the exciton, the positive biexciton, and the negative biexciton; this is also attributed to anisotropy effects and the difference in lateral extent of the electron and hole wave functions.
    Physical Review B 03/2006; 73(11). DOI:10.1103/PhysRevB.73.115322 · 3.66 Impact Factor

Publication Stats

236 Citations
56.82 Total Impact Points

Institutions

  • 2007–2013
    • NTT DATA Corporation
      Edo, Tōkyō, Japan
  • 2009
    • Nippon Telegraph and Telephone
      Edo, Tōkyō, Japan
  • 2008
    • NTT DOCOMO
      Edo, Tōkyō, Japan
  • 2006
    • Tokyo University of Science
      Edo, Tōkyō, Japan
  • 1992
    • Gunma University
      Maebashi, Gunma Prefecture, Japan