The Experts below are selected from a list of 20658 Experts worldwide ranked by ideXlab platform
Hitoshi Kawaguchi - One of the best experts on this subject based on the ideXlab platform.
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pump probe measurement of electron spin relaxation time in 110 oriented gaas algaas Multiple Quantum Well microposts
Applied Physics Express, 2012Co-Authors: Nobuhide Yokota, Kazuhiro Ikeda, Yoshihiro Tsunemi, Hitoshi KawaguchiAbstract:We measured the electron spin relaxation time τs in (110)-oriented GaAs/AlGaAs Multiple Quantum Well microposts using a pump probe technique with a time resolution of 1.3 ps. A long τs of 0.74 ns was obtained even for 0.5 µm posts in which the carrier lifetime τc was drastically shortened to 27 ps. Such long τs and short τc are suitable for fast switching of lasing circular polarizations in vertical-cavity surface-emitting lasers (VCSELs). Our rate equation analysis revealed that a τs much longer than the τc obtained in the measurement does not limit the switching speed of lasing circular polarizations in (110)-VCSELs.
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comparison of measurement techniques for electron spin relaxation time in a gaas algaas Multiple Quantum Well
Physica E-low-dimensional Systems & Nanostructures, 2012Co-Authors: Nobuhide Yokota, Kazuhiro Ikeda, Hitoshi KawaguchiAbstract:Abstract We compared the performance of three measurement techniques for electron spin relaxation time, i.e., polarization- and time-resolved photoluminescence (PTRPL) measurement, time-resolved reflectance (TRR) measurement, and time-resolved Kerr rotation measurement. With all three techniques similar electron spin relaxation times (0.83–1.2 ns) were obtained in a (110) GaAs/AlGaAs Multiple Quantum Well with excitation wavelengths near the heavy-hole exciton resonance at 77 K. We extracted the spin-independent contribution of the Coulomb interaction which obscures TRR signals as an offset without limiting the excitation wavelength to heavy-hole exciton resonance, using the degree of electron spin polarization simultaneously obtained by the PTRPL measurement. It was found that the Coulomb interaction contribution is dominant in TRR signals over both heavy- and light-hole exciton resonances.
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gain spectra and saturation power of asymmetrical Multiple Quantum Well semiconductor optical amplifiers
IEE Proceedings - Optoelectronics, 2005Co-Authors: V V Lysak, Hitoshi Kawaguchi, I A SukhoivanovAbstract:A new numerical model for calculating the steady-state gain properties of asymmetrical Multiple Quantum Well (MQW) semiconductor optical amplifiers (SOAs) is presented. The model consists of a rate-equation system for carriers in each Quantum Well, with an integrated gain model. Using this model, the calculated gain spectra and saturation characteristics of an asymmetrical 6-QW SOA are compared with those for symmetrical MQW SOAs. The asymmetrical MQW SOA is found to have a gain bandwidth of about 137 nm and a saturation power of -8.8 dB m at 202 mA, both greater than conventional symmetrical MQW SOAs at the same gain.
Harumasa Yoshida - One of the best experts on this subject based on the ideXlab platform.
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radiative and nonradiative recombination in an ultraviolet gan algan Multiple Quantum Well laser diode
Applied Physics Letters, 2010Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Kazuya Uchiyama, Hirofumi KanAbstract:We have experimentally investigated the radiative and nonradiative recombination in a GaN/AlGaN Multiple-Quantum-Well laser diode. The each carrier lifetime has been evaluated based on a rate equation analysis of light output-current characteristics of the laser diode. The estimated nonradiative carrier lifetime is 830 ps, and the Auger recombination is negligibly small at room temperature. At a threshold current density of 8 kA cm−2, the carrier density and the internal Quantum efficiency are estimated to be 2.6×1019 cm−3 and 34%, respectively. These results are responsible for experimental and theoretical analysis of optical and electrical properties in AlGaN-based laser diodes.
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demonstration of an ultraviolet 336 nm algan Multiple Quantum Well laser diode
Applied Physics Letters, 2008Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Hirofumi KanAbstract:We have demonstrated laser operation of an AlGaN Multiple-Quantum-Well (MQW) laser diode (LD) with a peak wavelength of 336.0 nm under pulsed current mode at room temperature. The LD was fabricated on a low-dislocation-density Al0.3Ga0.7N grown on a sapphire substrate using a hetero-facet-controlled epitaxial lateral overgrowth method. The laser emission is strongly transverse electric polarized with a peak output power of 3 mW and a differential external Quantum efficiency of 1.1%. This demonstration of the LD lasing in ultraviolet-AII spectral band (320–340 nm) suggests that the AlGaN MQW LDs can be potent devices opening a path to deeper ultraviolet LDs.
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A 342-nm ultraviolet AlGaN Multiple-Quantum-Well laser diode
Nature Photonics, 2008Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu KuwabaraAbstract:Short-wavelength UV laser diodes are required for applications ranging from sensing, data storage and materials processing. Here, an electrically driven semiconductor laser that operates at 342.3 nm, the shortest wavelength so far, is reported. The device emits milliwatt-scale powers at room temperature when driven by pulsed current. The realization of semiconductor laser diodes and light-emitting diodes that emit short-wavelength ultraviolet light is of considerable interest for a number of applications including chemical/biochemical analysis, high-density data storage and material processing. Group III nitride materials are one of the most promising candidates for fabricating such devices. Here we describe an AlGaN Multiple-Quantum-Well laser diode that emits light at 342 nm, the shortest wavelength ever reported for an electrically driven laser diode. To fabricate the laser, a low-dislocation-density AlGaN layer with an AlN mole fraction of 0.3 was grown on a sapphire substrate using a hetero facet-controlled epitaxial lateral overgrowth (hetero-FACELO) method^ 1 , 2 , 3 . An AlGaN Multiple-Quantum-Well structure was then grown on the high-quality AlGaN layer. Lasing at a wavelength of 342.3 nm was observed under pulsed current mode at room temperature.
Hirofumi Kan - One of the best experts on this subject based on the ideXlab platform.
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radiative and nonradiative recombination in an ultraviolet gan algan Multiple Quantum Well laser diode
Applied Physics Letters, 2010Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Kazuya Uchiyama, Hirofumi KanAbstract:We have experimentally investigated the radiative and nonradiative recombination in a GaN/AlGaN Multiple-Quantum-Well laser diode. The each carrier lifetime has been evaluated based on a rate equation analysis of light output-current characteristics of the laser diode. The estimated nonradiative carrier lifetime is 830 ps, and the Auger recombination is negligibly small at room temperature. At a threshold current density of 8 kA cm−2, the carrier density and the internal Quantum efficiency are estimated to be 2.6×1019 cm−3 and 34%, respectively. These results are responsible for experimental and theoretical analysis of optical and electrical properties in AlGaN-based laser diodes.
-
demonstration of an ultraviolet 336 nm algan Multiple Quantum Well laser diode
Applied Physics Letters, 2008Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Hirofumi KanAbstract:We have demonstrated laser operation of an AlGaN Multiple-Quantum-Well (MQW) laser diode (LD) with a peak wavelength of 336.0 nm under pulsed current mode at room temperature. The LD was fabricated on a low-dislocation-density Al0.3Ga0.7N grown on a sapphire substrate using a hetero-facet-controlled epitaxial lateral overgrowth method. The laser emission is strongly transverse electric polarized with a peak output power of 3 mW and a differential external Quantum efficiency of 1.1%. This demonstration of the LD lasing in ultraviolet-AII spectral band (320–340 nm) suggests that the AlGaN MQW LDs can be potent devices opening a path to deeper ultraviolet LDs.
Masakazu Kuwabara - One of the best experts on this subject based on the ideXlab platform.
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radiative and nonradiative recombination in an ultraviolet gan algan Multiple Quantum Well laser diode
Applied Physics Letters, 2010Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Kazuya Uchiyama, Hirofumi KanAbstract:We have experimentally investigated the radiative and nonradiative recombination in a GaN/AlGaN Multiple-Quantum-Well laser diode. The each carrier lifetime has been evaluated based on a rate equation analysis of light output-current characteristics of the laser diode. The estimated nonradiative carrier lifetime is 830 ps, and the Auger recombination is negligibly small at room temperature. At a threshold current density of 8 kA cm−2, the carrier density and the internal Quantum efficiency are estimated to be 2.6×1019 cm−3 and 34%, respectively. These results are responsible for experimental and theoretical analysis of optical and electrical properties in AlGaN-based laser diodes.
-
demonstration of an ultraviolet 336 nm algan Multiple Quantum Well laser diode
Applied Physics Letters, 2008Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu Kuwabara, Hirofumi KanAbstract:We have demonstrated laser operation of an AlGaN Multiple-Quantum-Well (MQW) laser diode (LD) with a peak wavelength of 336.0 nm under pulsed current mode at room temperature. The LD was fabricated on a low-dislocation-density Al0.3Ga0.7N grown on a sapphire substrate using a hetero-facet-controlled epitaxial lateral overgrowth method. The laser emission is strongly transverse electric polarized with a peak output power of 3 mW and a differential external Quantum efficiency of 1.1%. This demonstration of the LD lasing in ultraviolet-AII spectral band (320–340 nm) suggests that the AlGaN MQW LDs can be potent devices opening a path to deeper ultraviolet LDs.
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A 342-nm ultraviolet AlGaN Multiple-Quantum-Well laser diode
Nature Photonics, 2008Co-Authors: Harumasa Yoshida, Yoji Yamashita, Masakazu KuwabaraAbstract:Short-wavelength UV laser diodes are required for applications ranging from sensing, data storage and materials processing. Here, an electrically driven semiconductor laser that operates at 342.3 nm, the shortest wavelength so far, is reported. The device emits milliwatt-scale powers at room temperature when driven by pulsed current. The realization of semiconductor laser diodes and light-emitting diodes that emit short-wavelength ultraviolet light is of considerable interest for a number of applications including chemical/biochemical analysis, high-density data storage and material processing. Group III nitride materials are one of the most promising candidates for fabricating such devices. Here we describe an AlGaN Multiple-Quantum-Well laser diode that emits light at 342 nm, the shortest wavelength ever reported for an electrically driven laser diode. To fabricate the laser, a low-dislocation-density AlGaN layer with an AlN mole fraction of 0.3 was grown on a sapphire substrate using a hetero facet-controlled epitaxial lateral overgrowth (hetero-FACELO) method^ 1 , 2 , 3 . An AlGaN Multiple-Quantum-Well structure was then grown on the high-quality AlGaN layer. Lasing at a wavelength of 342.3 nm was observed under pulsed current mode at room temperature.
Nobuhide Yokota - One of the best experts on this subject based on the ideXlab platform.
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pump probe measurement of electron spin relaxation time in 110 oriented gaas algaas Multiple Quantum Well microposts
Applied Physics Express, 2012Co-Authors: Nobuhide Yokota, Kazuhiro Ikeda, Yoshihiro Tsunemi, Hitoshi KawaguchiAbstract:We measured the electron spin relaxation time τs in (110)-oriented GaAs/AlGaAs Multiple Quantum Well microposts using a pump probe technique with a time resolution of 1.3 ps. A long τs of 0.74 ns was obtained even for 0.5 µm posts in which the carrier lifetime τc was drastically shortened to 27 ps. Such long τs and short τc are suitable for fast switching of lasing circular polarizations in vertical-cavity surface-emitting lasers (VCSELs). Our rate equation analysis revealed that a τs much longer than the τc obtained in the measurement does not limit the switching speed of lasing circular polarizations in (110)-VCSELs.
-
comparison of measurement techniques for electron spin relaxation time in a gaas algaas Multiple Quantum Well
Physica E-low-dimensional Systems & Nanostructures, 2012Co-Authors: Nobuhide Yokota, Kazuhiro Ikeda, Hitoshi KawaguchiAbstract:Abstract We compared the performance of three measurement techniques for electron spin relaxation time, i.e., polarization- and time-resolved photoluminescence (PTRPL) measurement, time-resolved reflectance (TRR) measurement, and time-resolved Kerr rotation measurement. With all three techniques similar electron spin relaxation times (0.83–1.2 ns) were obtained in a (110) GaAs/AlGaAs Multiple Quantum Well with excitation wavelengths near the heavy-hole exciton resonance at 77 K. We extracted the spin-independent contribution of the Coulomb interaction which obscures TRR signals as an offset without limiting the excitation wavelength to heavy-hole exciton resonance, using the degree of electron spin polarization simultaneously obtained by the PTRPL measurement. It was found that the Coulomb interaction contribution is dominant in TRR signals over both heavy- and light-hole exciton resonances.
