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Uchiki, Hisao; Kobayashi, Takayoshi; Sakaki, Hiroyuki |
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Photoluminescence and energyâ€loss rates in GaAs quantum wells under highâ€density excitation |
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1987 |
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J. Appl. Phys. |
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62 |
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3 |
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1010-1016 |
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2DEG, GaAs/AlGaAs, heat flow, electron-phonon, hole-phonon, carrier-phonon, interactions |
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The timeâ€resolved luminescence spectra from excited conduction subbands in three samples of multiâ€quantumâ€well GaAs/AlxGa1-xAs (x=0.3 and 1) semiconductors with several well widths and barrier heights were obtained under highâ€density excitations by a 30â€ps pulsed laser at 532 nm, which generated electron–hole pairs to the concentration of 1010–1013/cm2 per well per pulse at 77 K. The temperature and the Fermi energy of electron were determined by fitting best the constructed timeâ€resolved spectrum to the observed, and the timeâ€dependent electron energy was obtained by using these parameters. The energyâ€loss rates of hot electrons are at least twice smaller than the calculated ones induced by the electronâ€polar phonon scattering, including the screening effect due to the high carrier density. |
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635 |
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Xiaolong Hu; Holzwarth, C.W.; Masciarelli, D.; Dauler, E.A.; Berggren, K.K. |
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Efficiently coupling light to superconducting nanowire single-photon detectors |
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Journal Article |
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2009 |
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IEEE Trans. Appl. Supercond. |
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19 |
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3 |
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336-340 |
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optical antennas; SNSPD |
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We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for the fiber coupling, the absorptance of the NbN nanowire for TE-like-polarized photons can reach 76% including coupling efficiency at the wavelength of 1550 nm by adding a silicon nitride waveguide and an inverse-taper coupler. |
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RPLAB @ gujma @ |
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647 |
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Annunziata, Anthony J.; Quaranta, Orlando; Santavicca, Daniel F.; Casaburi, Alessandro; Frunzio, Luigi; Ejrnaes, Mikkel; Rooks, Michael J.; Cristiano, Roberto; Pagano, Sergio; Frydman, Aviad; Prober, Daniel E. |
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Reset dynamics and latching in niobium superconducting nanowire single-photon detectors |
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2010 |
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J. Appl. Phys. |
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108 |
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8 |
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7 |
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SNSPD |
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We study the reset dynamics of niobium (Nb) superconducting nanowire single-photon detectors (SNSPDs) using experimental measurements and numerical simulations. The numerical simulations of the detection dynamics agree well with experimental measurements, using independently determined parameters in the simulations. We find that if the photon-induced hotspot cools too slowly, the device will latch into a dc resistive state. To avoid latching, the time for the hotspot to cool must be short compared to the inductive time constant that governs the resetting of the current in the device after hotspot formation. From simulations of the energy relaxation process, we find that the hotspot cooling time is determined primarily by the temperature-dependent electron-phonon inelastic time. Latching prevents reset and precludes subsequent photon detection. Fast resetting to the superconducting state is, therefore, essential, and we demonstrate experimentally how this is achieved. We compare our results to studies of reset and latching in niobium nitride SNSPDs. |
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RPLAB @ gujma @ |
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649 |
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Yamashita, Taro; Miki, Shigehito; Qiu, Wei; Fujiwara, Mikio; Sasaki, Masahide; Wang, Zhen |
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Temperature dependent performances of superconducting nanowire single-photon detectors in an ultralow-temperature region |
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2010 |
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IEEE Trans. Appl. Supercond. |
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21 |
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3 |
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336 - 339 |
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SNSPD |
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We report on the performance of a fiber-coupled superconducting nanowire single-photon detector (SNSPD) from 4 K down to the ultralow temperature of 16 mK for a 1550 nm wave length. The system detection efficiency (DE) increased with de creasing the temperature and reached the considerably high value of 15% with a dark count rate less than 100 cps below 1.5 K, even without an optical cavity structure. We also observed saturation of the system DE in its bias current dependency at 16 mK, which indicates that the device DE of our SNSPD nearly reached intrinsic DE despite the device having a large active area of 20 μm × 20 μm. The dark count was finite even at 16 mK and the black body radiation becomes its dominant origin in the low temperatures for fiber-coupled devices. |
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RPLAB @ gujma @ |
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656 |
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de Lange, Gert; Krieg, Jean-Michel; Honingh, Netty; Karpov, Alexandre; Cherednichenko, Sergey |
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Title |
Performance of the HIFI flight mixers |
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2008 |
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Proc. 19th Int. Symp. Space Terahertz Technol. |
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98-105 |
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HEB mixer applications, HEB applications |
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We summarize the technology and final results of the superconducting heterodyne SIS and HEB mixers that are developed for the HIFI instrument. Within HIFI 7 frequency bands cover the frequency range from 480 GHz to 1910 GHz. We describe the different device technologies and optical coupling schemes that are used to cover the frequency bands. The efforts of the different mixer teams that participate in HIFI have contributed to an instrument that will have unprecedented sensitivity and frequency coverage. |
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Groningen |
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1074 |
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