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Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol’tsman, G. N.; Demsar, J. |
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Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy |
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2011 |
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arXiv |
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NbN thin film, energy gap dynamics |
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Using time-domain Terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, \lambda = 1.1 +/- 0.1, which is in excellent agreement with theoretical estimates. |
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Duplicated as 641 |
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1388 |
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Dorenbos, S. N.; Heeres, R.W.; Driessen, E.F.C; Zwiller, V. |
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Efficient and robust fiber coupling of superconducting single photon detectors |
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2011 |
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arXiv |
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arXiv |
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6 |
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SSPD |
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We applied a recently developed fiber coupling technique to superconducting single photon detectors (SSPDs). As the detector area of SSPDs has to be kept as small as possible, coupling to an optical fiber has been either inefficient or unreliable. Etching through the silicon substrate allows fabrication of a circularly shaped chip which self aligns to the core of a ferrule terminated fiber in a fiber sleeve. In situ alignment at cryogenic temperatures is unnecessary and no thermal stress during cooldown, causing misalignment, is induced. We measured the quantum efficiency of these devices with an attenuated tunable broadband source. The combination of a lithographically defined chip and high precision standard telecommunication components yields near unity coupling efficiency and a system detection efficiency of 34% at a wavelength of 1200 nm. This quantum efficiency measurement is confirmed by an absolute efficiency measurement using correlated photon pairs (with $\lambda$ = 1064 nm) produced by spontaneous parametric down-conversion. The efficiency obtained via this method agrees well with the efficiency measured with the attenuated tunable broadband source. |
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arXiv:1109.5809 |
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RPLAB @ gujma @ |
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689 |
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Чулкова, Г. М.; Семенов, А. В.; Корнеев, А. А.; Кардакова, А. И.; Аверьев, Н. В.; Ан, П. П.; Казаков, А. Ю.; Трифонов, А. В. |
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Спектральная чувствительность сверхпроводникового однофотонного детектора |
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2011 |
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Журнал радиоэлектроники |
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Ж. радиоэлектрон. |
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11 |
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5 |
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SSPD; quantum efficiency; spectral sensitivity |
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We consider quantum efficiency dependence on photons' energy from hot spot model. Direction of quasiparticles diffusion drive across superconductive film. The maximal quantum efficiency is proportional to a probability of photon absorption. The spectral sensitivity of superconductive single photon detector does not have clearly expressed red limit. Changing regimes of work depends on a wavelength we can get high values of quantum efficiency in visible and infrared range which will be specified by the quality of fabrication of detectors and their consistency with the radiation.
Key words: superconducting single-photon detector, SSPD, quantum efficiency, spectral sensitivity.
В статье представлена зависимость квантовой эффективности от энергии фотона в рамках модели горячего пятна. Диффузия квазичастиц происходит в основном перпендикулярно направлению тока в областях с максимальной плотностью тока. Максимальная квантовая эффективность детектора пропорциональна вероятности поглощения фотона. Несмотря на квантовый характер работы сверхпроводникового однофотонного детектора, он не имеет четко выраженной красной границы. Изменяя режим работы в зависимости от длины волны можно в видимом и инфракрасном диапазонах получать высокие значения квантовой эффективности, которые будут определяться лишь качеством изготовления детекторов и степенью их согласования с излучением. |
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RPLAB @ gujma @ |
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Marsili, Francesco; Najafi, Faraz; Herder, Charles; Berggren, Karl K. |
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Electrothermal simulation of superconducting nanowire avalanche photodetectors |
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2011 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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98 |
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9 |
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3 |
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SNAP |
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We developed an electrothermal model of NbN superconducting nanowire avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single-photon detectors consisting of the parallel connection of N superconducting nanowires. We extrapolated the physical constants of the model from experimental data and we simulated the time evolution of the device resistance, temperature and current by solving two coupled electrical and thermal differential equations describing the nanowires. The predictions of the model were in good quantitative agreement with the experimental results. |
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RPLAB @ gujma @ |
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658 |
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Baek, Burm; Lita, Adriana E.; Verma, Varun; Nam, Sae Woo |
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Superconducting a-WxSi1–x nanowire single-photon detector with saturated internal quantum efficiency from visible to 1850 nm |
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2011 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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98 |
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25 |
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3 |
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SNSPD |
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We have developed a single-photon detector based on superconducting amorphous tungsten–silicon alloy (a-WxSi1–x) nanowire. Our device made from a uniform a-WxSi1–x nanowire covers a practical detection area (16 μm×16 μm) and shows high sensitivity featuring a plateau of the internal quantum efficiencies, i.e., efficiencies of generating an electrical pulse per absorbed photon, over a broad wavelength and bias range. This material system for superconducting nanowire detector technology could overcome the limitations of the prevalent nanowire devices based on NbN and lead to more practical, ideal single-photon detectors having high efficiency, low noise, and high count rates. |
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