Reiger E, Pan D, Slysz W, Jukna A, Sobolewski R, Dorenbos S, et al. Spectroscopy with nanostructured superconducting single photon detectors. IEEE J Select Topics Quantum Electron. 2007;13(4):934–43.
Abstract: Superconducting single-photon detectors (SSPDs) are nanostructured devices made from ultrathin superconducting films. They are typically operated at liquid helium temperature and exhibit high detection efficiency, in combination with very low dark counts, fast response time, and extremely low timing jitter, within a broad wavelength range from ultraviolet to mid-infrared (up to 6 mu m). SSPDs are very attractive for applications such as fiber-based telecommunication, where single-photon sensitivity and high photon-counting rates are required. We review the current state-of-the-art in the SSPD research and development, and compare the SSPD performance to the best semiconducting avalanche photodiodes and other superconducting photon detectors. Furthermore, we demonstrate that SSPDs can also be successfully implemented in photon-energy-resolving experiments. Our approach is based on the fact that the size of the hotspot, a nonsuperconducting region generated upon photon absorption, is linearly dependent on the photon energy. We introduce a statistical method, where, by measuring the SSPD system detection efficiency at different bias currents, we are able to resolve the wavelength of the incident photons with a resolution of 50 nm.
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Bulaevskii LN, Graf MJ, Kogan VG. Vortex-assisted photon counts and their magnetic field dependence in single-photon superconducting detectors. Phys Rev B. 2012;85(1):9.
Abstract: We argue that photon counts in a superconducting nanowire single-photon detector (SNSPD) are caused by the transition from a current-biased metastable superconducting state to the normal state. Such a transition is triggered by vortices crossing the thin and narrow superconducting strip from one edge to another due to the Lorentz force. Detector counts in SNSPDs may be caused by three processes: (a) a single incident photon with sufficient energy to break enough Cooper pairs to create a normal-state belt across the entire width of the strip (direct photon count), (b) thermally induced single-vortex crossing in the absence of photons (dark count), which at high-bias currents releases the energy sufficient to trigger the transition to the normal state in a belt across the whole width of the strip, and (c) a single incident photon of insufficient energy to create a normal-state belt but initiating a subsequent single-vortex crossing, which provides the rest of the energy needed to create the normal-state belt (vortex-assisted single-photon count). We derive the current dependence of the rate of vortex-assisted photon counts. The resulting photon count rate has a plateau at high currents close to the critical current and drops as a power law with high exponent at lower currents. While the magnetic field perpendicular to the film plane does not affect the formation of hot spots by photons, it causes the rate of vortex crossings (with or without photons) to increase. We show that by applying a magnetic field one may characterize the energy barrier for vortex crossings and identify the origin of dark counts and vortex-assisted photon counts.
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Чулкова ГМ, Семенов АВ, Корнеев АА, Кардакова АИ, Аверьев НВ, Ан ПП, et al. Спектральная чувствительность сверхпроводникового однофотонного детектора. Ж радиоэлектрон. 2011;11:5.
Abstract: 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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Sprengers JP, Gaggero A, Sahin D, Jahanmirinejad S, Frucci G, Mattioli F, et al. Waveguide superconducting single-photon detectors for integrated quantum photonic circuits. Appl Phys Lett. 2011;99(18):181110(1–3).
Abstract: The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (~0%) at telecom wavelengths, high timing accuracy (~0 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators.
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Henrich D, Dorner S, Hofherr M, Il'in K, Semenov A, Heintze E, et al. Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content. J Appl Phys. 2012;112.
Abstract: The spectral detection efficiency and the dark count rate of superconducting nanowire
single-photon detectors (SNSPD) have been studied systematically on detectors made from thin
NbN films with different chemical compositions. Reduction of the nitrogen content in the 4 nm
thick NbN films results in a decrease of the dark count rates more than two orders of magnitude
and in a red shift of the cut-off wavelength of the hot-spot SNSPD response. The observed
phenomena are explained by an improvement of uniformity of NbN films that has been confirmed
by a decrease of resistivity and an increase of the ratio of the measured critical current to the
depairing current. The latter factor is considered as the most crucial for both the cut-off
wavelength and the dark count rates of SNSPD. Based on our results we propose a set of criteria
for material properties to optimize SNSPD in the infrared spectral region. VC 2012 American
Institute of Physics. [http://dx.doi.org/10.1063/1.4757625]
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