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Jukna, A., Kitaygorsky, J., Pan, D., Cross, A., Perlman, A., Komissarov, I., et al. (2008). Dynamics of hotspot formation in nanostructured superconducting stripes excited with single photons. Acta Physica Polonica A, 113(3), 955–958.
Abstract: Dynamics of a resistive hotspot formation by near-infrared-wavelength single photons in nanowire-type superconducting NbN stripes was investigated. Numerical simulations of ultrafast thermalization of photon-excited nonequilibrium quasiparticles, their multiplication and out-diffusion from a site of the photon absorption demonstrate that 1.55 μm wavelength photons create in an ultrathin, two-dimensional superconducting film a resistive hotspot with the diameter which depends on the photon energy, and the nanowire temperature and biasing conditions. Our hotspot model indicates that under the subcritical current bias of the 2D stripe, the electric field penetrates the superconductor at the hotspot boundary, leading to suppression of the stripe superconducting properties and accelerated development of a voltage transient across the stripe.
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Henrich, D., Dorner, S., Hofherr, M., Il'in, K., Semenov, A., Heintze, E., et al. (2012). Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content. J. Appl. Phys., 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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Smirnov, K. V., Divochiy, A. V., Vakhtomin, Y. B., Sidorova, M. V., Karpova, U. V., Morozov, P. V., et al. (2016). Rise time of voltage pulses in NbN superconducting single photon detectors. Appl. Phys. Lett., 109(5), 052601.
Abstract: We have found experimentally that the rise time of voltage pulse in NbN superconducting single photon detectors increases nonlinearly with increasing the length of the detector L. The effect is connected with dependence of resistance of the detector Rn, which appears after photon absorption, on its kinetic inductance Lk and, hence, on the length of the detector. This conclusion is confirmed by our calculations in the framework of two temperature model.
D.Yu.V. acknowledges the support from the Russian Foundation for Basic Research (Project No. 15-42-02365). K.V.S. acknowledges the financial support from the Ministry of Education and Science of the Russian Federation (Contract No. 3.2655.2014/K).
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Annunziata, A. J., Quaranta, O., Santavicca, D. F., Casaburi, A., Frunzio, L., Ejrnaes, M., et al. (2010). Reset dynamics and latching in niobium superconducting nanowire single-photon detectors. J. Appl. Phys., 108(8), 7.
Abstract: 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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Maingault, L., Tarkhov, M., Florya, I., Semenov, A., Espiau de Lamaëstre, R., Cavalier, P., et al. (2010). Spectral dependency of superconducting single photon detectors. J. Appl. Phys., 107(11), 116103 (1 to 3).
Abstract: We investigate the effect of varying both incoming optical wavelength and width of NbN nanowires on the superconducting single photon detectors (SSPD) detection efficiency. The SSPD are current biased close to critical value and temperature fixed at 4.2 K, far from transition. The experimental results are found to verify with a good accuracy predictions based on the “hot spot model,” whose size scales with the absorbed photon energy. With larger optical power inducing multiphoton detection regime, the same scaling law remains valid, up to the three-photon regime. We demonstrate the validity of applying a limited number of measurements and using such a simple model to reasonably predict any SSPD behavior among a collection of nanowire device widths at different photon wavelengths. These results set the basis for designing efficient single photon detectors operating in the infrared (2–5 μm range).
This work was supported by European projects FP6 STREP “SINPHONIA” (Contract No. NMP4-CT-2005-16433) and IP “QAP” (Contract No. 15848).
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