%0 Journal Article %T Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors %A Ferrari, S. %A Kovalyuk, V. %A Hartmann, W. %A Vetter, A. %A Kahl, O. %A Lee, C. %A Korneev, A. %A Rockstuhl, C. %A Gol'tsman, G. %A Pernice, W. %J Opt. Express %D 2017 %V 25 %N 8 %F Ferrari_etal2017 %O exported from refbase (https://db.rplab.ru/refbase/show.php?record=1118), last updated on Sat, 01 May 2021 23:21:39 -0500 %X We investigate how the bias current affects the hot-spot relaxation dynamics in niobium nitride. We use for this purpose a near-infrared pump-probe technique on a waveguide-integrated superconducting nanowire single-photon detector driven in the two-photon regime. We observe a strong increase in the picosecond relaxation time for higher bias currents. A minimum relaxation time of (22 +/- 1)ps is obtained when applying a bias current of 50% of the switching current at 1.7 K bath temperature. We also propose a practical approach to accurately estimate the photon detection regimes based on the reconstruction of the measured detector tomography at different bias currents and for different illumination conditions. %K SSPD %K SNSPD %K photon counting %K Infrared %K Quantum detectors %K Integrated optics %K Multiphoton processes %K Photon statistics %P 8739-8750