PT Journal
AU Ferrari, S
   Kovalyuk, V
   Hartmann, W
   Vetter, A
   Kahl, O
   Lee, C
   Korneev, A
   Rockstuhl, C
   Gol'tsman, G
   Pernice, W
TI Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors
SO Opt. Express
JI Opt. Express
PY 2017
BP 8739
EP 8750
VL 25
IS 8
DE SSPD; SNSPD; photon counting; Infrared; Quantum detectors; Integrated optics; Multiphoton processes; Photon statistics
AB 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.
ER