The Cascade Switching of the Photon Number Resolving Superconducting Single-Photon Detectors

In this article, present the first detailed study of cascade switching in superconducting photon number resolving detectors. The detectors were made in the form of four parallel nanowires, coupled with the single-mode optical fiber and mounted into a closed-cycle refrigerator with a temperature of 2.1 K. We found out the value of additional false pulses (N_cas.sw.) appearing due to cascade switching and showed that it is possible to set up the detector bias current that corresponds to a high level of the detection efficiency and a low level of N_cas.sw. simultaneously. We reached the detection efficiency of 60% and N_cas.sw. = 0.3%.