Dark counts of superconducting nanowire single-photon detector under illumination

TL;DR

This paper investigates how illumination affects dark count rates in superconducting nanowire single-photon detectors, revealing that illumination can significantly increase dark counts and alter detection efficiency near the switching current.

Contribution

It introduces a time-correlated single-photon counting method to distinguish photon counts from dark counts, providing a more accurate measurement of DCR under illumination.

Findings

Dark count rate increases under illumination near the switching current.

Illumination can cause an abnormal increase in detection efficiency.

Suppression of the switching current explains the increased dark counts.

Abstract

An abnormal increase in the SDE was observed for superconducting nanowire single-photon detectors (SNSPDs) when the bias current (Ib) was close to the switching current (Isw). By introducing the time-correlated single-photon counting technique, we investigated the temporal histogram of the detection counts of an SNSPD under illumination. The temporal information helps us to distinguish photon counts from dark counts in the time domain. In this manner, the dark count rate (DCR) under illumination and the accurate SDE can be determined. The DCR under moderate illumination may be significantly larger than the conventional DCR measured without illumination under a high Ib, which causes the abnormal increase in the SDE. The increased DCR may be explained by the suppression of Isw under illumination.