Counting rate enhancements in superconducting nanowire single-photon detectors with improved readout circuits

TLDR

Counting rates of superconducting nanowire single‑photon detectors are typically limited to hundreds of MHz by their kinetic‑inductive reset time and capacitor coupling in conventional readout circuits. The authors design and demonstrate an improved readout circuit that shortens reset time and eliminates circuit limits. They implement this circuit and present a numerical model that explains the nonlinear dependence of counting rate on incident continuous‑wave optical power. The improved circuit quadruples the counting rate at the 3 dB compression point for a large active‑area detector, and the model captures the observed nonlinear behavior.

Abstract

Counting rates of superconducting nanowire single-photon detectors are usually estimated at hundreds of MHz by their kinetic-inductive reset time. This maximum is also limited by capacitor coupling effects in conventional readout circuits. In this Letter, we design and demonstrate an improved readout circuit that reduces the reset time and removes circuit limits. The counting rate at the 3 dB compression point is increased by four times for a large active area detector. We also discuss nonlinear dependences of the counting rate on the incident continuous-wave optical power and give a numerical model to explain our observations.