Temperature-dependence of detection efficiency in NbN and TaN SNSPD

TL;DR

This study systematically investigates how temperature affects the detection efficiency of TaN and NbN superconducting nanowire single-photon detectors, revealing a temperature-dependent cut-off wavelength and distinct efficiency behaviors.

Contribution

It provides the first detailed analysis of temperature effects on detection efficiency in TaN and NbN SNSPDs, including a qualitative model involving quasi-particle diffusion.

Findings

Cut-off wavelength increases as temperature decreases.

Detection efficiency varies distinctly at different wavelengths with temperature.

The results inform microscopic detection models.

Abstract

We present systematic measurements of the temperature-dependence of detection efficiencies in TaN and NbN superconducting nanowire single-photon detectors. We have observed a clear increase of the cut-off wavelength with decreasing temperature that we can qualitatively describe with a temperature-dependent diffusion coefficient of the quasi-particles created after photon absorption. Furthermore, the detection efficiency at wavelengths shorter than the cut-off wavelength as well as at longer wavelengths exhibit distinct temperature dependencies. The underlying causes and possible consequences for microscopic detection models are discussed.