Optically probing the detection mechanism in a molybdenum silicide superconducting nanowire single-photon detector

TL;DR

This study investigates the detection mechanism of a molybdenum silicide superconducting nanowire single-photon detector by analyzing its detection probability across various wavelengths and bias currents, revealing nonlinear energy-current relations.

Contribution

It provides the first detailed experimental characterization of the detection mechanism in MoSi SNSPDs, highlighting nonlinear energy-current relations and the influence of Fano fluctuations.

Findings

Detection probability varies nonlinearly with bias current.

Saturated detection efficiency observed across wavelengths.

Features indicative of Fano fluctuations and position effects.

Abstract

We experimentally investigate the detection mechanism in a meandered molybdenum silicide (MoSi) superconducting nanowire single-photon detector by characterising the detection probability as a function of bias current in the wavelength range of 750 to 2050 nm. Contrary to some previous observations on niobium nitride (NbN) or tungsten silicide (WSi) detectors, we find that the energy-current relation is nonlinear in this range. Furthermore, thanks to the presence of a saturated detection efficiency over the whole range of wavelengths, we precisely quantify the shape of the curves. This allows a detailed study of their features, which are indicative of both Fano fluctuations and position-dependent effects.