Experimental investigation of the detection mechanism in WSi nanowire superconducting single photon detectors

TL;DR

This study uses quantum detector tomography to analyze the detection mechanism in WSi nanowire superconducting single photon detectors, revealing energy-dependent response characteristics and a linear current-energy relation above a certain energy threshold.

Contribution

It provides the first detailed quantum tomography analysis of WSi SSPDs, highlighting the energy dependence of detection mechanisms and comparing them to NbN nanowires.

Findings

Detector response depends solely on total excitation energy.

Linear current-energy relation observed for energies above 0.8 eV.

Deviations from linearity occur at lower energies.

Abstract

We use quantum detector tomography to investigate the detection mechanism in WSi nanowire superconducting single photon detectors (SSPDs). To this purpose, we fabricated a 250nm wide and 250nm long WSi nanowire and measured its response to impinging photons with wavelengths ranging from $\lambda$ = 900 nm to $\lambda$ = 1650 nm. Tomographic measurements show that the detector response depends on the total excitation energy only. Moreover, for energies Et > 0.8eV the current energy relation is linear, similar to what was observed in NbN nanowires, whereas the current-energy relation deviates from linear behaviour for total energies below 0.8eV.