Superconducting detector of IR single-photons based on thin WSi films

TL;DR

This paper reports the development of WSi thin-film superconducting single-photon detectors with high efficiency, low dark counts, and improved absorption using cavity structures, demonstrating their potential for IR photon detection.

Contribution

The paper introduces a new fabrication process for high-quality WSi films and demonstrates enhanced detector performance with cavity structures for IR single-photon detection.

Findings

System detection efficiency reaches ~30% at 1550 nm

Cavity structures increase quantum efficiency to >65%

Dark count rate limited to 1 s^-1

Abstract

We have developed the deposition technology of WSi thin films 4 to 9 nm thick with high temperature values of superconducting transition (Tc~4 K). Based on deposed films there were produced nanostructures with indicative planar sizes ~100 nm, and the research revealed that even on nanoscale the films possess of high critical temperature values of the superconducting transition (Tc~3.3-3.7K ) which certifies high quality and homogeneity of the films created. The first experiments on creating superconducting single-photon detectors showed that the detectors SDE (system detection efficiency) with increasing bias current (Ib) reaches a constant value of ~30% (for 1550 nm) defined by infrared radiation absorption by the superconducting structure. To enhance radiation absorption by the superconductor there were created detectors with cavity structures which demonstrated a practically constant value of quantum efficiency >65% for bias currents Ib>=0.6Ic. The minimal dark counts level (DC) made 1 s^-1 limited with background noise. Hence WSi is the most promising material for creating single-photon detectors with record SDE/DC ratio and noise equivalent power (NEP).