Superconducting single-photon detectors with saturated dependence of quantum efficiency vs. bias current

TL;DR

This paper explores NbN superconducting single-photon detectors, demonstrating that finer films with lower Rs300/Rs20 ratios achieve saturated quantum efficiency near 94% at high bias currents, influenced by quantum corrections to conductivity.

Contribution

It shows that the saturation of quantum efficiency depends on film properties, particularly Rs300/Rs20, and identifies optimal conditions for high efficiency in NbN detectors.

Findings

Finer films with lower Rs300/Rs20 ratios improve saturation.

Maximum quantum efficiency of 94% at Ib/Ic~0.8 for 1.31 μm wavelength.

Quantum corrections to conductivity influence detector performance.

Abstract

It was investigated the possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency versus normalized bias current. It was shown that the saturation increases for the detectors based on finer films with a lower value of Rs300/Rs20. The decreasing of Rs300/Rs20 related to increasing influence of quantum corrections to conductivity of superconductors and, in its turn, to decreasing electron diffusion coefficient. The best samples has constant value of system quantum effi-ciency 94% at Ib/Ic~0.8 and wavelength 1.31 mkm.