Nonlinear response of telecom-wavelength superconducting single-photon detectors

TL;DR

This study investigates the nonlinear response of superconducting nanowire single-photon detectors at telecom wavelengths, revealing a small deviation from linearity due to competing effects and providing models for correction and understanding of multi-photon detection.

Contribution

It offers an empirical model for detector nonlinearity and insights into multi-photon detection mechanisms, advancing understanding of superconducting single-photon detectors.

Findings

Relative deviation from linearity is about 0.1% when flux doubles.

Nonlinearity results from a balance between saturation and multi-photon detection effects.

Empirical correction models effectively account for observed nonlinearities.

Abstract

We measure the nonlinearity of a telecom-wavelength superconducting nanowire single-photon detector via incoherent beam combination. At typical photon count rates and detector bias current, the observed relative deviation from a perfectly linear response is in the order of 0.1% when the flux is doubled. This arises from a balance between the counteracting nonlinearities of deadtime-induced detector saturation and of multi-photon detections. The observed behaviour is modelled empirically, which suffices for a correction of measured data. In addition, statistical simulations, taking into account the measured recovery of the detection efficiency, provide insight into possible mechanisms of multi-photon detection.