Reset dynamics and latching in niobium superconducting nanowire single-photon detectors

TL;DR

This paper investigates the reset dynamics of niobium superconducting nanowire single-photon detectors, highlighting how hotspot cooling time influences device latching and demonstrating methods for fast reset to enable reliable photon detection.

Contribution

It combines experimental measurements and numerical simulations to elucidate the cooling and latching mechanisms in Nb SNSPDs, providing insights for improving reset times.

Findings

Hotspot cooling time is mainly determined by electron-phonon inelastic time.

Latching occurs if cooling is too slow, preventing reset.

Fast cooling enables rapid reset and continuous photon detection.

Abstract

We study the reset dynamics of niobium (Nb) superconducting nanowire single-photon detectors (SNSPDs) using experimental measurements and numerical simulations. The numerical simulations of the detection dynamics agree well with experimental measurements, using independently determined parameters in the simulations. We find that if the photon-induced hotspot cools too slowly, the device will latch into a dc resistive state. To avoid latching, the time for the hotspot to cool must be short compared to the inductive time constant that governs the resetting of the current in the device after hotspot formation. From simulations of the energy relaxation process, we find that the hotspot cooling time is determined primarily by the temperature-dependent electron-phonon inelastic time. Latching prevents reset and precludes subsequent photon detection. Fast resetting to the superconducting state is therefore essential, and we demonstrate experimentally how this is achieved.