Laser-Induced Relaxation Oscillations in Superconducting Nanobridge Single Photon Detectors

TL;DR

This paper reports the discovery of laser-induced relaxation oscillations in superconducting nanowire single photon detectors, revealing new dynamics when illuminated with pulsed laser light and providing a model to explain these phenomena.

Contribution

It introduces the first observation of laser-induced relaxation oscillations in SNSPDs and presents a model that explains their origin without thermal effects.

Findings

Oscillations occur at ~19 MHz with pulsed laser illumination.

Oscillations show step-wise frequency increase and phase locking.

Model qualitatively matches experimental observations.

Abstract

We demonstrate novel laser-induced relaxation oscillations in superconducting nanowire single photon detectors (SNSPDs). These oscillations appear when a voltage biased NbTiN nanobridge detector is illuminated with intense pulsed laser light at a repetition rate of $\sim19\text{MHz}$. They differ from the well-known relaxation oscillations by a step-wise increase in frequency and phase locking of the oscillations to the laser pulses. We create a model that incorporates electrical feedback and excludes thermal effects to simulate and explain the origin of the observed laser-induced relaxation oscillations. Qualitative agreement to the experiment is achieved using realistic values for the parameters in the model.