Study of quasi-particle dynamics using the optical pulse response of asuperconducting resonator

TL;DR

This paper investigates the dynamics of quasi-particles in a superconducting resonator by analyzing its optical pulse response, developing a model to extract key parameters like recombination time and diffusion constant, aiding detector design.

Contribution

It introduces a time-dependent inductance model to analyze optical pulse responses, enabling detailed study of quasi-particle behavior in superconducting resonators.

Findings

Extracted quasi-particle recombination times

Measured spatial size of quasi-particle distribution

Determined quasi-particle diffusion constant

Abstract

We study the optical pulse response of a superconducting half-wavelength coplanar waveguide (CPW) resonator. We apply a short optical pulse to the center strip of the CPW resonator, where the current distribution shows antinodes or nodes for different resonance modes, and measure the frequency response. We develop a time-dependent variable inductance circuit model with which we can simulate the optical pulse response of the resonator. By fitting this model to experimental data, we extract the temporal kinetic inductance variations, which directly reflect the quasi-particle recombination with time and diffusion in space. We also retrieve the spatial size of the quasi-particle distribution and the quasi-particle diffusion constant. Our study is very useful for the design of photon-counting kinetic inductance detectors, and the method developed in this work provides a useful way to study the quasi-particle dynamics in the superconductor.