Imaging Local Sources of Intermodulation in Superconducting Microwave Devices

TL;DR

This paper introduces a novel laser scanning microscopy technique to spatially resolve intermodulation sources in superconducting microwave devices, revealing local nonlinearities in high-temperature superconductors.

Contribution

It presents the first spatially resolved measurements of intermodulation response in HTS superconducting resonators using a new laser scanning method.

Findings

First spatially resolved intermodulation measurements in HTS devices

Identification of local nonlinear regions in superconducting resonators

Demonstration of a new technique for probing superconducting device nonlinearity

Abstract

This work presents new experimental results on low-temperature (LT) characterization of local rf properties of passive superconducting (SC) microwave devices using a novel Laser Scanning Microscope (LSM). In this technique, a modulated laser beam is focused onto and scanned over the surface of a resonant SC device to probe the spatial distribution of rf current. The highly localized photo-induced change of the kinetic inductance of the SC device produces both a shift of the resonant frequency f_0 and change of the quality factor Q. An image of these changes is recorded as the laser spot is scanned over the device. We present the first measurements of spatially resolved intermodulation response in a High Temperature Superconducting (HTS) co-planar waveguide resonator, opening up a new window into the local origins of nonlinearity in the HTS materials.