Microwave response measurement and modeling of high-temperature superconducting thin-film detectors

We report here a model of a high temperature superconducting detector response to microwaves. The goal of the model is to approximate, based on microscopic theoretical results, the measured response of a superconducting detector to microwave frequency over a wide temperature range (from zero up to the critical temperature of the superconductor, T c ). In this work, the nonbolometric response is emphasized because its detector performance is better than the bolometric response. The nonbolometric response model is based on microwave enhancement of a thermal fluctuation voltage occurring in the networks of inherent Josephson junctions. Modeling the film as a distribution of granular connections with varying critical currents and temperatures yields results similar to those observed in microwave response measurements in granular Bi-Sr-Ca-Cu-O thin films. We also report here initial measurements and modeling of the microwave (9 GHz) response of a bi-epitaxial thin film showing the simultaneous presence of bolometric and nonbolometric response peaks in the same sample. The response in this Y-Ba-Cu-O thin films gives further evidence of microwave detection in the networks of inherent Josephson junctions presented at the grain boundaries of two epitaxial layers.