Microwave detection with high Tc superconducting thin films

Measurements were made of the microwave responses of YBaCuO superconducting thin films. The sample was a chemically etched line approximately 200 microns long and 20 microns wide. The measurements were performed in three different frequency ranges: 1-40 GHz, 90-100 GHz, and HeNe laser. Different kinds of responses were observed: a bolometric peak that can be easily related to dR /dt and a nonbolometric peak. The power dependence of the response was plotted for different bias currents. The response time was shorter than 1 microsec in most cases. The sensitivity was not comparable to that of semiconductor detectors, but it is shown how the design of this detector could be optimized to improve its sensitivity. The operating frequency range is superior to that of other detectors. A review of the different models regarding the response of superconducting thin films to photon irradiation is presented, and the experimental results are interpreted. (I.E.)