Microwave detection and mixing in Y-Ba-Cu-O thin films at liquid-nitrogen temperatures

Microwave properties of an Y-Ba-Cu-O microstrip detector have been studied at 24 GHz frequency band at the liquid-nitrogen temperature. The amplitude of the video detection signal was found to be proportional to the incident microwave power. Direct mixing action was also demonstrated, setting the upper limit for the film response time as short as 40 ps. Occurrence of microwave mixing in the absence of dc current bias was observed, suggesting the presence of the inverse Josephson effect. Physical properties of the detector response were very similar to the enhanced mode of detection, characteristic for granular superconducting films.