Enhanced mode detection for microwaves using a high-impedance YBCO-BiO composite superconductor

Abstract

We have developed a Josephson type microwave detector using a YBCO-BiO composite superconductor which uses the non-linear effect produced by a complex network of Josephson weak links at the grain boundary (enhanced mode detection). This composite superconductor was prepared by doping YBa 2 Cu 3 O x with Bi 2 O 3 , which causes high normal state resistance in the composite and enhances the Josephson effect at the grain boundary. It was found that the measured responsivity ( R MV ) improved by increasing the normal resistance ( R n ) of the detector through enhanced matching of the incident microwaves and the detector. An R MV of 180 V/W and NEP of 1.4×10 −14 W/Hz 1 2 were obtained with a detector having an R n of 13 Ω. These results suggest the feasibility of a practical detector having an R MV of more than 10 4 V/W which operates at 60 K by the enhanced mode detection of a high- T C superconductor.