ENHANCED MODE DETECTION FOR MICROWAVES USING A HIGH-IMPEDANCE YBCO-BIO COMPOSITE SUPERCONDUCTOR

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 (enha nced mode detection). This composite superconductor was prepared by do ping YBa2Cu3Ox with Bi2O3, which causes high normal state resistance i n the composite and enhances the Josephson effect at the grain boundar y. It was found that the measured responsivity (R(MV)) improved by inc reasing 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 x 10(-14) W/Hz1/2 were obtained with a detector hav ing an R(n) of 13 OMEGA. These results suggest the feasibility of a pr actical 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.