HIGH-FREQUENCY RESPONSE TO MILLIMETER-WAVE IRRADIATION OF YBACUO THIN-FILM AND CERAMIC

Microwave (35 GHz) and radiowave (9 MHz) responses of an YBaCuO thin f ilm and a ceramic to millimeter (mm) wave irradiation (31.5 GHz) have been studied by means of a quasioptical dielectric resonator with whis pering gallery modes and an inductive technique at micro- and radiowav es, respectively. The responses are shown to have a mixed nature inclu ding a sufficiently strong non-bolometric component. Relaxation of the surface resistance in time after the irradiation removal obeys the lo garithmic law implying the nucleation and flux creep of vortices induc ed by the irradiation is a mechanism of the response at temperatures 3 -10 K below the critical temperature T-c. Dependence of the microwave surface resistance R-s(mw) on the mm wave pump amplitude H-omega is we ll described by Halbritter's theory of vortex motion inside weak links . A correlation between dependences of the radiowave (rw) response on H-omega with that of R-s(mw) has been found. Thus the mechanism of rv- response is believed to arise from intergranular Josephson couplings. The latter conclusion is further confirmed by a comparison of the pump power dependence of the rw-response with that of conventional DC-resp onse found for granular HTSC in other recent experiments on the respon se to the subgap radiation.