OBSERVATION OF THE AC JOSEPHSON EFFECT UP TO THZ FREQUENCIES IN YBCO PBCO YBCO RAMP-TYPE JOSEPHSON-JUNCTIONS

We present the response to 100 GHz irradiation of high-T(c) Josephson junction devices for mixer/detector applications in the (sub-) mm wave range. These devices consist of a YBCO/PBCO/YBCO ramp-type junction c ombined with a planar logarithmic periodic antenna. The critical curre nt and the first two Shapiro steps modulate with 100 GHz power accordi ng to the resistively shunted junction (RSJ) model. At 10 K clear Shap iro steps have been observed up to a voltage of about 7.5 mV. This cor responds to phase locking of 3.6 THz AC Josephson oscillations by the 36th harmonic of the 100 GHz signal. The number of observed steps is c urrently limited by the available power, but they are present up to vo ltages strongly exceeding the I(c)R(n) product of the junction at all temperatures.