THZ MIXING PROPERTIES OF YBA2CU3O7-DELTA GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS ON BICRYSTAL SUBSTRATES

Using high-T-c grain boundary Josephson junctions (GBJJs) made of YBa2 Cu3O7-delta (YBCO) deposited across MgO bicrystal boundary, at TeraHer tz (THz) waveband we successfully demonstrated both fundamental and ha rmonic frequency mixing. Radiation from a far-infrared (FIR) laser was coupled to the junction, which was integrated with a planar bow-tie a ntenna, via an extended hyperhemispherical silicon lens. Fundamental m ixing manifested itself in the junction's DC current-voltage (I-V) cur ve as a third Shapiro step in addition to those two induced by the THz laser lines from a slightly misaligned resonator. In harmonic mixing between a THz laser line and a microwave local oscillator, the highest harmonic number we could get was 490 with a signal-to-noise-ratio of 9 dB at the intermediate frequency (IF). The IF output (P-IF) depended strongly on the bias voltage, the local oscillator power level, the h armonic number (N), etc. (C) 1997 Elsevier Science B.V.