Millimeter-wave radiation in high-T/sub c/ Josephson junctions

We have investigated millimeter-wave radiation from single Josephson junctions and small phase-locked Josephson junction arrays. Josephson junctions were fabricated on sapphire bicrystal substrates. Emission could be measured up to 110 GHz. Resonances in ten-junction circuits yield linewidths narrower than 200 MHz. This type of array might be useful for applications in integrated receiver systems.