A photomixer local oscillator for a 630-GHz heterodyne receiver

A photomixer local oscillator (LO) operating at the 630-GHz difference freq uency of two laser diodes was successfully demonstrated with a heterodyne d etector based on a niobium superconducting tunnel junction. The low-tempera ture-grown GaAs photomixer generated 0.20 mu W in the input spatial mode of the receiver. Using the photomixer LO, the double-sideband noise temperatu re of the receiver was 331 K-in good agreement with the 323-K noise tempera ture obtained when a multiplied Gunn oscillator generating 0.25 mu W was su bstituted for the photomixer.