Measurements of near-infrared frequency mixing by metal-semiconductor point-contact diodes

The performances of metal-semiconductor point-contact diodes as mixers in the near-infrared region were tested. Preliminary experiments were performed in order to phase-lock two diode lasers at 850 nm a few hundred gigahertz apart. GaSb, InAs, and InSb as semiconductor layers were used. The frequency bridge between the two lasers was covered by a Gunn diode frequency locked to a 1-GHz oscillator. A novel phase-lock circuit was tested on two diode lasers 72 GHz apart.