Development of THz harmonic mixer for QCL phase locking application

A practical solution using a THz optical source as a Local Oscillator (LO) for radio astronomy above 2 THz requires that the source to be frequency or phase locked. Therefore, it is crucial to enable a high conversion efficiency heterodyne mixer to produce a stable LO source that can operate at room temperature. Harmonically pumped 1.9-3.2 THz Schottky diode based mixers have been designed to enable high harmonic mixing. The harmonic mixers will be used to phase lock a Quantum Cascade Laser (QCL) to a stable microwave source. The design and characterization of a 1.9-3.2 THz harmonic mixer is presented.