Measurement of phase-correlation between optical modes of semiconductor lasers

Millimeter- and Terahertz-waves can be conveniently generated by photomixing, where the beating of two laser sources onto a photoconductive detector generates signals with a tunability that is much wider than what typically allowed by electronic techniques. Several methods have been proposed to reduce the linewidth of the mm-wave and THz-wave signals generated by photomixing, in order to meet applications' requirements (linewidth <100 kHz, phase noise <100 dBc @100 kHz offset) [1], and all of them are based on inducing a stable phase relationship between the original laser modes. A novel method to phase-lock two semiconductor laser modes oscillating at and is represented by mutual injection-locking assisted by Four Wave Mixing (FWM) generated using a third auxiliary mode at = (+)/2 as pump [2].