Compact optical millimetre-wave source using a dual-mode semiconductor laser

The authors demonstrate the optical generation of extremely narrow linewidth millimetre-wave signals between 40 and 60 GHz using a single-chip semiconductor laser. A dual-mode long-cavity multisection DFB semiconductor laser is driven at a subharmonic of the free-running-mode beat signal frequency to produce phase-locked millimetre waves with a 3 dB linewidth of less than 10 Hz and a 3 dB locking range of ~500 MHz.