Low-Noise Optical Injection Locking Of A Resonant Tunneling Diode To A Stable Optical Frequency Comb

Optical injection locking of a resonant tunneling diode (RTD) oscillator has been demonstrated using ultrashort pulses from a mode-locked Ti:sapphire laser operating at a 1 GHz pulse rate. The source of the optical signal is a mode-locked femtosecond laser whose optical frequency comb is phase locked to a H-maser stabilized frequency synthesizer. An exceptionally large capture range of more than 5 MHz is observed. The system produces stable microwave signals with low phase noise, which at 1 GHz is less than -74 dBc/Hz for a 10 Hz offset. The noise of the microwave injection-locked RTD signal matches that of the input optical pulses. (c) 2007 American Institute of Physics.