Coherence-controlled mm-wave generation using a frequency-shifting recirculating delay line

A photonic technique based on optical heterodyning for the generation of microwave and millimeter-wave signals is presented in this paper. Coherence control of a comb of time-delayed and frequency-shifted optical signals is used to selectively beat multiple optical signals together to produce a stable, spectrally pure microwave, or millimeter-wave signal. This approach is demonstrated by generating signals at 11.25 and 30 GHz. The linewidth of the generated signal is independent of the linewidth of the optical source employed, and is shown to be less than 100 Hz with sideband suppression >30 dB.