Wide-Spaced Optical Frequency Comb With Programmable Spacing

We introduce a novel approach for flexible generation of wide-spaced optical frequency combs. The comb is obtained from the cross phase modulation of a continuous-wave laser by a high-speed pulse train generated from a programmable pulse-rate multiplier. The multiplier provides an energy-efficient way for pulse-rate multiplication through electro-optic phase modulation followed by the temporal Talbot effect. In the demonstration, we multiply the rate of a 9.91-GHz optical pulse train by different factors of 3, 4, and 5. Subsequently, the multiplied pulses are applied to generate frequency combs spaced at 29.73, 39.64, and 49.55 GHz, respectively. The linewidths of the spectral lines are characterized. We also numerically investigate the influence of the deviation in modulation patterns on the suppression of the undesirable secondary comb peaks.