Tunable Broadband Electro-Optic Comb Generation Using an Optically Filtered Optoelectronic Oscillator

Tunable electrooptic combs are generated in an optoelectronic oscillator that is optically filtered using a 100 000 finesse Fabry-Pérot etalon. Optical and electrical outputs of the oscillator are combined in a series of external phase modulators to generate spectrally flat, broadband optical combs. Adjustment of a variable delay in the oscillator allows for tuning of output combline spacing to harmonics of the etalon's 1.5-GHz free spectral range. Experimental results demonstrate regeneratively created electrooptic combs whose comb teeth spacing can be tuned to 7.5, 9, 10.5, and 12 GHz, with center comb tooth linewidths on the order of hundreds of Hertz. In the best case, the output electrooptic modulation comb consists of 52 individual comblines within a 10-dB amplitude deviation over a span of approximately 5 nm. Linear pulse compression is used to demonstrate ultrashort pulses with a 2.6-ps autocorrelation pulse width at a repetition rate of 10.5 GHz.