Control and characterization of phase-modulated continuous-wave laser frequency combs
Spectral line-by-line shaping is a key enabler towards optical arbitrary waveform generation, which promises broad impact both in optical science and technology. Significant new physics arises in the line-by-line regime, where the shaped pulse fields generated from one laser pulse now overlap with those generated from adjacent pulses. This leads to coherent interference effects related to the properties of optical frequency combs which serve as the source in these experiments.
Phase-modulated continuous–wave (PMCW) laser frequency combs are chosen as the optical source within this dissertation for their relatively high frequency stability and ease of tuning. We experimentally demonstrate the followings: (1) 300 fs optical pulse train generations at 9 and 10 GHz rates by applying line-by-line control to PMCW combs. (2) 5 GHz optical arbitrary waveform generations using more than 100 comb lines. (3) Generations of reprogrammable microwave arbitrary waveforms at rates approaching 10 GHz. (4) Generation of nonlinearly broadened optical frequency combs from PMCW seed pulses using both anomalous and normally dispersive media. Broadened comb coherence properties are further analyzed using differential phase-shift keying decoding. (5) Quantitative analysis on the impact of static comb frequency stability on line-by-line shaped waveforms. (6) Systematic investigations on time-varying comb frequency-noise to intensity-noise conversion in line-by-line shaping.