Giant-chirp oscillator (GCO) pulses are dissipative solitons in the limit of huge normal dispersion. A long segment of normally-dispersive fiber is inserted, typically preceding the gain, and the filter bandwidth is reduced.
Pulses energies of tens of nJ can be obtained at MHz-level repetition rates. The resulting chirp is many times larger than the cavity dispersion, corresponding to pulses hundreds of ps long but compressible by factors of ~200 to sub-ps levels. However, optimal compression rarely results in dechirped durations of less than ~2 times the transform limit.
Importantly, GCO pulses are qualitatively distinct from noise bursts. Despite their long durations, the former remain coherent with a roughly linear chirp, and display the steep spectra of their dissipative soliton brethren even when viewed on a log scale.
In principle, a GCO replaces the seed oscillator, pulse picker, stretcher, and pre-amp of a high-energy CPA system.
1. W. H. Renninger, A. Chong, and F. W. Wise. “Giant-chirp oscillators for short-pulse fiber amplifiers.” Optics Letters 33, 24 (2008).
2. E. J. R. Kelleher, J. C. Travers, E. P. Ippen, Z. Sun, A. C. Ferrari, S. V. Popov, and J. R. Taylor. “Generation and direct measurement of giant chirp in a passively mode-locked laser.” Optics Letters 34, 22 (2009).
Animation credit: Walter Fu.