Overview of Evolution:
Pulse is highly up-chirped throughout the cavity. In both the temporal and spectral domains, the pulse broadens in normally-dispersive fiber and is then narrowed by a spectral filter, effecting modelocking.
All-normal-dispersion (ANDi) oscillators often yield the highest-energy pulses. A prototypical cavity comprises a normally-dispersive passive fiber followed by gain and another, shorter, passive fiber. After the output coupler, a spectral filter forms the feedback loop, with a width typically on the order of 10 nm at 1030 nm. The pulse energy is largely controlled by the filter bandwidth and the cavity dispersion, with more dispersive cavities requiring narrower filters. The output is a highly up-chirped pulse often with a distinctive steep, cat-ear spectrum, and optimal compression usually requires a GDD of several times the cavity dispersion.
All things being equal, dissipative solitons provide the highest energies of any known pulse evolution. In spite of their sharp spectral features, they can usually be compressed to within 20% of the transform limit with low secondary structure.
Pulses generally top out at ~20 nJ in ~200 fs, and improvement in one aspect is possible with compromises in the other. Optimizing for duration can yield sub-100 fs pulses at the few-nJ level, while giant chirp oscillators represent the opposite limit.
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5. P. Grelu and N. Akhmediev. “Dissipative solitons for mode-locked lasers.” Nature Photonics 6, 2 (2012).
Animation credit: Walter Fu.