High-energy femtosecond fiber lasers based on dissipative solitons

Virtually all practical femtosecond -pulse generation has been based on soliton formation, which is the compensation of a self-focusing nonlinear phase by anomalous dispersion. Although it has many advantageous properties, soliton like pulse -shaping also limits the stable pulse energy, and this lim it is severe in fiber lasers. Recent research has shown that it is possible to generate ultrashort pulses by a completely different mechanism: in a cavity with only normal-dispersion components, a stable highly -chirped pulse can be produced by the balance of spectral broadening and spectral filtering. Such a pulse balances amplitude modulations (gain and loss) as well as the phase modulations, and is referred to as a dissipative soliton. The pulse can be dechirped to the Fourier transform limit outside t he cavity. This approach allows the generation of ultrashort pulses from fiber lasers with much higher energies than was possible previously. In particular, lasers based on ordinary single -mode fiber generate 100 -fs and 30-nJ pulses, for average powers w ell above 1 W. These are the first fiber lasers to compete directly with the performance of solid -state lasers. Elimination of segments or components with anomalous dispersion produces simple and practical designs. Dissipative -soliton lasers can also be designed to generate high -energy pulses chirped to -1000 times the transform -limited duration, which should be valuable for chirped -pulse amplifiers. In addition to their potential for applications, normal -dispersion lasers provide a convenient setting fo r the study of dissipative solitons, which are of much current interest in the nonlinear -waves community. Theoretical and experimental results will be reviewed.