Nonlinear spectral transformation of partially coherent pulses of mode-locked fiber laser

All-normal dispersion fiber lasers mode-locked due to the effect of nonlinear polarization evolution (NPE) are simple and efficient tools for generation of pulses with different duration. These lasers feature reliable design and resistance to power damage, they can produce relatively high pulse energies without wave breaking and are able to operate in a variety of lasing regimes. Besides generation of commonly used stable trains of bell-shaped pulses, these lasers support partially mode-locked operation in which wave packets filled with quasi-stochastic ultra-short pulses are generated. Partially coherent pulses with relatively high energy levels have been discovered recently in fiber lasers comprising ultra-long oscillators and to the best of our knowledge, applications of such pulses have not as yet been studied. However, because these high-energy wave packets contain tightly-spaced femtosecond pulses with high peak power, their pulse structure may be useful in many applications including material processing, super-continuum generation, as well as other non-linear optical transformations.