Pulse dynamics in all-normal dispersion ultrafast fiber lasers

We present a numerical investigation of pulse shape evolution and pulse regime transformation in an all-normal dispersion mode-locked fiber laser. We found that the pump strength and spectral filtering had great effects on the properties of the generated dissipative solitons. The pulse had a parabolic intensity profile and linear chirp when the pump strength was large enough under certain bandwidth of the spectral filter. Such a parabolic pulse worked in the intermediate regime between the dissipative soliton and similariton; however, the pulse resembled a dissipative soliton. Pulse regime transformation will happen when the pump strength is large enough; the pulse will become multi-pulse, bound-state pulse, or noise-like pulse under different filter bandwidths and pump strengths. The results of our numerical simulations could offer a better understanding of the dynamics of all-normal dispersion mode-locked fiber lasers and also provide insight into the dissipative fiber laser systems.