Multipulse Dynamics of Dissipative Soliton Resonance in an All-Normal Dispersion Mode-Locked Fiber Laser

Multi-pulsing dissipative soliton resonance (DSR) in all-normal dispersion (ANDi) domain has been studied numerically and observed experimentally in a nonlinear amplifying loop mirror (NALM) based Yb-doped mode-locked fiber laser. Numerical simulation over a large number of roundtrips shows evolution of a multi-pulse Gaussian input field into multiple DSR pulses with equal flat-top amplitude and intra-pulse temporal separation. The dependence of stable multi-pulsing on the pump power has also been studied. The laser cavity delivered nano-second duration DSR pulses at 2.33-MHz repetition rate having a 3-dB spectral line width of 0.24 nm with rectangular shaped temporal profile. The pulse width could be tuned from 1.2 to 3.6 ns with the pump power. Pulse duration can be also varied by proper adjustment of the polarization controllers (PCs). At a certain high pump power, with precise adjustment of the PCs, one DSR pulse splits into multiple numbers of smaller duration pulses having equal amplitude, shape, width, and intra-pulse separation. There is no change in the nature of the spectrum under single and multi-pulse operation. The number of pulses can be varied with pump power and proper adjustment of the PCs. The pulses were observed to be stable for a constant period of 1 h in the absence of external perturbation. To the best of the author's knowledge, this is the first observation of multi-pulsing DSR in NALM-based mode-locked ANDi fiber laser.