Oscillatory Central-Frequency Pulling in Self-Starting Dynamics of NPR-Based Mode-Locked Soliton Fiber Laser

Self-starting dynamics of mode-locked lasers, as a complex dissipative nonlinear process, has attract extensive interests in fields of laser physics due to the stochastic and transient nature of their dynamics [1]. During the self-starting, a mode-locked pulse typically emerges from the noisy spikes from a noisy continuous-wave (CW) background, while the subsequent pulse dynamics features coupled evolutions of multiple parameters (e.g. pulse energy, optical bandwidth, and central-frequency) which remains rather complicated for clear interpretation. We report in this work our investigations of the oscillatory central-frequency pulling observed during the self-starting process in a typical mode-locked soliton fiber laser. The central frequency of the mode-locked soliton exhibits a damped oscillation that clearly coupled with the relaxation oscillation of the evolving soliton energy, which can be interpreted using the frequency pulling effect induced by NPR-related spectral filtering.