Stochastic collapse and recovery of optical solitons in harmonic mode-locked lasers under pump perturbations.

Harmonically mode-locked soliton fiber laser can host an ensemble of identical solitons in parallel, providing a unique many-body system for exploring the intrinsic stochasticity of soliton dynamics in nonlinear optical systems. We report in this work the experimental observation of parallel soliton dynamics under homogeneous perturbation in a harmonically mode-locked fiber laser. Given an abrupt and transient decrease in the pump power, the parallel solitons exhibit evolution trajectories of probabilistic nature, featuring prominent re-distribution of soliton energies followed by random collapse and recovery after the perturbation. We investigate statistical dependences of the soliton collapse upon the perturbation parameters, while revealing threshold behaviors of the recovery dynamics. This work provides unique insight into the stochasticity of the nonlinear soliton evolution in mode-locked fiber lasers and may help to improve laser stability.