Switching and vector characteristics of bound-state solitons in a graphene-based mode-locked fiber laser

A passive mode-locked erbium-doped fiber laser based on graphene operating in the anomalous dispersion state is designed in this paper. In this experiment, the complete convert process from traditional soliton pulses to soliton rains and bound-state (BS) soliton pulses, and ultimately to traditional soliton pulses, is achieved by adjusting the pump power and polarization controller (PC) to control factors such as nonlinearity, dispersion, and birefringence in the cavity. In the BS soliton state, switching between the 0 phase and π phase BS solitons is achieved. We also replaced the 20/80 coupler with the 30/70 coupler to achieve the soliton rains by varying the energy alteration of the intracavity pulse. When the pump power is increased to 350 mW, the laser generates multi-pulses and eventually forms a new BS. In addition, we also studied the soliton vector characteristics during this conversion process and found the polarization-locked vector soliton (PLVS). The research results enrich nonlinear vector soliton dynamics and provide valuable data for further theoretical studies.