Multi-soliton bound states in a figure-9 Er-doped fiber laser

This paper presents a self-starting, all-polarization-maintaining (PM) figure-9 Er-doped fiber laser that employs an integrated PM combiner. By adjusting the pump power and intracavity polarization state, the operating regime and pulse characteristics of the laser can be effectively controlled, enabling the generation of bound soliton states with tunable separations and orders. Multiple bound-state configurations, including double-, triple-, quadruple-, and sextuple-soliton states, were successfully generated. The formation mechanisms and characteristics of these different bound soliton states were analyzed, providing deeper insight into the interaction dynamics between multiple solitons and offering valuable guidance for further exploration of nonlinear dynamics in bound-state systems.