Evolution of multiple pulses and pump hysteresis phenomenon in a passively mode-locked Er-doped fiber laser based on an Sb₂S₃-PVA saturable absorber

The evolution of multiple pulses and the pump hysteresis phenomenon were observed in a passively mode-locked Er-doped fiber laser using an Sb2S3-PVA saturable absorber. As the pump power was increased, the generations of onefold, twofold and threefold pulses were meticulously documented. When the pump power was decreased, the evolution of fivefold and sixfold pulses was carefully recorded, accompanied by a clear pump hysteresis phenomenon. A thorough analysis was conducted to examine and reveal the inversely proportional relationship between the RF spectrum modulation periods and the total pulse intervals of the multi-pulse bunches including from onefold to sixfold pulses.