Multi-pulse dynamic patterns in a mode-locked erbium-doped fiber laser based on an Sb₂S₃-PVA saturable absorber

Multi-pulse dynamic patterns have been experimentally documented in a passively mode-locked (PML) erbium-doped fiber (EDF) laser using an Sb₂S₃-PVA saturable absorber (SA). The fundamental mode-locking operation, with a repetition rate of ∼3.22 MHz, a pulse width of ∼2.5 ps, a signal-to-noise ratio (SNR) of ∼50 dB and a peak power over 200 W, was achieved under a pump power from 280 to 360 mW with appropriate polarization states introduced by the polarization controllers (PCs). By rotating the orientation of the intra-cavity PCs carefully and slowly at a pump power of 350 mW, it was found that a multi-pulse bunch was transformed gradually from a single-pulse to a twelve-pulse bunch, with several intermediate transition states of multi-pulse bunches being observed. In addition, other characteristic modes including disordered multi-pulses and soliton rains have been experimentally observed by meticulously adjusting the polarization states of PCs at a pump power of 350 mW. Our systematic study clearly demonstrates that Sb₂S₃has potential as an effective SA for generating different operation states of multi-pulses in PML anomalous-dispersion EDF lasers.