Dynamical diversity of FWM-induced pulsating solitons in an ultrafast fiber laser

Pulsating solitons in fiber lasers embody a captivating phenomenon in nonlinear optics, combining the stability of solitons with the dynamic nature of pulsation. In recent years, real-time measurements have revealed a variety of pulsating solitons with distinct pulsation characteristics in fiber lasers, stemming from the intricate properties of dissipative systems. However, there are still rare studies focusing on the dynamical diversity of pulsating solitons in conventional soliton mode-locked lasers. Here, we report soliton pulsations induced by the four-wave mixing (FWM) in a conventional soliton fiber laser. Pulsating solitons including pulsating single solitons, synchronous and asynchronous double-soliton bunches, and soliton molecules (SMs) are observed. They all exhibit peak-dip alternation at the spectral center but present varying types of sidebands. The diversity of spectral pulsation characteristics is related to periodic variations in soliton parameters, the strength of dispersive wave radiation, and the relative phase between the soliton and the dispersive wave. These findings will expand the diversity of pulsating solitons with complicated spectral structures in nonlinear dissipative systems.