Control of Pulse-to-Pulse Interactions in a Ring Soliton Fiber Laser through Positioning of Saturable Absorber

The work presents a numerical and experimental study of pulse-to-pulse interactions occurring due to gain depletion and recovery in a soliton polarization-maintaining fiber laser. Specifically, it is demonstrated that the direction and magnitude of the interaction forces depend significantly on the stage of the combined evolution of the soliton and the dispersive wave occurring in the laser’s gain fiber. Numerical simulations demonstrate that by varying the position of the saturable absorber (SA) within the resonator, it is possible to control the soliton interaction occurring due to gain depletion and recovery. In particular, placing the SA immediately after the gain fiber enhances the pulse-to-pulse attraction, transforming the laser into a generator of coupled solitons or soliton bunches. Conversely, by optimizing the distance between the SA and the gain fiber, it is possible to enhance the repulsive interaction and ensure optimal conditions for stable harmonic mode locking with multi-GHz pulse repetition rates. The numerical simulation results are consistent with the experimental data.