Control of Soliton Interactions in All-PMF Laser via Saturable Absorber Positioning and Time-Dependent Gain Effects

Long-range soliton interactions governed by the gain depletion and recovery (GDR) mechanism in polarization-maintaining fiber (PMF) lasers are investigated both numerically and experimentally. We show that the direction and magnitude of the interaction forces strongly depend on the stage of cooperative evolution of solitons and dispersive waves within the gain fiber. The GDR mechanism enables control over soliton interactions by varying the position of the saturable absorber (SA) inside the cavity. In particular, placing the SA directly after the gain fiber promotes attractive forces, transforming the laser into a generator of bound solitons or soliton bunches. In contrast, selecting an optimal separation between the SA and the gain fiber enhances repulsive inter-soliton interactions and enables harmonic mode-locking (HML) with multi-GHz pulse repetition rates and improved stability. The results of numerical simulations are in good agreement with experimental observations.