Reverse Saturable Absorption Mechanism Induced Regime Transition of Pure Quartic Solitons in Fiber Lasers: A Numerical Study

Pure quartic solitons (PQSs) demonstrate distinct pulse dynamics and enhanced energy scalability compared to traditional solitons. In fiber lasers operating in anomalous fourth-order dispersion, recent investigations have primarily focused on PQS behavior governed by saturable absorption mechanisms. Here, the reverse saturable absorption mechanism (RSAM) is leveraged to modulate PQSs in a mode-locked fiber laser operating in the anomalous fourth-order dispersion regime. By altering the saturation energy and coefficient of RSAM, the laser undergoes state transitions between different PQSs including single solitons, bound-state solitons, and dissipative soliton resonance with spectral doublet. In each regime of PQSs, the formation dynamics and pulse characteristics such as pulse intensities and optical spectra are investigated, revealing that the RSAM promotes pulse splitting and generation of multi-pulse states of PQSs. Additionally, compared to conventional PQSs, the energy scaling ability of PQSs controlled by RSAM is enhanced. The results reveal the joint effect of pure fourth-order dispersion and RSAM on PQSs, presenting a novel approach for the modulation and control of PQSs in fiber laser systems.