Soliton bimodality and tunable Cherenkov radiation near zero dispersion induced by third-order dispersion

The intricate dynamics of ultrashort pulses in fiber lasers are profoundly shaped by the delicate interplay between dispersion and nonlinearity. While second-order dispersion (SOD) plays a dominant role in soliton formation, the influence of third-order dispersion (TOD) becomes particularly critical in regimes where dispersion approaches zero. This near-zero dispersion regime gives rise to complex and rich phenomena that remain only partially understood. In this study, we present both experimental and analytical investigations into the effects of TOD on soliton dynamics within a mode-locked fiber laser operating close to its zero-dispersion wavelength. By meticulously tuning the net cavity SOD to near-zero values, we demonstrate-both experimentally and analytically-that TOD acts as a dominant perturbation mechanism in this regime. Specifically, TOD induces pulse splitting, governs the behavior of dispersive waves, and facilitates the emergence of Cherenkov radiation across both normal and anomalous dispersion regimes. Our findings underscore the significant role of TOD as a perturbation mechanism, shedding new light on its significance in nonlinear optics. These results not only pave the way for novel multi-wavelength laser generation techniques but also deepen our fundamental understanding of perturbed soliton dynamics in confined, dissipative systems.