Dynamics of the spectral pulsation in multi-soliton fiber lasers

Abstract Recent progress in real-time measurement techniques has enabled the exploration of intricate pulsation dynamics in multi-soliton complexes within ultrafast fiber lasers. Leveraging the dispersive Fourier transform (DFT) technique, we investigate various multi-soliton states, including soliton-soliton pair, molecule-molecule pair, and soliton-molecule pair. We here demonstrate that under the combined action of nonlinear effects and intracavity dispersion, the soliton-soliton pair exhibits asynchronous spectral pulsation characterized by a peak-dip intensity alternation at the central wavelength. Furthermore, in other multi-soliton pulsating states, nonlinear effects mediate interactions among pulses within soliton molecules (SMs), leading to periodic energy exchange. This oscillatory energy flow modulates the relative phase and temporal separation, thereby modifying the resulting spectral interference patterns. These findings provide profound insights into the intrinsic evolutionary dynamics of multi-soliton phenomena in fiber lasers.