Dynamics of Vector Soliton Singlets and Pairs in Self-Mode-Locked Tm-Doped Fibre Lasers

Abstract: Vector solitons present unique optical pulses characterised by coupled orthogonal polarisation components, offering rich, multidimensional dynamics. Their enhanced degrees of freedom make them highly versatile for exploring nonlinear wave phenomena and enabling advanced applications in optical communications and ultrafast technologies. Despite significant recent progress, the intricate dynamics of vector soliton generation remain largely unexplored, particularly their interaction and coupling mechanisms. This study characterises soliton build-up dynamics in a self-mode-locked Tm-doped fibre laser, where both cavity birefringence and distributed saturable absorber play significant roles in the intracavity pulse shaping. The recorded single-shot spectra using the Dispersive Fourier Transform technique reveal generation regimes of singlet solitons and loosely bound two-pulse states. In later case, the observed intensity-dependent temporal splitting of vector soliton polarisations is also affected by the repulsive forces due to the interaction with synchronised and unsynchronised dispersive waves, governing the transition from transient pulse formation to steady-state generation. This study enhances our understanding of vector soliton dynamics and sets a solid foundation for further advanced exploration of their generation regimes across a wide range of nonlinear photonic systems.