Ultrafast Fiber Lasers

Vector solitons present unique optical pulses characterised by coupled orthogonal polarisation components, offering rich, multidimensional dynamics. Their increased 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 in terms of 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, obtained using the time-stretch dispersive Fourier transform technique, reveal the generation regimes of singlet solitons and loosely bound vector soliton pairs. In the latter case, the observed intensity-dependent temporal splitting of vector soliton polarizations 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 expands the understanding of vector soliton dynamics by considering both gain dynamics and rare-earth ion exchange. While specific to the Tm-doped system studied here, these findings pave the way for further advanced exploration of distributed mode-locking mechanisms and resulting generation regimes across a wide range of nonlinear photonic systems.