XPM-Induced Vector Asymmetrical Soliton with Spectral Period Doubling in Mode-Locked Fiber Laser

Cross phase modulation (XPM) can induce soliton trapping in nonlinear medium, which has been employed to achieve vector soliton, optical switching, and optical analog of gravity-like potentials. Here, the first observation of a novel soliton operation is reported whose wavelength exhibits redshift and blueshift periodically in a mode-locked fiber laser under appropriate birefringence and dispersion map. XPM dominates the dynamics by inducing and sustaining the vector asymmetrical soliton (VAS) with spectral period doubling, and exhibits a unique trajectory of pulse trapping. The XPM-induced VAS is an idiosyncratic steady state featured with asymmetry in the model based on the coupled Ginzburg-Landau equation, which depicts the distinct pulse features in comparison with vector soliton, soliton molecule, and traditional period-doubling evolutions. The two orthogonal polarized directions of mode-locked fiber laser can be regarded as the XPM-coupled dissipative resonators guiding the further study of the optical nonlinear dynamics and chaos for soliton, which is helpful to laser design and brings useful insights into nonlinear science and applications.