Dual-state vector soliton in mode-locked fiber laser

Vector soliton originates from the soliton trapping dynamics via cross-phase modulation (XPM) which has been used to achieve supercontinuum, optical switching and optical analog of gravity-like potentials. Dual-state vector soliton (DSVS) is reported in mode-locked fiber laser under appropriate birefringence. Two vector soliton states emitted alternatively display double-peak and Lorentz-shaped spectral profile, respectively. The two orthogo-nally polarized components of the double-peak spectrum exhibit obvious redshift and blueshift, respectively, while the frequency shift for the other state is limited even with the reversed shift direction, which illustrates a unique vector soliton evolution dynamic. DSVS originates from the pulse trapping induced by XPM, as well as the periodical evolution and frequency shift induced by self-phase modulation under dispersion-managed condition. The vector period-doubling phenomenon will further enrich the understanding about soliton, and also guide the design of mode-locked laser.