Dual-wavelength mode-locked fiber laser based on tungsten disulfide saturable absorber

We report on the generation of dual-wavelength mode-locked laser pulse in an Er-doped ring-shaped fiber cavity with WS2 nanosheets based saturable absorber (SA), emitting at wavelength of 1531.8 nm and 1556.7 nm. The WS2 nanosheets were precipitated on the head face of fiber patch cord via light precipitation method. By adjusting the polarization of lasing mode, the gain of the Er-doped fiber laser was effectively controlled and the stable dual-wavelength mode-locking operation was achieved. Our investigation revealed WS2's extraordinary nonlinear properties, which make it an excellent material for saturable absorber for passively mode-locked fiber lasers.