Switchable SP Dual-Wavelength Mode-Locked TDFL Incorporating a PM-FBG and SESAM

A switchable single-polarization (SP) dual-wavelength mode-locked thulium-doped fiber laser using the polarization maintaining fiber Bragg grating and semiconductor saturable absorber mirror is proposed in 2- $\mu \text{m}$ band. By adjusting the polarization controller, stable dual-wavelength pulse lasing operation and SP single-wavelength pulse lasing operation are obtained. The dual-wavelength pulse lasing operation is obtained at 1940.97 and 1941.73 nm. In the SP single-wavelength pulse lasing state, the polarization extinction ratios are higher than 30 dB, the SP pulse duration are 3.75 and 3.73 ps.