Dual-Wavelength Single-Longitudinal-Mode Tm-Doped Fiber Laser Using PM-CMFBG

We have demonstrated a dual-wavelength thulium-doped fiber laser with single-longitudinal-mode (SLM) operation at $\sim 2$ - $\mu \text{m}$ region. A polarization-maintaining chirped Moire fiber Bragg grating was employed as a polarization-dependent narrow-band filter, to suppress multilongitudinal-mode oscillation. Single-and dual-wavelength switchable operation was achieved by simply adjusting the polarization controller. We also showed that the laser lines retained SLM operation with the additional benefit of single polarization. Meanwhile, the dependence of each laser wavelength on the pump power was also investigated in detail.