A multiwavelength thulium-doped silica fiber laser incorporating a highly nonlinear fiber

A multiwavelength Tm³⁺-doped silica fiber laser incorporating a highly nonlinear fiber is presented. In the laser cavity, a nonlinear polarization rotation (NPR) based fiber loop mirror is used to overcome the mode competition and a polarization-maintaining fiber Sagnac loop mirror is used as the filter. The 150 m highly nonlinear fiber can improve the NPR effect in the laser cavity, which can increase the number of output channels. By adjusting the polarization state of the polarization controllers properly, stable multiwavelength operation at the 2 μm spectrum can be obtained at room temperature. It can achieve 15 output channels within a 10 dB bandwidth from 1990 to 2007.5 nm. The channel spacing of the multiwavelength Tm³⁺-doped silica fiber laser is 1.22 nm. Moreover, the performance of the laser is investigated for different pump powers and fibers. (paper)