Wavelength-switchable dual-wavelength thulium-doped fiber laser utilizing photonic crystal fiber

A dual-wavelength thulium-doped fiber laser with a wide switchable single-wavelength range is demonstrated by employing a polarization-maintaining photonic crystal fiber. A new type of comb filter is designed and its spectrum is simulated. A nonlinear polarization rotation module is inserted into the laser cavity to suppress intense gain competition. An output power instability as low as 0.84 dB has been attained. The switchable range of single-wavelength operation is 43.64 nm, and the slope efficiency is 1.79%, attained by optimizing the splicer parameter between the polarization-maintaining photonic crystal fiber and the single-mode fiber. There are five regions of dual-wavelength output from 1978.04 to 1986.51 nm, and the maximum and minimum wavelength intervals are 6.11 nm and 1.9 nm.