High-efficiency continuous-wave Tm-doped fiber laser with a single fiber Bragg grating at 1942 nm

We report a continuous-wave Tm-doped fiber (TDF) laser with a single fiber Bragg grating (FBG). The Fresnel effect presenting in the passive fiber end-face and high-reflectivity FBG established the resonator. The peak wavelength of the laser was 1942.25 nm with a spectral linewidth of 194 pm. The maximum output power was 37.5 W, corresponding to a slope efficiency of 63.7% with a beam quality factor of M-2 similar to 1.51. To the best of our knowledge, this is the highest slope efficiency of a TDF laser pumped by 793 nm laser diode.