Spectrum narrowing of high power Tm: fiber laser using a volume Bragg grating.

Efficient operation of a cladding pumped high power Tm: fiber laser with a volume Bragg grating (VBG) as wavelength selective and spectrally narrowing element is reported. The laser yielded over 112 W of diffraction limited output at 1988 nm with a spectral linewidth of ~12 pm for 279 W of launched pump power, corresponding to a slope efficiency with respect to launched pump power of 43.4%. No discernable difference was observed in terms of output power and slope efficiency when using a broadband highly reflective mirror in place of the VBG.