Wavelength control and spectral narrowing of high power fiber lasers using volume Bragg gratings

We report on the novel use of volume Bragg gratings for effective spectrum narrowing and wavelength control of high power Tm-doped fiber lasers in the ´eyesafe´ 2 μm spectral region. Over 130 W of diffraction limited output has been yielded with a spectral linewidth of ~ 10 pm. The operating wavelength was continuously tunable from 1926 to 1998 nm, with >; 110 W output power over a tuning range of 68 nm from 1930 nm to 1998 nm. A relatively narrow linewidth of ~ 2.0 pm (FWHM) has been generated using a grating pair in serial configuration. Simultaneous dual-wavelength operation has been demonstrated by combining volume Bragg gratings of different specifications and using a simple resonator configuration for wavelength selection. The prospects for further improvement in performance will be discussed.