Widely tunable dual-wavelength operation of a high-power Tm:fiber laser using volume Bragg gratings

We report on high-power operation of a widely tunable dual-wavelength Tm:fiber laser in the 2 microm spectral region using volume Bragg gratings and a simple resonator configuration for wavelength selection. The wavelength splitting range is continuously tunable from 1 to 50 nm (0.1-3.8 THz), with >115 W of diffraction-limited total output power for wavelength separations of <40 nm. A maximum output power of 118 W was obtained for 279 W of launched pump power at 792 nm, corresponding to a slope efficiency with respect to launched pump power of 45%. The prospects for further improvement in performance are discussed.