Fig. 1. Diagrammatic sketch of the experimental setup.

Fig. 2. Water absorption spectrum near 1908 nm (plotted using HITRAN data^[11]) and laser wavelength shift.

Fig. 3. Dependence of the laser wavelength on temperature without active cooling in the VBG: (a) wavelength at different output power and corresponding temperature under different output power; (b) fitting of the relationship between wavelength and temperature, and corresponding theoretical curve.

Fig. 4. Comparison of CW laser performance, including (a) output power and (b) wavelength under different heat dissipation methods for the VBG.

Fig. 5. Beam quality at different average power levels: (a) beam quality of 160 W Tm:YLF laser without active cooling; (b) beam quality of 202 W Tm:YLF laser with microchannel cooling.

Fig. 6. Spectrum of the Tm:YLF laser.