Diode-pumped high efficient Tm:YLF laser output at 1908 nm with near-diffraction limited beam quality

High power and high beam quality continuous wave Tm:YLF laser by the dual-end-pumped is presented in this letter. The highest output power reaches 21.3 W when the totally input pump power is 54.6 W. The optical conversion efficiency is 39.0% and the slope efficiency is 47.3% With an F-P etalon in, the cavity, the output center wavelength is tuned to 1908 nm with about 0.5 nm FWHM. With the optimal cavity, the beam quality factor M-2 can be similar to 1.1. As we know, our work is the first time to investigate the Tm:YLF laser output spectrum with an F-P etalon in the cavity, and acquire near-diffraction limited laser output.