Tunable continuous-wave laser operation of Tm³⁺:BaY₂F₈ near 2.3  µm

We report, for the first time to our knowledge, tunable continuous-wave laser action in the Tm³⁺:BaY₂F₈ (BYF) crystal near 2.3 µm. In the experiments, a BYF crystal doped with 3 at. % thulium was end pumped with a narrow-linewidth, tunable Ti³⁺:sapphire laser with up to 920 mW of incident power. Lasing was achieved for the two pump polarizations of E//x and E//y. The best power performance was obtained in the case of E//x, double-end pumping, where 100 mW of output power was obtained at 2290 nm with 920 mW of pump power and 1% output coupler. The laser could be continuously tuned from 2233 to 2385 nm. Excitation spectra for E//x and E//y pumping were measured in the 760-810 nm range, and the optimum pumping wavelength was determined to be 779 nm for E//x. By using the lifetime and lasing threshold data, the stimulated emission cross section at 2290 nm was further determined to be (0.66±0.06)×10^-24m².