Upconversion versus Pr-deactivation for efficient 3 μm laser operation in Er

Erbium-doped BaY₂F₈ is evaluated as a potential material for a laser diode pumped 3-μm laser. It is shown that the metastable Er⁴I_13/2 level is efficiently quenched by the addition of a small amount of Pr, while still leaving the ⁴I_11/2 lifetime fairly long. Measurement of the ⁴I_11/2 and ⁴I_13/2 lifetimes in Er, Pr:BaY₂F₈ for 1-100% Er with 0.1-1% Pr show that the ⁴I_13/2 lifetime can be up to 10 times shorter than ⁴I_11/2. To compare this with upconversion type operation of this laser, the authors measured the upconversion coefficients α for 5, 10, 20, 50, and 100% Er:BaY₂F₈ and compared these to previous measurements for LiYF₄. These show a similar concentration dependence in both hosts, although BaY₂F₈ appears to have a slightly higher ratio of α_13/2 to α_11/2. Laser performance under argon and diode pumping are presented to compare upconversion operation in BaY₂F₈ and LiYF₄, and quasi-4-level operation in Er, Pr:LiYF₄ laser