UP-CONVERSION VERSUS PR-DEACTIVATION FOR EFFICIENT 3 MU-M LASER OPERATION IN ER

Erbium-doped BaY2F8 is evaluated as a potential material for a laser diode pumped 3-mu-m laser. We show that the metastable Er 4I13/2 level is efficiently quenched by the addition of a small amount of Pr, while still leaving the 4I11/2 lifetime fairly long. Measurements of the 4I11/2 and 4I13/2 lifetimes in Er, Pr:BaY2F8 for 1-100% Er with 0.1-1% Pr show that the 4I13/2 lifetime can be up to 10 times shorter than 4I11/2. To compare this with upconversion type operation of this laser, we have measured the upconversion coefficients alpha for 5, 10, 20, 50, and 100% Er:BaY2F8 and compare 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 (alpha)13/2 to (alpha)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.