Comparative investigation of diode-pumped Tm3+:YAlO3 lasers: influence of doping concentration

Abstract

We investigated the effect of thulium ion concentration on the continuouswave power performance of diode single-end-pumped Tm 3+:YAlO3 (Tm:YAP) lasers operating at 2 μm by using crystals with 1.5%, 3%, and 4% Tm3+ concentration. Best results were obtained with the 1.5% Tm3+: YAP crystal. Spectroscopic measurements and rate-equation analysis suggest that cross relaxation should already be effective at 1.5% Tm3+ concentration. Increase in reabsorption losses, non-radiative decay rates, and internal heating are likely causes of power degradation with increasing ion concentration. By using the laser efficiency data, the effective stimulated emission cross section was determined to be 4.2×10-21 cm2 at 1.94 μm, in agreement with previous results.