EFFECT OF RADIATION TRAPPING ON FLUORESCENCE LIFETIME AND EMISSION CROSS-SECTION MEASUREMENTS IN SOLID-STATE LASER MEDIA

Radiation trapping causes significant lengthening of the measured fluorescence lifetime in optically thin solid-state laser gain media, which leads to underestimates of the stimulated emission cross section by as much as 30%. A measurement technique is demonstrated that greatly reduces radiation trapping in Yb:YAG, a prototypical quasi-three-level laser medium. The radiative lifetime of the F-2(5/2) manifold was measured to be 0.951 ms at 300 K, which is more than 10% lower than any previous measurement. This more-accurate radiative lifetime gives a 1.03-mum peak effective stimulated emission cross section of 2.3 x 10(-20) cm2. Our measurement technique is expected to be most relevant for three-level and quasi-three-level laser media.