Free of reabsorption upper-state lifetime measurements by the method of transient gratings.

Light reabsorption and radiation trapping can noticeably distort fluorescence decay in solid-state laser gain media with a partial overlap of absorption and emission bands. In this paper, the upper-state lifetime measurements in laser materials by the method of transient gratings are discussed. A theoretical model for description of reabsorption in a thin layer is developed. It is shown that under certain conditions reabsorption has no effect on the transient time of refractive index grating and thus the true upper-state lifetime can be measured. Some experimental results confirming effectiveness of the technique are presented.