MODEL PREDICTING THE TEMPERATURE-DEPENDENCE OF THE GAIN COEFFICIENT AND THE EXTRACTABLE STORED ENERGY DENSITY IN ND-PHOSPHATE GLASS LASERS

We have constructed a model that will be useful in designing Nd: phosphate glass lasers that are heated when run repetitively, continuously, or in the burst mode. The model predicts the temperature dependence of the gain coefficient and the extractable stored energy density. Changes in the populations of the upper and lower laser levels are described by Boltzmann distributions. The generalized Einstein relations are used to relate the stimulated-emission and absorption cross sections. Variations of the cross sections with temperature have been inferred from measurements of the threshold energies of a flash-lamp-pumped rod oscillator, over the range 288 to 365 K. With only a single input of the gain coefficient at one temperature, our model predicts the gain coefficient and the extractable stored energy density at other temperatures.