DYNAMIC-MODEL OF MULTIPASS ULTRASHORT-PULSE LASER-AMPLIFIERS AND ITS APPLICATION

We developed a dynamic model for evaluating the gain and amplified spo ntaneous emission of multipass ultrashort-pulse laser amplifiers. This model takes into account the time dependence of the population invers ion that is due to the time-varying pump power and the evolution of th e amplified spontaneous emission. For gain media of a short upper-stat e lifetime, a time-dependent analysis is essential for the model to ex tend beyond order-of-magnitude estimation. We verified the model with a femtosecond dye laser amplifier. The calculated output energy is acc urate to within +/-5% of the experimental data. We utilized this model to optimize the conversion efficiency of the dye laser amplifier unde r low-energy pumping. An efficiency of 2.3% is achieved with an optima l pump energy of only 4 mu J. (C) 1997 Optical Society of America.