Abstract

In this work the method of statistical simulation allowing to calculate an interaction of a laser pulse with nonlinear absorbing many-level medium when the time duration of the pulse is equal to longitudinal characteristic relaxation time has been suggested and realized. The two problems were solved by this method. The first problem was the one of laser energy storage on the metastable level of the medium atoms. The space and time characteristics of this inverted medium of plane geometry were calculated. The amplification coefficient of forbidden transition versus different parameters of this problem was obtained. Using Asl as an example the mechanism of two-step photoionization of atoms and mechanism of formation of inversion of the population between a metastable level and a ground state (mechanism of accumulation of laser radiation energy in volume) are investigated. It is shown that due to the "imprisonment" (trapping) of reemited photons leads to the sharp decrease both of the length of interaction between laser radiation and medium, and the length of accumulation of laser radiation energy in volume. In this case the gain factor of inverted medium is one order of magnitude less than that obtained by theoretical estimates (neglecting this effect). The algorithm suggested allows solving these problems within multi-pulse mode taking into account the collision and diffusion processes.

© 1996 IEEE