Soliton dynamics in a two-level medium with pumping

A perturbation theory is developed for a system of evolution equations close to integrable systems in the method of inverse scattering with a spectral parameter depending on variables. This theory is used for analyzing the evolution features for soliton light pulses in a two-level medium with the upper level pumping taking into account linear and nonlinear losses as well as dispersion. Various modes of soliton evolution (including the random mode) in such a system are investigated numerically. It is shown that anomalies in the dependence of soliton parameters on the length of the laser medium appear in the presence of nonuniform broadening in the case when the upper level pumping rate and inverse population losses are functions of detuning. The contribution from the radiative component of the solution is also analyzed taking into account perturbations; it is shown that this contribution can be disregarded in a certain range of parameters. (C) 2001 MAIK "Nauka/Interperiodica".