Modelling of kinetics of atomic ensemble in a light field using the langevin equation

Numerical simulation of kinetics of atomic ensemble in resonant non-uniformly polarized laser field within the bounds of quasiclassical approximation is considered on the basis of step-by-step integration of Langevin equation (LE). Characteristic properties of this equation are the vortextype component in the light-induced force and anisotropy of tensor of dissipation in the regular force, as well as coordinate dependence and anisotropy of correlation tensor of the random force. Various algorithms of step-by-step integration of LE are presented. For a two-dimensional (2D) model the influence of vortex-type component in force and the influence of anisotropy of processes of dissipation and diffusion are investigated for the coordinate and momentum distributions of atoms which are obtained by means of modelling of dynamics of single particle in accordance with LE. Some features in three-beam 2D configuration of light field are considered for kinetic distributions, which are formed on basis of various schemes of step-by-step integration of LE.