Numerical modelling of the propagation of high-power laser radiation in sodium vapour

Numerical modelling is reported of the propagation of laser radiation in a resonant three-level medium. The transient nature and the spatial inhomogeneity of the investigated processes are taken into account. It is shown that the radiation is scattered into narrow cones and that the number and vertex angles of these cones depend on the experimental conditions. The spatiotemporal spectrum of the radiation field emerging from the scattering medium and the dependence of this spectrum on the laser radiation frequency are compared with the results of experiments carried out under similar conditions. The calculated and experimental results are shown to agree under various scattering conditions when the spectral distributions of the scattered-radiation field are qualitatively different.