Numerical investigation of the operation of unstable telescopic resonators allowing for diffraction and saturation in the active medium

Numerical solutions of parabolic wave equations, describing the interaction between active media of various types with the irradiation field in an unstable telescopic resonator, are used in an analysis of the influence of the nature of the nonlinearity of the active medium on the angular distribution (directionality) of the laser radiation. A two-level model of an active medium with a homogeneous gain saturation is considered, as well as a more general two-level model and a model of an active medium with excitation transfer in fastflow lasers. It is shown that the nonlinearity of an active medium with a homogeneous gain saturation does not affect the angular distribution of the output radiation, whereas the inhomogeneity of a fast-flow active medium may cause a drift of the direction of the laser radiation.