Influence of the active-medium inhomogeneity and of aperture stops on the output-beam parameters of a CO2 laser

A determination is made of the shape of a radiation beam inside and outside an arbitrary stable resonator of a single-mode CO₂ laser, as a function of the discharge parameters and of the resonator geometry and taking into account the radial inhomogeneity of the radiation density, of the unsaturated gain, and of the saturation parameter. An investigation is made of the effect of intracavity aperture stops on the shape of the beam. The method of successive approximations is used to take into account the coupling between the resonator diffraction losses and the parameters of the medium and of the radiation beam. A considerable difference is found between the spatial characteristics of the radiation beam in passive (empty) and in active (activemedium containing) resonators, with and without aperture stops.