Divergence of the radiation from a solid-state laser with a stable cavity and with intracavity apertures

A modified matrix model is proposed for stable cavities with intracavity Gaussian apertures, which approximate real apertures. This model differs from the known ones by a better grounded approach to selection of the Gaussian aperture parameters. Analytic relationships are derived for calculating the energy divergence angle of the output radiation and of the beam diameter at the output mirror position under multimode emission conditions. It is shown that the spatial characteristics of the beam are determined by the aperture diameter and by the complex magnification, which is an analogue of the geometric magnification used in the description of unstable cavities. The calculated results are in good agreement with experimental data.