Influence of diagonal shocks and intracavity absorbing zones on the characteristics of radiation from a CO2 gasdynamic laser with a large-aperture unstable resonator

The problem of the distribution of the complex amplitude of an electromagnetic field in the interior of an active large-aperture unstable resonator of a CO₂ gasdynamic laser with a large Fresnel number (N_F~200) is solved numerically in the three-dimensional case. The method of approximate calculation of the two-dimensional Kirchhoff integral, in accordance with specially derived quadrature expressions of higher precision, is used in numerical integration of the paraxial wave equation. A numerical method is applied in a theoretical investigation of the influence of diagonal shocks in the active medium and of absorbing intracavity zones on the characteristics of the output radiation of a CO₂ gasdynamic laser. The kinetics of vibrational relaxation is described by a fairly complete three-temperature model in combination with equations of nonequilibrium gasdynamics considered in the jet approximation.