Numerical analysis of the propagation of a radiation pulse at a wavelength of 10.6 microns through absorbing media

Attention is given to the nonstationary self-consistent problem concerning the transmission of a collimated Gaussian beam from a CO2 laser through an immobile CO2-N2 gas mixture with allowance for nonlinear effects of resonant absorption and heat conduction. The effects of saturation and nonlinear vibrational energy exchange on the self-defocusing of the beam are examined. The numerical analysis is carried out on the basis of the simultaneous solution of the parabolic quasi-optic equation for the complex amplitude of the electric field and the equations of vibrational kinetics and heat conduction for the medium. It is concluded that the failure to account for the nonlinear effects investigated here can lead to significant errors in the determination of the amplitude-phase characteristics of light beams.