Transmission of laser radiation by an optical discharge plasma and the channel discharge model

An experimental investigation was made of the structure of optical discharges in air and in argon in a quasi-cw CO₂ laser beam. Measurements of the fraction of the laser power transmitted by the discharge plasma and of the power density at the center of the focal spot, when the plasma was present, showed that the heating of the plasma in the beam propagation zone to temperatures above 17 kK was accompanied by its bleaching in the beam and by a peaking of the beam intensity distribution in the focal plane. A channel model of the optical discharge is proposed to provide an analytical description of its temperature distribution in the laser beam. Sufficient conditions for the discharge bleaching regime are determined.