Strong thermal self-action of a laser beam in gases and liquids

Solutions which approximately describe the effect of strong thermal self-ac tion of a laser beam in weakly absorbing media (gases and liquids) have bee n obtained. This paper considers the regimes of thermal conductivity, trans verse flows of gases at subsonic and supersonic velocities, transonic nonli near regime, and gravitational convection in a horizontal beam. Assuming th at the shape of transverse intensity distribution is constant, and that the wave front can be approximated by a second-power polynomial, ordinary diff erential equations and their solutions for average transverse dimensions of beams have been obtained. These approximate solutions are in satisfactory agreement with exact solutions. (C) 1999 American Institute of Physics. [S1 063-7761(99)01007-0].