Propagation of laser radiation in a medium with a slow-response chemical nonlinearity

An investigation is made of the dynamics of the propagation of laser radiation in a medium where chemical reactions are taking place. Absorption of radiation energy heats the medium and speeds up the reactions. It is found that if products having optical properties other than those of the initial material are formed in the chemical reaction, a new mechanism of radiation self-interaction, i.e., a slow-response chemical nonlinearity, is observed in the medium. Cases of strongly (when the medium is weakly nonlinear) and moderately (when the medium is strongly nonlinear) exothermic reactions are considered. An investigation is made of the role of diffraction effects. It is shown that in a medium with a chemical nonlinearity a "chemical" focusing lens overcomes the diffraction effects if the product of the radiation energy and the reaction product concentration exceeds a critical value.