Degenerate four-wave interaction based on photodissociation of chemically active media

An analysis is made of a nonlinear interaction of laser radiation with a chemically active medium in which a branched-chain reaction takes place. This reaction enhances greatly the contrast of phase gratings formed as a result of photodecomposition. The example of a gaseous mixture of hydrogen disulfide with oxygen is used in a theoretical investigation of a degenerate four-wave interaction in the course of photodissociation of CS₂ molecules and subsequent reactions of the dissociation products. The dynamics of reflection is calculated for different CS₂ concentrations and radiation intensities, and it is shown that a high efficiency can be achieved in such systems.