Journal of Physics A Mathematical and General
The Thirring model as an approximation to the theory of two-photon propagation
A. M. Kamchatnov, Heinz Steudel, Alexander A. Zabolotskii
Abstract
We consider the two-photon propagation process under the two-fold approximation that (i) the excitation of the upper level of medium molecules remains small during the process, (ii) the intensity of one of the two participating electromagnetic waves is always small compared to that of the other wave. It is then shown that in the limit of the strong dynamical Stark effect the equations describing this process can be reduced to the classical Thirring model equations. This reduction permits one to develop a much simpler theory of wave interaction than was possible in the case of the original equations. As an example, the periodic solutions of two-photon propagation are considered and the Whitham modulational equations are obtained. The different forms of U - V pairs for the Thirring model are discussed in the appendix. Analogous theory can be developed for the stimulated Raman scattering process.