Journal of Mathematical Physics
Nonlinear Light Propagation in a Resonant Medium and Causality
R. C. T. da Costa
Abstract
The propagation of an optical pulse through a system of two-level atoms embedded in a host medium of constant refractive index n is considered. It is shown that the values of the solutions of the nonlinear system of coupled Maxwell and Schrödinger equations at time t at a point z, in the McCall-Hahn approximation, depend only on data contained in the interval [z - c/nt, z] at t = 0. Thus, information cannot be transmitted through this medium with velocity greater than c/n. Apparent violations of this property in the case of self-induced transparency are explained.