Propagation of an optical pulse in a resonant nonequilibrium medium

An analysis is made of the evolution of a light pulse in a two-level resonant medium as a function of the degree of preliminary excitation by another pulse. It is shown that, in addition to self-induced transparancy observed under certain conditions associated with the degree of excitation of the atomic system, resonance scattering is also found due to the existence of macroscopic polarization of the medium. This scattering is not observed when the medium is in a noncoherent state. The transverse reversible relaxation time T*₂ can be determined from the variation of the scattering intensity.