Propagation of coherent excitons and photons in a crystal

An investigation is made of the possibility of the existence of self-induced transparency due to excitons in semiconductors. Solutions are obtained of a nonlinear material equation for excitons and of the wave equation for photons in the form of steady-state wave packets (solitons and antisolitons) of a highfrequency carrier. Conditions for the existence of bleaching and darkening waves are determined as a function of the carrier wave vectors for each of the two polariton branches and as a function of the sign of the exciton-exciton interaction constant and exciton concentration.