Abstract
A systematic method to treat the steady propagation of a coherent light pulse in a dielectric medium is developed, paying special attention to the effect of polariton formation. The nonlinear optical Bloch equation and the Maxwell equation are solved simultaneously by means of the method of series expansion in powers of a small parameter which is related to the pulse width. It is shown that, besides the usual self-induced transparency pulse, steady pulse solutions exist also in the case where the pulse width is much longer than the reciprocal of the polariton gap frequency. This result suggests that steady propagation may be realized also in dense dielectric media such as crystals in which the polariton effect is marked.