Optical spatial shock waves in photorefractive media

We show that the evolution equations describing the two-wave mixing interac tion between two codirectional optical beams in photorefractive media can a llow spatial shock-wave solutions. Our analysis indicates that these kink-t ype wavefronts move together at an angle that falls outside the initial +/- theta sector of propagation. The apparent direction of propagation and the spatial widths of these optical shock-wave beams are directly related to t heir relative intensity.