A set of coupled-mode equations is developed to describe the multiwave diffraction of light in two-dimensional nonlinear superlattices, and is solved by numerical methods. At low incident intensities, the solution is time-independent and shows that bistable behavior may appear in the incident-diffracted relations. With an increasing incident intensity, the solution becomes unstable and eventually turns chaotic through the route of intermittance. The threshold intensity for chaos varies with the index-modulation strengths of the superlattice. If the relaxation time of the Kerr-form nonlinearity exceeds the transmission time, only stable solutions are obtained.

• Received 22 April 1994

DOI:https://doi.org/10.1103/PhysRevA.50.5197