Second-harmonic resonant excitation in optical periodic structures with nonlinear anisotropic layers

We propose a method to derive a system of ordinary differential equations (coupling equations) in order to analyze nonlinear wave processes inside lossless layered periodic media. We solve the problem associated with the interaction between the first- and second-harmonic waves inside a structure with anisotropic nonlinear dielectric layers. An arbitrary angle between the wave propagation direction and the structure interfaces is considered. The method takes into account both the nonlinear processes occurring at the slab interfaces and the nonlinear terms that depend differently on the field components. We derive analytically the phase matching conditions that provide the maximum interaction between the first- and second-harmonic waves. A physical explanation of the increase in efficiency of the wave coupling that takes place at the frequency near the passband edges is given. [S1063-651X(98)04111-7].