Optical limiting and intensity-dependent diffraction from low-contrast nonlinear periodic media: Coupled-mode analysis

The method of multiple scales is used to develop a procedure for obtaining coupled-mode equations in low-contrast nonlinear photonic crystals periodic in one, two, or three dimensions. Coupled-mode equations for three coupled modes in a two-dimensional (2D) hexagonal lattice are obtained in this way and solved numerically. We show that 2D low-contrast nonlinear photonic crystals support optical limiting and intensity-dependent diffraction.