Enhancement of third order nonlinearity calculated for two-dimensional photonic crystal

Using the finite difference time domain method, we calculated light propagation characteristics in a two dimensional photonic crystal, which is composed of triangular lattice airholes in a third-order nonlinear medium. The results showed the characteristic change of the transmission spectrum resulting in the strong saturation of the response, and the sufficiently low transmission loss with the help of projection-type airholes at input and output interfaces. The three-dimensional calculation also indicated the low transmission loss obtained in a realistic photonic crystal slab. Such characteristics are expected in a continuous spectral range near the Gamma point of the second photonic band, owing to an overlap of two bands, which is unique in the two-dimensional lattice. It is applicable for an all-optical switch, an optical power limiter, a pulse reshaping device, and so forth.