Modelling of Induced Gratings in Nonlinear Optics

In this paper, we present a multiharmonic model able to allow for general nonlinear optical media [1]. As a particular example, two- and three-photon processes are considered here. The numerical model is based on the finite element method that allows to take into account the inhomogeneities of the refraction index due to the nonlinearities. It consists of several harmonic equations at various frequencies coupled via some nonlinear terms. As an illustration we propose a simple homogeneous uniform slab made of non-linear material but illuminated by three plane waves in order to create an artificial periodic structure with a fictitious permittivity. This system exhibits a non trivial and quite complex behavior because of the induced diffraction grating.