An all-purpose three-dimensional finite element model for crossed-gratings

We demonstrate the accuracy of the Finite Element Method (FEM) to characterize an arbitrarily shaped crossed-grating in a multilayered stack illuminated by an arbitrarily polarized plane wave under oblique incidence. To our knowledge, this is the first time that 3D diffraction efficiencies are calculated using the FEM. The method has been validated using classical cases found in the literature. Finally, to illustrate the independence of our method towards the shape of the diffractive object, we present the global energy balance resulting of the diffraction of a plane wave by a lossy thin torus crossed-grating.