Exploiting Symmetries for the Analysis of Metasurfaces with a Multimodal Approach

We propose an efficient quasi-numerical approach to compute the dispersion diagram of periodic structures with 2-D periodicity when the primitive cell possesses internal symmetries. In this situation, symmetry planes can be imposed and the study of the unit cell can be simplified to several 1-D scenarios resulting from the boundary conditions imposed by the symmetry planes. This approach involves dealing with simpler geometries and is particularly advantageous in terms of CPU effort. Here, the underlying computational method is the multimodal transfer matrix method. This method is used to analyze a square unit cell in a parallel plate waveguide whose motif is one circular hole in one plate and two square holes in the other plate.