Project Title: MMP Computation of Periodic Structures


The 3D MMP code for computational electromagnetics is a powerful tool for very accurate and reliable solutions of scattering and antenna problems. It includes a large library of basis functions that are analytic solutions of the Maxwell equations. Gratings and bi-periodic structures are of considerable interest in optics, radio science, and nano science. Most of the available codes for periodic structures are very time-consuming, not very reliable, or adapted to special cases. Previous attempts of MMP computations based on the Floquet theory were also rather inefficient. We now have implemented periodic boundary conditions as a new type of boundary conditions and Rayleigh expansions as a new type of periodic basis functions. Together with appropriate transformations, these features allow to compute the electromagnetic field in one cell of the periodic structure in exactly the same way as in ordinary scattering problems. This technique allows us to compute arbitrary gratings and bi-periodic structures with 3D MMP. Comparisons with results obtained with the well-known modal method have shown, that 3D MMP is not only extremely efficient but also reliable and accurate. Since 3D MMP includes Surface Impedance Boundary Conditions (SIBC), one can also obtain simplified solutions when materials with a good conductivity are present. In order to illustrate the capability of 3D MMP, we have simulated an anisotropic chiral slab by a bi-periodic array of helical structures. Our results are in excellent agreement with the theory of chiral media.

Contacts: Ch.Hafner, IFH, ETZG95, ETH Zentrum, CH-8092 Zurich

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Index Terms: Computational Electromagnetics, Gratings, Chiral media