Common choices are SiN, GaN or TiO2 for the visible spectrum and Si and GaAs for the infra-red spectrum. In addition, the material should be transparent for the spectrum of interest. The pillars are made of a high refractive index material. Many meta-surface use sub-wavelength cylinders as the basic building block for the metasurface (). Nevertheless, the solutions found by both methods should be the same. RCWA first transforms the equations to the frequency domain (both time-frequency and spatial frequency). In FDTD the Maxwell equations are discretized directly in both time and space. However both solve the Maxwell equations via a different mathematical and numerical approach. Since exact solutions are not known for the sub-wavelength structures that make up a meta-atom, a validation is performed by comparing the results of different methods.įDTD and RCWA both model the same underlying physical laws. Some of the most common methods are FEM, FDTD and RCWA.Ī common question with any simulation method is whether the calculation produces physically accurate results. Their design is thus done by numerical method, known as full-wave solvers. The design of these structures requires a full solution of Maxwell’s equations in three dimensions.įor such sub-wavelength calculations there are (in general) no exact solutions. Meta-surfaces rely on sub-wavelength structures to manipulate light in different ways such as phase delay, polarization conversion, specific dispersion. Benchmark Comparison for the transmission and phase delay of a cylindrical nano-rod.Convergence checks to determine which settings give reliable results.A comparison is made to the widely known finite difference time domain (FDTD) method. In that spirit this article investigates the accuracy of the Rigorous Coupled Wave analysis (RCWA) methods implemented in the PlanOpSim software. It is a common saying that all models are wrong but some models are useful.
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