To improve upon a fundamental limit on transmission of an in-plane plasmonic metasurface device, Out-of-Plane (OOP, i.e. 3D-thin-film) metasurface plasmonic phase elements were designed using genetic algorithm techniques to work in the infrared, λ = 8 μm, and these were fabricated as a beamsteerer using membrane projection lithog- raphy and characterized using scatterometry to measure the Bidirectional Transmittance Distribution Function (BTDF) of the device. BTDF was measured as a function of scatter angle for four different polarization con- figurations: co-polarization and cross-polarization for two orthogonal linear polarization states and simulated using a finite element method (FEM) solver to generate the near fields of each phase element of the device and a Stratton-Chu formulation to propagate to the far field. The measurements showed the designed beamsteering from the device, but also a strong zero-order diffraction not present in the simulations. This disagreement be- tween models and measurements motivated this study to understand what was causing the differences. To that end, FEM models which reduced the coupling between adjacent elements of the beamsteerer were designed to examine methods that would better simulate measurements. Details of the models are discussed. Future work will focus on finding the root cause for this decrease in coupling.
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