Power Losses in Highly Conducting Lamellar Gratings

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Abstract
We compare approaches based on a surface impedance approximation and a perturbation analysis with a rigorous modal technique for the calculation of the diffraction properties of highly conducting lamellar gratings. We show the surface impedance approximation to be inaccurate even for good metals at a wavelength of 10 μm. The perturbation theory results can be quite accurate, but their region of applicability is limited. We demonstrate that the rigorous technique can be used for lamellar gratings made of materials with a complex refractive index of very large modulus.