Anisotropic Metamaterial as an Antireflection Layer at Extreme Angles

A novel antireflection (AR) theory based on an anisotropic metamaterial is presented in this paper. Based on this theory, we derive the required anisotropic material parameters for perfecting matching at a particular frequency for a particular angle of incidence, including extreme angles. For a proof of concept, the anisotropic AR layers are synthesized with metamaterial structures and near perfect matching is demonstrated in simulation at 88 degrees incidence for both transverse-electric and transverse-magnetic polarizations. For experimental validation, the AR layer is redesigned to match at 60 degrees in order to avoid spill-over losses in the quasi-optical measurement due to the finite substrate size. Excellent agreement is observed between the simulation and measurement results.