Anti-Reflection Structured Surfaces
Anti-reflection structured (ARS) surfaces can be regarded as a subset of surface-relief gratings. Unlike typical gratings, ARS surfaces have subwavelength periods that enable only the reflected and transmitted zeroth order to propagate (higher diffraction orders are evanescent). ARS surfaces have been shown both theoretically and experimentally to exhibit extremely low reflectivities over broad spectral bandwidths and wide field-of-views (see, for example, Refs. 1 and 2). Unlike thin-film coatings, ARS surfaces are created by etching a surface-relief pattern directly into a substrate. Consequently, ARS surfaces do not experience cohesion problems or problems with thermal expansion mismatches, as do thin-film coatings. Analysis of ARS surfaces are performed using both vector diffraction theory and effective medium theories (EMTs).
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