Subwavelength metal grating metamaterial for polarization-selective optical antireflection coating

A metamaterial structure consisting of a one-dimensional metal/air-gap subwavelength grating is investigated for optical antireflection for a germanium surface in the infrared regime. For incident light polarized perpendicularly to the metal grating lines, the metamaterial exhibits effective dielectric properties, and the Fabry–Perot-like resonance results in the elimination of the reflection and the enhancement of optical transmission. It is found that the subwavelength grating metamaterial antireflection structure does not require a deep-subwavelength grating period, which is advantageous for device fabrication. Optical transmittance as high as 93.4% with complete elimination of the reflection is shown in the midwave infrared range.