Broadband antireflective coatings based on two-dimensional arrays of subwavelength nanopores

摘要

A broadband thin-film antireflective coating (ARC)-a regular array of nanopores in a dielectric substrate-is studied theoretically and experimentally. Tuning the geometrical parameters of the array allows for strong suppression of reflection. For a fused silica substrate, reflectivity is lower than 1% over a range with a relative bandwidth, 60%-70%, reaching 0.05% in the minimum. The underlying physics is the spatial dispersion in the porous medium which enables phase compensation for the partially reflected waves in a broad band. This allows for more broadband antireflection than any flat homogeneous single-layer ARC can provide. Importantly, the studied ARC is universal for any transparent dielectric substrate.