Double-layer broadband antireflection coatings for grazing incidence angles

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Abstract
This paper presents the methodology for the design of double-layer antireflection (AR) coatings for grazing incidence angles for a given state of polarization. The designs are based on commonly used thin-film materials with the optical constants that can be realized by using standard evaporation techniques. The performance of some AR stacks has been computed, and the effect on spectral reflectance with variation in the thickness of the high-index layer, angle of incidence, and the refractive indices of the materials used for the inner and outer layers has been studied with a view to selecting a suitable design that gives the lowest reflectance over the widest wavelength range. The AR stacks show a reflectance of <0.5% over most parts of the visible and near-infrared regions of the spectrum.