Subwavelength-structured antireflective surfaces on glass

The usability of porous sol-gel coatings and periodic or stochastic subwavelength surface-relief structures for low-cost broadband antireflective (AR) surfaces on glass and on plastics was studied experimentally. Porous sol-gel coatings were produced by dip-coating on glass. Large-area periodic subwavelength surface-relief master structures were manufactured by holographic exposure of photoresist and transferred into nickel by electroforming. Stochastic surface-relief master structures were produced by a PVD process. The surface-relief structures were replicated in organically modified sol-gel materials on glass and in acrylic materials by embossing. With porous sol-gel coatings and periodic subwavelength surface-relief master structures, hemispherical reflectance values of < 1% were achieved for non-absorbing planar sheets. In the case of stochastic surface-relief structures, scatter could not be avoided. Therefore, only very low values of the specular reflectance ( < 0.5%) were achieved with this approach.