Subwavelength-structured antireflective surfaces on glass

The usability of porous sol-gel coatings and periodic or stochastic subwave length surface-relief structures for low-cost broadband antireflective (AR) surfaces on glass and on plastics was studied experimentally. Porous sol-g el coatings were produced by dip-coating on glass. Large-area periodic subw avelength surface-relief master structures were manufactured by holographic exposure of photoresist and transferred into nickel by electroforming. Sto chastic surface-relief master structures were produced by a PVD process. Th e 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, h emispherical reflectance values of <1% were achieved for nonabsorbing plana r sheets. In the case of stochastic surface-relief structures, scatter coul d not be avoided. Therefore, only very low values of the specular reflectan ce (0.5%) were achieved with this approach. (C) 1999 Elsevier Science S.A. All rights reserved.