GRADED-INDEX AR COATINGS FOR LARGE ANGLES OF INCLINATION

Antireflective coatings consisting of a single layer of glass with a g raded variation in refractive index offer advantages over multi-layer coatings. These include a weaker dependence on angle of incidence at l arge angles and a flatter response to different wavelengths over the v isible. Consequently, graded-index films are desirable in automotive a pplications where colorless coatings are required. A sol-gel process i s presented for the formation of a graded-index coating of MgO-SiO2 wi th in-diffused fluorine. Refractive index variations over a range 1.46 -1.40 are achieved over a few hundred micrometers. A theoretical analy sis of the angular and wavelength dependence of the reflectivity of un coated, single-layer coated, triple-layer coated and graded-index-laye r coated samples was performed and compared with experimentally derive d films. Good agreement between model and experiment was observed.