Mark F. Best

Graded-index AR coatings for large angles of inclination

Abstract Antireflective coatings consisting of a single layer of glass with a graded variation in refractive index offer advantages over multi-layer coatings. These include a weaker dependence on angle of incidence at large angles and a flatter response to different wavelenghts over the visible. Consequently, graded-index films are desirable in automotive applications where colorless coatings are required. A sol-gel process is presented for the formation of a graded-index coating of MgOSiO 2 with in-diffused fluorine. Refractive index variations over a range 1.46-1.40 are achieved over a few hundred micrometers. A theoretical analysis of the angular and wavelength dependence of the reflectivity of uncoated, single-layer coated, triple-layer coated and graded-index-layer coated samples was performed and compared with experimentally derived films. Good agreement between model and experiment was observed.