RELATIONSHIP BETWEEN OPTICAL INHOMOGENEITY AND FILM STRUCTURE

The inhomogeneity of the refractive index in optical thin films has often been represented by an assembly of two homogeneous layers, one usually being rather thinner than the other and with a refractive index further removed from that of the ideal single layer. In this present study the inhomogeneity is related more directly to the physical structure of the layers and especially to the form of their columnar grains. In order to derive the optical properties of a columnar solid, techniques for the calculation of the refractive index of arrays of columns are necessary, and a number of possible techniques are compared. The inhomogeneity in films of zinc sulphide, cryolite and titanium dioxide is interpreted in terms of the columnar model of film structure and its relationship with other aspects, such as packing density, is examined. © 1979.