Optics of Thin Metal Films

The theory of reflectance and transmittance of light at oblique incidence on a thin metal film is developed in terms of the optical constants n and k. The appropriate substitutions of the complex quantity (n+ik) for the index of refraction in the standard formulas for a dielectric film are justified by physical considerations of energy conservation at the boundary and angle of propagation in the metal. The final formulas for this general case are very complicated, but the availability of computer techniques makes them of practical value for experimental determinations of the optical constants of a metal.