Optical constants of a system consisting of transparent film on an absorbing substrate



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Texas Tech University


New methods are evaluated for experimentally obtaining the optical constants of a system composed of an absorbing substrate overlaid by a transparent film. The methods require the use of two samples having the same substrate and film materials but differing film thicknesses. The constants which are determined are the refractive index and the respective thicknesses of the two films and the refractive index and extinction coefficient of the substrates. Analysis is based on relations derived at crossing points of the reflectance versus incident angle curves for the two samples. The film thicknesses and refractive index may be obtained solely from crossing point data. In order to determine the substrate constants, an additional measurement must be made of the reflectance of the film - substrate system at Brewster's angle. The sensitivity of the optical constant determinations to errors in experimentally obtained reflectance and angle measurements is explored by numerical analysis.



Thin films -- Optical properties