Use of an Evaporated Dielectric Film for Determining the Optical Constants of a Metal I

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Abstract
The technique for determining the optical constants of a metal by overcoating it with a dielectric film of known optical constants has been investigated critically for the case of a lead fluoride film on aluminum. Accurate measurements were made of the thickness of the lead fluoride film, and the transmittances, reflectances, and wavelengths of the interference maxima and minima for samples of lead fluoride on quartz and lead fluoride on aluminum. All calculations were performed with the aid of a computer using a multilayer film program. It has been found that, for the case studied, the method will not work in the ultraviolet and visible regions of the spectrum because of the extreme sensitivity of the reflectance to scattering in the lead fluoride film. In the infrared, the method does not give accurate unique values for the optical constants of aluminum.