Determining optical constants using an infrared ellipsometer.

In the infrared region high refractive index coating materials, such as PbTe and Ge, are normally semiconductors. Their optical constants n, k, and d are strongly dependent on the deposition process. For the most practical coating designs, the layers are usually not very thick, of the order of a half or quarter wavelength, and are weakly absorbing. To determine the optical constants of such thin films using an infrared ellipsometer, some problems exist which must be solved: (1) the precision of n, k, and d and (2) multiple solutions. In this paper these problems are solved by theoretical analysis and experimental arrangement. Experimental results are given and an experimental measurement method is presented.