Abstract

In infrared region, some high refractive index materials for optical coatings, such as PbTe and Ge, are generally weakly absorbed. Their extinction coefficient k varies from 0.001 to 0.02 with different deposition condition. To determine optical constants of weakly absorbed thin films the most often used method is R,T method [1],[2], but it is not adequate for very thin films, for example, in such a case that optical thickness is less than half of the wavelength. To determine the optical constants of these coatings one of the methods is ellipsometry, but it is usually used for strong absorbed thin films [1], [3]. In this paper, the measurement method and results of weakly absorbed thin films using ellipsometer combined with spectrophotometer and alpha-step profilometer are described and presented. It should be pointed out that some of our methods are not new, however using these methods, the optical constants of weakly absorbed thin films have been effectively measured and some useful results have been obtained.

© 1988 Optical Society of America