PRECISION OF BREWSTER-ANGLE METHODS FOR OPTICAL THIN-FILMS

We compare the precision of the Abeles Brewster-angle method for thin films, in which coated and uncoated regions of the substrate are illum inated by p-polarized light and Hacskaylo's Brewster-angle method, in which a small fraction of s-polarized light is admitted. Hacskaylo's B rewster-angle method has been reported to yield a higher precision, bu t this is not supported by our analysis. Approximate expressions that we derive for the precision and the direct iterative solutions both sh ow that the precision of the two Brewster-angle methods is the same wh en the limiting factor is ability to detect the irradiance match.