Comparison of Reflection Methods for Measuring Optical Constants without Polarimetric Analysis, and Proposal for New Methods based on the Brewster Angle

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Abstract
The pairs of observations at non-normal incidence which specify the various reflection methods of determining the optical constants n and k are compared as to their arithmetical sensitivity to changes in n and k and hence as to their theoretical suitability. Only the simple methods which do not require polarimetric analysis are considered. The comparison of sensitivity is done by inspection of charts prepared from computed tables and which cover a wide range of n and k. A previously unnoticed property of the Fresnel equations at 45° incidence allows any method, not just one in which a ratio of reflectivities is measured, to be employed without a standard reflector. Experimental factors as well as theoretical sensitivity are considered, and the use of the Brewster angle as one observation is proposed. An exact analysis of the Brewster condition has been made, which leads to explicit equations applicable to two proposed methods. The distinction between the Brewster angle and the principal angle of incidence, which are often confused, is emphasized.

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