Two-film reflection polarizers: Theory and application

An analysis is made of reflection polarizers consisting of two transparent films on an absorbing substrate. A method is described for determining the angles of incidence at which the reflectance of either component of polarization is extinguished. It is demonstrated that polarized light can be obtained over a finite range of incidence angles. This is in contrast to a polarizer having a single transparent film, where polarization occurs only at a specific angle of incidence. At each angle of incidence in the polarizing range, any one of a number of discrete thicknesses of the films can be used to obtain polarized light; and the procedures for finding these thicknesses are described. Numerical application of the theory was made for metallic substrates that range from good to intermediate reflectors. The results serve to illustrate most of the significant characteristics of two-film polarizers. It was shown that two-film systems can yield reasonably high values of the unextinguished component, with minimal sensitivity of the extinguished component to offdesign conditions.