The angular sensitivity of Brewster-angle reflection polarizers (BARP) is first studied approximately by determining the Taylor series expansion of the parallel reflectance Rp as a function of angle of incidence ø near the Brewster angle øB. Subsequently, exact and explicit equations are derived that determine the lower and upper limits, øl and øu, of the range of ø, that includes øB, over which Rp or the extinction ratioER is below a stated limit L. Examples are given of Ge and Si IR BARP for which øl and øu are calculated for L from 10-6 to 10-1 in ascending multiplicative steps of 10.
R. M. A. Azzam, "Angular sensitivity of Brewster-angle reflection polarizers: an analytical treatment," Appl. Opt. 26, 2847-2850 (1987)