An infrared polarizer is described utilizing the difference in the reflection coefficients for the parallel and perpendicular components of polarization at the principal angle for a germanium-mercury interface. Because of the high degree of polarization observed, two reflections are considered sufficient for most purposes. Such a polarizer should be useful for the wavelength range of two microns to two-tenths of a millimeter; this range could be varied somewhat by choosing other dielectrics.
N. J. HARRICK, "Infrared Polarizer," J. Opt. Soc. Am. 49, 379-380 (1959)