Wavelength bandwidth and other design aspects for film-substrate reflection polarizers

The performance characteristics of film-substrate reflection polarizers consisting of an absorbing film on a metallic substrate are investigated. Monochromatic polarized light is obtained for certain discrete values of incidence angle and film thickness, corresponding to given values of the optical constants and the wavelength. The departures from perfect polarization due to operation at off-design wavelengths are examined. Three additional criteria are also employed to appraise polarizer quality. It is found that by proper choice of the extinction coefficient of the film, all four criteria of quality can be satisfied. For substrates having intermediate values of reflectance, very small film extinction coefficients appear to be appropriate. When the substrate is highly reflecting, somewhat larger extinction coefficients are required.