Extinction of the p and s polarizations of a wave on reflection at the same angle from a transparent film on an absorbing substrate: applications to parallel-mirror crossed polarizers and a novel integrated polarimeter
The p- and s-polarized components of light can be suppressed on reflection at the same angle of incidence from an absorbing substrate coated by a transparent thin film if the wave is refracted in the film at 45° and the constraint Re[(ε2 - α)/(l -α)]1/2 = α + | ε2 - α| is satisfied, where 2α and ε2 are the ratios of dielectric constants of the film and substrate, respectively, to that of the ambient. For high-reflectance metal substrates (|ε2| » 1), α≈ 1, the ratio of film to ambient refractive index approaches √2, and the unextinguished reflectances approach 1. The least film thicknesses required to suppress the p and s polarizations are in the ratio 2:1. The analysis is applied to Si and Al substrates in the near UV-visible-near-IR spectral range. It is found that the film refractive index and thickness should be controlled to within ±0.01 and ±5 Å, respectively, for an A1 substrate at 550 nm. Significant applications are proposed that include parallel-mirror crossed polarizers, a novel polarimeter that integrates the polarization-analysis and photodetection functions, high-reflectance crossed thin-film reflection polarizers integrated on the same substrate, and division-of-wavefront polarizing beam splitters.
Journal of the Optical Society of America A
R. M. A. Azzam, "Extinction of the p and s polarizations of a wave on reflection at the same angle from a transparent film on an absorbing substrate: applications to parallel-mirror crossed polarizers and a novel integrated polarimeter," J. Opt. Soc. Am. A 2, 189-197 (1985)