INTERFEROMETRIC ENHANCEMENT OF CHIRAL ASYMMETRIES - ELLIPSOMETRY WITH AN OPTICALLY-ACTIVE FABRY-PEROT-INTERFEROMETER

Light propagation through an optically active Fabry-Perot interferometer, consisting of an isotropic chiral layer separating two homogeneous achiral media, is analyzed with an interest in the manifestations of chiral asymmetry in the reflected wave. It is shown that the differential reflection of circularly polarized light and the optical rotation and the ellipticity of incident linearly polarized light can be enhanced by several orders of magnitude (depending on reflection geometry, layer thickness, and optical parameters) under conditions of moderate to high levels of reflectance. This would provide a practical experimental approach to investigating chiral structure and interactions in systems not easily amenable to study, such as weakly chiral thin films and layers, both transparent and absorbing. (Previously proposed and confirmed enhancement techniques, based on multiple total external reflection, could be usefully applied only to absorbing chiral media.) Two experimental configurations of particular potential interest employ (1) total internal reflection and (2) metallic reflection at the second chiral-achiral interface. For a sufficiently thick chiral layer the reflectance of polarization orthogonal to that of the incident wave should be directly observable even under conditions of ordinary reflection. It is also shown that, in contrast to wide belief, reflection at normal incidence from an isotropic chiral medium can manifest optical activity (under appropriate circumstances when the ambient achiral media are birefringent).