Optical circular dichroism of vacuum-deposited film stacks

We report on optical circular dichroism of chiral multilayer SiOx films obtained by a novel vacuum deposition technique. The film layers were deposited at an oblique incidence angle to render them optically anisotropic, and were stacked such that the optic axes of the layers spiral in a helical fashion about the substrate normal. The resulting film stacks display both wavelength and polarization selectivity, in analogy with organic cholesteric liquid crystals aligned in the planar texture, Reflectance spectra of two films of opposite chirality are presented. Both film stacks are tuned to reflect in the visible and were prepared using obliquely deposited SiOx, Calculated spectra using a Berreman's 4 x 4 matrix approach agree well with the experimental findings. It is concluded that vacuum-deposited chiral film stacks hold promise for use as high-efficiency polarizers and other novel optical components. (C) 1998 Elsevier Science B.V.