Nominal model for structure-property relations of chiral dielectric sculptured thin films

The Bruggeman formalism is implemented to estimate the permittivity dyadics of chiral dielectric sculptured thin films (STFs), called thin-film helicoidal bianisotropic mediums (TFHBMs), modelled as helicoidally arranged stacks of ellipsoidal inclusions in vacuum. Spectral maximums of several observable optical properties of axially excited TFHBM slabs are examined as functions of inclusion shape, volume fraction and orientation. Changes in the transverse aspect ratio of the ellipsoidal inclusions significantly affect the predicted optical properties of the TFHBM. A critical value for the transverse aspect ratio of the ellipsoids can be found such that optical activity disappears when all other parameters are fixed. The orientation of the inclusions significantly affects the value of optical property maximums, and can be made to suppress optical activity completely. A distribution of orientations decreases various measures of optical activity.