ELECTROMAGNETIC-WAVE PROPAGATION IN SUPER-CHOLESTERIC MATERIALS PARALLEL TO THE HELICAL AXIS

Analytic solutions are presented tor the propagation of electromagnetic waves along the helical axis of a super-cholesteric material. The fabrication of such a material is envisaged as a two-step process: first, identical, electrically small objects (inclusions) characterized by uniaxial polarizability dyadics are randomly dispersed in an isotropic host medium, all objects being aligned parallel to one another, to form a composite. The composite is effectively a bianisotropic uniaxial medium, its uniaxial nature expressed through an optical director fixed in space. Second, layers of such uniaxial composites are stacked on top of each other such that the optical director varies from layer to layer in a helicoidal way so that the typical periodically inhomogeneous structure of a cholesteric liquid crystal emerges. Exact solutions for the axial wave propagation problem are obtained. Possible realizations and technological applications of the super cholesterics are discussed.