Review of surface-wave propagation at the planar interface of a columnar or chiral sculptured thin film and an isotropic substrate

Electromagnetic surface waves are known to propagate along metal-dielectric interfaces (surface plasmon-polaritons) as well as along dielectric-dielectric interfaces (Dyakonov waves) if the two dielectrics have different spatial symmetries. Columnar and sculptured thin films, which are optically biaxial nanomaterials, may be grown on either metallic or dielectric substrates. Both surface plasmon-polaritons and Dyakonov waves can exist at the interface of a thin film and an appropriate substrate. The direction of propagation relative to the thin-film morphology is, in general, limited, and depends on the material and the vapor deposition angle used during fabrication. At the interface of a chiral sculptured thin film and an isotropic dielectric substrate, surface-wave propagation occurs over a much wider angular range and may allow for the first experimental observation of a Dyakonov wave. The characteristic properties of the surface wave, such as phase speed and decay rate, are dependant on the direction of propagation and the vapor deposition angle. As engineered nanomaterials, thin films offer a controllable medium for surface-wave propagation which may be tailored to exhibit specific characteristics. The porosity of the thin films may also offer certain technological advantages.