The canonical problem of the propagation of surface-plasmon-polariton (SPP) waves localized to the planar interface of a metal and a sculptured nematic thin film (SNTF) that is periodically nonhomogeneous along the direction normal to the interface was formulated. Solution of the dispersion equation obtained thereby confirmed the possibility of exciting multiple SPP waves of the same frequency or color. However, these SPP waves differ in phase speed, field structure, and the e-folding distance along the direction of propagation.
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.
Surface waves (SWs) are localized waves that travel along the planar interface between two different mediums
when certain dispersion relations are satisfied. If both mediums have purely dielectric constitutive properties,
the characteristics of SW propagation are determined by the anisotropy of both mediums. Surface waves are then
called Dyakonov SWs (DSWs), after Dyakonov who theoretically established the possibility of SW propagation
at the planar interface of an isotropic dielectric and a positive uniaxial dielectric. Since then, DSW propagation
guided by interfaces between a variety of dielectrics has been studied. With an isotropic dielectric on one
side, the dielectric on the other side of the interface can be not only positive uniaxial but also biaxial. DSW
propagation can also occur along an interface between two uniaxial or biaxial dielectrics that are twisted about
a common axis with respect to each other but are otherwise identical.
Recently, DSW propagation has been studied taking (i) uniaxial dielectrics such as calomel and dioptase
crystals; (ii) biaxial dielectrics such as hemimorphite, crocoite, tellurite, witherite, and cerussite; and (iii)
electro-optic materials such as potassium niobate. With materials that are significantly anisotropic, the angular
regime of directions for DSW propagation turns out to be narrow. In the case of naturally occurring crystals,
one has to accept the narrow angular existence domain (AED). However, exploiting the Pockels effect not only
facilitates dynamic electrical control of DSW propagation, but also widens the AED for DSW propagation.
Surface-wave propagation at the planar interface of a columnar thin film (CTF) -- a biaxial dielectric medium -- and an isotropic dielectric substrate may occur over a narrow range of propagation directions, range being dependent on (i) the bulk matgerial that is evaporated to deposit the CTF, (ii) the vapor incidence angle used for the deposition, and (iii) the refractive index of the substrate material.
The piecewise homogeneity approximation is used to investigate the
optical response of chiral sculptured thin films with perturbations
in the angle of rise. Changes in the reflectances and transmittances of normally incident, circularly polarized light are calculated for
both sinusoidal and step perturbations for a range of wavelengths, using experimentally determined material parameters. The feasibility of using a single manufacturing process to fabricate a normal dielectric mirror as well as a selective circular Bragg effect mirror is demonstrated.
An exact matrix polynomial series solution for oblique propagation in chiral sculptured thin films and chiral smectic liquid crystals is analyzed. The convergence of the series is investigated via calculations for a range of wavelengths, incidence angles, and material parameters. Implementation of this method is compared with the piecewise uniform permittivity approximation method.
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