Dyakonov-Tamm Surface Electromagnetic Waves Guided By The Interface Between Chiral Sculptured Thin Films

The Dyakonov-Tamm surface electromagnetic wave is a new type of surface electromagnetic wave, which has important potential applications in optical sensing and waveguiding. In this thesis, Dyakonov-Tamm electromagnetic waves guided by the planar interface of two dissimilar chiral sculptured thin films (STFs) were systematically investigated.The planar interfaces result from the chiral STFs being dissimilar in (ⅰ) orientation about the helical axis, (ⅱ) structural handedness, (ⅲ) structural period, (ⅳ) vapor incidence angle, (ⅴ) material type, or (ⅵ) various combinations thereof.The theory for the propagation of Dyakonov-Tamm electromagnetic waves guided by the planar interface of two dissimilar chiral STFs was formulated using Maxwell equations and Floquet-Lyapunov theorem, and a dispersion equation was obtained. Standard numerical methods-the search, the bisection, and the Newton-Raphson methods-were sequentially employed to find real-valued relative wavenumberκ/k0 that satisfies the dispersion equation of Dyakonov-Tamm electromagnetic wave. The spatial profiles of the magnitudes of electric and magnetic fields components for representative solutions were examined. The degree of localization to the interface, described by four decay constants was also ascertained.For the interface between two chiral STFs that differ in orientation about the helical axis and/or structural handedness, either 2 or 3 multiple Dyakonov-Tamm electromagnetic waves were found to propagate, with different phase speeds and degrees of localization to the interface, depending on the orientation about the helical axis (angular offset). For the interface between two chiral STFs that differ in structural period or vapor incidence angle or material type, only one Dyakonov-Tamm electromagnetic wave was found to propagate for specific range of angular offset, when the difference between structural period or vapor incidence angle or permittivity properties of materials are sufficiently large. For the interface between two chiral STFs that differ in combination thereof, only one Dyakonov-Tamm electromagnetic wave was found.The spatial profiles of the electric and magnetic fields and the degree of localization indicate that all the Dyakonov-Tamm electromagnetic waves guided by the planar interface of two dissimilar chiral STFs are strongly localized to the interface. The most localized Dyakonov-Tamm electromagnetic waves are essentially confined to within 2 structural periods on either side of interface. When either orientation about the helical axis or structural handedness changes across the interface, the spatial profiles and the degrees of localization on both sides of the interface are similar-because the permittivity dyadics on both sides do not differ much. However, if the dissimilarity is in structural period or vapor incidence angle or material type or combination thereof, the spatial profiles and the degrees of localization are quite different on the two sides of the interface-because the permittivity dyadics on both sides differ very much.