From the beginning of the 20th century, researchers have been interested in surface electromagnetic waves guided by planar interfaces of dissimilar mediums. Much initial research on surface-plasmon waves and surface-plasmonpolariton waves stemmed from theoretical curiosity, but the development of new experimental techniques propelled commercial exploitation for optical sensors of chemical and biological species. Additional surface waves called Dyakonov waves, Tamm waves, and Dyakonov-Tamm waves have emerged during the last 25 years. Experimental observation of Dyakonov waves was reported only in 2009, but the rapid development of experimental apparatus during the 1990s suggests that theoretical predictions will soon be evaluated experimentally, leading to further development of optical detection systems and optical circuitry.
The solution of a dispersion equation indicates the theoretical existence of multiple modes of surface plasmon polariton wave propagation at the planar interface of a metal and a chiral sculptured thin film (STF). One mode appears to occur over a wide range of the structural period of the chiral STF, while all other modes exist only above some minimum value of the structural period, the minimum value being different for each mode. In order to excite the different modes, the interface can be incorporated in the commonplace Kretschmann configuration, for which our calculations show that the efficient excitation of different modes would require different numbers of structural periods of the chiral STF.
Surface waves, named here as Dyakonov-Tamm waves, can exist at the planar interface of an isotropic dielectric material and a chiral sculptured thin film (STF). Due to the periodic nonhomogeneity of a chiral STF, the range of the refractive index of the isotropic material is smaller but the range of the propagation direction in the interface plane is much larger, in comparison to those for the existence of Dyakonov waves at the planar interface of an isotropic dielectric material and a columnar thin film.
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