Dyakonov-Tamm waves guided by the planar interface of a rugate filter and a columnar thin film

Dyakonov-Tamm waves guided by a planar interface of an anisotropic, homogeneous dielectric material, and an isotropic, periodically nonhomogeneous dielectric material was investigated in a canonical boundary-value problem. The former material was taken to be a columnar thin film (CTF) and the latter was a rugate filter. Dyakonov-Tamm waves are surface electromagnetic waves that have negligible propagation losses. In the chosen setup, multiple Dyakonov-Tamm waves of different phase speeds, degrees of localization, and spatial field profiles, but of the same frequency were found to exist. The effect of direction of propagation with respect to the morphologically significant plane of the CTF, the phase and the amplitude of modulation of the rugate filter was investigated. The number of Dyakonov-Tamm waves depends on the direction of propagation with respect to the morphologically significant plane of the CTF. The relative wavenumber and the degree of localization of the Dyakonov-Tamm waves increase with an increase in the amplitude of modulation of the rugate filter.