Dyakonov surface waveguide modes in asymmetric interfacial strip waveguide

Abstract

We report a theoretical prediction of Dyakonov surface waveguide modes that propagate along a flat strip interfacial waveguide formed by two anisotropic materials, bounded by metal on one side and air on the other. We demonstrate that due to asymmetric metal/air boundary conditions, surface waves can exist in such a system regardless of the type of optical anisotropy. The asymmetric waveguide with negative anisotropy supports a strongly localized solution, whereas in the case of positive anisotropy, the mode intensity decays slowly with distance from the interface. We also analyze the dispersion and field structure of these waves using perturbation theory in the approximation of weak anisotropy. We demonstrate that, irrespective of the type of optical anisotropy, Dyakonov surface waveguide modes exhibit a high degree of circular polarization, reaching values of ±1 at certain distances from the boundaries. Our results are consistent with numerical simulations using the finite element method. We believe this work opens new opportunities for the experimental investigation of Dyakonov surface waves and their practical applications.