Guided and leaky surface plasmon polariton modes on a planar structure with uniaxially anisotropic material on top of a metal thin film

The surface plasmon polariton modes existing on a two-interface structure composed of a metal thin film having infinite cover region made of uniaxially anisotropic dielectric material and infinite substrate region made of isotropic dielectric material are analyzed based on a finite-element eigenmode solver. The dispersion characteristics with the optic axis of the uniaxial material rotated in the plane parallel to the interfaces are investigated. In addition to the pure guided modes, possible leaky modes resulting from the material anisotropy are carefully determined by designing suitable perfectly matched layers in the solver to correctly calculate the complex-valued modal propagation constants.