Quasiguided surface plasmon excitations in anisotropic materials

We present a theoretical study of surface plasmon polaritons in a configuration where a metal layer is bounded by a homogeneous anisotropic dielectric. We consider uniaxial and biaxial dielectrics with the optical axis lying in the plane defined by the metal/dielectric interface. Through a systematic study of the in-plane surface plasmon dispersion relation we confirm the existence of several propagation regimes for different values and signs of the birefringence. We report the discovery of the existence of quasiguided surface plasmon polaritons characterized by non-null radiative components. We identify the conditions for the existence of such modes, and explain their peculiar properties in terms of the hybridization of radiative and guided modes.