The Surface polaritons with negative group velocity at the vacuum-resonant dielectric interface

Abstract

Abstract Surface polaritons most clearly manifest their properties when the processes of energy dissipation are neglected. In this case, they are collective excitations that propagate exclusively along the interface, and the energy flux of surface polaritons deep into the medium becomes zero. A more realistic model of a surface polariton assumes that dissipation processes are always present. In this case, the surface polariton partially penetrates deep into the medium due to the appearance of the real part of the propagation constant in this direction. It should be emphasized that in the region of existence of a surface polariton, the dielectric constant of the medium has strong frequency dependence; therefore, by virtue of the Kramers-Kronig relations, the dielectric constant must have an imaginary part, which is precisely responsible for the dissipation processes. In this paper we show that when surface polaritons are considered at the vacuum-resonance insulator boundary and strict allowance for dissipation, frequency regions arise in which surface polaritons have a negative group velocity and the dielectric acquires the properties of a metamaterial.