Relations between group, energy, and phase velocities of surface electromagnetic waves in half-infinite bianisotropic homogeneous media

This paper proves the equality of the group velocity and the energy velocity for surface electromagnetic waves on the interface between two bianisotropic homogeneous half-infinite nonabsorbing dielectrics. It is also shown that the projection of the energy velocity on the direction of propagation is equal to the phase velocity provided that the material constants do not depend on the frequency. Moreover, this equality holds true locally, i.e., the energy velocity along the direction of propagation coincides with the phase velocity at any distance from the interface. The obtained relations holds true in magneto-optically active media as well. It is assumed that the media are of generic crystallographic symmetry, so, when deriving the desired equalities, no simplifications due to a specific crystallographic symmetry are used.