Backward Plane Waves in Homogeneous Isotropic Media

摘要

Plane waves in passive and active magnetodielectric media are considered. It is shown that only forward (ordinary) waves can propagate in homogeneous and isotropic media with positive values of the real parts of the permittivity and permeability, and only backward waves, which have the oppositely directed phase velocity and energy flux, can propagate in media with negative values of these characteristics.