Abstract
In this paper, we study the electromagnetic fields propagating through a slab which permittivity and permeability are simultaneously negative. We show that symmetry properties of the wave solution remove all ambiguity in the choice of the sign of the wave numbers inside the slab. Upon developing the Green's functions in terms of plane waves, growing "evanescent" waves in the direction of power flow are shown to exist inside the slab. As an illustration, the perfect imaging property of a slab where ∈1 = -∈0 and μ1 = -μ0 is verified.