Restricted equivalence of paired epsilon-negative and mu-negative layers to a negative phase-velocity material (alias left-handed material)

The time-harmonic electromagnetic responses of (a) a bilayer made of an epsilon-negative layer and a mu-negative layer, and (b) a single layer of a negative phase-velocity material are compared. Provided all layers are electrically thin, a restricted equivalence between (a) and (b) exists. The restricted equivalence depends on the linear polarization state and the transverse wavemmber. Implications for perfect lenses and parallel-plate waveguides are considered.