Causality and electromagnetic properties of active media.
Several results concerning active media or metamaterials are proved and discussed. In particular, we consider the permittivity, permeability, wave vector, and refractive index, and discuss stability, refraction, gain, and fundamental limitations resulting from causality.
Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway.
Bertil
B
Nistad
Johannes
J
Skaar