Causality in the resonance behavior of metamaterials

A rigorous full wave analysis of bianisotropic split ring resonator (SRR) metamaterials is presented for different electromagnetic field polarization and propagation directions. An alternative physical explanation for SRR resonance band gaps is gained by revealing the fact that an imaginary wave number leads to the SRR resonance. The field distribution over SRRs is then expanded into Floquet modes for further examination. As is shown, the metamaterial resonance is engendered by the evanescent modes which accords with the full wave analysis.