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Asymmetric transmission in planar chiral split-ring metamaterials: Microscopic Lorentz-theory approach

The electronic Lorentz theory is employed to determine the electromagnetic response of planar split-ring metamaterials. Starting from the dynamics of individual free carriers, the effective permittivity tensor of the metamaterial is calculated. Whenever the split ring lacks in-plane mirror symmetry, the corresponding permittivity tensor has a crystallographic structure of an elliptically dichroic medium, and the metamaterial exhibits optical properties of planar chiral structures. Its transmission spectra are different for right-handed vs. left-handed circular polarization of the incident wave, so the structure changes its transmittance when the direction of incidence is reversed. The magnitude of this change is shown to be related to the geometric parameters of the split ring. The proposed approach can be straightforwardly generalized to a wide variety of metal-dielectric metamaterial geometries.