Dual-band electromagnetically induced transparency effect in a concentrically coupled asymmetric terahertz metamaterial.

We propose a scheme to achieve a dual-band electromagnetically induced transparency (EIT) effect in a planar terahertz metamaterial (MM), comprising an inner circular split ring resonator (CSRR) concentrically coupled to an outer asymmetric two-gap circular split ring resonator (ASRR). The scheme is numerically and theoretically analyzed. The dual-band EIT effect occurs as a result of the near field coupling between the resonant modes of the resonators comprising the MM configuration. It is observed that the dual-band EIT effect in the MM structure could be modulated with an in-plane rotation of the CSRR structure. The dual-band EIT effect is also examined by varying the asymmetry of the ASRR and the size of the inner CSRR. A theoretical model based upon the four-level tripod-system provides an intuitive explanation about the underlying coupling mechanism responsible for the dual-band EIT effect in the proposed MM structure. Our study could be significant in the development of multi-band slow light devices, narrowband absorbers, etc., in the terahertz regime. [ABSTRACT FROM AUTHOR]