Chiral metamaterials with negative refractive index

Chiral metamaterials have shown extraordinary capability to change the polarization state of light. It has been proposed chiral media with large chirality can be used to make negative index materials. Recently, we demonstrate experimentally and numerically that metamaterials based on bi-layer rosette structure, bi-layer cross-wires and non-planar chiral SRRs, give giant optical activity, circular dichroism, and negative refractive index. The presented chiral designs offer very simple geometry and an efficient way to realize negative refractive index in a large spectra range from microwave frequency up to optical regime. We also develop a retrieval procedure for chiral materials which works successfully for circularly polarized waves. By adding active materials in chiral metamaterials design, we propose an active chiral metamaterial with tunable optical activity.