Left-handed behavior of split-ring resonators: Optical measurements and numerical analysis

The periodic double-ring split-ring resonator (SRR) array was one of the first proposed magnetic metamaterials for the realization of a negative index of refraction. We experimentally and numerically study double-ring SRRs on silicon substrates in the midinfrared frequency regime. For light at normal incidence, we observe that an electric resonance in the outer ring and a magnetic resonance in the inner ring exist at similar frequencies in our sample, which suggests that the double-ring SRR array could simultaneously have a negative permittivity and a negative permeability, or a left-handed behavior. Our conjecture are confirmed by numerical simulations. We also propose a left-handed metamaterial composed of two single-ring SRRs in each unit cell. The left-handed behaviors in the two metamaterials studied here originate only from the SRR itself. Thus, there are no metallic continuous wires involved in the devices compared to conventional left-handed SRR metamaterials.