Tunable symmetric and asymmetric resonances in an asymmetrical split-ring metamaterial

We demonstrate the coexistence of two tunable symmetric and asymmetric resonances in a metamaterial composed of asymmetrical split-rings (ASRs) patterned on a dielectric layer numerically and experimentally. The full-wave simulation and measurement results demonstrate that the metamaterial reveals a symmetric cross-polarization transmission band with a ripple-free peak and asymmetric co-polarization transmission bands characterized by trapped-mode resonances. Both symmetric and asymmetric resonances can be easily tuned via the incident angle of electromagnetic waves. The resonant excitation and coupling of the electric and magnetic dipole moments contribute to the conversion of two orthogonal linear polarizations. The ASR metamaterial shows a directionally asymmetric transmission for both linearly and circularly polarized waves for large angles of incidence. The proposed ASR metamaterial is of importance to develop novel metamaterial-based devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757961]