High-efficiency cross-polarization conversion metamaterial using spiral split-ring resonators

We report on a high-efficiency cross-polarization conversion metamaterial design consisting of novel spiral split-ring resonators (SRRs). Numerical simulations on the resonant electric field and surface current distributions demonstrate that the cross-polarization response is attributed to the charge accumulation in the horizontal SRR gap. The dependencies of resonance frequency on the structural parameters of the SRR reveal that an inductive-capacitive resonance dominates the SRR. We further show that the polarization conversion efficiency can be significantly enhanced by integrating two orthogonal gratings, which enable a linear polarization wave to be rotated to its orthogonal direction with a high efficiency of similar to 90%. These results offer a way to engineer novel high-performance metamaterial polarization devices.