Perfect terahertz-wave polarization rotator using dual Fabry–Perot-like cavity resonance metamaterial

A novel kind of terahertz ultrathin perfect polarization rotator (UPPR) based on the composite metamaterial is proposed and numerically demonstrated in this paper. The proposed UPPR is constructed by two electric dipole resonant polarization selectors on the two sides and a cross-shaped polarization converter in the center between two dielectric layers as spacers. This typical structure forms a dual Fabry–Perot cavity-like resonance, leading to an enhanced 90° polarization rotation with polarization conversion ratio reaching 99.9%. Quantitative analysis is given to reveal the underlying principle of the UPPR and the detailed design guidelines are also provided for the others to accomplish this kind of UPPR in other frequency bands at will, such as in microwave and infrared regions. In a way, we believe this kind of UPPR, i.e., the polarization selector–polarization converter–polarization selector type, can enrich the metamaterial community for achieving the perfect polarization rotation.