A composite-metamaterial-based terahertz-wave polarization rotator with an ultrathin thickness, an excellent conversion ratio, and enhanced transmission

We integrated the polarization convertibility of asymmetric split-ring resonators with the polarization selectivity of S-shape resonators for realizing a composite-metamaterial-based 90-degree ultrathin polarization rotator (UTPR) with a 50.4-μm thickness in the terahertz-gap region. By introducing the Fabry-Perot resonance into the UTPR, the measured transmission is maximized to 0.48 at 1.04 THz, leading to the polarization-conversion ratio up to 97.7%. Compared to other waveplates composed by pile-stacking birefringent metamaterials, the UTPR possesses less loss from the intrinsic resonances because it comprises only two layers of the resonators, and can evade from dichroism effects due to the unique working mechanism.