A compact half and quarter-wave plate based on bi-layer anisotropic metasurface

In this letter, an ultrathin bi-layer metasurface, which exhibits half- and quarter-wave plate operation at different resonance frequencies in the microwave regime, is realized and experimentally demonstrated. The proposed metasurface not only transforms linear and circular polarizations to their corresponding cross polarizations but also achieves linear-to-circular and circular-to-linear polarization conversion in different frequency regimes. Moreover, the quarter-wave plate operation of the metasurface is quite robust to the variations in the incidence angle both for transverse-electric and transverse-magnetic polarizations. The physical mechanism behind half- and quarter-wave plate operation is elucidated through surface current distribution. Analytical results for the refractive index further elaborate on the operation of the metasurface.