Tunable Metasurfaces: A Polarization Rotator Design

Metasurfaces have enabled unprecedented control over electromagnetic waves, providing new opportunities in areas such as wireless communications, energy harvesting, imaging, and cloaking. Despite significant progress in this area, most metasurface designs provide static functionalities. Here, we theoretically propose and experimentally validate a transparent metasurface with dynamically tunable properties. Notably, we present an electronically tunable metasurface that is capable of rotating the polarization of an arbitrarily polarized incident wave, without changing its axial ratio. The designed polarization rotator consists of a tunable birefringent structure sandwiched between two +/- 45 degrees rotated metasurface-based quarter-wave plates. The birefringent structure is a bandpass metasurface which relies on integrated varactor diodes for tunability. Through a simple biasing mechanism, different voltages are applied to the diodes to rotate the polarization of a transmitted wave. The proposed idea may find application in various areas where dynamic polarization control is required.