Polarization conversion at multiple angles in the terahertz regime via a metasurface with two crossed L-shaped elements

Although remarkable advances have been made over the past decades, more functional devices suitable for practical systems are needed to further facilitate the development and application of terahertz technology. Among them, polarization devices are essential in terahertz systems. In this work, a metasurface with a multi-angle polarization conversion function is proposed. The device is composed of a top metal structure layer, a dielectric spacer, and a bottom metal film. The unit cell in the metal structure layer consists of two L-shaped elements which are symmetric about the -45 degrees axis and rotated clockwise and counterclockwise around the center, respectively. Cross-polarization conversion can be achieved when the metal structure is in its original position. When the structure is rotated counterclockwise at a certain angle around the center, oblique polarization conversion can be realized within the same frequency band. If we keep rotating the structure, more polarization conversion angles can be achieved. Compared with recent reports, the structure proposed here is more flexible in polarization conversion and more suitable for practical applications and has great potential in the terahertz field.