Simultaneous Perfect Bending and Polarization Rotation of Electromagnetic Wavefront Using Chiral Gradient Metasurfaces

We introduce chiral gradient metasurfaces that allow perfect transmission of the incident wave into a desired direction and simultaneous perfect rotation of the polarization of the refracted wave with respect to the incident one. In the lossless limit, transmission can reach 100% with a single metasurface layer. Besides using gradient polarization densities that provide bending of the refracted wave with respect to the incident one, the use of metasurface inclusions that are chiral allows the polarization of the refracted wave to be rotated. We suggest a possible realization of the proposed device by discretizing the required equivalent-surface polarization densities and synthesizing the chiral discrete polarizabilities with properly sized helical inclusions at each discretization point. By using only a single optically thin layer of chiral inclusions, we are able to deflect a normal incident plane wave to a refracted plane wave at 45° with a 72% power efficiency that is accompanied by a 90° polarization rotation. The proposed concepts and the design method may find practical applications in polarization-rotation devices in microwaves as well as in optics, especially when the incident power is required to be deflected.