Cascaded metasurface for simultaneous control of transmission and reflection.

Due to the strong capability to control electromagnetic (EM) wave, metasurfaces have garnered considerable interest and brought in many intriguing EM functional devices. However, most of such devices can only work in either transmitted or reflected mode, and it is still very challenging to achieve a simultaneous control of reflection and transmission in one device. Here, we present a cascaded metasurface which integrates the resonant and geometrical phase cells, to manipulate the transmitted and reflected wave independently. By specific design of phase distribution, the reflected and transmitted wavefront can be respectively reshaped on the shared aperture at two different frequency bands. As a proof of concept, a bidirectional beam deflector is realized by our metasurface and experimentally demonstrated at the microwave region. Both simulated and experimental results show that the transmitted and reflected beams can be simultaneously deflected to the predesigned angles. Furthermore, this metasurface exhibits isotropic EM responses under the different linear polarized wave in the reflected mode, while behaves anisotropic EM responses under the different circular polarized waves in the transmitted mode. Our approach provides a simple way to realize full-space EM manipulation, which could be developed for potential applications in mutlifunctional devices and integrated systems.