High-Efficiency and Full-Space Manipulation of Electromagnetic Wave Fronts with Metasurfaces

Metasurfaces offer great opportunities to control electromagnetic (EM) waves, but currently most metadevices work either in pure reflection or pure transmission mode, leaving half of the EM space completely unexplored. Here, we propose an alternative type of metasurface, composed of specifically designed meta-atoms with polarization-dependent transmission and reflection properties, to efficiently manipulate EM waves in the full space. As a proof of concept, three microwave metadevices are designed, fabricated, and experimentally characterized. The first two metadevices can bend or focus EM waves at different sides (i.e., transmission and reflection sides) of the metasurfaces, depending on the incident polarization, while the third one changes from a wave bender for the reflected wave to a focusing lens for the transmitted wave as the excitation polarization is rotated, with all of these functionalities exhibiting very high efficiencies (in the range of 85%-91%) and total thickness similar to lambda/8. Our findings significantly expand the capabilities of metasurfaces in controlling EM waves, and can stimulate high-performance multifunctional metadevices facing more challenging and diversified application demands.