Broadband achromatic wavefront tailoring with high-efficiency reflective metadevices

Metasurfaces have exhibited unprecedented capabilities to manipulate electromagnetic (EM) waves, but many of them suffer from frequency dispersions, which significantly degrade their performance. Although extensive efforts have been devoted to the design of achromatic metasurfaces at optical frequencies, their microwave counterparts are less studied, with a few attempts suffering from large thicknesses. Here, based on high-efficiency meta-atoms exhibiting tailored reflection phases of both resonant and geometric origins, we propose a generic scheme to design achromatic metasurfaces for controlling EM far-field wavefronts within microwave broadband. We follow the proposed strategy to design and fabricate three achromatic metadevices, and experimentally demonstrate that they can realize anomalous reflection, focusing, and Bessel beam generations, respectively, at every frequency within 8-10 GHz. Our work paves the road for realizing high-performance achromatic metadevices in low-frequency domains, which may find many applications such as radar detection, microwave imaging, and wireless communications.