Programmable flip-metasurface with dynamically tunable reflection and broadband undistorted transmission

We introduce a programmable flip-metasurface that can dynamically control the reflection while leaving the transmitted wavefront undistorted in an ultra-broad spectrum, i.e., the same as that of the incidence. This metasurface is constructed by unique meta-atoms that can be dynamically switched between two flip states, which correspond to the spatial inversion of each other. Due to the reciprocity principle and spatial inversion symmetry, the transmission is independent of the flip states, regardless of the frequency. While the reflection can be conveniently controlled by tuning the flip states. Dynamical steering of the reflected waves, such as diffuse reflection, focusing, and beam-splitting, is numerically and experimentally validated along with unaffected transmission. Our finding opens an approach to dynamically modulate reflections without affecting transmission, which could have broad potential applications ranging from wireless communications to stealth technology.