Reconfigurable phase-change metasurfaces from efficient wavefront manipulation to perfect absorption

Reconfigurable electromagnetic (EM) devices with simultaneous small-footprint and high-efficiency are urgently on demand in the fields of optics and nanophotonics. However, it is still a great challenge to achieve this goal based on current design methods especially in infrared and visible bands. Here, a generalized methodology is proposed for highly efficient reconfigurable EM manipulation via the combination of subwavelength-scale metasurface with tunable phase-change material (PCM). As a proof of concept, several broadband metadevices operating in the infrared region are theoretically and numerically investigated. When PCM is in the amorphous state (corresponding to the phase manipulation mode), these devices can, respectively, achieve beam deflection, focusing and meta-holography. When PCM changes to crystalline state (corresponding to the amplitude control mode), they all behave as perfect absorbers with angular tolerance up to 40°. Further investigations also indicate that the designed devices can operate predictably and usefully across the continuous variation in crystal fraction. It is believed that the provided versatile metasurface platform may enable many fascinating applications such as dynamic beam steering, information encryption and active display.