Reprogrammable Digital Holograms and Multibit Spatial Energy Modulation Using a Reflective Metasurface

Holography has been extensively studied as a vital method to tailor wavefronts of electromagnetic waves. Compared to conventional holography, metasurface-based holography generally presents the advantages of unprecedented resolution, low noise, and high precision. Moreover, by using the modified weighted Gerchberg–Saxton algorithm, energy can be freely allocated in the focal spots of metasurface-based holographic images. In this paper, a reconfigurable metasurface incorporating electronically biased varactor diodes is designed to flexibly generate holographic images and to realize multibit spatial energy modulation for different channels in the full reflective semi-space. The different holographic images including focusing spots, numbers, and letters are fulfilled at different detecting planes and operating frequencies by implementing appropriate phase profiles to the metasurface. Furthermore, 1-bit and 2-bit spatial energy modulations for different channels are also performed to demonstrate the flexible control ability of the proposed metasurface. Simulations and measurements are carried out to validate the strategy of such full reflection space holographic imaging manipulation concept, which paves the way for a plethora of applications such as security, near-field wireless communication, 3D virtual reality technology, and information processing.