Broadband terahertz holography using isotropic VO2 metasurfaces

Vanadium dioxide (VO 2 ) exhibits exceptional phase transition characteristics that enable dynamic manipulation of electromagnetic wave. In this study, a novel design of bilayer isotropic metasurface is introduced. It leverages insulating-to-metallic phase transition of VO 2 to enable broadband holography for terahertz wave. For the metallic VO 2 , the upper VO 2 antennas reflect incident terahertz wave and generate hologram. For the insulating VO 2 , incident wave is reflected by the lower gold antennas and the same hologram is generated with frequency doubling. Working frequencies of the designed holograms are 1.2 THz for metallic VO 2 and 1.9 THz for insulating VO 2 . Due to the broadband performance under each state, the proposed metasurface can achieve holography within 1.0-2.1 THz. It is noteworthy that the generated holograms under two states of VO 2 remain entirely independent, and another metasurface that achieves frequency-multiplexed holograms is presented. Our design may have possible applications in holographic display and information encryption.