Terahertz generation of multichannel grayscale image and vortex based on phase change metasurface

• The designed metasurface only requires different orientations of meta -atoms to achieve the established function, and the design is convenient and simple. • Our design achieves simultaneous near-field grayscale images and far-field vortex in different states of VO 2 . • The simulated images exhibit exceptional fidelity, ultralow inter-channel crosstalk, and an outstanding operational bandwidth. In recent years, the rapid development of metamaterial and metasurface has brought revolutionary breakthroughs in electromagnetic manipulation. However, achieving multi-channel grayscale imaging and orbital angular momentum (OAM) modulation by a single metasurface remains a significant challenge. This study innovatively integrates the thermally responsive vanadium dioxide (VO 2 ) into metasurface. By ingeniously combining Malus’s law and Pancharatnam-Berry (PB) phase, multi-channel grayscale image and vortex are achieved in terahertz range. Simulation outcomes show that as VO 2 is metallic, the metasurface can generate grayscale images of “C” and “D” in the near field while producing an OAM mode with l = 1 . Conversely, when VO 2 transitions to its insulating state, the metasurface can generate grayscale images of “U” and “V” in the near field while producing an OAM mode with l = - 1 . This design not only offers outstanding multi-channel control capabilities and low crosstalk but also provides cutting-edge technological pathways for future integration of grayscale images and OAM technologies