Tripolarization-channel holograms generated by terahertz reflective bilayer-metasurface

• Cross-shaped meta-atoms are designed to fully utilize the capacity of Jones matrix for independent control of six-channel holograms. • The designed metasurface is based on phase change material VO 2 , which allows switching holograms by changing polarization and VO 2 state. • Generated holograms are virtually crosstalk free and exhibit notable broadband properties. Metasurfaces are expected to flexibly manipulate amplitude, phase and polarization of electromagnetic wave. By independently controlling phase distribution of different polarization channels, different holograms can be generated in corresponding channels. The method of switching holograms through changing the polarization channel has garnered significant research attention. However, implementing multifunctional devices on a single metasurface still presents considerable challenges. In this work, application of bilayer-metasurface in holographic imaging is explored based on vanadium dioxide (VO 2 ). Utilizing the difference between optical properties of insulating state and metallic state of VO 2 at different temperatures, temperature-controlled tunable holographic imaging is successfully realized. When VO 2 is metallic, the upper metasurface modulates electromagnetic wave and realizes specific holograms in three different polarization channels (e.g., the letters “T”, “O”, and “P”). As VO 2 is the insulator, the lower metasurface modulates electromagnetic wave and realizes another set of holograms in three different polarization channels (e.g., the letters “X”, “M”, and “U”). This novel design provides more possibilities for multi-channel holography.