Multifunctional ultrawideband terahertz metasurfaces with full space modulation

Abstract

In the field of metasurface technology, it is a major challenge to realize full-space multifunctional integration under ultra-wide bandwidth. In this study, we propose an innovative full-space terahertz (THz) metasurface design strategy that utilizes the cascaded mirror Fabry-Perot (F-P) cavity structure combined with the phase transition properties of vanadium dioxide (VO₂) to realize dynamic functional modulation of the metasurface in full space over an ultra-wide bandwidth. The proposed metasurface demonstrates exceptional capabilities within the 0.9–1.9 THz range, including polarization conversion (PC) for both linearly and circularly polarized waves in reflection mode, linear-to-circular polarization conversion (LTCPC), asymmetric transmission (AT), and circular dichroism (CD). Particularly noteworthy is the ability of the metasurface to work not only on transmission or reflection space alone, but also to modulate both spaces simultaneously. In order to demonstrate its full-space modulation capability in a wide bandwidth, the generation of a focused vortex beam is realized in the upper surface, and high-quality imaging is achieved in the lower surface space. Meanwhile, by adjusting the relative rotation angles of the metal layer structures, efficient PC is achieved in the reflection space and circular dichroism is exhibited in the transmission space. This design, characterized by full-space tunability and multifunctionality, offers innovative approaches for THz device integration and application while providing valuable insights for future optical device design.