Spin-decoupled dual-channel VO ₂ metasurface for multifunctional terahertz phase modulation

This study presents a temperature-reconfigurable terahertz metasurface for multi-channel and multifunctional wavefront control. The design integrates the composite phase control principle, a reflective shared-aperture layout, and the phase-change material vanadium dioxide (<i>V</i><i>O</i>₂) to achieve spin-decoupled manipulation of circularly polarized waves. Two spin-decoupled 2-bit coding meta-atoms enable a dual-channel holographic display. Crucially, the metasurface's functionality is dynamically switched by the state of <i>V</i><i>O</i>₂. When <i>V</i><i>O</i>₂ is in its metallic phase under vertical linear polarization, the structure deflects four asymmetric beams. In contrast, when <i>V</i><i>O</i>₂ is insulating, it generates four vortex beams from a left-handed circularly polarized (LCP) incident wave and creates a dual-focus reflection from a right-handed circularly polarized (RCP) wave. This work provides a paradigm for efficient, independent wavefront control of LCP/RCP waves and multifunctional operation in the terahertz regime.