Metasurface based on VO2-Ge2Sb2Te5 with multi-modes: cross-polarization conversion, reversible linear dichroism and absorption

To address the limitations of conventional metasurfaces, including single-function operation, structural complexity, and narrow application scope, we propose a VO₂-Ge₂Sb₂Te₅ (GST225)-based multifunctional switchable terahertz metasurface. By utilizing the unique properties of the two phase-change materials (PCMs) and controlling their phase transitions, the metasurface dynamically switches between three functional modes: cross-polarization conversion, reversible linear dichroism (LD), and absorption. The polarization conversion mode achieves over 90% efficiency in the 2.52–3.92 THz range and exhibits incident polarization insensitivity. The reversible LD mode enables switching between dichroism values of +0.956 and −0.959 at 1.57 THz through actively controlled PCMs. The absorption mode demonstrates broadband performance, maintaining over 60% absorption rate across a 4 THz bandwidth and exhibiting dual-peak spectral characteristics. Leveraging these operational modes, we introduce three distinct encryption schemes. The proposed metasurface serves as a versatile integration platform, offering potential applications in polarization detection and image encryption.