Multifunctional metasurface for absorption and polarization conversion based on VO₂ and graphene in terahertz band

Abstract This study presents a dual-functional switchable metasurface based on graphene and VO 2 , designed for terahertz polarization conversion and absorption. When VO 2 is in metallic state with graphene’s Fermi level at 0.9 eV, the structure achieves an absorption rate exceeding 0.9 across 1.42–3.26 THz (78.6% relative bandwidth), exhibiting wide-angle incidence capability and polarization-insensitive absorption behavior. Under insulating VO 2 conditions, the metasurface functions as a polarization converter. Graphene Fermi level modulation enables operational bandwidth expansion, achieving polarization conversion ratio (PCR) exceeding 90% for linear-to-linear polarization conversion (LTL PC) over 0.99–3.84 THz (118% relative bandwidth), while maintaining ellipticity χ is less than −0.9 for linear-to-circular polarization conversion (LTC PC) at 3.8–4.0 THz (5.1% relative bandwidth). This multi-functional metasurface combines high-efficiency absorption, broadband tunable polarization conversion, and tunable performance, thus offering significant potential for tunable broadband terahertz converters, radar communication, electromagnetic stealth, and terahertz modulation applications.