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

This study presents a dual-functional switchable metasurface based on graphene and VO2, designed for terahertz polarization conversion and absorption.When VO2 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 properties. Under insulating VO2 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-tocircular 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 adaptable performance, thus offering significant potential for for tunable broadband terahertz converters, radar communication, electromagnetic stealth, and terahertz modulation applications.