Terahertz ultra-broadband and multi-frequency narrowband perfect absorber based on compound metamaterial

A perfect absorber in the terahertz band with ultra-broadband and triple narrowband is achieved, using Vanadium Dioxide (VO2) and patterned graphene hybrid metamaterials, which can be converted by adjusting the temperature. When only VO(2 )is present in the structure, the absorption spectrum shows broadband absorption in metallic phases of VO2. Adding graphene to metallic VO2, the absorption bandwidth over 95% is expanded to 5.5THz, which is 1.9 times broader compared to the absence of graphene, and the absorption bandwidth over 99% increases to 1.72THz. Adding graphene to insulating VO2, three narrowband absorptions appear with absorption rates approaching 100%. Polarization characteristics show that ultra-broadband is insensitive to polarization angle, while multi-frequency narrowband exhibits sensitivity. Therefore, the proposed tunable multifunctional absorber can greatly optimize the absorption capacity of ultra-broadband and multi-frequency narrow bands, demonstrating great potential in future practical applications.