Ultra-wideband switchable multifunctional terahertz hypersurfaces based on graphene and VO2

Abstract Hypersurfaces have become an important part of terahertz wave communication and imaging due to their strong terahertz wave modulation capability, low loss and easy conformal. This paper introduces the design of an ultra-wideband switchable multifunctional hypersurface incorporating vanadium dioxide VO 2 and graphene. The proposed hypersurface is capable of achieving ultra-wideband absorption, multimodal creation of orbital angular momentum (OAM) waves, and radar cross-section (RCS) reduction. When VO 2 undergoes a transition to its metallic phase at 68 °C, with the graphene chemical potential set to 0 eV, the system exhibits an ultra-wideband absorption mode on the hypersurface. In this state, it attains an absorption efficiency greater than 90% within the 5.65–13 THz range, resulting in a relative absorption bandwidth of 78.82%. At a temperature of 25 °C, in the insulating phase of VO 2 , and with the chemical potential of graphene set to 0.7 eV,hypersurface has an absorption efficiency of over 90% within the 4.4–8.3 THz range, reaching a relative absorption bandwidth of 61.4%. The effect of polarization and incident angle on the absorber’s performance in the operational state is further investigated. In the insulating phase of VO 2 , with the graphene chemical potential at 0 eV, the design of eight engineered cells, each exhibiting unique reflective phases, facilitates a 2 π phase coverage across the 4.9–7.6 THz frequency range. This configuration generates orbital angular momentum (OAM) waves with high mode purity, while also attaining radar cross-section (RCS) reduction across a broad range of incidence angles. The hypersurface is evaluated to demonstrate stable performance across angles from 0° to 45° and is capable of reducing radar scattering by over 10 dB in radar scattering interface. Through this study, it is shown that the multifunctional hypersurface has a promising application in future terahertz communication, terahertz beam modulation, and imaging detection.