Ultra-wideband terahertz absorber with switchable multiple modes based on graphene and vanadium dioxide metamaterials

This article proposes a dynamic switchable broadband absorber based on graphene and vanadium dioxide (VO₂). The temperature could adjust the conductivity of VO₂, and external voltage could alter the conductivity of graphene. Therefore, they can be used for broadband absorption that can be switched between low and high frequencies and for achieving coupled ultra-wideband absorption. When the Fermi level of graphene is 0.9e V and VO₂ is in a non-metallic state, the absorber can achieve absorption of over 90 % in the range of 2.55 THz-4.86 THz. When the Fermi level of graphene is 0.1e V and VO₂ is in a metallic state, the absorber can achieve absorption of over 90 % in the range of 4.30 THz-9.40 THz. When the Fermi level of graphene is 0.6e V and VO₂ is in a metallic state, the absorber can achieve absorption of over 90 % in the range of 2.32 THz-9.80 THz. The absorber only partially depends on the incident angle of the incident light, simulation results show that when the incident angle is below 50 degrees, more than 90 % of the absorption bandwidth changes less. The absorber has no relation to the polarization angle of the incident light, and can keep its original property at any polarization angle. This structure has potential applications in electromagnetic wave stealth devices, optical switches and filters.