ObjectiveWith the continuous advancement of research on terahertz metamaterial broadband absorbers, tuning their absorption performance has become increasingly important. However, this tuning process often leads to a degradation of the original broadband absorption capabilities and makes the absorber more sensitive to polarization and incident angles. To address this issue, a terahertz broadband tunable metamaterial absorber based on graphene and vanadium dioxide (VO₂) as tuning materials is proposed.MethodsThe absorber in this paper has four layers, which are the bottom metal plate made of gold, the dielectric layer made of PMI, the two resonant layers made of VO₂ and graphene. The resonant structure is a split-ring to ensure the broadband absorption, and the VO₂ is used to turn the absorption amplitude of absorber for its characteristic of phase transition. Furthermore, the turning of working frequency is achieved by graphene of which the conductivity can be changed by adjusting its chemical potential.Results and DiscussionsThe bandwidth of the proposed absorber with an absorption rate exceeding 90% can reach 6.35 THz, when the conductivity of VO₂ is 200000 S/m and the chemical potential of graphene is and 0.01 eV. The absorption mechanism is analyzed by means of reflection theory and impedance matching principle, and the absorber's performance is tested by plotting absorption curves under various conditions, including different polarization states, conductivity of VO₂ and Fermi energy levels of graphene. The study results will show that the absorption rate of the broad absorption band can be significantly adjusted by the conductivity of VO₂ and the frequency of a absorption peak can changed by the Fermi energy of graphene. Meanwhile, the proposed absorber possesses the characteristics of polarization insensitivity and shows good absorption for waves under incident angles from 0° to 50°.ConclusionsThrough the comparison and analysis of the absorption curves under different conditions, it is found that the proposed metamaterial absorber possesses the characteristics of tunability, broadband absorption polarization insensitivity and wideangle absorption.