Hui Li and Jiang Yu
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| The electric field distribution of the proposed absorber at different perfect resonance frequencies (a-b) Top view; (c-d) Side view when the conductivity of VO2 is set to 200000S/m. |
In this paper, we propose a terahertz bifunctional absorber with broadband and dual-band absorbing properties based on a hybrid graphene-vanadium dioxide (VO2) metamaterial configuration. When VO2 is in the insulating state and the Fermi energy of graphene is set to 0.8 eV, the designed device behaves as a tunable perfect dual-band absorber. The operating bandwidth and magnitude of the dual-band spectrum can be continuously adjusted by changing the Fermi energy of graphene. When VO2 is changed from insulator to metal, the designed system can be regarded as a broadband absorber, it has a broad absorption band in the range of 1.45-4.37 THz, and the corresponding absorptance is more than 90%. The simulation results indicate that the absorptance can be dynamically changed from 17% to 99% by adjusting the conductivity of the VO2 when the Fermi energy of graphene is fixed at 0.01 eV. Besides, both dual absorption spectrum and broad absorption spectrum maintain a strong polarization-independent characteristic and operate well at wide incident angles. Furthermore, we have introduced the interference theory to explain the physical mechanism of the absorption from an optical method. Therefore, our designed system can be applied in many promising fields like cloaking and switch.
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