Broadband tunable terahertz metasurface absorber based on complementary-wheel-shaped graphene

We present a simple design for a broadband tunable terahertz metasurface absorber (MSA), which is composed of a periodic array of complementary-wheel-shaped (CWS) graphene sheets and a lossy polyimide layer backed with a ground-plane. Numerical simulation results show that the absorbance of the proposed MSA achieves over 90% for the frequency range of 1.77 THz to 4.16 THz with the relative bandwidth of about 80.6% when Ef = 1.0 eV, and the absorbance is up to 93.6% and 99.8% at 2.07 and 3.83 THz. The proposed MSA is polarization-insensitive and wide-angle for both transverse-electric (TE) and transverse-magnetic (TM) waves. Fabry-Perot interference theory is used to analyze the mechanism of the MSA, and the theoretical results are agreement well with sim-ulations. The absorption performance of the MSA can be flexibly adjusted by changing the Fermi energy level of the graphene. The simulated absorbance of the MSA can be adjusted from 19% to nearly 100% by changing the Ef from 0.1 eV to 1.0 eV, which is consistent well with theoretical calculation. In addition, absorption properties of the MSA are also can be adjusted by changing the geometrical parameters of the unit-cell structure. Due to its simple structure and strong tunability, the proposed MSA has potential application prospects in the fields of tunable filtering, detection, sensing and so on.