Polarization Insensitive Broadband Concentric- Annular-Strip Octagonal Terahertz Graphene Metamaterial Absorber

In this paper, a polarization insensitive terahertz (THz) graphene metamaterial absorber (MA) with wide bandwidth is proposed, which consists of three concentric annular strips and one octagonal unit graphene structures. By adjusting the positions of the annular strips and octagonal unit, and optimizing the length and width of each individual strip, the hybridization effect and stacking effect can be fully enhanced, and the whole structure can ensure wide and strong absorption performance. The designed MA can maintain the absorptivity above 90% in the range of 1.027-1.958THz, and most of them are above 95%. Meanwhile, the absorption spectrum under different polarization conditions also show that the proposed THz graphene MA structure is insensitive to polarization and incident angle. The electric field intensity distribution illustrates the mechanism of broadband absorption. Moreover, the conductivity of graphene can be adjusted by external gate voltage, which brings tunable absorption results. Finally, the THz MA absorber based on concentric gradient design has the advantages of tunability, high absorption, broadband, incident angle and polarization insensitivity, which can provide a helpful reference for the design of other absorbers to broaden the bandwidth and enhance the absorption.