Abstract-Multi-mode Tunable Absorber Based on Graphene Metamaterial

Ning Hu, Peiguo Liu, Li-an Bian, Qihui Zhou, Chenxi, Liu Jihong Zhang, Hanqing Liu,


https://www.sciencedirect.com/science/article/pii/S0749603618310565

In this paper, a novel design of metamaterial absorber (MA) with multi modes and tunability characteristics in terahertz (THz) range is presented. The MA consists of patterned gold-graphene on the top layer, graphene sheet and gold ground separated by SiO2. The chemical potential of patterned graphene and graphene sheet can be tuned independently. Thus, the regulation flexibility of MA is greatly enhanced. For demonstration, the proposed MA is investigated using circuit analogy method and the distributions of the electric field are also discussed in detail to explore underlying mechanism. Numerical calculations are stimulated in a commercial full-wave solver and indicate that the proposed MA possesses excellent absorption properties. There are three perfect absorption ($\ge 99.2\text{\%}$) modes at 2.4 THz, 4.2 THz and 7.2 THz respectively. Under the regulation of chemical potential, the proposed MA could serve as single-frequency or dual-frequency absorber without change of physical structure. When working as single-frequency absorber, the MA could be regulated between different modes during a large frequency range and the absorption peaks could also be regulated within the same mode during a relative smaller frequency range. Furthermore, the MA has two absorption peaks at 2.4 THz and 7.2 THz ($\ge 95\text{\%}$) simultaneously as dual-frequency absorber. The proposed MA shows promising application potentials due to the flexible modulation and functions and this work provides a new perspective for the design of tunable THz absorbers based on graphene.

Abstract-Dynamically tunable electromagnetically induced transparency analogy in terahertz metamaterial

Chenxi Liu, 

Peiguo Liu, 

Lian Bian, 

Qihui Zhou, 

Gaosheng Li, 

Hanqin Liu

http://www.sciencedirect.com/science/article/pii/S0030401817308684
A metamaterial analogy of tunable electromagnetically induced transparency (EIT) is theoretically investigated in terahertz regime. The proposed metamaterial consists of vertical gold strips and horizontal graphene wires, which perform as bright elements and dark elements, respectively. The EIT-like phenomenon can be induced by bright–dark mode coupling on condition of structural lateral displacement. Numerical result reveals that the EIT-like effect remains noticeable with a wide range of incidence polarization angles. Most importantly, by manipulating gate voltages, the EIT window can be dynamically controlled without refabricating the structure. The amplitude modulation depth can reach 81%, 79%, and 68% respectively at three characteristic frequencies as Fermi energy changes in the scope of 0.8–1.0 eV. Furthermore, a sensitivity of 0.95 THz per refractive index unit (RIU) is realized varying the refractive index in the surrounding medium. This structure provides potential applications for detectors, sensors, and modulators.