In this paper, tunable dual plasmon-induced transparency (PIT) is achieved by using a monolayer graphene metamaterial in the terahertz region, which consists of two graphene strips of different sizes and a graphene ring. As the dual PIT effect is induced by the destructive interference between the two quasi-dark modes and the bright mode, we propose a four-level plasmonic system based on the linearly coupled Lorentzian oscillators to explain the mechanism behind the dual PIT. It is proved that the theoretical results agree well with the simulation results. Most importantly, the sensing properties of the designed device have been investigated in detail and we found that it can exhibit high sensitivities and figure of merit (FOM). Furthermore, the dual PIT windows can be effectively modulated by changing the Fermi energy of the graphene layer and the angle of incidence. Thus, the proposed graphene-based metamaterial can hold wide applications for switches, modulators, and multi-band refractive index sensors in the terahertz region.

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In this paper, we theoretically demonstrate a dual-band independently tunable absorber consisting of a stacked graphene nanodisk and graphene layer with nanohole structure, and a metal reflector spaced by insulator layers. This structure exhibits a dipole resonance mode in graphene nanodisks and a quadrupole resonance mode in the graphene layer with nanoholes, which results in the enhancement of absorption over a wide range of incident angles for both TE and TM polarizations. The peak absorption wavelength is analyzed in detail for different geometrical parameters and the Fermi energy levels of graphene. The results show that both peaks of the absorber can be tuned dynamically and simultaneously by varying the Fermi energy level of graphene nanodisks and graphene layer with nanoholes structure. In addition, one can also independently tune each resonant frequency by only changing the Fermi energy level of one graphene layer. Such a device could be used as a chemical sensor, detector or multi-band absorber.

In this paper, we design a polarization-independent and angle-insensitive broadband THz graphene metamaterial absorber based on the surface plasmon-polaritons resonance. Full-wave simulation is conducted, and the results show that the designed metamaterial absorber has an absorption above 99% in the frequency range from 1.23 THz to 1.68 THz, which refers to a very high standard. Furthermore, the absorber has the properties of tunability, and the absorption can be nearly adjusted from 1% to 99% by varying the Fermi energy level of the graphene from 0 eV to 0.7 eV. In the simulation, when the incident angles of TE and TM waves change from 0° to 60°, the average absorption keeps greater than 80%. The proposed absorber shows promising performance, which has potential applications in developing graphene-based terahertz energy harvesting and thermal emission.