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A dispersive weakly conditionally stable finite-difference time-domain (WCS-FDTD) method for the efficient simulations of the graphene-based absorbers with fine structures in two directions is proposed in this paper. It is based on the auxiliary differential equation technique and the hybrid implicit explicit difference technique. The maximum time step size of this method is only determined by the largest spatial discretization. The numerical results demonstrate that the dispersive WCS-FDTD method has high computational accuracy and the computational time is greatly reduced compared with the dispersive FDTD method and the dispersive HIE-FDTD method.

A dispersion hybrid implicit-explicit finite-difference time-domain (HIE-FDTD) method is proposed for simulating the graphene-based absorber at terahertz frequencies. The surface conductivity of the graphene derived from the Kubo formula is incorporated into the conventional HIE-FDTD algorithm by using the auxiliary differential equation technique. The time step size of this method is not related with the fine cells inside the graphene layer. The simulation result of the infinite graphene sheet shows that the dispersion HIE-FDTD method has high computational accuracy and the computational time is greatly reduced compared with the dispersion FDTD method. By using the dispersion HIE-FDTD method, it is validated that the graphene sheet can be used as a broadband absorber.

Recently graphene has attracted tremendous attention for its excellent properties Numerous novel graphene-based devices have come out, showing great potential of graphene for tunable applications at THz band In this paper, by stacking a monolayer of graphene on the top of the polymer substrate, a graphene-based tunable absorber is obtained owning to the voltage-controllable conductivity of graphene. Furthermore, the absorption spectra for different chemical potentials is discussed in detail. The resonance frequency of the absorber is blue-shift with increasing chemical potential. In addition, the proposed absorber shows a good stability with various polarizations due to the symmetry of the structure. These simulated results will provide approaches to obtain dynamically switchable absorbers with a compact dimension, and such design also has potential applications in THz detection, thermal emitters, sensors and THz stealth technology.

Recently graphene has attracted tremendous attention for its excellent properties. Numerous novel graphene-based devices have come out, showing great potential of graphene for applications at the terahertz band. In this paper, by placing monolayer graphene deposited on top of a SiO2/Si substrate, a tunable graphene-based dipole antenna owing to the voltage-controllable conductivity of graphene is obtained. The resonance frequency of the proposed antenna is blue-shift with increasing chemical potential. Furthermore, the radiation gain of the antenna can increase from 3.7dBi to 5.5dBi by adjusting the chemical potential. These simulated results will provide approaches using graphene in reconfigurable antennas.