Tunable THz absorption in graphene-based heterostructures

Abstract

We investigate THz absorption properties of graphene-based heterostructures by using characteristics matrix method based on conductivity. We demonstrate that the proposed structure can lead to perfect THz absorption because of strong photon localization in the defect layer of the heterostructure. The THz absorption may be tuned continuously from 0 to 100% by controlling the chemical potential through a gate voltage. By adjusting the incident angle or the period number of the two PCs with respect to the graphene layer, one can tailor the maximum THz absorption value. The position of the THz absorption peaks can be tuned by changing either the center wavelength or the thicknesses ratio of the layers constituting the heterostructure. Our proposal may have potentially important applications in optoelectronic devices.

Inversion Method Characterization of Graphene-Based Coordination Absorbers Incorporating Periodically Patterned Metal Ring Metasurfaces

“…A single layer of graphene between the upper gold rings and the SiO 2 substrate is pictured as a honeycomb structure. Within the operating wavelengths, the dispersion of dielectric constant of SiO 2 [ 33 ] is negligible and therefore fixed at ε SiO2 = 3.9, and the permittivity of gold can be expressed as ε = 1 − ( /( ω 2 + i ωγ)) using the Drude model [ 34 ] with the value of constant plasma frequency ω p = 1.36 × 10 16 rad/s and collision frequency γ = 3.33 × 10 13 rad/s. The graphene is simulated in COMSOL by setting the surface current density.…”

Plasmonic Absorption Enhancement in Elliptical Graphene Arrays

“…The silicon dioxide structure, close to the graphene array, has the thickness d. The bottom is silicon. The refractive index of silicon is n si = 3.4, and the relative permittivity of silicon dioxide is ε d = 3.9 [ 16 , 17 , 18 ]. Here, a plane wave with incident angle θ is used to illuminate this system, and the x - z plane is taken as the plane of incident.…”

Graphene-Based Perfect Absorption Structures in the Visible to Terahertz Band and Their Optoelectronics Applications

“…Thus, many perfect absorption structures based on graphene plasmons have been proposed, such as narrowband perfect absorption structure in the mid-IR [18], dual-band perfect absorption structures in the THz [19,20], multi-band perfect absorption structures in the mid-IR [21,22], broadband perfect absorption structures in the THz [23,24], and coherent perfect absorption structures in the mid-IR and THz [25,26]. Meanwhile, without exciting the graphene plasmons, some graphene-based perfect absorption structures were also demonstrated by using the impedance matching concept [27] or special designs [28,29,30] in the THz band, and by using the big incident angle in the mid-IR band [31]. In the visible and near-IR band, graphene can hardly support plasmons due to the limits of doping or gating level, and the absorption of graphene was normally enhanced by coupling graphene with metallic or dielectric resonant structures.…”