Graphene based tunable metamaterial absorber and polarization modulation in terahertz frequency

Abstract

Graphene can be utilized in designing tunable terahertz devices due to its tunability of sheet conductivity. In this paper, we combine the metamaterial having unit cell of cross-shaped metallic resonator with the double layer graphene wires to realize polarization independent absorber with spectral tuning at terahertz frequency. The absorption performance with a peak frequency tuning range of 15% and almost perfect peak absorption has been demonstrated by controlling the Fermi energy of the graphene that can be conveniently achieved by adjusting the bias voltage on the graphene double layers. The mechanism of the proposed absorber has been explored by a transmission line model and the tuning is explained by the changing of the effective inductance of the graphene wires under gate voltage biasing. Further more, we also propose a polarization modulation scheme of terahertz wave by applying similar polarization dependent absorbers. Through the proposed polarization modulator, it is able to electrically control the reflected wave with a linear polarization of continuously tunable azimuth angle of the major axis from 0° to 90° at the working frequency. These design approaches enable us to electrically control the absorption spectrum and the polarization state of terahertz waves more flexibly.

Resonance enhanced absorption in a graphene monolayer using deep metal gratings

“…Graphene patch arrays of cross shapes [16] and square shapes [17] have also been demonstrated for absorption enhancement. In addition, graphene can be used together with other structures, such as gratings and photonic crystals to enhance its absorption [18][19][20][21][22][23][24][25]. For example, Gao et al [26] and Zhan et al [27] utilized a dielectric surface-relief grating to excite the surface plasmon wave in graphene, which also enhanced graphene absorption.…”

Tunable graphene-based mid-infrared plasmonic wide-angle narrowband perfect absorber

“…Currently, a great diversity of graphene-based metamaterials373839 have been devised for enhancing optical absorption, such as, graphene discs40, ribbons41, rings42, even the monolayer graphene coated by metallic gratings43. Herein, we propose a wide-angle plasmonic narrowband perfect absorber based on the periodic double-layer graphene ribbon arrays separated from a metallic ground plate by an ultra-thick dielectric layer.…”

A Polarization-Dependent Frequency-Selective Metamaterial Absorber with Multiple Absorption Peaks

“…A certain progress has been made in broadband MAs developing [14,15]. Meanwhile, some studies on tunable absorbers [16,17] and multiband absorbers [18][19][20] have been performed. Currently, research is focused on absorbers intended for application in polarization imaging and polarization detecting.…”