A Polarization-Insensitive and Wide-Angle Terahertz Absorber with Ring-Porous Patterned Graphene Metasurface

Abstract

A broadband terahertz (THz) absorber, based on a graphene metasurface, which consists of a layer of ring-porous patterned structure array and a metallic mirror separated by an ultrathin SiO2 dielectric layer, is proposed and studied by numerical simulation. The simulated results show that the absorptivity of the absorber reaches 90% in the range of 0.91–1.86 THz, and the normalized bandwidth of the absorptivity is 68.6% under normal incidence. In the simulation, the effects of the geometric parameters of the structure on the absorption band have been investigated. The results show that the absorber is insensitive to the incident polarization angle for both transverse electric (TE) and transverse magnetic (TM) under normal incidence. In addition, the absorber is not sensitive to oblique incidence of the light source under TE polarization conditions, and has an approximately stable absorption bandwidth at the incident angle from 0° to 50°. The absorption band can be adjusted by changing the bias voltage of the graphene Fermi level without varying the nanostructure. Furthermore, we propose that a two-layer graphene structure with the same geometric parameters is separated by a dielectric layer of appropriate thickness. The simulated results show that the absorptivity of the two-layer absorber reaches 90% in the range of 0.83-2.04 THz and the normalized bandwidth of the absorptivity is 84.3% under normal incidence. Because of its excellent characteristics based on graphene metamaterial absorbers, it has an important application value in the field of subwavelength photonic devices.

Multi-channel terahertz focused beam generator based on shared-aperture metasurface

“…In addition, the thickness of the silicon dioxide is 40 µm. [24] In order to meet the gradient phase, eight kinds of coding elements are designed and illustrated in Table 1, where ϕ is the gradient phase of the corresponding unit cell, and α is the rotation angle of the unit cell along the y axis. The corresponding reflection coefficient (CRC) and phases under RCP wave incidence are shown in Figs.…”

Independently tunable concentric graphene ring resonators based ultrathin broadband THz absorber

“…A phase change material based annular rings with the hybrid of graphene have also been utilized for developing the broadband absorber [30]. Recently, few absorbing structures have been developed with the usage of multiple graphene annular rings which can offer the multiple resonances for providing the multiband, and narrowband absorption spectra [26][27][28][29][31][32][33][34]. A broad absorption spectrum can also be achieved with the usage of a complex graphene ring-based structure.…”

An electrical/thermal dual-controlled quad-functional terahertz metasurface absorber

“…10,11 Perfect absorption of THz waves is important for THz detectors, 12 sensors, 13,14 and stealth applications, 15–17 so how to achieve efficient absorption of THz waves has emerged as a crucial area of research. However, conventional THz absorbing materials with a single function, such as MXenes, 18,19 transition metal sulfides, 20 metal oxides, 21 metal powders, 22,23 and carbon-based nanomaterials, 24 are inadequate to meet the demands of complex working environments.…”