Tunable broadband terahertz absorber based on a single-layer graphene metasurface

Abstract

In this paper, a broadband and tunable terahertz absorber based on a graphene metasurface in a sandwiched structure is introduced. A single-layered graphene patterned with hollow-out squares is applied in this design, which is continuously connected to provide convenience for electrical tuning and fabrication. Plasmonic coupling and hybridization inside the graphene pattern can significantly enhance the absorption bandwidth. Moreover, polarization-insensitive and omnidirectional performances are also guaranteed by the symmetrical design. Full wave simulations demonstrate that the absorber exhibits over 90% absorbance within 1.14∼3.31 THz with a fractional bandwidth up to 97.5%. The device reveals tunable absorbance from 14% to almost 100% by manipulating the graphene chemical potential from 0 to 0.9 eV. When the incident angle sweeps up to 55°, the absorbance remains more than 90% from 1.77 to 3.42 THz for TE polarization, while over 90% absorbance maintains around 3.3 THz for TM polarization. These superior abilities guarantee the applicability of the presented absorber in THz cloaking, tunable sensor and photovoltaic devices.

High-Quality Graphene-Based Tunable Absorber Based on Double-Side Coupled-Cavity Effect

“…For the structure, monolayer graphene is modeled as a conductive surface with thickness D g = 0.35 nm in the simulations. The surface conductivity σ(ω, µ c , Γ, T) in THz range can be expressed by the Drude model according to the Kubo formula, as given by [15],…”

“…In order to solve this problem, some strategies have been proposed. For instance, high-efficiency absorbers have been realized by designing graphene patterns with different shapes, such as split ring, fishing-net and E-shaped models [14,15]. Another method is to use periodic metal units to excite surface plasmon polaritons to enhance the absorption of graphene [16][17][18][19][20][21].…”

A Review: The Functional Materials-Assisted Terahertz Metamaterial Absorbers and Polarization Converters

“…Many classical discrete graphene patterns, including target-patterned graphene resonator [73], various graphene square resonators in one unit cell [74], graphene disks [75], hexagonal spider web structure [76] and so on, are used to construct broad-band metamaterial absorbers. Furthermore, some continuous graphene layers, including continuous graphene microstructures [67,[77][78][79][80][81][82] and nonstructured graphene films [68,83,84], are also used to construct the broad-band terahertz metamaterial absorbers. Y. N. Jiang et al proposed, fabricated, and characterized a terahertz metamaterial absorber treating patterned graphene [77].…”

“…In 2020, J. Z. Han et al introduced a broad-band and switchable metamaterial absorber using a sandwiched graphene microstructure [78]. As shown in Figure 6a, a single-layer graphene microstructure with hollow-out squares is treated.…”

Active control of dual electromagnetically induced transparency in terahertz graphene-metal hybrid metasurfaces

“…They have ultra-high degree of freedom in designing the propagations of electromagnetic waves, and have attracted enormous research interest over the whole electromagnetic field (Glybovski et al, 2016;Sun et al, 2019). The internal working mechanism of metasurfaces is to use the local resonance-determined phase, amplitude and polarization manipulation ability of the composed meta-atoms to control the spectral responses and wavefronts of the output waves (Wang et al, 2015;Meng et al, 2019;Han and Chen, 2020;Sun et al, 2020;Venkatesh et al, 2020;He et al, 2021;Kim et al, 2021). Among them, one potential application of metasurfaces is to mimic the quantum phenomena as it offers a smart route to achieve corresponding optical modulations in a classical way.…”