A tunable broadband THz absorber using periodic arrays of graphene disks

Khani, Amir Ali Mohamad; Aghaee, Toktam; Mazloum, Jalil; Jamali, Morteza

doi:10.1108/compel-09-2021-0339

Cited by 17 publications

(2 citation statements)

References 22 publications

(23 reference statements)

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“…According to Equation (7), changing gate bias leads to changing chemical potential which forces the device to react differently. 17 In this way, two operational modes are defined with corresponding chemical potentials, tabulated in Table 1.…”

Section: Simulation Resultsmentioning

confidence: 99%

Two directional THz wave duplexer and filter based on graphene disks and rings

Khani

Fouladian

Mazloum

2023

Int J Numerical Modelling

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Coating both sides of a dielectric spacer with graphene patterns, leads to a tunable meta surface which acts as a THz duplexer. Two separate channels, reflection and transmission are considered as outputs ports while the aim is to minimize absorption ration. The presented structure consists of periodic arrays of graphene patterns on both sides of silicon dioxide as substrate. Moreover, the patterns include disks and rings are biased differently compared to conventional patterns which makes it possible to achieve tunable behaviors versus external bias. utilizing equivalent circuit models (ECM) for graphene patterns and dielectric, the whole structure is modeled by passive RLC branches.According to the simulation outputs, the presented structure can transmit and reflect incident THz waves at desired frequencies in 0.1 THz to 30 THz which makes it an ideal candidate for manipulating THz waves in terms of transmission and reflection. The THz duplexer can transmit and reflect incident waves at 1-3.3 THz as wide-band and 1.05 THz as narrow-band operation. Such a tunable device is in great demand for indoor communications, security, less harmful medical imaging and space related researches.

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Section: Simulation Resultsmentioning

confidence: 99%

Two directional THz wave duplexer and filter based on graphene disks and rings

Khani

Fouladian

Mazloum

2023

Int J Numerical Modelling

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“…DLP laser lithography enables the production of metal grids or patches on top of graphene, facilitating the generation of tunability effects. Graphene's tunability for different voltages can be achieved by using an ion gel composed of ion gel (Khani et al, 2022a(Khani et al, , 2022bAghaee and Orouji, 2020a, 2020b, 2020c.…”

Section: Introductionmentioning

confidence: 99%

An optoelectronic Coupler based on graphene patterns and SU-8 photoresist

Zandi,

Fouladian,

Mazloum

2024

COMPEL

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Purpose The purpose of this research is to efficiently separate incident terahertz (THz) waves into distinct transmission and reflection channels by minimizing the absorption ratio. So, the optical systems operating within the THz frequency range can developed. To achieve a multi-band response, four different periodic arrays of graphene patterns are used. These arrays are strategically stacked on both sides of three SU-8 photoresists, serving as dielectric materials. Consequently, each layer exhibits a unique influence on the device's response, and by applying four external bias voltages, the behavior of the device can be precisely controlled and adjusted. Design/methodology/approach A novel optoelectronic device operating in the THz frequency range is introduced, using periodic arrays of graphene patterns and SU-8 photoresist dielectrics. The design of this device is based on meta-surface principles, using both the equivalent circuit model (ECM) and transmission line concept. The output of the device is a THz coupler implemented by analyzing the reflection and transmission channels. The structure is characterized using the ECM and validated through comprehensive full-wave simulations. By representing the electromagnetic phenomenon with passive circuit elements, enabling the calculation of absorption, reflection and transmission through the application of the theory of maximum power transfer. Findings Based on simulation results and theoretical analysis, the proposed device exhibits sensitivity to gate biasing, enabling efficient reflection and transmission of THz waves. The device achieves reflection and transmission peaks exceeding across the five distinct THz bands 90%, and its behavior can be tuned by external gate biasing. Moreover, the device's sensitivity to variations in geometrical parameters and chemical potentials demonstrates its reliable performance. With its outstanding performance, this high-performance meta-surface emerges as an ideal candidate for fundamental building blocks in larger optical systems, including sensors and detectors, operating within the THz frequency band. Originality/value The proposed device covers a significant portion of the THz gap through the provision of five adjustable peaks for reflection and transmission channels. Additionally, the ECM and impedance matching concept offers a simplified and time-efficient approach to designing the meta-surface. Leveraging this approach, the proposed device is effectively represented using passive circuit elements such as inductors, capacitors and resistors, while its performance is validated through the utilization of the finite element method (FEM) as a full-wave simulation tool. This combination of circuit modeling and FEM simulation contributes to the robustness and accuracy of the device's performance evaluation.

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Adjustable graphene disk‐based THz absorber for biomedical sensing: Theoretical description

Soltani Zanjani,

Sadrnia

2024

Engineering Reports

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As a basic building block, the THz wave absorber has intense imaging, sensing, and nondestructive testing applications. There are several methods for tuning THz absorbers, including electricity modulation, light modulation, mechanical tuning, using phase change materials, liquid crystal, flexible materials, MEMS technology, and thermally tuning vanadium dioxide. The choice of tuning method depends on the specific application and the desired performance characteristics of the THz absorber. In this work, we report a theoretical description of mechanically tunable THz absorber based on overlapping periodic arrays of graphene nano‐disks. The basis of this work is based on the movement of a dielectric surface covered on both sides with graphene disks. This surface moves on a fixed plane while the distance between these two surfaces is free space. Also, the fixed surface consists of a relatively thick layer of gold at the bottom, dielectric on it, and graphene disk patterns on the dielectric. Now, by moving the movable surface in the horizontal direction, it is possible to adjust the amount of absorption in different frequencies of the terahertz (THz) band. Additionally, an equivalent RLC circuit model is developed and theoretical results match with simulated data. The proposed mechanically tunable THz absorber can be exploited in various emerging applications such as sensing due to its capability of covering all of the THz gap and beyond with multiple absorption peaks.

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A tunable broadband THz absorber using periodic arrays of graphene disks

Cited by 17 publications

References 22 publications

Two directional THz wave duplexer and filter based on graphene disks and rings

Two directional THz wave duplexer and filter based on graphene disks and rings

An optoelectronic Coupler based on graphene patterns and SU-8 photoresist

Adjustable graphene disk‐based THz absorber for biomedical sensing: Theoretical description

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