scholarly journals A Non-Volatile Tunable Terahertz Metamaterial Absorber Using Graphene Floating Gate

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 333
Author(s):  
Jinjun Bai ◽  
Wei Shen ◽  
Jia Shi ◽  
Wei Xu ◽  
Shusheng Zhang ◽  
...  
Keyword(s):  
Physical Mechanism ◽  
Metamaterial Absorber ◽  
Floating Gate ◽  
Center Frequency ◽  
Field Energy ◽  
The Finite Element Method ◽  
Photoelectric Detection ◽  
Potential Applications ◽  
Simulation Results ◽  
Metal Absorber

Based on the graphene floating gate, a tunable terahertz metamaterial absorber is proposed. Compared with the traditional graphene–dielectric–metal absorber, our absorber has the property of being non-volatile and capacity for anti-interference. Using the finite element method, the paper investigates the absorption spectra, the electric field energy distribution, the tunability and the physical mechanism. In addition, we also analyse the influence of geometry, polarization and incident angles on the absorption. Simulation results show that the bandwidth of the absorption above 90% can reach up to 2.597 THz at the center frequency of 3.970 THz, and the maximum absorption can be tuned continuously from 14.405% to 99.864% by controlling the Fermi level from 0 eV to 0.8 eV. Meanwhile, the proposed absorber has the advantages of polarization insensitivity and a wide angle, and has potential applications in imaging, sensing and photoelectric detection.

scholarly journals An Ultra-thin Multiband Terahertz Metamaterial Absorber and Sensing Applications

2021 ◽  
Author(s):  
Jinjun Bai ◽  
Wei Shen ◽  
Shasha Wang ◽  
Meilan Ge ◽  
Tingting Chen ◽  
...  
Keyword(s):  
Refractive Index ◽  
Metamaterial Absorber ◽  
Field Energy ◽  
Absorption Mechanism ◽  
Energy Distributions ◽  
Perfect Absorption ◽  
Sensing Applications ◽  
At Resonance ◽  
Potential Applications ◽  
Electromagnetic Field Energy

Abstract We propose an ultra-thin multiband terahertz metamaterial absorber, whose thickness is only 3.8μm. Simulation results show that we can get four narrow absorption peaks with near-perfect absorption in the 4.5 THz-6.0 Thz frequency range. The resonance absorption mechanism is interpreted by the electromagnetic field energy distributions at resonance frequency. Moreover, we also analyze the sensing performances of the absorber in the refractive index and the thickness of the analyte. The refractive index and thickness sensitivities of the sensor are 0.471THz/RIU, 36.594THz/RIU and the FOMs are 8.887RIU -1 , 938.308RIU -1 , respectively. The absorber has potential applications in photodetector, multi-spectral imaging and biosensors.

scholarly journals Analysis and Design of Single-Phase Unidirectional Transducers with High Directivity

2021 ◽  
Vol 11 (16) ◽  
pp. 7500
Author(s):  
Xueping Sun ◽  
Shaobo Ge ◽  
Xiuting Shao ◽  
Shun Zhou ◽  
Wen Wang ◽  
...  
Keyword(s):  
Reflection Coefficient ◽  
Insertion Loss ◽  
Single Phase ◽  
Center Frequency ◽  
The Finite Element Method ◽  
Analysis And Design ◽  
Saw Devices ◽  
Optimal Value ◽  
Simulation Results ◽  
The Relationship

Electrode-width-controlled (EWC) single-phase unidirectional transducers (SPUDT) contribute to reduction of insertion loss of surface acoustic wave (SAW) devices due to their strong unidirectional properties. In this work, we propose a method to optimize the unidirectionality of EWC-SPUDT based on our research results that the unidirectionality of the EWC-SPUDT cell is strongly related to its reflectivity and its unidirectional angle. Furthermore, in order to ensure strong unidirectionality to achieve low insertion loss, a simulator based on the finite element method (FEM) is used to study the relationship between geometrical configuration of the EWC-SPUDT cell and its reflection coefficient, as well as its transduction coefficient. Simulation results indicate that the reflection coefficient of the optimized EWC-SPUDT cell composed of 128° YX lithium niobite (LiNbO3) substrate and Al electrodes with thickness of 0.3μm reaches the optimal value of 5.17% when the unidirectional angle is designed to be −90°. A SAW delay line is developed with the optimized EWC-SPUDT cell without weighing, and the simulation results are verified by experiments. The experimental results show that the directivity exceeds 30 dB at the center frequency and the insertion loss is just 6.7 dB.

scholarly journals Dual-Band Perfect Metamaterial Absorber Based on an Asymmetric H-Shaped Structure for Terahertz Waves

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2193 ◽  
Author(s):  
Taiguo Lu ◽  
Dawei Zhang ◽  
Peizhen Qiu ◽  
Jiqing Lian ◽  
Ming Jing ◽  
...  
Keyword(s):  
Metamaterial Absorber ◽  
Dual Band ◽  
Interference Theory ◽  
Metamaterial Structure ◽  
Terahertz Waves ◽  
Potential Applications ◽  
Band Absorption ◽  
Perfect Metamaterial Absorber ◽  
Simulation Results ◽  
Absorption Frequencies

We designed an ultra-thin dual-band metamaterial absorber by adjusting the side strips’ length of an H-shaped unit cell in the opposite direction to break the structural symmetry. The dual absorption peaks approximately 99.95% and 99.91% near the central resonance frequency of 4.72 THz and 5.0 THz were obtained, respectively. Meanwhile, a plasmon-induced transmission (PIT) like reflection window appears between the two absorption frequencies. In addition to theoretical explanations qualitatively, a multi-reflection interference theory is also investigated to prove the simulation results quantitatively. This work provides a way to obtain perfect dual-band absorption through an asymmetric metamaterial structure, and it may achieve potential applications in a variety of fields including filters, sensors, and some other functional metamaterial devices.

scholarly journals Graphene Based Controllable Broadband Terahertz Metamaterial Absorber with Transmission Band

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2409 ◽  
Author(s):  
Qihui Zhou ◽  
Song Zha ◽  
Peiguo Liu ◽  
Chenxi Liu ◽  
Li-an Bian ◽  
...  
Keyword(s):  
Sandwich Structure ◽  
Graphene Layer ◽  
Electromagnetic Compatibility ◽  
Transmission Band ◽  
Frequency Selective Surface ◽  
Metamaterial Absorber ◽  
Potential Applications ◽  
Transmission Window ◽  
Simulation Results ◽  
Broadband Terahertz

A graphene-based controllable broadband terahertz metamaterial absorber with transmission band is presented in this paper. It consists of a graphene-SiO2-frequency selective surface (FSS) sandwich structure. The sinusoidal graphene layer supports continuous plasmonic resonances, forming a broad electric-tuning absorbing band. Bandpass FSS constructs a transmission window outside the absorbing band. The simulation results indicate that the absorption from 0.5 THz to 1 THz can be tuned continuously from 0.4 to 0.9 with angle and polarization independence. A transparent window peaking at 1.65 THz maintains high transmittance over 0.7. The metamaterial absorber has potential applications for detection, stealth, filtering, and electromagnetic compatibility.

scholarly journals Ultrathin and Optically Transparent Microwave Absorber Based on Flexible Silver Nanowire Film

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1583
Author(s):  
Yanfei Dong ◽  
Dingwang Yu ◽  
Guochao Li ◽  
Yulin Cao ◽  
Youde Ruan ◽  
...  
Keyword(s):  
Physical Mechanism ◽  
Equivalent Circuit Model ◽  
Optical Transmittance ◽  
Metamaterial Absorber ◽  
Silver Nanowire ◽  
Wide Angle ◽  
Optically Transparent ◽  
Potential Applications ◽  
Sandwiched Structure ◽  
Angle Property

The design of an optically transparent and flexible metamaterial absorber was presented and fabricated. For this purpose, we use two different patterned silver nanowire films separated by the space layer, forming a transparent sandwiched structure with an ultrathin thickness. By analyzing the equivalent circuit model and distribution of electric field and current, the absorption physical mechanism has been theoretically investigated. The results show that the structure can achieve above 0.8 absorptions from 6 GHz to 18 GHz, and at the same time, this absorber also can obtain wide-angle property. The optical transmittance of the fabricated absorber exceeds 82% in the visible band. The results demonstrate that transparency and flexibility are the additional benefits that make the proposed absorber suitable for various potential applications.

scholarly journals Stereo Perfect Metamaterial Absorber Based on Standing Gear-Shaped Resonant Structure With Wide-Incident-Angle Stability

2020 ◽  
Vol 8 ◽  
Author(s):  
Guangsheng Deng ◽  
Kun Lv ◽  
Hanxiao Sun ◽  
Zhiping Yin ◽  
Jun Yang
Keyword(s):  
Incident Angle ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Dielectric Substrate ◽  
Metamaterial Absorber ◽  
Center Frequency ◽  
Resonant Structure ◽  
Potential Applications ◽  
Angle Stability ◽  
Perfect Metamaterial Absorber

In this work, a single-band metamaterial absorber (MA) based on a three dimensional (3D) resonant structure is presented. The unit cell is composed of a standing gear-shaped resonator, which is embedded in the dielectric substrate. The proposed 3D MA is ultrathin with a total thickness of 2.3 mm, corresponding 0.077λ0 at its center frequency. The simulation results demonstrate a high absorption peak at 10.1 GHz with absorptivity of 99.9%. The proposed 3D MA is insensitive to the polarization of the incident wave due to its rotationally symmetric structure. Moreover, the proposed 3D MA exhibits a wide-incident-angle stability, as absorptivity of more than 85% can be achieved for both TE and TM incidences with incident angle up to 60°. Most importantly, multiband electromagnetic wave absorption of the stereo MA can be enabled by adjusting the structural parameters of the standing gear. The proposed structure is compatible with 3D printing technology and has potential applications in electromagnetic shielding.

scholarly journals Theoretical Analysis of Terahertz Dielectric–Loaded Graphene Waveguide

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 210
Author(s):  
Da Teng ◽  
Kai Wang
Keyword(s):  
Photonic Devices ◽  
Effective Index ◽  
The Finite Element Method ◽  
Index Method ◽  
Modal Properties ◽  
Terahertz Region ◽  
Effective Index Method ◽  
Integration Density ◽  
Device Integration ◽  
Potential Applications

The waveguiding of terahertz surface plasmons by a GaAs strip-loaded graphene waveguide is investigated based on the effective-index method and the finite element method. Modal properties of the effective mode index, modal loss, and cut-off characteristics of higher order modes are investigated. By modulating the Fermi level, the modal properties of the fundamental mode could be adjusted. The accuracy of the effective-index method is verified by a comparison between the analytical results and numerical simulations. Besides the modal properties, the crosstalk between the adjacent waveguides, which determines the device integration density, is studied. The findings show that the effective-index method is highly valid for analyzing dielectric-loaded graphene plasmon waveguides in the terahertz region and may have potential applications in subwavelength tunable integrated photonic devices.

scholarly journals A Metawindow with Optimised Acoustic and Ventilation Performance

2021 ◽  
Vol 11 (7) ◽  
pp. 3168
Author(s):  
Gioia Fusaro ◽  
Xiang Yu ◽  
Zhenbo Lu ◽  
Fangsen Cui ◽  
Jian Kang
Keyword(s):  
Natural Ventilation ◽  
Noise Control ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Noise Mitigation ◽  
Acoustic Performance ◽  
Potential Applications ◽  
Ventilation Performance ◽  
Sound Reduction ◽  
Window Design

Crucial factors in window performance, such as natural ventilation and noise control, are generally conceived separately, forcing users to choose one over the other. To solve this dualism, this study aimed to develop an acoustic metamaterial (AMM) ergonomic window design to allow noise control without dependence on the natural ventilation duration and vice versa. First, the finite element method (FEM) was used to investigate the noise control performance of the acoustic metawindow (AMW) unit, followed by anechoic chamber testing, which also served as the validation of the FEM models. Furthermore, FEM analysis was used to optimise the acoustic performance and assess the ventilation potential. The numerical and experimental results exhibited an overall mean sound reduction of 15 dB within a bandwidth of 380 to 5000 Hz. A good agreement between the measured and numerical results was obtained, with a mean variation of 30%. Therefore, the AMW unit optimised acoustic performance, resulting in a higher noise reduction, especially from 50 to 500 Hz. Finally, most of the AMW unit configurations are suitable for natural ventilation, and a dynamic tuned ventilation capacity can be achieved for particular ranges by adjusting the window’s ventilation opening. The proposed designs have potential applications in building acoustics and engineering where natural ventilation and noise mitigation are required to meet regulations simultaneously.

FEMLIB: An Object-Oriented Framework for Optimization and Simulation

1995 ◽  
Author(s):  
Michael M. Tiller ◽  
Jonathan A. Dantzig
Keyword(s):  
Material Properties ◽  
Object Oriented ◽  
The Finite Element Method ◽  
Simulation And Optimization ◽  
Gradient Based ◽  
Level Problem ◽  
Simulation Results ◽  
Optimization And Simulation ◽  
High Level ◽  
Simulation Parameters

Abstract In this paper we discuss the design of an object-oriented framework for simulation and optimization. Although oriented around high-level problem solving, the framework defines several classes of problems and includes concrete implementations of common algorithms for solving these problems. Simulations are run by combining these algorithms, as needed, for a particular problem. Included in this framework is the capability to compute the sensitivity of simulation results to the different simulation parameters (e.g. material properties, boundary conditions, etc). This sensitivity information is valuable in performing optimization because it allows the use of gradient-based optimization algorithms. Also included in the system are many useful abstractions and implementations related to the finite element method.

A Two Step Damage Prognosis Method for Beam-Like Truss Structures

2014 ◽  
Vol 578-579 ◽  
pp. 1092-1095
Author(s):  
Hao Kai Jia ◽  
Ling Yu
Keyword(s):  
Finite Element Method ◽  
Strain Energy ◽  
Truss Structure ◽  
Truss Structures ◽  
Second Step ◽  
The Finite Element Method ◽  
Modal Strain Energy ◽  
Damage Prognosis ◽  
Modal Curvature ◽  
Simulation Results

In this study, a two step damage prognosis method is proposed for beam-like truss structures via combining modal curvature change (MCC) with modal strain energy change ratio (MSECR). Changes in the modal curvature and the elemental strain energy are selected as the indicator of damage prognosis. Different damage elements with different damage degrees are simulated. In the first step, the finite element method is used to model a beam-like truss structure and the displacement modes are got. The damage region is estimated by the MCC of top and bottom chords of a beam-like truss structure. In the second step, the elemental MSECR in the damage region is calculated and the maximum MSECR element is deemed as the damage element. The simulation results show that this method can accurately locate the damage in the beam-like truss structure.

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