Tunable Broadband THz Waveband Absorbers Based On Graphene for Digital Coding

A method of coding patterns is proposed to achieve flexible control of absorption response at terahertz frequencies. The designed absorber consists of an Au-graphene pattern layer, a SiO2 layer and a metal reflective layer. Among them, we use concentrical circle structure to achieve broadband absorption, and adjust graphene’s Fermi level to achieve tunable absorption. In addition, we propose an encoding method that can achieve flexible control of the absorption response at the terahertz frequency based on the external voltage applied on the graphene membrane, thereby having a programmable function. We also use COMSOL to simulate the electric field distribution diagram to explain the underlying physical mechanism. The programmable broadband adjustable absorber proposed in this paper has potential application prospects in the fields of optical equipment, information transmission, digital coding and artificial intelligence (AI).

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The Influence of Stoichiometry on the Index of Refraction of Cobalt Ferrite Samples at Terahertz Frequencies

MRS Advances ◽

10.1557/adv.2017.355 ◽

2017 ◽

Vol 2 (58-59) ◽

pp. 3663-3666

Author(s):

Alan F. N. Boss ◽

Antonio C. C. Migliano ◽

Ingrid Wilke

Keyword(s):

Cobalt Ferrite ◽

State Of The Art ◽

Secondary Phase ◽

Index Of Refraction ◽

Terahertz Frequency ◽

Chemical Homogeneity ◽

X Ray ◽

Nickel Cobalt ◽

Cobalt Ferrites ◽

Terahertz Frequencies

ABSTRACT We report an experimental study on the terahertz frequency dielectric properties of manganese cobalt ferrites (MnxCo1−xFe2O4) and nickel cobalt ferrites (NixCo1-xFe2O4) with three different stoichiometry each, x=0.3, x=0.5 and 0.7. Particularly, we present a comparison and discussion of the terahertz frequency indices of refraction of these two ferrites compositions. MnxCo1−xFe2O4 and NixCo1-xFe2O4 pellets with different Mn/Co and Ni/Co ratios (x=0.3, x=0.5 and x=0.7) were prepared by state-of-the-art ceramic processing. The morphology and chemical homogeneity of these ferrites were characterized by energy dispersive x-ray spectroscopy. We observed that the indexes of refraction for manganese cobalt ferrites are 3.22, 3.71 and 3.67 for ratios of 0.3, 0.5 and 0.7, respectively. In the case of nickel cobalt ferrite, the indexes of refraction are 3.53, 3.57 and 3.47 for ratios of 0.3, 0.5 and 0.7 respectively. We notice a substantial difference in the index of refraction for the Mn0.3Co0.7Fe2O4. This difference may be correlated to a secondary phase formed in this sample.

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A MoS2-based broadband and multiband metamaterial absorber in the visible band

Modern Physics Letters B ◽

10.1142/s0217984920503972 ◽

2020 ◽

Vol 34 (34) ◽

pp. 2050397

Author(s):

Shitong Song ◽

Fanyi Liu ◽

Limei Qi ◽

Zhao Zhang ◽

Haodong Wang ◽

...

Keyword(s):

Physical Mechanism ◽

Impedance Matching ◽

Dielectric Substrate ◽

Metamaterial Absorber ◽

Matching Theory ◽

Broadband Absorber ◽

Broadband Absorption ◽

Visible Band ◽

Relative Bandwidth ◽

New Perspective

A broadband MoS2-based absorber composed of Ag rod/MoS2/dielectric/Ag is proposed in the visible band. The relative bandwidth is 65% for the absorption above 80%. The absorber also has the properties of polarization-independence and wide-angle absorption. Impedance matching theory is used to analyze the physical mechanism of the broadband absorption. By investigating the absorption property of each part of the absorber, it is found that the absorption is enhanced by introducing the two-dimensional material MoS2. The broadband absorber can be changed to be multiband absorber by changing the thickness of dielectric substrate. This structure provides a new perspective to enhance absorption in the visible band and has promising applications in solar cells.

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Design and Analysis of High Absorber Based on Sub-Wavelength Grating Structure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.872.89 ◽

2017 ◽

Vol 872 ◽

pp. 89-93

Author(s):

Kun Li ◽

Yu Qing Xiong ◽

Sheng Zhu Cao ◽

Kai Feng Zhang ◽

Hu Wang ◽

...

Keyword(s):

Finite Difference Time Domain ◽

Electric Field Distribution ◽

Layer Structure ◽

Single Layer ◽

Double Layers ◽

Broadband Absorption ◽

Grating Structure ◽

Difference Time ◽

High Absorption ◽

Sub Wavelength

Two kinds of high absorber were designed based on sub-wavelength grating structure for aluminum substrate. The absorption and electric field distribution of these two structures were calculated by using the finite difference time domain method. One absorber was obtained by using Al2O3/SiO2 double layers and Al rectangular sub-wavelength layer which has high absorption peaks both in TE polarization and TM polarization in infrared spectrum. Another absorber was a single layer structure with a triangular sub-wavelength grating structure which had a broadband absorption in TE polarization at spectral range of 300-1000nm.Simulation results showed that the absorption of this absorber increase and then decreases with the increasing of the height of sub-wavelength grating. The average absorption reached the maximum when the height of grating was 800nm.

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Numerical Demonstrations of Negative Refraction Properties in a Closed-Ring Pair Metamaterial under Parallel Incidence

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.815.121 ◽

2013 ◽

Vol 815 ◽

pp. 121-125

Author(s):

Fang Fang

Keyword(s):

Field Distribution ◽

Electric Field Distribution ◽

Physical Mechanism ◽

Negative Refraction ◽

Plasma Oscillation ◽

Resonant Mode ◽

Phase Changes ◽

Electric Response ◽

Closed Ring ◽

Ring Pair

In this paper, we investigate numerically the negative refraction properties of a closed-ring pair (CRP) structure metamaterial under parallel incidence. The surface currents and magnetic-field distribution are demonstrated to the physical mechanism of the negative refraction of the CRP. It is found that the electric response is attributed to the plasma oscillation of electrons and resulting in negative permittvity. However, the magnetic response origins from the antsymmetric resonant mode, which is excited by the edges of up and down of the CRP structure. In addition, the electric field distribution based on wedge-shaped and parallelogram-shaped models and the backward wave propagation from the phase changes in the moving picture are shown to further confirm the negative refraction.

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Achieving broadband absorption and polarization conversion with a vanadium dioxide metasurface in the same terahertz frequencies

Optics Express ◽

10.1364/oe.391066 ◽

2020 ◽

Vol 28 (8) ◽

pp. 12487 ◽

Cited By ~ 18

Author(s):

Zhengyong Song ◽

Jiahe Zhang

Keyword(s):

Vanadium Dioxide ◽

Polarization Conversion ◽

Broadband Absorption ◽

Terahertz Frequencies

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Two-Terminal Active Devices for Terahertz Sources

International Journal of High Speed Electronics and Systems ◽

10.1142/s0129156403001788 ◽

2003 ◽

Vol 13 (02) ◽

pp. 395-427 ◽

Cited By ~ 14

Author(s):

G. I. Haddad ◽

J. R. East ◽

H. Eisele

Keyword(s):

Power Generation ◽

State Of The Art ◽

Great Promise ◽

Electromagnetic Spectrum ◽

Terahertz Frequency ◽

Frequency Range ◽

Terahertz Frequency Range ◽

Active Devices ◽

New Device ◽

Terahertz Frequencies

The terahertz frequency range of the electromagnetic spectrum holds great promise for many applications including sensing, imaging, and communications. However, the availability of solid-state sources with reasonable power levels is well recognized as one of the major obstacles for systems applications in this frequency range. Here, the state of the art of active two-terminal devices is reviewed and high-lighted with some exemplary experimental results. The potential, capabilities, and limitations of two-terminal devices regarding power generation at terahertz frequencies are discussed. Furthermore, a new device is described that has the potential of circumventing some of the limitations of existing devices.

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Encoding Method and Pseudohomophone Effects in Episodic Recognition

PsycEXTRA Dataset ◽

10.1037/e528942014-612 ◽

2014 ◽

Author(s):

Sonny Li ◽

Marcus Taft

Keyword(s):

Encoding Method

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Time Dependances of the Resistance Coefficients of Polymeric Materials

INEOS OPEN ◽

10.32931/io2016a ◽

2020 ◽

Vol 3 ◽

Author(s):

A. V. Matseevich ◽

◽

A. A. Askadskii ◽

Keyword(s):

Time Dependence ◽

Physical Mechanism ◽

Polymeric Materials ◽

Resistance Coefficient ◽

Constant Stress ◽

Time To Rupture ◽

Structure Sensitive ◽

Material Durability ◽

Resistance Coefficients ◽

Extremal Character

One of the possible approaches to the analysis of a physical mechanism of time dependence for the resistance coefficients of materials is suggested. The material durability at the constant stress is described using the Zhurkov and Gul' equations and the durability at the alternating stress—using the Bailey criterion. The low strains lead to structuring of a material that is reflected in a reduction of the structure-sensitive coefficient in these equations. This affords 20% increase in the durability. The dependence of the resistance coefficient assumes an extremal character; the maximum is observed at the time to rupture lg tr ≈ 2 (s).

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