scholarly journals Electrically Tunable Broadband Terahertz Absorption with Hybrid-Patterned Graphene Metasurfaces

Nanomaterials ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 562 ◽  
Author(s):  
Longfang Ye ◽  
Xin Chen ◽  
Guoxiong Cai ◽  
Jinfeng Zhu ◽  
Na Liu ◽  
...  
Keyword(s):  
Incident Angle ◽  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Single Layer Graphene ◽  
Terahertz Waves ◽  
Broadband Absorption ◽  
Terahertz Sensing ◽  
Axisymmetric Configuration ◽  
Broadband Terahertz

We numerically demonstrate a broadband terahertz (THz) absorber that is based on a hybrid-patterned graphene metasurface with excellent properties of polarization insensitivity, wide-angle, and active tunability. Our design is made up of a single-layer graphene with periodically arranged hybrid square/disk/loop patterns on a multilayer structure. We find that broadband absorption with 90% terahertz absorbance and the fractional bandwidth of 84.5% from 1.38 THz to 3.4 THz can be achieved. Because of the axisymmetric configuration, the absorber demonstrates absolute polarization independence for both transverse electric (TE) and transverse magnetic (TM) polarized terahertz waves under normal incidence. We also show that a bandwidth of 60% absorbance still remains 2.7 THz, ranging from 1.3 THz to 4 THz, for a wide incident angle ranging from 0° to 60°. Finally, we find that by changing the graphene Fermi energy from 0.7 eV to 0 eV, the absorbance of the absorbers can be easily tuned from more than 90% to lower than 20%. The proposed absorber may have promising applications in terahertz sensing, detecting, imaging, and cloaking.

scholarly journals Efficient Broadband Truncated-Pyramid-Based Metamaterial Absorber in the Visible and Near-Infrared Regions

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 784 ◽  
Author(s):  
Phuc Toan Dang ◽  
Tuan V. Vu ◽  
Jongyoon Kim ◽  
Jimin Park ◽  
Van-Chuc Nguyen ◽  
...  
Keyword(s):  
Communication Systems ◽  
Near Infrared ◽  
Cell Structure ◽  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Broadband Absorption ◽  
Polarization Insensitive ◽  
Truncated Pyramid

We present a design of an ultra-broadband metamaterial absorber in the visible and near- infrared regions. The unit cell structure consists of a single layer of metallic truncated-pyramid resonator-dielectric-metal configuration, which results in a high absorption over a broad wavelength range. The absorber exhibits 98% absorption at normal incidence spanning a wideband range of 417–1091 nm, with >99% absorption within 822–1054 nm. The broadband absorption stability maintains 95% at large incident angles up to 40° for the transverse electric (TE)-mode and 20° for the transverse magnetic (TM)-mode. Furthermore, the polarization-insensitive broadband absorption is presented in this paper by analyzing absorption performance with various polarization angles. The proposed absorber can be applied for applications such as solar cells, infrared detection, and communication systems thanks to the convenient and compatible bandwidth for electronic THz sources.

scholarly journals A Co-Polarization Broadband Radar Absorber for RCS Reduction

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1668 ◽  
Author(s):  
Thtreswar Beeharry ◽  
Riad Yahiaoui ◽  
Kamardine Selemani ◽  
Habiba Ouslimani
Keyword(s):  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Center Frequency ◽  
Transmission Line Model ◽  
Absorption Mechanism ◽  
Broadband Absorption ◽  
Electric And Magnetic Fields ◽  
Physical Insight ◽  
Good Agreement

In this article, a single layer co-polarization broadband radar absorber is presented. Under normal incidence, it achieves at least 90% of absorption from 5.6 GHz to 9.1 GHz for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Our contribution and the challenge of this work is to achieve broadband absorption using a very thin single layer dielectric and it is achieved by rotating the resonating element by 45°. An original optimized Underlined U shape has been developed for the resonating element which provides a broadband co-polarization absorption. The structure is 12.7 times thinner than the wavelength at the center frequency. To understand the absorption mechanism, the transmission line model of an absorber and the three near unity absorption peaks at 5.87 GHz, 7.16 GHz and 8.82 GHz have been used to study the electric and magnetic fields. The physical insight of how the three near unity absorption peaks are achieved has also been discussed. After fabricating the structure, the measurements were found to be in good agreement with the simulation results. Furthermore, with the proposed original UUSR resonating element, the operational bandwidth to thickness ratio of 6.43 is obtained making the proposed UUSR very competitive.

scholarly journals Dual-Tunable Broadband Terahertz Absorber Based on a Hybrid Graphene-Dirac Semimetal Structure

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1096
Author(s):  
Jiali Wu ◽  
Xueguang Yuan ◽  
Yangan Zhang ◽  
Xin Yan ◽  
Xia Zhang
Keyword(s):  
Fermi Energy ◽  
Incident Angle ◽  
Normal Incidence ◽  
Surface Conductivity ◽  
Chemical Doping ◽  
Absorption Bandwidth ◽  
Terahertz Absorber ◽  
Dirac Semimetal ◽  
High Absorption ◽  
Broadband Terahertz

A dual-controlled tunable broadband terahertz absorber based on a hybrid graphene-Dirac semimetal structure is designed and studied. Owing to the flexible tunability of the surface conductivity of graphene and relative permittivity of Dirac semimetal, the absorption bandwidth can be tuned independently or jointly by shifting the Fermi energy through chemical doping or applying gate voltage. Under normal incidence, the device exhibits a high absorption larger than 90% over a broad range of 4.06–10.7 THz for both TE and TM polarizations. Moreover, the absorber is insensitive to incident angles, yielding a high absorption over 90% at a large incident angle of 60° and 70° for TE and TM modes, respectively. The structure shows great potential in miniaturized ultra-broadband terahertz absorbers and related applications.

scholarly journals Bidirectional Angle-Tolerant Polarization-Tuned Filtering and Wide-Range Refractive Index Sensing Based on Metal Film Coated Nanograting

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Wenli Cui ◽  
Qiannan Wu ◽  
Bo Chen ◽  
Xufeng Li ◽  
Xiaolin Luo ◽  
...  
Keyword(s):  
Refractive Index ◽  
Metal Film ◽  
High Performance ◽  
Incident Angle ◽  
Single Layer ◽  
Transverse Magnetic ◽  
Photonic Devices ◽  
Biomedical Sensors ◽  
Dual Channel ◽  
Wide Range

The miniaturization and integration of photonic devices are new requirements in the fast-growing optics field. In this paper, we focus on a feature-rich sub-wavelength nanograting-coated single-layer metal film. The numerical results show that the reflection behaviors of this proposed structure can realize bidirectional dual-channel ultra-narrowband polarized filtering and bidirectional wavelength-modulated sensing in a wide refractive index (RI) range from 1.0 to 1.4 for incident angle of 10° with transverse-magnetic (TM) polarized illumination at wavelengths between 550 nm to 1500 nm. Moreover, the bidirectional properties of filtering and sensing are not obviously decreased when increasing incident angle from 10° to 30°, and decreasing incident angle from 10° to 0°. The calculated RI sensitivity can be up to 592 nm/RIU with a high figure of merit (FOM) of 179.4 RIU−1. More to the point, this nanograting has a simple structure and is less sensitive to the height and shape of grating ridge, which provides great convenience for the fabrication of devices. The other thing that is going on is that this structure can also realize synchronously tunable color filtering, including green to red, with high color purity in the visible band by choosing the period. The underlying physical mechanism is analyzed in detail, and is primarily attributed to surface plasmon polariton (SPP) resonance and dipole resonance at double plasmon resonance wavelengths. This work has tremendous potential in developing multipurpose and high-performance integrated optical devices such as spectral filters, colored displays and plasmon biomedical sensors.

scholarly journals A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 860 ◽  
Author(s):  
Fu Chen ◽  
Yongzhi Cheng ◽  
Hui Luo
Keyword(s):  
Energy Level ◽  
Graphene Sheet ◽  
Fermi Energy ◽  
Single Layer ◽  
Dielectric Substrate ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Absorption Capacity ◽  
Fermi Energy Level ◽  
Broadband Absorption

We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

scholarly journals Reflected and transmitted second harmonics generation by an obliquely p-polarized laser pulse incident on vacuum-magnetized plasma interface

2017 ◽  
Vol 35 (3) ◽  
pp. 551-560
Author(s):  
M. Ghorbanalilu ◽  
Z. Heidari
Keyword(s):  
Magnetic Field ◽  
Laser Pulse ◽  
Critical Angle ◽  
Incident Angle ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Magnetized Plasma ◽  
Laser Plasma Interaction ◽  
Simultaneous Process

AbstractThe transmitted and reflected second harmonics (SH) generation by an oblique p-polarized laser pulse irradiated on vacuum-magnetized plasma interface is investigated. The laser pulse propagates through a homogenous, underdense, and transversely magnetized plasma. The transverse magnetic field plays the role of a self-generated magnetic field produced in laser plasma interaction. It is shown that if the transmitted and reflected SH components investigated as a simultaneous process, the maximum SH power deviates from previous reports specially near the critical angle. The deviation increases with laser field intensity and plasma density. The results reveal that the conversion efficiency increases slightly by increasing incident angle and drastically enhances near the critical angle. We show that the transmitted SH power decreases by increasing the magnetic field strength, in contrast to the normal incidence, which the SH power is increased. The comparison revealed that the SH efficiency is greater for transmitted component, while the reflected component is more proper for technical and experimental applications. This paper not only conforms the previous reports for angle far from the critical but also modifies them for the SH generation near the critical angle. Moreover, this paper gives a new insight for SH generation by a magnetized plasma.

scholarly journals Polarization-Insensitive Broadband THz Absorber Based on Circular Graphene Patches

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2709
Author(s):  
Jiajia Qian ◽  
Jun Zhou ◽  
Zheng Zhu ◽  
Zhenzhen Ge ◽  
Shuting Wu ◽  
...  
Keyword(s):  
Incident Angle ◽  
Structural Parameters ◽  
Single Layer Graphene ◽  
Localized Surface Plasmon ◽  
Wide Angle ◽  
Absorption Bandwidth ◽  
Broadband Absorption ◽  
Simulation And Optimization ◽  
Symmetrical Configuration ◽  
Polarization Insensitive

A polarization-insensitive broadband terahertz absorber based on single-layer graphene metasurface has been designed and simulated, in which the graphene metasurface is composed of isolated circular patches. After simulation and optimization, the absorption bandwidth of this absorber with more than 90% absorptance is up to 2 THz. The simulation results demonstrate that the broadband absorption can be achieved by combining the localized surface plasmon (LSP) resonances on the graphene patches and the resonances caused by the coupling between them. The absorption bandwidth can be changed by changing the chemical potential of graphene and the structural parameters. Due to the symmetrical configuration, the proposed absorber is completely insensitive to polarization and have the characteristics of wide angle oblique incidence that they can achieve broadband absorption with 70% absorptance in the range of incident angle from 0° to 50° for both TE and TM polarized waves. The flexible and simple design, polarization insensitive, wide-angle incident, broadband and high absorption properties make it possible for our proposed absorber to have promising applications in terahertz detection, imaging and cloaking objects.

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

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1410 ◽  
Author(s):  
Hongyang Shen ◽  
Fengxiang Liu ◽  
Chunyang Liu ◽  
Dong Zeng ◽  
Banghong Guo ◽  
...  
Keyword(s):  
Absorption Band ◽  
Dielectric Layer ◽  
Incident Angle ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Photonic Devices ◽  
Geometric Parameters ◽  
Polarization Angle ◽  
Terahertz Absorber ◽  
Polarization Insensitive

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.

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