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

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2824
Author(s):  
Qiong Wang ◽  
Zhengbiao Ouyang ◽  
Mi Lin ◽  
Yaoxian Zheng
Keyword(s):  
Graphene Layer ◽  
Chemical Potential ◽  
Superior Performance ◽  
Monolayer Graphene ◽  
Geometrical Parameters ◽  
Complete Absorption ◽  
Absorption Performance ◽  
Two Peaks ◽  
Cavity Effect ◽  
Coupled Cavity

Graphene-based devices have important applications attributed to their superior performance and flexible tunability in practice. In this paper, a new kind of absorber with monolayer graphene sandwiched between two layers of dielectric rings is proposed. Two peaks with almost complete absorption are realized. The mechanism is that the double-layer dielectric rings added to both sides of the graphene layer are equivalent to resonators, whose double-side coupled-cavity effect can make the incident electromagnetic wave highly localized in the upper and lower surfaces of graphene layer simultaneously, leading to significant enhancement in the absorption of graphene. Furthermore, the influence of geometrical parameters on absorption performance is investigated in detail. Also, the device can be actively manipulated after fabrication through varying the chemical potential of graphene. As a result, the frequency shifts of the two absorption peaks can reach as large as 2.82 THz/eV and 3.83 THz/eV, respectively. Such a device could be used as tunable absorbers and other functional devices, such as multichannel filters, chemical/biochemical modulators and sensors.

scholarly journals Smart optical cross dipole nanoantenna with multibeam pattern

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seyyed Mohammad Mehdi Moshiri ◽  
Najmeh Nozhat
Keyword(s):  
Radiation Pattern ◽  
Chemical Potential ◽  
Monolayer Graphene ◽  
Absorption Characteristic ◽  
Radiation Beam ◽  
Directional Radiation ◽  
Chemical Potentials ◽  
Different Types ◽  
Absorption Power ◽  
Maximum Directivity

AbstractIn this paper, an optical smart multibeam cross dipole nano-antenna has been proposed by combining the absorption characteristic of graphene and applying different arrangements of directors. By introducing a cross dipole nano-antenna with two V-shaped coupled elements, the maximum directivity of 8.79 dBi has been obtained for unidirectional radiation pattern. Also, by applying various arrangements of circular sectors as director, different types of radiation pattern such as bi- and quad-directional have been attained with directivities of 8.63 and 8.42 dBi, respectively, at the wavelength of 1550 nm. The maximum absorption power of graphene can be tuned by choosing an appropriate chemical potential. Therefore, the radiation beam of the proposed multibeam cross dipole nano-antenna has been controlled dynamically by applying a monolayer graphene. By choosing a suitable chemical potential of graphene for each arm of the suggested cross dipole nano-antenna without the director, the unidirectional radiation pattern shifts ± 13° at the wavelength of 1550 nm. Also, for the multibeam nano-antenna with different arrangements of directors, the bi- and quad-directional radiation patterns have been smartly modified to uni- and bi-directional ones with the directivities of 10.1 and 9.54 dBi, respectively. It is because of the graphene performance as an absorptive or transparent element for different chemical potentials. This feature helps us to create a multipath wireless link with the capability to control the accessibility of each receiver.

scholarly journals Coupling of waveguide mode and graphene plasmons

2021 ◽  
Vol 255 ◽  
pp. 07002
Author(s):  
Jiří Petráček ◽  
Jiří Čtyroký ◽  
Vladimír Kuzmiak ◽  
Pavel Kwiecien ◽  
Ivan Richter
Keyword(s):  
Low Power ◽  
Graphene Layer ◽  
Waveguide Mode ◽  
Chemical Potential ◽  
Temperature Sensing ◽  
Graphene Layers ◽  
Optical Wavelength ◽  
Electro Optic ◽  
Photonic Waveguides ◽  
Graphene Plasmons

Photonic waveguides with graphene layers have been recently studied for their potential as fast and low-power electro-optic modulators with small footprints. We show that in the optical wavelength range of 1.55 μm, surface plasmons supported by the graphene layer with the chemical potential exceeding ~0.5 eV can couple with the waveguide mode and affect its propagation. This effect might be possibly utilized in technical applications as a very low-power amplitude modulation, temperature sensing, etc.

scholarly journals “Fast” Plasmons Propagating in Graphene Plasmonic Waveguides with Negative Index Metamaterial Claddings

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1637
Author(s):  
Zeyang Zhao ◽  
Shaojian Su ◽  
Hengjie Zhou ◽  
Weibin Qiu ◽  
Pingping Qiu ◽  
...  
Keyword(s):  
Group Velocity ◽  
Integrated Circuit ◽  
Negative Refraction ◽  
Chemical Potential ◽  
Refraction Index ◽  
Monolayer Graphene ◽  
Plasmonic Waveguides ◽  
Chemical Potential Difference ◽  
Positive Group ◽  
The Core

We propose the monolayer graphene plasmonic waveguide (MGPW), which is composed of graphene core sandwiched by two graphene metamaterial (GMM) claddings and investigate the properties of plasmonic modes propagating in the waveguide. The effective refraction index of the GMMs claddings takes negative (or positive) at the vicinity of the Dirac-like point in the band structure. We show that when the effective refraction index of the GMMs is positive, the plasmons travel forward in the MGPW with a positive group velocity (vg > 0, vp > 0). In contrast—for the negative refraction index GMM claddings—a negative group velocity of the fundamental mode (vg < 0, vp > 0) appears in the proposed waveguide structure when the core is sufficiently narrow. A forbidden band appears between the negative and positive group velocity regions, which is enhanced gradually as the width of the core increases. On the other hand, one can overcome this limitation and even make the forbidden band disappear by increasing the chemical potential difference between the nanodisks and the ambient graphene of the GMM claddings. The proposed structure offers a novel scheme of on-chip electromagnetic field and may find significant applications in the future high density plasmonic integrated circuit technique.

Graphene-based microwave coaxial antenna for microwave ablation: thermal analysis

2020 ◽  
pp. 1-9
Author(s):  
Burak Uzman ◽  
Adem Yilmaz ◽  
Hulusi Acikgoz ◽  
Raj Mittra
Keyword(s):  
Relaxation Time ◽  
Microwave Ablation ◽  
Graphene Layer ◽  
Heat Dissipation ◽  
Chemical Potential ◽  
Treatment Time ◽  
Slot Antenna ◽  
Necrotic Tissue ◽  
Cancerous Tissue ◽  
High Impedance

Abstract In this study, the problem of backward heating in microwave ablation technique is examined and an electromagnetic solution based on the use of high impedance graphene material is presented for its mitigation. In this context, a one-atom-thick graphene layer is added on the coaxial double slot antenna. In addition to the electromagnetic behavior, thermal effects caused by the graphene-covered antenna are emphasized. The graphene's conductivity being highly dependent on its chemical potential and the relaxation time, a parametric study is performed to determine a range of tolerances within which the graphene-coated antenna outperform a typical graphene-free antenna. The range of values is found to be 0 < μ c < 0.5 eV and τ < 0.4 ps, for the chemical potential and the relaxation time, respectively. The backward heating problem being prevented, the ablation region is ensured to be spherical around the tip of the antenna. Effects of the graphene layer to the heat dissipation in the tissue, the necrotic tissue ratio (damage to the cancerous tissue of the caused by electromagnetic energy), and the treatment time using the coaxial double slot antenna were examined. The results show that the heat dissipation is concentrated around the slots (region of cancerous tissue) and a higher necrotic tissue ratio can be achieved with a graphene-covered double slot antenna in a shorter time.

Customizing coaxial stacking VS2 nanosheets for dual-band microwave absorption with superior performance in the C- and Ku-bands

2020 ◽  
Vol 8 (17) ◽  
pp. 5923-5933 ◽  
Author(s):  
Deqing Zhang ◽  
Huibin Zhang ◽  
Junye Cheng ◽  
Hassan Raza ◽  
Tingting Liu ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Strong Absorption ◽  
Superior Performance ◽  
Dual Band ◽  
Absorption Performance

Engineering microwave absorption materials with absorption in multiple bands and strong absorption performance in the C-band remains challenging to date.

Graphene Layers on Silicon Carbide Studied by Raman Spectroscopy

2008 ◽  
Vol 600-603 ◽  
pp. 567-570 ◽  
Author(s):  
Jonas Röhrl ◽  
Martin Hundhausen ◽  
Konstantin V. Emtsev ◽  
Thomas Seyller ◽  
Lothar Ley
Keyword(s):  
Silicon Carbide ◽  
Raman Spectroscopy ◽  
Light Scattering ◽  
Graphene Layer ◽  
Monolayer Graphene ◽  
Spectroscopy Study ◽  
Graphene Layers ◽  
Layer Graphene ◽  
Micro Raman Spectroscopy ◽  
Few Layer Graphene

We present a micro-Raman spectroscopy study on single- and few layer graphene (FLG) grown on the silicon terminated surface of 6H-silicon carbide (SiC). On the basis of the 2D-line (light scattering from two phonons close to the K-point in the Brillouin zone) we distinguish graphene mono- from bilayers or few layer graphene. Monolayers have a 2D-line consisting of only one component, whereas more than one component is observed for thicker graphene layers. Compared to the graphite the monolayer graphene lines are shifted to higher frequencies. We tentatively ascribe the corresponding phonon hardening to strain in the first graphene layer.

scholarly journals Исследование фотоотклика графена, полученного методом химического осаждения из газовой фазы

2020 ◽  
Vol 54 (9) ◽  
pp. 833
Author(s):  
А.В. Бабичев ◽  
С.А. Кадинская ◽  
K.Ю. Шубина ◽  
А.А. Васильев ◽  
А.А. Блохин ◽  
...  
Keyword(s):  
Graphene Layer ◽  
Optical Pumping ◽  
Chemical Vapor ◽  
Resonance Wavelength ◽  
Bragg Reflector ◽  
Structural Quality ◽  
Monolayer Graphene ◽  
Distributed Bragg Reflector ◽  
Base Structure

The paper presents the results of experiments in the fabrication and research of properties of photodetector structures on the basis of monolayer graphene produced by chemical vapor deposition. The base structure was the geometry of a Ta2O5 vertical microcavity with a lower dielectric SiO2/Ta2O5 distributed Bragg reflector with a resonance wavelength of about 850 nm. The conditions were optimized for the transfer and fabrication of mesas in the graphene layer on the microcavity surface. The diagnostics of the structural quality of graphene after the fabrication of mesas in the graphene layer and contact pads by Raman spectroscopy evidence the monolayer structure of graphene with a low singularity strength in its spectrum that is responsible for the structure imperfection. The photocurrent value at local optical pumping was measured.

scholarly journals Graphene-Based Cylindrical Pillar Gratings for Polarization-Insensitive Optical Absorbers

2019 ◽  
Vol 9 (12) ◽  
pp. 2528 ◽  
Author(s):  
Muhammad Fayyaz Kashif ◽  
Giuseppe Valerio Bianco ◽  
Tiziana Stomeo ◽  
Maria Antonietta Vincenti ◽  
Domenico de Ceglia ◽  
...  
Keyword(s):  
Near Infrared ◽  
Monolayer Graphene ◽  
Geometrical Parameters ◽  
Guided Mode ◽  
Rigorous Coupled Wave Analysis ◽  
Dielectric Gratings ◽  
Method Effects ◽  
Polarization Insensitive ◽  
Rigorous Coupled Wave ◽  
Infrared Frequencies

In this study, we present a two-dimensional dielectric grating which allows achieving high absorption in a monolayer graphene at visible and near-infrared frequencies. Dielectric gratings create guided-mode resonances that are exploited to effectively couple light with the graphene layer. The proposed structure was numerically analyzed through a rigorous coupled-wave analysis method. Effects of geometrical parameters and response to the oblique incidence of the plane wave were studied. Numerical results reveal that light absorption in the proposed structure is almost insensitive to the angle of the impinging source over a considerable wide angular range of 20°. This may lead to the development of easy to fabricate and experimentally viable graphene-based absorbers in the future.

Enhanced Photon Tunneling by Surface Plasmon–Phonon Polaritons in Graphene/hBN Heterostructures

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
B. Zhao ◽  
Z. M. Zhang
Keyword(s):  
Heat Transfer ◽  
Surface Plasmon ◽  
Chemical Potential ◽  
Near Field ◽  
Tunneling Probability ◽  
Monolayer Graphene ◽  
Field Energy ◽  
Support Surface ◽  
Photon Tunneling ◽  
Phonon Polaritons

Enhancing photon tunneling probability is the key to increasing the near-field radiative heat transfer between two objects. It has been shown that hexagonal boron nitride (hBN) and graphene heterostructures can enable plentiful phononic and plasmonic resonance modes. This work demonstrates that heterostructures consisting of a monolayer graphene on an hBN film can support surface plasmon–phonon polaritons that greatly enhance the photon tunneling and outperform individual structures made of either graphene or hBN. Both the thickness of the hBN films and the chemical potential of graphene can affect the tunneling probability, offering potential routes toward passive or active control of near-field heat transfer. The results presented here may facilitate the system design for near-field energy harvesting, thermal imaging, and radiative cooling applications based on two-dimensional materials.

Improving the depth resolution of STEM-ADF sectioning by 3D deconvolution

Microscopy ◽  
2020 ◽  
Author(s):  
A Ishizuka ◽  
K Ishizuka ◽  
R Ishikawa ◽  
N Shibata ◽  
Y Ikuhara ◽  
...  
Keyword(s):  
Graphene Layer ◽  
Depth Resolution ◽  
Real Space ◽  
Dark Field ◽  
Entropy Method ◽  
Three Dimensions ◽  
Single Atom ◽  
Monolayer Graphene ◽  
Scanning Transmission ◽  
Annular Dark Field

Abstract Although the possibility of locating single atom in three dimensions using the scanning transmission of electron microscope (STEM) has been discussed with the advent of aberration correction technology, it is still a big challenge. In this report we have developed deconvolution routines based on maximum entropy method (MEM) and Richardson-Lucy algorithm (RLA), which are applicable to the STEM annular dark-field (ADF) though-focus images to improve the depth resolution. The new 3D deconvolution routines require a limited defocus-range of STEM-ADF images that covers a whole sample and some vacuum regions. Since the STEM-ADF probe is infinitely elongated along the optical axis, a 3D convolution is performed with a 2D convolution over xy-plane using the 2D fast Fourier transform (FFT) in reciprocal space, and a 1D convolution along the z-direction in real space. Using our new deconvolution routines, we have processed simulated focal series of STEM-ADF images for single Ce dopants embedded in wurtzite-type AlN. Applying the MEM, the Ce peaks are clearly localized along the depth, and the peak width is reduced down to almost one half. We also applied the new deconvolution routines to experimental focal series of STEM-ADF images of a monolayer graphene. The RLA gives smooth and high-P/B ratio scattering distribution, and the graphene layer can be easily detected. Using our deconvolution algorithms, we can determine the depth locations of the heavy dopants and the graphene layer within the precision of 0.1 and 0.2 nm, respectively, Thus, the deconvolution must be extremely useful for the optical sectioning with 3D STEM-ADF images.

Sign in / Sign up

Export Citation Format

Share Document