scholarly journals Towards Perfect Absorption of Single Layer CVD Graphene in an Optical Resonant Cavity: Challenges and Experimental Achievements

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 352
Author(s):  
Abedin Nematpour ◽  
Maria Luisa Grilli ◽  
Laura Lancellotti ◽  
Nicola Lisi
Keyword(s):  
Incident Angle ◽  
Resonant Cavity ◽  
Experimental Studies ◽  
Single Layer ◽  
Absorption Enhancement ◽  
Perfect Absorption ◽  
Cvd Graphene ◽  
Graphene Layers ◽  
Absorption Increase ◽  
Fabry Perot

Graphene is emerging as a promising material for the integration in the most common Si platform, capable to convey some of its unique properties to fabricate novel photonic and optoelectronic devices. For many real functions and devices however, graphene absorption is too low and must be enhanced. Among strategies, the use of an optical resonant cavity was recently proposed, and graphene absorption enhancement was demonstrated, both, by theoretical and experimental studies. This paper summarizes our recent progress in graphene absorption enhancement by means of Si/SiO2-based Fabry–Perot filters fabricated by radiofrequency sputtering. Simulations and experimental achievements carried out during more than two years of investigations are reported here, detailing the technical expedients that were necessary to increase the single layer CVD graphene absorption first to 39% and then up to 84%. Graphene absorption increased when an asymmetric Fabry–Perot filter was applied rather than a symmetric one, and a further absorption increase was obtained when graphene was embedded in a reflective rather than a transmissive Fabry–Perot filter. Moreover, the effect of the incident angle of the electromagnetic radiation and of the polarization of the light was investigated in the case of the optimized reflective Fabry–Perot filter. Experimental challenges and precautions to avoid evaporation or sputtering induced damage on the graphene layers are described as well, disclosing some experimental procedures that may help other researchers to embed graphene inside PVD grown materials with minimal alterations.

scholarly journals The electronic thickness of graphene

2020 ◽  
Vol 6 (11) ◽  
pp. eaay8409 ◽  
Author(s):  
Peter Rickhaus ◽  
Ming-Hao Liu ◽  
Marcin Kurpas ◽  
Annika Kurzmann ◽  
Yongjin Lee ◽  
...  
Keyword(s):  
Graphene Layer ◽  
Finite Thickness ◽  
Tight Binding ◽  
Single Layer ◽  
Energy Difference ◽  
Quantum Capacitance ◽  
Density Range ◽  
Dielectric Thickness ◽  
Graphene Layers ◽  
Fabry Perot

When two dimensional crystals are atomically close, their finite thickness becomes relevant. Using transport measurements, we investigate the electrostatics of two graphene layers, twisted by θ = 22° such that the layers are decoupled by the huge momentum mismatch between the K and K′ points of the two layers. We observe a splitting of the zero-density lines of the two layers with increasing interlayer energy difference. This splitting is given by the ratio of single-layer quantum capacitance over interlayer capacitance Cm and is therefore suited to extract Cm. We explain the large observed value of Cm by considering the finite dielectric thickness dg of each graphene layer and determine dg ≈ 2.6 Å. In a second experiment, we map out the entire density range with a Fabry-Pérot resonator. We can precisely measure the Fermi wavelength λ in each layer, showing that the layers are decoupled. Our findings are reproduced using tight-binding calculations.

Experimental demonstration of mid-IR absorption enhancement in single layer CVD graphene

2020 ◽  
Vol 45 (14) ◽  
pp. 3861 ◽  
Author(s):  
Abedin Nematpour ◽  
Nicola Lisi ◽  
Rosa Chierchia ◽  
Maria Luisa Grilli
Keyword(s):  
Single Layer ◽  
Absorption Enhancement ◽  
Ir Absorption ◽  
Experimental Demonstration ◽  
Cvd Graphene

scholarly journals Si Substrate-Based Metamaterials for Ultrabroadband Perfect Absorption in Visible Regime

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Qi Han ◽  
Lei Jin ◽  
Yongqi Fu ◽  
Weixing Yu
Keyword(s):  
Incident Angle ◽  
Si Substrate ◽  
Perfect Absorption ◽  
Photonic Circuits ◽  
Si Photonics ◽  
Fabry Perot ◽  
Absorbing Property ◽  
Photonics Devices

We report the broadband efficient light absorbing property of a structure of quadrangular frustum pyramid array in visible regime. The structure can absorb light efficiently with an average absorptivity of 0.98 over the whole visible waveband. In addition, it is found that this kind of super light absorbing can maintain an average of 0.9 for a wide incident angle range. The perfect absorbing property of the metamaterial-based nanoring array is attributed to the effect of the Fabry-Perot resonance. The structure is possible to be used as a type of Si photonics devices in future photonic circuits.

Experimental near infrared absorption enhancement of graphene layers in an optical resonant cavity

2019 ◽  
Vol 30 (44) ◽  
pp. 445201 ◽  
Author(s):  
Abedin Nematpour ◽  
Nicola Lisi ◽  
Angela Piegari ◽  
Laura Lancellotti ◽  
Guohang Hu ◽  
...  
Keyword(s):  
Infrared Absorption ◽  
Near Infrared ◽  
Resonant Cavity ◽  
Absorption Enhancement ◽  
Graphene Layers

scholarly journals A Perfect Absorber Based on Similar Fabry-Perot Four-Band in the Visible Range

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 488 ◽  
Author(s):  
Pinghui Wu ◽  
Congfen Zhang ◽  
Yijun Tang ◽  
Bin Liu ◽  
Li Lv
Keyword(s):  
Near Infrared ◽  
Layer Structure ◽  
Incident Angle ◽  
Middle Layer ◽  
Absorption Efficiency ◽  
Visible Range ◽  
Polarization Angle ◽  
Perfect Absorber ◽  
Perfect Absorption ◽  
Fabry Perot

A simple metamaterial absorber is proposed to achieve near-perfect absorption in visible and near-infrared wavelengths. The absorber is composed of metal-dielectric-metal (MIM) three-layer structure. The materials of these three-layer structures are Au, SiO2, and Au. The top metal structure of the absorber is composed of hollow three-dimensional metal rings regularly arranged periodically. The results show that the high absorption efficiency at a specific wavelength is mainly due to the resonance of the Fabry–Perot effect (FP) in the intermediate layer of the dielectric medium, resulting in the resonance light being trapped in the middle layer, thus improving the absorption efficiency. The almost perfect multiband absorption, which is independent of polarization angle and insensitivity of incident angle, lends the absorber great application prospects for filtering and optoelectronics.

Graphene-based dual-band near-perfect absorption in Rabi splitting between topological edge and Fabry-Perot cavity modes

2021 ◽  
Author(s):  
Tongtong Wei ◽  
zengping su ◽  
yueke wang
Keyword(s):  
Strong Coupling ◽  
Fermi Energy ◽  
Incident Angle ◽  
Optical Switches ◽  
Dual Band ◽  
Perfect Absorption ◽  
Rabi Splitting ◽  
Cavity Modes ◽  
Fabry Perot ◽  
Mode Tem

Abstract We propose a graphene embedded one-dimensional (1D) topological photonic crystal heterostructure, where the strong coupling occurs between the topological edge mode (TEM) and the Fabry-Perot cavity mode (CM). It is shown that the strong coupling leads to the hybridization between TEM and CM, with a Rabi splitting. Based on finite element method (FEM), a dual-band near-perfect absorption, which can be actively tuned by the Fermi energy of the graphene and incident angle, is found in the Rabi splitting region. Theoretically, the TEM-CM coupling can be analyzed by the classic oscillator model. In particular, when the Fermi energy of graphene slightly increases around 0.4 eV, the dual-band near-perfect absorption shows a rapid decrease from one to zero, which offers a possible way for absorption optical switches.

scholarly journals Extraordinary Optical Transmission by Hybrid Phonon–Plasmon Polaritons Using hBN Embedded in Plasmonic Nanoslits

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1567
Author(s):  
Shinpei Ogawa ◽  
Shoichiro Fukushima ◽  
Masaaki Shimatani
Keyword(s):  
Optical Transmission ◽  
Hexagonal Boron Nitride ◽  
Incident Angle ◽  
Optical Filters ◽  
Extraordinary Optical Transmission ◽  
Light Manipulation ◽  
Rigorous Coupled Wave Analysis ◽  
Fabry Perot ◽  
Hyperbolic Dispersion ◽  
Rigorous Coupled Wave

Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel light manipulation. In this study, the transmission properties of embedded hBN in metallic one-dimensional (1D) nanoslits were theoretically investigated using a rigorous coupled wave analysis method. Extraordinary optical transmission (EOT) was observed in the type-II Reststrahlen band, which was attributed to the hybridization of HPPs in hBN and SPRs in 1D nanoslits. The calculated electric field distributions indicated that the unique Fabry–Pérot-like resonance was induced by the hybridization of HPPs and SPRs in an embedded hBN cavity. The trajectory of the confined light was a zigzag owing to the hyperbolicity of hBN, and its resonance number depended primarily on the aspect ratio of the 1D nanoslit. Such an EOT is also independent of the slit width and incident angle of light. These findings can not only assist in the development of improved strategies for the extreme confinement of IR light but may also be applied to ultrathin optical filters, advanced photodetectors, and optical devices.

scholarly journals Independently Tunable Multipurpose Absorber with Single Layer of Metal-Graphene Metamaterials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 284
Author(s):  
Chen Han ◽  
Renbin Zhong ◽  
Zekun Liang ◽  
Long Yang ◽  
Zheng Fang ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Fermi Level ◽  
Potential Application ◽  
Single Layer ◽  
Wide Band ◽  
Metamaterial Absorber ◽  
Unit Cell ◽  
Perfect Absorption ◽  
Solar Energy Harvesting ◽  
Band Absorption

This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption values higher than 99%. The mechanism of absorption was analyzed theoretically. The independent tunability of the metamaterial absorber (MA) was realized by varying the Fermi level of graphene under a set of resonators. Furthermore, multi-band and wide-band absorption were observed by the proposed structure upon increasing the number of resonators and resizing them in the unit cell. The obtained results demonstrate the multipurpose performance of this type of absorber and indicate its potential application in diverse applications, such as solar energy harvesting and thermal absorbing.

Angle and polarization-independent miniaturized UWB FSS design

2021 ◽  
pp. 1-9
Author(s):  
Yanning Yuan ◽  
Yuchen Zhao ◽  
Xiaoli Xi
Keyword(s):  
Design Method ◽  
Incident Angle ◽  
Stop Band ◽  
Single Layer ◽  
Wireless Systems ◽  
Frequency Selective Surface ◽  
Ultra Wideband ◽  
Band Frequency ◽  
Gain Enhancement ◽  
Polarization Independent

Abstract A single-layer ultra-wideband (UWB) stop-band frequency selective surface (FSS) has several advantages in wireless systems, including a simple design, low debugging complexity, and an appropriate thickness. This study proposes a miniaturized UWB stop-band FSS design. The proposed FSS structure consists of a square-loop and metalized vias that are arranged on a single layer substrate; it has an excellent angle and polarization-independent characteristics. At an incident angle of 60°, the polarization response frequencies of the transverse electric and magnetic modes only shifted by 0.003 f0 and 0.007 f0, respectively. The equivalent circuit models of the square-loop and metallized vias structure are analysed and the accuracy of the calculation is evaluated by comparing the electromagnetic simulation. The 20 × 20 array constitutes an FSS reflector with a unit size of 4.2 mm × 4.2 mm (less than one-twentieth of the wavelength of 3 GHz), which realizes an UWB quasi-constant gain enhancement (in-band flatness is <0.5 dB). Finally, the simulation results were verified through sample processing and measurement; consistent results were obtained. The FSS miniaturization design method proposed in this study could be applied to the design of passband FSS (complementary structure), antennas and filters, among other applications.

scholarly journals Finite Element Prediction for the Internal Stresses of (Ti,Al)N Coatings

2016 ◽  
Vol 61 (1) ◽  
pp. 149-152 ◽  
Author(s):  
L.W. Żukowska ◽  
A. Śliwa ◽  
J. Mikuła ◽  
M. Bonek ◽  
W. Kwaśny ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Computer Simulation ◽  
Finite Element ◽  
Experimental Studies ◽  
Single Layer ◽  
Internal Stresses ◽  
Pvd Coatings ◽  
Properties Of Coatings ◽  
Gradient Coatings ◽  
Element Method

The general topic of this paper is the computer simulation with use of finite element method (FEM) for determining the internal stresses of selected gradient and single-layer PVD coatings deposited on the sintered tool materials, including cemented carbides, cermets and Al2O3+TiC type oxide tool ceramics by cathodic arc evaporation CAE-PVD method. Developing an appropriate model allows the prediction of properties of PVD coatings, which are also the criterion of their selection for specific items, based on the parameters of technological processes. In addition, developed model can to a large extent eliminate the need for expensive and time-consuming experimental studies for the computer simulation. Developed models of internal stresses were performed with use of finite element method in ANSYS environment. The experimental values of stresses were calculated using the X-ray sin2ψ technique. The computer simulation results were compared with the experimental results. Microhardness and adhesion as well as wear range were measured to investigate the influence of stress distribution on the mechanical and functional properties of coatings. It was stated that occurrence of compressive stresses on the surface of gradient coating has advantageous influence on their mechanical properties, especially on microhardness. Absolute value reduction of internal stresses in the connection zone in case of the gradient coatings takes profitably effects on improvement the adhesion of coatings. It can be one of the most important reasons of increase the wear resistance of gradient coatings in comparison to single-layer coatings.

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