scholarly journals Dynamic Absorption Enhancement and Equivalent Resonant Circuit Modeling of Tunable Graphene-Metal Hybrid Antenna

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3187
Author(s):  
Zaka Ullah ◽  
Illani Nawi ◽  
Gunawan Witjaksono ◽  
Nelson Tansu ◽  
Muhammad Irfan Khattak ◽  
...  
Keyword(s):  
Resonance Frequency ◽  
Far Infrared ◽  
Circuit Model ◽  
Absorption Peak ◽  
Absorption Enhancement ◽  
Resonant Circuit ◽  
Multilayer Graphene ◽  
Imaging Device ◽  
Enhanced Absorption ◽  
Metal Antenna

Plasmonic antennas are attractive optical components of the optoelectronic devices, operating in the far-infrared regime for sensing and imaging applications. However, low optical absorption hinders its potential applications, and their performance is limited due to fixed resonance frequency. In this article, a novel gate tunable graphene-metal hybrid plasmonic antenna with stacking configuration is proposed and investigated to achieve tunable performance over a broad range of frequencies with enhanced absorption characteristics. The hybrid graphene-metal antenna geometry is built up with a hexagon radiator that is supported by the Al2O3 insulator layer and graphene reflector. This stacked structure is deposited in the high resistive Si wafer substrate, and the hexagon radiator itself is a sandwich structure, which is composed of gold hexagon structure and two multilayer graphene stacks. The proposed antenna characteristics i.e., tunability of frequency, the efficiency corresponding to characteristics modes, and the tuning of absorption spectra, are evaluated by full-wave numerical simulations. Besides, the unity absorption peak that was realized through the proposed geometry is sensitive to the incident angle of TM-polarized incidence waves, which can flexibly shift the maxima of the absorption peak from 30 THz to 34 THz. Finally, an equivalent resonant circuit model for the investigated antenna based on the simulations results is designed to validate the antenna performance. Parametric analysis of the proposed antenna is carried out through altering the geometric parameters and graphene parameters in the Computer Simulation Technology (CST) studio. This clearly shows that the proposed antenna has a resonance frequency at 33 THz when the graphene sheet Fermi energy is increased to 0.3 eV by applying electrostatic gate voltage. The good agreement of the simulation and equivalent circuit model results makes the graphene-metal antenna suitable for the realization of far-infrared sensing and imaging device containing graphene antenna with enhanced performance.

scholarly journals Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments

2016 ◽  
Vol 113 (16) ◽  
pp. 4266-4271 ◽  
Author(s):  
Jianfei Peng ◽  
Min Hu ◽  
Song Guo ◽  
Zhuofei Du ◽  
Jing Zheng ◽  
...  
Keyword(s):  
Developing Countries ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Urban Environments ◽  
Absorption Enhancement ◽  
Ambient Conditions ◽  
Climatic Impact ◽  
Atmospheric Aging ◽  
Enhanced Absorption ◽  
Direct Radiative Forcing

Black carbon (BC) exerts profound impacts on air quality and climate because of its high absorption cross-section over a broad range of electromagnetic spectra, but the current results on absorption enhancement of BC particles during atmospheric aging remain conflicting. Here, we quantified the aging and variation in the optical properties of BC particles under ambient conditions in Beijing, China, and Houston, United States, using a novel environmental chamber approach. BC aging exhibits two distinct stages, i.e., initial transformation from a fractal to spherical morphology with little absorption variation and subsequent growth of fully compact particles with a large absorption enhancement. The timescales to achieve complete morphology modification and an absorption amplification factor of 2.4 for BC particles are estimated to be 2.3 h and 4.6 h, respectively, in Beijing, compared with 9 h and 18 h, respectively, in Houston. Our findings indicate that BC under polluted urban environments could play an essential role in pollution development and contribute importantly to large positive radiative forcing. The variation in direct radiative forcing is dependent on the rate and timescale of BC aging, with a clear distinction between urban cities in developed and developing countries, i.e., a higher climatic impact in more polluted environments. We suggest that mediation in BC emissions achieves a cobenefit in simultaneously controlling air pollution and protecting climate, especially for developing countries.

Analytical circuit model for split ring resonators in the far infrared and optical frequency range

Metamaterials ◽  
2009 ◽  
Vol 3 (2) ◽  
pp. 57-62 ◽  
Author(s):  
V. Delgado ◽  
O. Sydoruk ◽  
E. Tatartschuk ◽  
R. Marqués ◽  
M.J. Freire ◽  
...  
Keyword(s):  
Far Infrared ◽  
Circuit Model ◽  
Ring Resonators ◽  
Optical Frequency ◽  
Frequency Range ◽  
Split Ring ◽  
Split Ring Resonators ◽  
Optical Frequency Range

Analysis of the White Circuit System of the NSRRC TLS Booster

2013 ◽  
Vol 740 ◽  
pp. 817-822
Author(s):  
Chen Yao Liu ◽  
Yao Ching Hsieh ◽  
Kuo Bin Liu ◽  
Din Goa Huang
Keyword(s):  
Electron Beam ◽  
Energy Range ◽  
Light Source ◽  
Capacitor Bank ◽  
Measurement Data ◽  
Beam Current ◽  
Circuit Model ◽  
Repetition Frequency ◽  
Resonant Circuit ◽  
Electron Beam Current

At the Taiwan Light Source (TLS), the booster ring provides energy injection at repetition frequency 10 Hz with injection capability in the top-up mode. To obtain the wide acceleration energy range 50 -- 1.5 GeV, a 'White-circuit' topology has been chosen. The White circuit is, briefly, a biased resonant circuit in which the energy is transferred between the booster bending magnets and a large capacitor bank. The White circuit uses a resonance axiom to ramp the current of the bending magnets. The peak current is 2300 A; the bending magnets can accelerate the energy of the booster electron beam current from 50 MeV to 1.5 GeV with the White circuit system. We analyze the characteristic of the White circuit to get a circuit model. Using the circuit model to simulate impedance and phase are identical with the measurement data of the White circuit. The results are described in this paper.

LANDAU LEVEL SPECTROSCOPY OF DIRAC-LIKE FERMIONS IN MULTILAYER GRAPHENE

2009 ◽  
Vol 23 (12n13) ◽  
pp. 2665-2666
Author(s):  
M. POTEMSKI
Keyword(s):  
Silicon Carbide ◽  
Optical Properties ◽  
Landau Level ◽  
Visible Region ◽  
Far Infrared ◽  
Dispersion Relations ◽  
Thin Layers ◽  
Multilayer Graphene ◽  
Graphite Sheet ◽  
Graphene Layers

The results of spectroscopic (magneto-transmission and Raman scattering) studies1–8 of multilayers of carbon which are thermally decomposed from carbon-terminated surface of silicon carbide, and of thin layers of highly oriented pyrolytic and natural graphite were presented. Those carbon multilayers on silicon carbide which are not directly affected by the SiC / C interface and which in consequence are nearly charge neutral show the magneto-optical properties identical with the properties characteristic of a single graphite sheet, graphene. Inter Landau level transitions in this multilayer graphene have been studied in a wide spectral range from far-infrared to almost visible region. The dispersion relations of electronic states are found to reflect the form of the Dirac cone with almost perfect electron-hole symmetry and only weak deviations from linearity at high energies. Cyclotron resonance transition in multilayer graphene can be observed in magnetic fields down to 40 mT, and its width is practically independent on temperature up to 300 K. Such parameters as carrier mobility and minimal conductivity as well as the possibility to probe the immediate vicinity of the Dirac point were evaluated and discussed in detail. For comparison, the magneto-optical properties of thin layers of bulk graphite were also reported. The Dirac like electronic dispersion relations are also found in these systems, but only in the vicinity of the particular (H) point of the Brillouin zone. In general, the measured spectra are, however, more complex and reflect the three-dimensional character of graphene layers with Bernal stacking. Note from Publisher: This article contains the abstract only.

Temperature-dependent far-infrared response of epitaxial multilayer graphene

2013 ◽  
Vol 102 (23) ◽  
pp. 231906 ◽  
Author(s):  
Yan-Feng Lao ◽  
A. G. Unil Perera ◽  
Kristin Shepperd ◽  
Feng Wang ◽  
Edward H. Conrad ◽  
...  
Keyword(s):  
Far Infrared ◽  
Multilayer Graphene ◽  
Temperature Dependent ◽  
Far Infrared Response
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