scholarly journals Effect of Unit Cell Shape on Switchable Infrared Metamaterial VO2 Absorbers/Emitters

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Feifei Ren ◽  
Jinxin Gu ◽  
Hang Wei ◽  
Gaoping Xu ◽  
Jiupeng Zhao ◽  
...  
Keyword(s):  
Cell Shape ◽  
Structure Optimization ◽  
Metamaterial Absorber ◽  
Metallic State ◽  
Spectral Absorption ◽  
Symmetric Structure ◽  
Sensing Technology ◽  
Spacer Layer ◽  
Unit Cells ◽  
Magnetic Polariton

Metamaterial absorber/emitter is an important aspect of infrared radiation manipulation. In this paper, we proposed four simple switchable infrared metamaterial absorbers/emitters with Ag/VO2 disks on the Ag plane employing triangle, square, hexagon, and circle unit cells. The spectral absorption peaks whose intensities are above 0.99 occur at ~4 μm after structure optimization when VO2 is in insulating state and disappear when VO2 becomes metallic state. The simulated electromagnetic field reveals that the spectral absorption peaks are attributed to the excitation of magnetic polariton within the insulating VO2 spacer layer, whose values exceed 1.59 orders of magnitude higher than the incident magnetic field. Longer resonant wavelength would be excited in square arrays because its configuration is a better carrier of charges at the same spans. For absorption stability, the absorbers/emitters with square and circular structures do not have any change with the polarization angles changing from 0° to 90°, due to the high rotational symmetric structure. And four absorbers/emitters reveal similar shifts and attenuations under different incident angles. We believed that the switchable absorber/emitter demonstrates promising applications in the sensing technology and adaptive infrared system.

scholarly journals Design of A Perfect Metamaterial Absorber for Microwave Applications

2021 ◽  
Vol 22 (1) ◽  
pp. 1-4
Author(s):  
Khalid Al-Badri
Keyword(s):  
Normal Incidence ◽  
Metamaterial Absorber ◽  
Absorption Bands ◽  
Band Frequency ◽  
Image Sensing ◽  
Rectangular Patch ◽  
Low Profile ◽  
X Band ◽  
Unit Cells ◽  
Perfect Metamaterial Absorber

In this manuscript, a multi-band and low-profile metamaterial absorber with polarisation independence from 00 to 450 is presented. The proposed metamaterial structure is composed of a single ring with a rectangular patch, consisting of periodic unit cells with a size of 150mm × 250mm × 1.5mm. The structure exhibits three absorption peaks under normal incidence, which cover the X-band. According to the results, the desired material can excellently absorb the electromagnetic wave signal, with an outstanding absorption rate of about 95% at the microwave x-band frequency. The proposed structure shows three absorption bands where two of them exceed 90% absorption level. The results displayed a high Q-factor of 103.5 at a resonance frequency of 8.58 GHz and the figure of merit (FOM) is 98.4, which can be used to enhance the sensor sensing, narrowband band filter and image sensing. The proposed structure is fabricated, and experiments are carried out to validate the design principle. Strong agreements are observed between the measured and the corresponding simulated results.

scholarly journals Gain-Enhanced Metamaterial Absorber-Loaded Monopole Antenna for Reduced Radar Cross-Section and Back Radiation

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1247
Author(s):  
Heijun Jeong ◽  
Yeonju Kim ◽  
Manos M. Tentzeris ◽  
Sungjoon Lim
Keyword(s):  
Cross Section ◽  
Radar Cross Section ◽  
Metamaterial Absorber ◽  
Monopole Antenna ◽  
Magnetic Conductor ◽  
Low Profile ◽  
Before And After ◽  
Unit Cells ◽  
Lumped Elements ◽  
Peak Gain

This paper proposes a gain-enhanced metamaterial (MM) absorber-loaded monopole antenna that reduces both radar cross-section and back radiation. To demonstrate the proposed idea, we designed a wire monopole antenna and an MM absorber. The MM absorber comprised lumped elements of subwavelength unit cells and achieved 90% absorbance bandwidth from 2.42–2.65 GHz. For low-profile configurations, the MM absorber was loaded parallel to and 10 mm from the monopole antenna, corresponding to 0.09 λ0 at 2.7 GHz. The monopole antenna resonated at 2.7 GHz with a 3.71 dBi peak gain and 2.65 GHz and 6.46 dBi peak gain, before and after loading the MM absorber, respectively. Therefore, including the MM absorber increased peak gain by 2.7 dB and reduced back radiation by 15 dB. The proposed antenna radar cross-section was reduced by 2 dB compared with a monopole antenna with an artificial magnetic conductor.

A light weight and broadband metamaterial absorber with 3D cube unit cells

2018 ◽  
Vol 124 (6) ◽  
Author(s):  
Guorui Zhang ◽  
Li Wang ◽  
Yang Zhou ◽  
Peiheng Zhou ◽  
Haiyan Chen ◽  
...  
Keyword(s):  
Metamaterial Absorber ◽  
Light Weight ◽  
Unit Cells

Applications of Wavelet Penalty Function in De-Noising for Hyperspectral Images

2012 ◽  
Vol 263-266 ◽  
pp. 2498-2501
Author(s):  
Ji Ning Yan ◽  
Ke Fa Zhou ◽  
Li Sun ◽  
Yan Fang Qin ◽  
Shu Guang Zhou ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Penalty Function ◽  
Random Noise ◽  
Gaussian White Noise ◽  
Spectral Absorption ◽  
Sensing Technology ◽  
Quantitative Remote Sensing ◽  
Feature Information ◽  
Absorption Features ◽  
Level 2

With the development of the hyperspectral remote sensing technology, the level of quantitative remote sensing has risen greatly, but varying degrees of random noise is contained. To optimize the use of the remote sensing images and to improve the effectiveness and accuracy of discriminating ground objects according to spectral absorption features, random noise removing is necessary. Aimed at the distribution characteristics of the random point noise of HJ_1A HSI data level 2 product, eliminate the Gaussian white noise by soft-thresholding filtering based on the Birge-Massart penalty function in wavelet domain. And the result shows that the method can not only remove the additive noise effectively, but also retain most of the feature information and edge details of the original image. Therefore, the method could provide necessary support for quantitative use of HJ_1A HSI data.

scholarly journals An Ultrathin, Triple-Band Metamaterial Absorber with Wide-Incident-Angle Stability for Conformal Applications at X and Ku Frequency Band

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Guangsheng Deng ◽  
Kun Lv ◽  
Hanxiao Sun ◽  
Jun Yang ◽  
Zhiping Yin ◽  
...  
Keyword(s):  
Free Space ◽  
High Efficiency ◽  
Incident Angle ◽  
Surface Current ◽  
Normal Incidence ◽  
Metamaterial Absorber ◽  
Angle Of Incidence ◽  
Perfect Absorption ◽  
Absorption Frequency ◽  
Unit Cells

AbstractAn ultrathin and flexible metamaterial absorber (MA) with triple absorption peaks is presented in this paper. The proposed absorber has been designed in such a way that three absorption peaks are located at 8.5, 13.5, and 17 GHz (X and Ku bands) with absorption of 99.9%, 99.5%, and 99.9%, respectively. The proposed structure is only 0.4 mm thick, which is approximately 1/88, 1/55, and 1/44 for the respective free space wavelengths of absorption frequency in various bands. The MA is also insensitive due to its symmetric geometry. In addition, the proposed structure exhibits minimum 86% absorption (TE incidence) within 60° angle of incidence. For TM incidence, the proposed absorber exhibits more than 99% absorptivity up to 60° incidence. Surface current and electric field distributions were investigated to analyze the mechanism governing absorption. Parameter analyses were performed for absorption optimization. Moreover, the performance of the MA was experimentally demonstrated in free space on a sample under test with 20 × 30 unit cells fabricated on a flexible dielectric. Under normal incidence, the fabricated MA exhibits near perfect absorption at each absorption peak for all polarization angles, and the experimental results were found to be consistent with simulation results. Due to its advantages of high-efficiency absorption over a broad range of incidence angles, the proposed absorber can be used in energy harvesting and electromagnetic shielding.

ADSORPTION OF Cs ON Si(111)-(7 × 7) SURFACES: SITE PREFERENCE AND THE NEAR-METALLIC STATE OF Cs

2001 ◽  
Vol 08 (06) ◽  
pp. 633-639 ◽  
Author(s):  
A. C. PAPAGEORGOPOULOS ◽  
M. KAMARATOS
Keyword(s):  
Elevated Temperatures ◽  
Thermal Desorption Spectroscopy ◽  
Atomic Radius ◽  
Metallic Surface ◽  
Site Preference ◽  
Metallic State ◽  
Unit Cells ◽  
Saturation Coverage ◽  
Surface Saturation ◽  
High Degree

This study involves the adsorption of Cs on Si (111)-(7 × 7) surfaces at room and elevated temperatures, with increasing coverage of Cs to saturation, in ultrahigh vacuum (UHV) conditions. The techniques of low energy electron diffraction (LEED), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS) and work function (WF) measurements were utilized. A WF change at the minimum, found to be Δϕ=-3.2 eV at an approximate 0.23 ML Cs coverage, corresponds to half the saturation coverage. We propose that, at that coverage, the adatom dangling bonds of the Si (111)-(7 × 7) substrate are completely filled. At saturation coverage (0.47 ML), Cs forms a single saturation layer in a near-metallic surface state, where the atomic radius of the Cs adatoms is likely to be 2.2× 10-8 cm. The surface exhibits a high degree of disorder with 0.47 ML of adsorbed Cs, and it is likely that the adsorbate remains in cluster-like domains within the center of the disordered 7×7 unit cells, instead of evenly covering the Si surface. Saturation coverage of Cs on Si (111)-(7 × 7) surfaces exhibits a WF value 0.5 eV less than that of pure metallic Cs. Cesium adatoms form a stronger bond to the Si (111)-(7 × 7) surface than to Ni(100), with a calculated energy of 1.64 eV/atom. The induced surface disorder and strong binding energy are evidence of the strong Cs–Si interaction, which most likely prevents the formation of a purely metallic Cs overlayer.

scholarly journals Invariance of initiation mass and predictability of cell size inEscherichia coli

2016 ◽  
Author(s):  
Fangwei Si ◽  
Dongyang Li ◽  
Sarah E. Cox ◽  
John T. Sauls ◽  
Omid Azizi ◽  
...  
Keyword(s):  
Cell Size ◽  
Cell Shape ◽  
Predictive Power ◽  
Physiological State ◽  
Growth Conditions ◽  
Replication Initiation ◽  
Total Cell ◽  
Steady State Condition ◽  
Unit Cells ◽  
Extensive Growth

SummaryIt is generally assumed that the allocation and synthesis of total cellular resources in microorganisms are uniquely determined by the growth conditions. Adaptation to a new physiological state leads to a change in cell size via reallocation of cellular resources. However, it has not been understood how cell size is coordinated with biosynthesis and robustly adapts to physiological states. We show that cell size inEscherichia colican be predicted for any steady-state condition by projecting all biosynthesis into three measurable variables representing replication initiation, replication-division cycle, and the global biosynthesis rate. These variables can be decoupled by selectively controlling their respective core biosynthesis using CRISPR interference and antibiotics, verifying our predictions that different physiological states can result in the same cell size. We performed extensive growth inhibition experiments, and discovered that cell size at replication initiation per origin, namely the initiation mass or “unit cell,” is remarkably invariant under perturbations targeting transcription, translation, ribosome content, replication kinetics, fatty acid and cell-wall synthesis, cell division, and cell shape. Based on this invariance and balanced resource allocation, we explain why the total cell size is the sum of all unit cells. These results provide an overarching framework with quantitative predictive power over cell size in bacteria.

scholarly journals Nanoplasmonic Pyramidal Metamaterial Absorber at Optical Frequencies

2022 ◽  
Author(s):  
Muhammad Amin ◽  
Saleh Abdullah Basamed ◽  
Ahmed Salem Qniqoon ◽  
Faisal Aied Alshabibi ◽  
Saleh Mohammed Ba Raean ◽  
...  
Keyword(s):  
Light Absorption ◽  
Thermal Imaging ◽  
Resonant Absorption ◽  
Metamaterial Absorber ◽  
Spectral Absorption ◽  
Perfect Absorption ◽  
Wide Range ◽  
Thermal Emitters ◽  
Polarization Independent ◽  
Absorption Characteristics

Abstract A pyramidal shaped metamaterial absorber (PMA) supports broadband and polarization independent resonant absorption at optical frequencies. The PMA is designed by stack of alternative plasmonic/dielectric multilayers. These nanoplasmonic pyramids offers resonant absorption characteristics at wide range of optical frequencies. The optimized PMA structure allows 76% spectral absorption and nearly perfect absorption (over 90%) at several bands between range of 400 nm – 1500 nm wavelength. These light absorption characteristics of PMA are useful for photodetection, thermal imaging, thermal emitters, and solar cells etc.

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