A metamaterial lens based on transformation optics for horizontal radiation of OAM vortex waves
09 Mar 2021-Journal of Applied Physics (AIP Publishing LLCAIP Publishing)-Vol. 129, Iss: 10, pp 104101
TL;DR: In this paper, an innovative method to produce omnidirectional OAM beams based on spatial transformation is proposed at microwave frequencies for potential applications in wireless communications, which can be potentially implemented with an all-dielectric medium showing a gradient permittivity distribution.
Abstract: Vortex electromagnetic waves carrying orbital angular momentum (OAM) have been widely discussed for potential applications in wireless communications. Belonging to the Laguerre–Gaussian beams family, such type of waves present a hollow conical shape and divergence characteristics along with a directional radiation. In this paper, an innovative method to produce omnidirectional OAM beams based on spatial transformation is proposed at microwave frequencies. As a proof-of-concept demonstration, a lens with omnidirectional radiation in the horizontal plane is designed and simulated with an incident vortex beam carrying the OAM mode l = +2. The designed lens can be potentially implemented with an all-dielectric medium showing a gradient permittivity distribution. Furthermore, the proposed lens presents good performances over a wide operational bandwidth spanning from 8 to 17 GHz. By converting the directional beam to an omnidirectional one, the proposed method opens the door to the potential development of microwave vortex antenna systems.
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TL;DR: In this paper , a triple-band metamaterial absorber (MMA) is proposed, which is composed of a traditional metal-dielectric-metal structure and three perfect absorption peaks exceeding 99% are acquired at 3.72 GHz, 5.86 GHz, and 10.54 GHz.
Abstract: A triple-band metamaterial absorber (MMA) which is composed of a traditional metal-dielectric-metal structure is proposed in this paper, three absorption peaks are located at S-band, C-band and X-band, respectively. The design parameters are obtained by the methods of controlling variables and iterative optimization, and three perfect absorption peaks exceeding 99% are acquired at 3.72 GHz, 5.86 GHz, and 10.54 GHz after numerical calculation and analysis. Subsequently, the impedance matching conditions for absorption are proved through the analysis of equivalent electromagnetic parameters. For the proposed MMA, polarization independent characteristic, which is produced from the symmetry properties of the structure is verified, and it also has a stability of incident angle in both TE and TM modes from the result of the analysis of oblique incident response. In addition, its absorption mechanisms and methods are discussed and analyzed through electromagnetic field and surface current distributions. At the same time, the triple-band absorption performances of the proposed MMA derived from the material losses, 2D microstructure of the top layer and dimension parameters have also been calculated and investigated through the discussing of certain parameters individually. Finally, the absorption performance of the MMA is tested through experiments, and experimental results are basically same as the simulation results. Compared with other studies, the MMA proposed in this paper has higher absorption peaks at the resonance points, and the thickness is only 0.013 times of the longest working wavelength, which has a thinner thickness. The proposed MMA can be utilized in the areas of the decrease of Radar-Cross-Section, electromagnetic shielding, sensing and other applications.
7 citations
01 Dec 2022
TL;DR: In this article , the authors investigated the metamaterial-based electromagnetic wave absorber using full wave finite element method, which consists of gold-magnesium oxide-germanium-gold-germannium layers and rings-disk shape resonators over top of the proposed structure.
Abstract: • In the present work, we investigate the metamaterial based electromagnetic wave absorber using full wave finite element method. • Our model consists of gold-magnesium oxide-germanium-gold-germanium layers and rings-disk shape resonators over top of the proposed structure. • The circular symmetric nature of these resonators, enhance the localized surface plasmon resulting more electromagnetic power absorption occur. • Metamaterials have potential applications such as energy harvesting, hot electrons generation, detectors, imaging, defense, etc. • The average absorption of this model is above 90 % from 12.8 μ m to 17.8 μ m and including 100 % (at 9.1 μ m and 17.8 μ m ). In this paper, we propose a design of metamaterials-based polarization insensitive, broadband electromagnetic (EM) wavebands absorber in the long-wave infrared (LWIR) region. The proposed model consists multilayer of gold-magnesium oxide-germanium-gold-germanium layers from the bottom to the top of the structure. The top surface of our proposed metamaterial structure consists of rings and disk-shape resonators. Using the finite element method, the electromagnetic properties of the metamaterials are investigated in terms of reflectance and absorbance. We find that excitation of localized surface plasmon resonance gives rise to highly localized electromagnetic resonance with the structure. Due to the circularly symmetric nature of the ring resonator, the numerical results show that the proposed design of metamaterial has average absorption (above 90 %) from 12.8 μm to 17.8 μm for both transverse electric (TE) and transverse magnetic (TM) polarization over a wide range of incidence angle. Along with this, it can absorb EM waves completely (100 %) at a particular wavelength of 9.1 μm and 17.8 μm. These results show the proposed model configuration may have wide application in energy harvesting and another optoelectronic area.
2 citations
References
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TL;DR: The data further characterize the ultrastructural analysis of the KD mouse model, and support recent theories of a dying-back mechanism for neuronal degeneration, which is independent of demyelination.
Abstract: Krabbe disease (KD) is a neurodegenerative disorder caused by the lack of β- galactosylceramidase enzymatic activity and by widespread accumulation of the cytotoxic galactosyl-sphingosine in neuronal, myelinating and endothelial cells. Despite the wide use of Twitcher mice as experimental model for KD, the ultrastructure of this model is partial and mainly addressing peripheral nerves. More details are requested to elucidate the basis of the motor defects, which are the first to appear during KD onset. Here we use transmission electron microscopy (TEM) to focus on the alterations produced by KD in the lower motor system at postnatal day 15 (P15), a nearly asymptomatic stage, and in the juvenile P30 mouse. We find mild effects on motorneuron soma, severe ones on sciatic nerves and very severe effects on nerve terminals and neuromuscular junctions at P30, with peripheral damage being already detectable at P15. Finally, we find that the gastrocnemius muscle undergoes atrophy and structural changes that are independent of denervation at P15. Our data further characterize the ultrastructural analysis of the KD mouse model, and support recent theories of a dying-back mechanism for neuronal degeneration, which is independent of demyelination.
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Abstract: Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum. An astigmatic optical system may be used to transform a high-order Laguerre-Gaussian mode into a high-order Hermite-Gaussian mode reversibly. An experiment is proposed to measure the mechanical torque induced by the transfer of orbital angular momentum associated with such a transformation.
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