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Scattering Cancellation and Plasmonic Cloaking
Published in Filippo Capolino, Applications of Metamaterials, 2017
The scattering cancellation technique may present several inherent advantages over this coordinate transformation cloaking devices: relatively larger bandwidth and robustness, simplicity of design, thinner cloak requirements, the possibility of letting the designer choose whether to design a cloak available for any object, by combining the plasmonic cloak with an impenetrable cavity, or better tailoring the cloak design for the specific object to be cloaked, and finally the possibility of the wave to penetrate the cloaked region without producing a sensible scattering, which may be employed to capture and observe the fields that penetrate the cloaked region without being perceived by the surrounding. In this way, an observer (sensor or detector) placed in the cloaked region may capture the outside fields without its presence being possibly detected.
Structural optimization scheme for acoustic cloaking structures considering general surfaces
Published in Engineering Optimization, 2022
To hide an object from incoming electromagnetic, elastic or acoustic waves, the concepts of cloaking devices have been introduced. First of all, so-called carpet cloaks have been of interest and researched by Schurig et al. (2006), Cummer and Schurig (2007), Dubois et al. (2017), Esfahlani et al. (2016), Liang and Li (2012), Ma et al. (2014), Song et al. (2016), Tang et al. (2014), Wang, Chan, and Luk (2016), Zhai et al. (2016), Mei and Wu (2014), Zigoneanu, Popa, and Cummer (2014) and Zhu et al. (2015a). Surfaces with different impedances along their tangent lines reflect waves randomly and the metasurface technique aims to restore waves reflected from flat surfaces. Normally, man-made layers are added in order to create phase shifting of the reflected waves. State-of-the-art technology utilizes the phase gradient along surfaces to control the reflected or transmitted wavefront. As a result, it is possible to tune the travelling length of the wave and correct the reflected wave. One of the limitations of existing metasurfaces or metamaterials lies in the fact that they exhibit their best performance at a single frequency or at several discrete frequencies. Indeed, it is still an important issue to broaden their working frequencies with a single structure.
A polarization-independent and broadband microwave metamaterial absorber based on three-dimensional structure
Published in Journal of Modern Optics, 2018
Hailong Huang, Hui Xia, Zhibo Guo, Shengxiang Huang, Hongjian Li, Yishan Wu
Figure 2(a) and (b) show the calculated absorptance spectra for TE and TM mode, respectively. As shown in Figure 2(a), it is noted that the absorptance curve of TE polarized wave consists of two resonance points, which are 72.9 and 96.7 GHz with absorptance efficiency 99.8 and 98.9%, respectively, and the corresponding absorptance bandwidth of 39.6 GHz can be obtained. From Figure 2(b), we can find that the absorptance spectrum of TM polarized wave shows the same curve trend and resonance points with that in Figure 2(a). The results shown in Figure 2 have demonstrated that our proposed three-dimensional MMA is polarization-insensitive and has the same absorptance for TE and TM polarized wave due to the symmetric structure. Using a MMA it is possible to design a cloaking device so that it absorbs light perfectly, and rendering it invisible over a certain range of frequency due to no light can be reflected by the surface of the objects. From the above results, it is found that the proposed MMA can absorb EM waves perfectly in a certain frequency range, and thus working as a cloaking device in corresponding frequency region.