Full-wave finite-difference time-domain simulation of electromagnetic cloaking structures
Yan Zhao, Christos Argyropoulos, Yang Hao
发表信息：
Y. Zhao, C. Argyropoulos and Y. Hao, "Full-wave finite-difference time-domain simulation of electromagnetic cloaking structures," Optics Express, vol. 16, No. 9, pp. 6717-6730, 2008.
This paper proposes a radial dependent dispersive finite-difference time-domain method for the modelling of electromagnetic cloaking structures. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in dispersive FDTD simulations. Numerical simulations demonstrate that under ideal conditions, objects placed inside the cloak are `invisible' to external electromagnetic fields. However for the simplified cloak based on linear transformations, the back scattering has a similar level to the case of a PEC cylinder without any cloak, rendering the object still being `visible'. It is also demonstrated numerically that the simplified cloak based on high-order transformations can indeed improve the cloaking performance.
Based on electromagnetic and acoustic transformation theory, a new strategy has been presented in this article to implement double invisibility cloaking, which has not been done yet. By applying a combination of four conventional cloaking methods, for cloaking an object by electromagnetic and acoustic waves, which are two essential methods for objects detection (sonar, radar, eye, ear, camera ...), the object will be blind or deaf, while it will be undetectable acoustically and electromagnetically simultaneously. In deaf mode structure, the object has an interaction with electromagnetic waves;…
Electromagnetic cloaking of cylindrical objects by multilayer or uniform dielectric claddings
我们表明，介电，甚至完全导电的圆柱体可以通过均匀或分层的电介质包覆，而不需要任何外来的或磁性材料的参数。特别是，我们首先提出了一个简单的分析概念，可以准确地描述在可见光谱中的锥形银盘获得的隐身效果。模型结构最初在[S. A. Tretyakov，P. Alitalo，O.卢科宁角R. Simovski，Phys. Rev. Lett. Vol.103，p.103905，2009]，其中仅数值地研究了其在光学频率中作为斗篷的操作。我们严格地模拟这种配置作为一个多层介质覆盖周围的隐形物体，与实际设备的模拟结果非常吻合。使用均匀或多层介质覆盖的概念，相对介电常数大于1，然后成功地扩展到不可穿透的对象，如导电圆柱体的隐身。
A number of errors, both mathematical and conceptual, are identified, in a recent article by Farhat \textit{et al.}\ [Phys.\ Rev.\ Appl.\ \textbf{11}, 044089 (2019)] on cloaking of thermal waves in solids, and corrected. The differences between the two thermal flux laws considered in the latter article are also critically discussed, specifically showing that the chosen model does not, in fact, correspond to the Maxwell--Cattaneo hyperbolic (wave) theory of heat transfer.
The ability to control electromagnetic fields, heat currents, electric currents, and other physical phenomena by coordinate transformation methods has resulted in novel functionalities, such as cloaking, field rotations, and concentration effects. Transformation optics, as the underlying mathematical tool, has proven to be a versatile approach to achieve such unusual outcomes relying on materials with highly anisotropic and inhomogeneous properties. Most applications and designs thus far have been limited to functionalities within a single physical domain. Here we present transformation optics…
We present the design of an innovative wire antenna able to automatically hide or reveal its presence depending on the waveform of the received/transmitted signal. This unconventional behavior is achieved through the use of a novel waveform-selective cloaking metasurface exploiting a meander-like unit cell loaded with a lumped-element circuit capable to engineer the scattering of the antenna depending on the waveform of the impinging signal. Due to the time-domain response of the lumped-element circuit, the antenna is able switching its scattering behavior when interacts with either a pulsed w…
In this study, the design of a directional cloaking based on the Luneburg lens system is proposed and its operating principle is experimentally verified. The cloaking concept is analytically investigated via geometrical optics and numerically realized with the help of the finite-difference time-domain method. In order to benefit from its unique focusing and/or collimating characteristics of light, the Luneburg lens is used. We show that by the proper combination of Luneburg lenses in an array form, incident light bypasses the region between junctions of the lenses, i.e., the "dark zone." Hence…
The application of transformation optics to the development of intriguing electromagnetic devices can produce weakly anisotropic or isotropic media with the assistance of quasi-conformal and/or conformal mapping, as opposed to the strongly anisotropic media produced by general mappings; however, it is typically limited to two-dimensional applications. By addressing the conformal mapping between two manifolds embedded in three-dimensional space, we demonstrate that electromagnetic surface waves can be controlled without introducing singularity and anisotropy into the device parameters. Using fr…
This paper presents a technique, combining the integral equations (IE) and the Generalized Sheet Transition Conditions (GSTCs) with bianisotropic susceptibility tensors, to compute electromagnetic wave scattering by cylindrical metasurfaces -- forming two-dimensional porous cavities -- of arbitrary cross sections. Moreover, it applies this technique to two problems -- cloaking with circular and rhombic shapes and illusion optics with an elliptic shape -- that both validate it, from comparison with specifications used in an exact synthesis of the metasurfaces, and reveal interesting capabilitie…
The procedure for obtaining a difference equation, the solution of which is the components of the electric (or magnetic) field at the chosen set of volume points of the resonator chain, was developed. We started with the wave equation with boundary conditions and obtained the difference equation without boundary conditions. Boundary conditions were included into the coefficients of the difference equation for the electric field. As the obtained equation connects the field values in different points (in general case, on an infinite set of points), the proposed procedure represents a nonlocal mo…
