Article

# Cylindrical Invisibility Cloak with Simplified Material Parameters is Inherently Visible

Department of Microelectronics and Applied Physics, Royal Institute of Technology, Electrum 229, 16440 Kista, Sweden.
(Impact Factor: 7.51). 01/2008; 99(23):233901. DOI: 10.1103/PhysRevLett.99.233901
Source: PubMed

ABSTRACT

It was proposed that perfect invisibility cloaks can be constructed for hiding objects from electromagnetic illumination [J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006)10.1126/science.1125907]. The cylindrical cloaks experimentally demonstrated [D. Schurig, Science 314, 977 (2006)10.1126/science.1133628] and theoretically proposed [W. Cai, Nat. Photon. 1, 224 (2007)10.1038/nphoton.2007.28] have however simplified material parameters in order to facilitate easier realization as well as to avoid infinities in optical constants. Here we show that the cylindrical cloaks with simplified material parameters inherently allow the zeroth-order cylindrical wave to pass through the cloak as if the cloak is made of a homogeneous isotropic medium, and thus visible. To all high-order cylindrical waves, our numerical simulation suggests that the simplified cloak inherits some properties of the ideal cloak, but finite scatterings exist.

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Available from: Min Qiu, Sep 01, 2014
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• "This singular structure implies not only difficulties in practice, but also in analysis. To avoid using the singular structure, regularized schemes have been proposed in [46] [8] [52] [45] [23] [17]. "
##### Article: On a regularized scheme for approximate acoustic cloaking using transformation optics
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ABSTRACT: In this paper, we study approximate cloaking for the Helmholtz equation in 3d where the cloaking device is based on transformations which blow up a cylinder of fixed height and small cross section of radius $\eps$ into the cloaked region. Assuming the zero Dirichlet boundary condition is imposed on the boundary of the cloaked region, we show that the degree of visibility is of order $\eps$ as $\eps$ goes to 0. This fact is quite surprising since it is known that the degree of visibility, for the scheme using transformations which blow up a small region of diameter $\eps$ into the cloaked region, is of order $\eps$ in 3d and $1/ |\ln \eps|$ in 2d. To understand the relation between these contexts, we as well revisit the known estimates and show that the degree of visibility is of order $\eps^{d-1}$ ($d=2,3$) for the scheme using transformations which blow up a small {\it ball} of diameter $\eps$ into the cloaked region as long as the zero Dirichlet boundary condition is imposed on the boundary of the cloaked region. The symmetry of the cross section and of the ball are crucial so that these results hold.
Full-text · Article · Sep 2013 · SIAM Journal on Mathematical Analysis
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• "The main theoretical task is to define and analyze the properties of the appropriate notion of weak (and physical) solution[2],[22]. To avoid the use of singular materials, regularized schemes have been proposed in[1],[3],[9],[19],[20],[24]. The trade-off is that one no longer attains perfect cloaking, but only approximate cloaking. "
##### Article: Approximate cloaking for the full wave equation

Full-text · Article · Jan 2012
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• "Transformation optics [1], [2] provides a new design methodology allowing unprecedented manipulation of electromagnetic wave propagation, with the invisible cloak as the most prominent example [3] [4] [5] [6]. Besides, a wide variety of applications other than cloaking has been recently presented, such as field concentrators [6], [7], transparent device [8] [9] [10], beam shifters [11], field rotator [12], waveguide bends and corners [13], etc. "
##### Article: Arbitrary Shape Electromagnetic Transparent Device Based on Laplace's Equation
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ABSTRACT: Transparent device is deliberately-designed elec-tromagnetic structure that is transparent to electromag-netic wave. It can be used as a radome structure which is capable of protection antenna inside without sacrificing its performance. In this paper, two-dimensional (2D) arbi-trary shape electromagnetic transparent device is designed based on transformation optics. Laplace's equation is adopted to construct the coordinate mapping between the original space and the transformed space. The design method is flexibly extended to three-dimensional (3D) case, which greatly enhances the applicability of transparent device. The protection of a horn antenna is taken as an example to show the effectiveness of the transparent device. Since the performance of the transparent device is independent on the inner antenna, it can be designed sepa-rately. Full-wave simulations are made to validate the results.
Preview · Article · Apr 2011 · Radioengineering