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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• "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.
SIAM Journal on Mathematical Analysis 09/2013; 45(5). DOI:10.1137/120902124 · 1.27 Impact Factor
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• "Inspired by the pioneering work above, many further investigations on invisible cloaking have been conducted. Chen et al. [10] analysed spherical cloaks analytically in the Mie scattering model; Noor et al. [11] analysed isotropic, homogeneous plasmonic cloak; Zharova et al. [12] investigated the inverse cloak and proposed that the concept could be used as the perfectly matched layers (PMLs); Isic et al. [13] studied the imperfect cylindrical cloak and Yan et al. [14] discussed the cylindrical cloak with simplified parameters. Also, there are many full-wave simulations on the cloak based on the finite-element method (FEM) and/or finite-difference time-domain method [15] [16]. "
##### Article: Electromagnetic characteristics of metamaterial cloak covered dielectric cylinder illuminated by electric line source
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ABSTRACT: Electromagnetic characteristics of the dielectric cylinder covered by the cylindrical cloak are investigated in detail. Analytical expressions of electric field are derived and validated. Furthermore, effects of different kinds of loss on the performance of the cloak are studied. It is shown that if loss does not follow the same property as the constitutive tensor of the anisotropic and inhomogeneous cloak, electric fields could transmit into the inner dielectric cylinder. The authors believe that the results are helpful for practical applications.
IET Microwaves Antennas & Propagation 11/2010; DOI:10.1049/iet-map.2009.0256 · 0.91 Impact Factor
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• "Chen et al. analyzed cylindrical and spherical cloaks analytically in the Mie scattering model [12- 14]. Zharova et al. investigated the inverse cloak, and proposed that the concept could be used as the perfectly matched layers (PMLs) [15], Isic et al. studied the imperfect cylindrical cloak[16], Yan et al. discussed the cylindrical cloak with simplified parameters [17]. Also, there were many full-wave simulations on the cylindrical and/or spherical cloaking using numerical methods based on the method of finite element (FEM) and/or finite-difference time-domain method (FDTD)[18] [19]; furthermore, elliptical–cylindrical cloaks were also investigated in [20] [21] [22], and we did some research on regular polygonal cloak[23]. "
##### Conference Paper: Three dimensional axiolitic cloak based on coordinate transformation
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ABSTRACT: Arbitrary three dimensional axiolitic cloaks are proposed and designed based on the coordinate transformation theory. First, the general expressions of constitutive tensors of the three dimensional axiolitic cloaks are derived, then there are some full-wave simulations of the cloaks that are composed of inhomogeneous and anisotropic metamaterials, which will bend incoming electromagnetic waves and guide them to propagate around inner region, such electromagnetic waves will return to their original propagation directions without distorting the waves outside the axiolitic cloak. The results of full-wave simulations validate the general expressions of constitutive tensors of the three dimensional axiolitic cloaks we derived.
Microwave Conference, 2009. APMC 2009. Asia Pacific; 01/2010