Beam steering based on coordinate transformation of Fermat spiral configurations
TL;DR: In this paper, a two-dimensional transformational electromagnetic (T-E) device formed by configuring a circular disc with a Fermat spiral is realized by tuning the phase of the emanating wave in the T-E medium, antenna switching and beam steering are made possible.
Abstract: A two-dimensional transformational electromagnetic (T-E) device formed by configuring a circular disc with a Fermat spiral is realized. By tuning the phase of the emanating wave in the T-E medium, antenna switching and beam steering are made possible. To simplify the permittivity and permeability tensors of the proposed T-E device, a gradient index approach is employed using purely dielectric material, which is then realized using photonic crystals. The results are verified numerically using full wave simulations.
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TL;DR: A perfect 3D invisibility cloak is achieved by shrinking the wrapped object to sufficiently small dimensions as compared to the operating frequency and an electromagnetic concentrator is obtained by replacing the coated object of the amplifying device with a compression medium.
Abstract: In this work, a general method is presented for the design of arbitrarily shaped 3D illusion devices with piecewise homogeneous parameters based on geometric divisions and linear coordinate transformations. Three illusion devices that can reshape the sizes or positions of the wrapped objects are demonstrated, namely, shrinking, amplifying, and shifting devices. The shrinking device can shrink a larger object into a smaller one with different material parameters, whereas the amplifying device can enlarge a smaller object into a larger one, and a shifting device can generate a new image with an identical size but located at a different position. In addition, based on the presented shrinking device, a perfect 3D invisibility cloak is achieved by shrinking the wrapped object to sufficiently small dimensions as compared to the operating frequency. An electromagnetic concentrator is also obtained by replacing the coated object of the amplifying device with a compression medium. The presented design approach can be easily extended to the design of other electromagnetic devices and even to other physical fields. It is believed that the presented piecewise homogeneous devices are more practicable in reality and can accelerate the potential applications of illusion devices in both military and commercial fields.
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TL;DR: This work shows how electromagnetic fields can be redirected at will and proposes a design strategy that has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.
Abstract: Using the freedom of design that metamaterials provide, we show how electromagnetic fields can be redirected at will and propose a design strategy. The conserved fields-electric displacement field D, magnetic induction field B, and Poynting vector B-are all displaced in a consistent manner. A simple illustration is given of the cloaking of a proscribed volume of space to exclude completely all electromagnetic fields. Our work has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.
7,811 citations
TL;DR: This work describes here the first practical realization of a cloak of invisibility, constructed with the use of artificially structured metamaterials, designed for operation over a band of microwave frequencies.
Abstract: A recently published theory has suggested that a cloak of invisibility is in principle possible, at least over a narrow frequency band. We describe here the first practical realization of such a cloak; in our demonstration, a copper cylinder was "hidden" inside a cloak constructed according to the previous theoretical prescription. The cloak was constructed with the use of artificially structured metamaterials, designed for operation over a band of microwave frequencies. The cloak decreased scattering from the hidden object while at the same time reducing its shadow, so that the cloak and object combined began to resemble empty space.
6,830 citations
TL;DR: A general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics is developed, which can be applied to escape detection by other electromagnetic waves or sound.
Abstract: An invisibility device should guide light around an object as if nothing were there, regardless of where the light comes from. Ideal invisibility devices are impossible, owing to the wave nature of light. This study develops a general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics. The imperfections of invisibility can be made arbitrarily small to hide objects that are much larger than the wavelength. With the use of modern metamaterials, practical demonstrations of such devices may be possible. The method developed here can also be applied to escape detection by other electromagnetic waves or sound.
3,850 citations
TL;DR: An experimental realization of a cloak design that conceals a perturbation on a flat conducting plane, under which an object can be hidden, and results indicate that this type of cloak should scale well toward optical wavelengths.
Abstract: The possibility of cloaking an object from detection by electromagnetic waves has recently become a topic of considerable interest. The design of a cloak uses transformation optics, in which a conformal coordinate transformation is applied to Maxwell's equations to obtain a spatially distributed set of constitutive parameters that define the cloak. Here, we present an experimental realization of a cloak design that conceals a perturbation on a flat conducting plane, under which an object can be hidden. To match the complex spatial distribution of the required constitutive parameters, we constructed a metamaterial consisting of thousands of elements, the geometry of each element determined by an automated design process. The ground-plane cloak can be realized with the use of nonresonant metamaterial elements, resulting in a structure having a broad operational bandwidth (covering the range of 13 to 16 gigahertz in our experiment) and exhibiting extremely low loss. Our experimental results indicate that this type of cloak should scale well toward optical wavelengths.
1,405 citations
TL;DR: In this article, a square electromagnetic cloak and an omni-directional electromagnetic field concentrator are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations.
Abstract: The technique of applying form-invariant, spatial coordinate transformations of Maxwell’s equations can facilitate the design of structures with unique electromagnetic or optical functionality. Here, we illustrate the transformation-optical approach in the designs of a square electromagnetic cloak and an omni-directional electromagnetic field concentrator. The transformation equations are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations. The two devices presented demonstrate that the transformation optic approach leads to the specification of complex, anisotropic and inhomogeneous materials with well directed and distinct electromagnetic behavior.
770 citations