Metamaterials and the Control of Electromagnetic Fields
10 Jun 2007-
TL;DR: A new class of materials, metamaterials, whose properties are engineered by controlling their nanostructure, open new vistas in optics and offer the possibility of lenses that can resolve details finer than the wavelength of light.
Abstract: A new class of materials, metamaterials, whose properties are engineered by controlling their nanostructure, open new vistas in optics and offer the possibility of lenses that can resolve details finer than the wavelength of light.
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TL;DR: In this article, the effects of geometric anisotropy on a two-dimensional metamaterial composed of a rectangular array of elliptic cylinders were analyzed and an effective medium theory was derived.
Abstract: Materials with anisotropic material parameters can be utilized to fabricate many fascinating devices, such as hyperlenses, metasolids, and one-way waveguides. In this study, we analyze the effects of geometric anisotropy on a two-dimensional metamaterial composed of a rectangular array of elliptic cylinders and derive an effective medium theory for such a metamaterial. We find that it is possible to obtain a closed-form analytical solution for the anisotropic effective medium parameters, provided the aspect ratio of the lattice and the eccentricity of the elliptic cylinder satisfy certain conditions. The derived effective medium theory not only recovers the well-known Maxwell-Garnett results in the quasi-static regime, but is also valid beyond the long-wavelength limit, where the wavelength in the host medium is comparable to the size of the lattice so that previous anisotropic effective medium theories fail. Such an advance greatly broadens the applicable realm of the effective medium theory and introduces many possibilities in the design of structures with desired anisotropic material characteristics. A real sample of a recently theoretically proposed anisotropic medium, with a near-zero index to control the flux, is achieved using the derived effective medium theory, and control of the electromagnetic waves in the sample is clearly demonstrated.
80 citations
TL;DR: In this paper, a variety of tunable metamaterials using different methods of control are presented and discussed and discussed in this review paper, where the authors show that natural materials can not perform efficient interaction with terahertz (THz) radiation.
Abstract: Remarkable progress in terahertz (THz) sources and detectors is followed by the necessity of manipulating of terahertz radiation. Since natural materials can not perform efficient interaction with THz radiation, artificial structures called metamaterials are designed to overcome “THz gap” in this area. A variety of tunable metamaterials using different methods of control are presented and discussed in this review paper.
49 citations
Cites background from "Metamaterials and the Control of El..."
...Electromagnetic MTM have enabled numerous exotic electromagnetic phenomena, such as negative or zero dielectric permittivity, negative or zero magnetic permeability, double-negative refractive index, perfect lensing, cloaking etc [3], [4]....
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TL;DR: A topical review of metamaterials in acoustic wave science, with particular attention given to fundamental principles of acoustic metamMaterials for realizing the extraordinary acoustic properties such as negative, near-zero and approaching-infinity parameters.
Abstract: Artificially structured materials with unit cells at sub-wavelength scale, known as metamaterials, have been widely used to precisely control and manipulate waves thanks to their unconventional properties which cannot be found in nature. In fact, the field of acoustic metamaterials has been much developed over the past 15 years and still keeps developing. Here, we present a topical review of metamaterials in acoustic wave science. Particular attention is given to fundamental principles of acoustic metamaterials for realizing the extraordinary acoustic properties such as negative, near-zero and approaching-infinity parameters. Realization of acoustic cloaking phenomenon which is invisible from incident sound waves is also introduced by various approaches. Finally, acoustic lenses are discussed not only for sub-diffraction imaging but also for applications based on gradient index (GRIN) lens.
45 citations
TL;DR: In this article, the authors proposed a negative index of refraction (NIR) design for chiral isotropic metamaterials with arrays of a sole structure, which gave the highest possible rank of isotropy.
Abstract: Chiral isotropic metamaterials with a negative index of refraction design consisting of arrays of a sole structure are proposed. The Cn point group is selected based on its chiral and isotropic properties. A circuit analysis model is obtained for the double negative NIR passband design. The structure's orientation provides flexibility to adjust the properties. Structure modification, based on the capacitance and inductance value, controls the locations of the structure's effective material parameters and the double negative NIR passband. These proposed designs give the highest possible rank of isotropy. The negative index of refraction is also validated.
19 citations
TL;DR: In this article, a simple and accurate equivalent circuit for coupled complementary metasurfaces (CCMTS) comprised of slots and their Babinet complement, dipoles is proposed.
Abstract: Coupled complementary metasurfaces (CCMTS) exhibit a passband whose frequency is several times lower than that of the individual metasurface (MTS) passband frequency. In this paper, we explain this phenomenon and propose a simple and accurate equivalent circuit for CCMTS comprised of slots and their Babinet complement, dipoles. An equivalent circuit is extracted from a coupled EFIE–MFIE equation using a synthetic basis function. The same procedure can be conveniently applied to any CCMTS. The model allows one to estimate the large downshift of resonant frequency and the bandwidth utilizing a simple formula. When used in a subresonant regime, the unit cell may have a dimension of a tenth of a free space wavelength with a moderate value of permittivity between the complementary layers.
17 citations
Cites background from "Metamaterials and the Control of El..."
...These elements, also called metaatoms, can be used to produce exotic electromagnetic properties (like negative refractive index) which are not naturally available [2]....
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References
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TL;DR: The authors' simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver, which resolves objects only a few nanometers across.
Abstract: Optical lenses have for centuries been one of scientists’ prime tools. Their operation is well understood on the basis of classical optics: curved surfaces focus light by virtue of the refractive index contrast. Equally their limitations are dictated by wave optics: no lens can focus light onto an area smaller than a square wavelength. What is there new to say other than to polish the lens more perfectly and to invent slightly better dielectrics? In this Letter I want to challenge the traditional limitation on lens performance and propose a class of “superlenses,” and to suggest a practical scheme for implementing such a lens. Let us look more closely at the reasons for limitation in performance. Consider an infinitesimal dipole of frequency v in front of a lens. The electric component of the field will be given by some 2D Fourier expansion,
10,974 citations
10,495 citations
TL;DR: These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root ofɛ·μ for the frequencies where both the permittivity and the permeability are negative.
Abstract: We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials.
8,477 citations
TL;DR: In this paper, it was shown that microstructures built from nonmagnetic conducting sheets exhibit an effective magnetic permeability /spl mu/sub eff/, which can be tuned to values not accessible in naturally occurring materials.
Abstract: We show that microstructures built from nonmagnetic conducting sheets exhibit an effective magnetic permeability /spl mu//sub eff/, which can be tuned to values not accessible in naturally occurring materials, including large imaginary components of /spl mu//sub eff/. The microstructure is on a scale much less than the wavelength of radiation, is not resolved by incident microwaves, and uses a very low density of metal so that structures can be extremely lightweight. Most of the structures are resonant due to internal capacitance and inductance, and resonant enhancement combined with compression of electrical energy into a very small volume greatly enhances the energy density at critical locations in the structure, easily by factors of a million and possibly by much more. Weakly nonlinear materials placed at these critical locations will show greatly enhanced effects raising the possibility of manufacturing active structures whose properties can be switched at will between many states.
8,135 citations
TL;DR: A composite medium, based on a periodic array of interspaced conducting nonmagnetic split ring resonators and continuous wires, that exhibits a frequency region in the microwave regime with simultaneously negative values of effective permeability and permittivity varepsilon(eff)(omega).
Abstract: We demonstrate a composite medium, based on a periodic array of interspaced conducting nonmagnetic split ring resonators and continuous wires, that exhibits a frequency region in the microwave regime with
8,057 citations