Showing papers by "John B. Pendry published in 2008"
TL;DR: A new type of cloak is discussed: one that gives all cloaked objects the appearance of a flat conducting sheet that has the advantage that none of the parameters of the cloak is singular and can in fact be made isotropic.
Abstract: A new type of cloak is discussed: one that gives all cloaked objects the appearance of a flat conducting sheet. It has the advantage that none of the parameters of the cloak is singular and can in fact be made isotropic. It makes broadband cloaking in the optical frequencies one step closer.
1,419Â 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.
770Â citations
TL;DR: This work applies finite, embedded coordinate transformations to the design of several devices, including a parallel beam shifter and a beam splitter, both of which are reflectionless and exhibit unusual electromagnetic behavior as confirmed by 2D full-wave simulations.
Abstract: Transformation optics offers an unconventional approach to the control of electromagnetic fields. The transformation optical structures proposed to date, such as electromagnetic "invisibility" cloaks and concentrators, are inherently reflectionless and leave the transmitted wave undisturbed. Here, we expand the class of transformation optical structures by introducing finite, embedded coordinate transformations, which allow the electromagnetic waves to be steered or focused. We apply the method to the design of several devices, including a parallel beam shifter and a beam splitter, both of which are reflectionless and exhibit unusual electromagnetic behavior as confirmed by 2D full-wave simulations.
496Â citations
TL;DR: Through acoustic scattering theory, the mass density and bulk modulus of a spherical shell that can eliminate scattering from an arbitrary object in the interior of the shell are derived--in other words, a 3D acoustic cloaking shell.
Abstract: Through acoustic scattering theory we derive the mass density and bulk modulus of a spherical shell that can eliminate scattering from an arbitrary object in the interior of the shell—in other words, a 3D acoustic cloaking shell. Calculations confirm that the pressure and velocity fields are smoothly bent and excluded from the central region as for previously reported electromagnetic cloaking shells. The shell requires an anisotropic mass density with principal axes in the spherical coordinate directions and a radially dependent bulk modulus. The existence of this 3D cloaking shell indicates that such reflectionless solutions may also exist for other wave systems that are not isomorphic with electromagnetics.
460Â citations
TL;DR: The design of adaptive beam bends and beam splitters with arbitrary bend and split angles by use of finite embedded coordinate transformations are described and it is observed that a pure transformation-optical design cannot result in a reflectionless beam expander/compressor.
Abstract: We describe the design of adaptive beam bends and beam splitters with arbitrary bend and split angles by use of finite embedded coordinate transformations. The devices do not exhibit reflection at the entrance or exit surfaces. It is shown that moderate and practically achievable values of the relative permittivity and permeability can be obtained for beam bends and splitters with both small and large bend radius. The devices are also discussed in the context of reconfigurable metamaterials, in which the bend and split angles can be dynamically tuned. The performance of adaptive beam bends and splitters is demonstrated in full wave simulations based on a finite-element method. Furthermore, the design of an adaptively adjustable transformation-optical beam expander/compressor is presented. It is observed that a pure transformation-optical design cannot result in a reflectionless beam expander/compressor.
289Â citations
TL;DR: A scheme that exploits transitions between positive and negative frequencies to mimic negative refraction at an interface and hence to make a negatively refracting lens is proposed, which under ideal circumstances can exhibit subwavelength resolution, limited only by the strength of the time-reversed signal.
Abstract: Time reversal and negative refraction have been shown to be intimately linked processes. We propose a scheme that exploits transitions between positive and negative frequencies to mimic negative refraction at an interface and hence to make a negatively refracting lens. The theory applies equally to electromagnetic and acoustic waves. We also propose an experimental realization, and under ideal circumstances this lens can exhibit subwavelength resolution, limited only by the strength of the time-reversed signal.
190Â citations
TL;DR: In this paper, the authors proposed a structure permeated by a fluid and designed so that the composite medium, the metafluid, has an anisotropic density tensor, and a compressibility of choice.
Abstract: Recent theory shows that sound can be controlled and directed almost at will provided that suitable materials can be found. Here, we propose a structure permeated by a fluid and designed so that the composite medium, the metafluid, has an anisotropic density tensor, and a compressibility of choice.
156Â citations
TL;DR: In this article, the authors describe the use of finite embedded coordinate transformations to design a medium that can be incorporated into a waveguide bend or corner, rendering the structure reflectionless.
Abstract: Transformation optics is a recently appreciated approach for designing complex electromagnetic media. Here, we describe the extension of transformation optical techniques to include waveguide boundary conditions. We illustrate the use of finite embedded coordinate transformations to design a medium that can be incorporated into a waveguide bend or corner, rendering the structure reflectionless. The expected behavior of the waveguide bends is confirmed with numerical simulations.
142Â citations
TL;DR: The first experimental realization of a non-resonant metamaterial designed to operate at zero frequency is presented, and the corresponding effective permeability is calculated, which agrees well with theoretical predictions.
Abstract: Electromagnetic metamaterials are a class of materials that have been artificially structured on a subwavelength scale. They are currently the focus of a great deal of interest because they allow access to previously unrealizable properties such as a negative refractive index. Most metamaterial designs have so far been based on resonant elements, such as split rings, and research has concentrated on microwave frequencies and above. Here, we present the first experimental realization of a non-resonant metamaterial designed to operate at zero frequency. Our samples are based on a recently proposed template for an anisotropic magnetic metamaterial consisting of an array of superconducting plates. Magnetometry experiments show a strong, adjustable diamagnetic response when a field is applied perpendicular to the plates. We have calculated the corresponding effective permeability, which agrees well with theoretical predictions. Applications for this metamaterial may include non-intrusive screening of weak d.c. magnetic fields.
126Â citations
TL;DR: In this article, modified thin wire structures are used as metamaterials for simulating the negative electrical response of a plasma, and modified designs can essentially eliminate the longitudinal dispersion and restore the simple local model.
Abstract: Thin wire structures are commonly used as 'metamaterials' for simulating the negative electrical response of a plasma. In this they are only partially successful: transverse modes are convincingly reproduced but problems arise from highly dispersive longitudinal modes which can be excited by externally incident radiation and impair the validity of the simple local plasma model. We show how modified designs can essentially eliminate the longitudinal dispersion and restore the simple local model.
105Â citations
Patent•
06 Feb 2008
TL;DR: In this article, the authors define an electromagnetic distance between first and second locations substantially greater than a physical distance between the first and the second locations, and the first two locations may be occupied by antennas having an inter-structure coupling (such as a near-field coupling) that is a function of the electromagnetic distance.
Abstract: Apparatus, methods, and systems provide electromagnetic compression. In some approaches the electromagnetic compression is achieved with metamaterials. In some approaches the electromagnetic compression defines an electromagnetic distance between first and second locations substantially greater than a physical distance between the first and second locations, and the first and second locations may be occupied by first and second structures (such as antennas) having an inter-structure coupling (such as a near-field coupling) that is a function of the electromagnetic distance. In some approaches the electromagnetic compression reduces the spatial extent of an antenna near field.
TL;DR: RPT via a surface plasmon polariton state permits evanescent light waves with large wavenumbers to be conveyed through the metamaterial, which is the mechanism for sub-wavelength imaging recently demonstrated with a super-lens.
Abstract: We report resonant photon tunneling (RPT) through one-dimensional metamaterials consisting of alternating layers of metal and dielectric. RPT via a surface plasmon polariton state permits evanescent light waves with large wavenumbers to be conveyed through the metamaterial. This is the mechanism for sub-wavelength imaging recently demonstrated with a super-lens. Furthermore, we find that the RPT peak is shifted from the reflectance dip with increasing the number of Al layers, indicating that the shift is caused by the losses in the RPT.
Patent•
21 Oct 2008
TL;DR: In this paper, the authors provide an overview of methods and systems for both emitting and negatively-refractive focusing of electromagnetic energy, where the transformation medium may include an artificially-structured material such as a metamaterial.
Abstract: Apparatus, methods, and systems provide emitting and negatively-refractive focusing of electromagnetic energy. In some approaches the negatively-refractive focusing includes negatively-refractive focusing from an interior field region with an axial magnification substantially less than one. In some approaches the negatively-refractive focusing includes negatively-refractive focusing with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.
TL;DR: In this paper, it was shown that a properly designed combination of incident light waves would be almost completely transmitted and this remarkable result has been shown experimentally in the presence of disordered materials such as milk or snow.
Abstract: Thick layers of disordered materials, such as milk or snow, scatter light so that very little of it gets through. Theorists say that a properly designed combination of incident light waves would be almost completely transmitted and we now have experimental proof of this remarkable result.
Patent•
30 Jul 2008
TL;DR: In this article, the authors provide a focus adjustment approach using a transformation medium, where the transformation medium may include an artificially-structured material, such as a metamaterial.
Abstract: Apparatus, methods, and systems provide focusing, focus-adjusting, and sensing. In some approaches the focus-adjusting includes providing an extended depth of focus greater than a nominal depth of focus. In some approaches the focus-adjusting includes focus-adjusting with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.
Patent•
05 Sep 2008
TL;DR: In this article, the authors provide an extended depth of field greater than a nominal depth of fields, where the transformation medium may include an artificially-structured material such as a metamaterial.
Abstract: Apparatus, methods, and systems provide emitting, field-adjusting, and focusing of electromagnetic energy. In some approaches the field-adjusting includes providing an extended depth of field greater than a nominal depth of field. In some approaches the field-adjusting includes field-adjusting with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.
Patent•
29 Sep 2008
TL;DR: In this article, the authors present a system for negatively-refractive focusing and sensing of electromagnetic energy, which includes an interior focusing region with an axial magnification substantially greater than one.
Abstract: Apparatus, methods, and systems provide negatively-refractive focusing and sensing of electromagnetic energy. In some approaches the negatively-refractive focusing includes providing an interior focusing region with an axial magnification substantially greater than one. In some approaches the negatively-refractive focusing includes negatively-refractive focusing with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.
Patent•
27 Oct 2008
TL;DR: In this paper, the electromagnetic compression is achieved with metamaterials, where the electromagnetic distance between the first and second locations is greater than the physical distance 250 between the said locations.
Abstract: An apparatus comprises an electromagnetic compression structure 200 located between first and second spatial locations 201, 202. Electromagnetic waves from either of the said locations 201, 202 propagate through at least a portion of the structure 200 to reach respective remote locations 231, 232. The electromagnetic distance between the first and second locations 201, 202 is greater than the physical distance 250 between the said locations 201, 202. The spatial locations 201, 202 each may have means to generate and/or receive electromagnetic radiation such as an antenna or antenna array. The at least two said means may be coupled in a near field manner that is a function of the electromagnetic distance between them. Other apparatus, methods, and systems for providing electromagnetic compression are disclosed. In some approaches the electromagnetic compression is achieved with metamaterials. In some approaches the electromagnetic compression reduces the spatial extent of an antenna near field.
Patent•
23 Oct 2008
TL;DR: In this paper, the design, fabrication and structures of the devices exploit the properties of reactive composite materials (RCM) and reaction products thereof, and they can interact with or modify propagation of electromagnetic waves.
Abstract: Devices and components that can interact with or modify propagation of electromagnetic waves are provided. The design, fabrication and structures of the devices exploit the properties of reactive composite materials (RCM) and reaction products thereof.
01 Jan 2008
TL;DR: In this article, the authors apply quasiconformal mapping in transformation optics and show that the anisotropy within the cloak remains a constant that can be made very small.
Abstract: We apply quasiconformal mapping in transformation optics. The anisotropy within the cloak remains a constant that can be made very small. A cloak is designed to turn an object into a conducting plane.
19 Oct 2008
TL;DR: In this paper, the authors apply quasiconformal mapping in transformation optics and show that the anisotropy within the cloak remains a constant that can be made very small.
Abstract: We apply quasiconformal mapping in transformation optics. The anisotropy within the cloak remains a constant that can be made very small. A cloak is designed to turn an object into a conducting plane.