Showing papers by "David Schurig published in 2008"

Design of electromagnetic cloaks and concentrators using form-invariant coordinate transformations of Maxwell’s equations

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.

Optical design of reflectionless complex media by finite embedded coordinate transformations.

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.

Scattering Theory Derivation of 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.

Material parameters and vector scaling in transformation acoustics

Abstract: The degree to which the coordinate transformation concept first demonstrated for electromagnetic waves can be applied to other classes of waves remains an open question. In this work, we thoroughly examine the coordinate transformation invariance of acoustic waves. We employ a purely physical argument to show how the acoustic velocity vector must transform differently than the E and H fields in Maxwell's equations, which explains why acoustic coordinate transformation invariance was not found in some previous analyses. A first principles analysis of the acoustic equations under arbitrary coordinate transformations confirms that the divergence operator is preserved only if velocity transforms in this physically correct way. This analysis also yields closed-form expressions for the bulk modulus and mass density tensor of the material required to realize an arbitrary coordinate transformation on the acoustic fields, which we show are equivalent to forms presented elsewhere. We demonstrate the computation of these material parameters in two specific cases and show that the change in velocity and pressure gradient vectors under a nonorthogonal coordinate transformation is precisely how these vectors must change from purely physical arguments. This analysis confirms that all of the electromagnetic devices and materials that have been conceived using the coordinate transformation approach are also in principle realizable for acoustic

An aberration-free lens with zero F-number

Abstract: Starting from the Luneberg lens index profile, we apply the transformation design method to the problem of far-field imaging of (infinitely) distant objects. This analysis yields a single element lens with a planar image surface, zero aberrations of all orders, zero F-number and (in some cases) constant aperture for all angles of incidence.

Electromagnetic compression apparatus, methods, and systems

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.

Emitting and negatively-refractive focusing apparatus, methods, and systems

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.

Focusing and sensing apparatus, methods, and systems

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.

Emitting and focusing apparatus, methods, and systems

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.

Negatively-refractive focusing and sensing apparatus, methods, and systems

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.

Electromagnetic radiation compression

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.

Finite-embedded coordinate designed transformation-optical devices

Abstract: The design method for complex electromagnetic materials is expanded from form-invariant coordinate transformations of Maxwell's equations to finite embedded coordinate transformations Embedded transformations allow the transfer of electromagnetic field manipulations from the transformation-optical medium to another medium, thereby allowing the design of structures that are not exclusively invisible A topological criterion for the reflectionless design of complex media is also disclosed and is illustrated in conjunction with the topological criterion to design a parallel beam shifter and a beam splitter with unconventional electromagnetic behavior

Transformation-optical design of reconfigurable optical devices

Abstract: The design method for complex electromagnetic materials is expanded from form-invariant coordinate transformations of Maxwell's equations to finite embedded coordinate transformations. Embedded transformations allow the transfer of electromagnetic field manipulations from the transformation-optical medium to another medium, thereby allowing the design of structures that are not exclusively invisible. A topological criterion for the reflectionless design of complex media is also disclosed and is illustrated in conjunction with the topological criterion to design a parallel beam shifter and a beam splitter with unconventional electromagnetic behavior.

Optical and metamaterial devices based on reactive composite materials

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.