Showing papers on "Transformation optics published in 2008"
TL;DR: Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices, compact resonators and highly directional sources.
Abstract: Metamaterials are artificially engineered structures that have properties, such as a negative refractive index, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation in metals. Such thin structures are analogous to a monolayer of atoms, making it difficult to assign bulk properties such as the index of refraction. Negative refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide. Three-dimensional (3D) optical metamaterials have come into focus recently, including the realization of negative refraction by using layered semiconductor metamaterials and a 3D magnetic metamaterial in the infrared frequencies; however, neither of these had a negative index of refraction. Here we report a 3D optical metamaterial having negative refractive index with a very high figure of merit of 3.5 (that is, low loss). This metamaterial is made of cascaded 'fishnet' structures, with a negative index existing over a broad spectral range. Moreover, it can readily be probed from free space, making it functional for optical devices. We construct a prism made of this optical NIM to demonstrate negative refractive index at optical frequencies, resulting unambiguously from the negative phase evolution of the wave propagating inside the metamaterial. Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices, compact resonators and highly directional sources.
2,025 citations
TL;DR: In this paper, the authors demonstrate frequency-agile terahertz metamaterials operating in the far-infrared by incorporating semiconductors in critical regions of metallic split-ring resonators.
Abstract: Metamaterials exhibit numerous novel effects1,2,3,4,5 and operate over a large portion of the electromagnetic spectrum6,7,8,9,10. Metamaterial devices based on these effects include gradient-index lenses11,12, modulators for terahertz radiation13,14,15 and compact waveguides16. The resonant nature of metamaterials results in frequency dispersion and narrow bandwidth operation where the centre frequency is fixed by the geometry and dimensions of the elements comprising the metamaterial composite. The creation of frequency-agile metamaterials would extend the spectral range over which devices function and, further, enable the manufacture of new devices such as dynamically tunable notch filters. Here, we demonstrate such frequency-agile metamaterials operating in the far-infrared by incorporating semiconductors in critical regions of metallic split-ring resonators. For this first-generation device, external optical control results in tuning of the metamaterial resonance frequency by ∼20%. Our approach is integrable with current semiconductor technologies and can be implemented in other regions of the electromagnetic spectrum. Metamaterials that possess frequency tunability enable new device functions. By external optical control through the incorporation of semiconductors in metallic split-ring resonators, the researchers provide an elegant solution to frequency-agile terahertz metamaterials.
787 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
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.
496 citations
Posted Content•
TL;DR: In this paper, the relationship between optics and general relativity is discussed, expressed more precisely between geometrical ideas normally applied in general relativity and the propagation of light, or electromagnetic waves in general, in materials.
Abstract: Metamaterials are beginning to transform optics and microwave technology thanks to their versatile properties that, in many cases, can be tailored according to practical needs and desires. Although metamaterials are surely not the answer to all engineering problems, they have inspired a series of significant technological developments and also some imaginative research, because they invite researchers and inventors to dream. Imagine there were no practical limits on the electromagnetic properties of materials. What is possible? And what is not? If there are no practical limits, what are the fundamental limits? Such questions inspire taking a fresh look at the foundations of optics and at connections between optics and other areas of physics. In this article we discuss such a connection, the relationship between optics and general relativity, or, expressed more precisely, between geometrical ideas normally applied in general relativity and the propagation of light, or electromagnetic waves in general, in materials. We also discuss how this connection is applied: in invisibility devices, perfect lenses, the optical Aharonov-Bohm effect of vortices and in analogues of the event horizon.
334 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.
289 citations
TL;DR: In this article, a wave collimator, a far-zone and near-zone focusing flat optical lenses and a right-angle bend for propagating beam fields are presented.
Abstract: The transformation optics technique is applied to design three novel devices—a wave collimator, far-zone and near-zone focusing flat optical lenses and a right-angle bend for propagating beam fields. The structures presented in this paper are all two-dimensional (2D), however, the transformation optics design methodologies can be easily extended to develop 3D versions of these optical devices. The required values of the permittivity and the permeability tensors are derived for each of the three devices considered here. Furthermore, the functional performance of each device is verified using full-wave electromagnetic simulations. A wave collimator consists of a 2D rectangular cylinder where the fields (cylindrical waves) radiated by an embedded line source emerge normal to the top and bottom planar interfaces thereby producing highly directive collimated fields. Next, a far-zone focusing lens for a 2D line source is created by transforming the equi-amplitude equi- phase contour to a planar surface. It is also demonstrated that by aligning two far- zone focusing flat lenses in a back-to-back configuration, a near-zone focusing lens is obtained. Finally, a 2D square cylindrical volume is transformed into a cylinder with a fan-shaped cross section to design a right-angle bend device for propagating beam fields.
222 citations
Book•
26 Sep 2008
TL;DR: The concept of negative refraction was introduced in this article, where the wave-vector and its consequences were investigated in anisotropic and chiral media with negative refractive index materials.
Abstract: Introduction General historical perspective The concept of metamaterials Modeling the material response Phase velocity and group velocity Metamaterials and homogenization procedure Metamaterials and Homogenization of Composites The homogenization hypothesis Limitations and consistency conditions Forward problem Inverse problems: retrieval and constitutive parameters Homogenization from averaging the internal fields Generalization to anisotropic and bianisotropic media Designing Metamaterials with Negative Material Parameters Negative dielectric materials Metamaterials with negative magnetic permeability Metamaterials with negative refractive index Chiral metamaterials Bianisotropic metamaterials Active and nonlinear metamaterials Negative Refraction and Photonic Bandgap Materials Photonic crystals and bandgap materials Band diagrams and iso-frequency contours Negative refraction and flat lenses with photonic crystals Negative refraction versus collimation or streaming Media with e < 0 and < 0: Theory and Properties Origins of negative refraction Choice of the wave-vector and its consequences Anisotropic and chiral media Energy and Momentum in Negative Refractive Index Materials Causality and energy density in frequency dispersive media Electromagnetic energy in left-handed media Momentum density, momentum flow, and transfer in media with negative material parameters Limit of plane waves and small losses Traversal of pulses in materials with negative material parameters Plasmonics of Media with Negative Material Parameters Surface electromagnetic modes in negative refractive materials Waveguides made of negative index materials Negative refraction of surface plasmons Plasmonic properties of structured metallic surfaces Surface waves at the interfaces of nonlinear media Veselago's Lens Is a Perfect Lens Near-field information and diffraction limit Mathematical demonstration of the perfect lens Limitations due to real materials and imperfect NRMs Issues with numerical simulations and time evolution Negative stream of energy with a perfect lens configuration Effects of spatial dispersion Designing Super Lenses Overcoming the limitations of real materials Generalized perfect lens theorem The perfect lens in other geometries Brief Report on Electromagnetic Invisibility Concept of electromagnetic invisibility Excluding electromagnetic fields Cloaking with localized resonances Appendix A: The Fresnel Coefficients for Reflection and Refraction Appendix B: The Dispersion and Fresnel Coefficients for a Bianisotropic Medium Appendix C: The Reflection and Refraction of Light across a Material Slab References Index
219 citations
TL;DR: In this paper, a technique to retrieve effective metamaterial parameters for arbitrary angles of incidence is introduced, which employs the complex reflection and/or transmission coefficients of a finite slab.
Abstract: We introduce a technique to retrieve effective metamaterial parameters for arbitrary angles of incidence. It employs the complex reflection and/or transmission coefficients of a finite slab. Explicit expressions for both polarizations are derived and the constraints to be met for obtaining unique solutions are discussed. The method is applied to the fishnet structure. It turns out that all retrieved parameters strongly depend on the lateral wave vector component due to the complexity of the metamaterial structure. Thus, these parameters are mere wave parameters rather than global material parameters. The physical effects behind this behavior are very likely anisotropy and spatial dispersion.
213 citations
TL;DR: Conceptual studies and numerical simulations are performed for imaging devices that transform a near-field pattern into magnified far-zone images and are based on high-order spatial transformation in cylindrical domains.
Abstract: Conceptual studies and numerical simulations are performed for imaging devices that transform a near-field pattern into magnified far-zone images and are based on high-order spatial transformation in cylindrical domains. A lens translating a near-field pattern from an almost circular input boundary onto a magnified far-field image at a flat output boundary is considered. The lens is made of a metamaterial with anisotropic permittivity and permeability both depending on a single "scaling" parameter of the transformation. Open designs of the lens with a truncated body (3/4-body and 1/4-body lenses) are suggested and analyzed. It is shown that the ideal full lens and the 3/4-body lens produce identical images. Numerical simulations of 1/4-body designs indicate that further truncation of the lens could limit its performance. A light concentrator "focusing" far-zone fields into a nanometer-scale area is also considered.
213 citations
TL;DR: In this paper, the design of arbitrarily shaped electromagnetic (EM) concentrators and their potential applications are studied. But the design is restricted to the case of a rectangular concentrator, which is much more efficient and easier than the existing techniques.
Abstract: We study the design of arbitrarily shaped electromagnetic (EM) concentrators and their potential applications. To obtain closed-form formulas of EM parameters for an arbitrarily shaped concentrator, we employ nonuniform rational B-spline (NURBS) to represent the geometrical boundary. Using the conformally optical transformation of NURBS surfaces, we propose the analytical design of arbitrarily shaped concentrators, which are composed of anisotropic and inhomogeneous metamaterials with closed-form constitutive tensors. The designed concentrators are numerically validated by full-wave simulations, which show perfectly directed EM behaviors. As one of the potential applications, we demonstrate a way to amplify plane waves using a rectangular concentrator, which is much more efficient and easier than the existing techniques. Using NURBS expands the generality of the transformation optics and could lead toward making a very general tool that would interface with commercial softwares such as 3D STUDIOMAX and MAYA.
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.
TL;DR: The application of NURBS in the design of arbitrary cloaks shows transformation optics to be a very general tool to interface with commercial softwares like 3D STUDIOMAX and MAYA.
Abstract: To design conformally invisible cloaks for arbitrarily shaped objects, we use the nonuniform rational $B$-spline (NURBS) to represent the geometrical modeling of the arbitrary object. Based on the method of optical transformation, analytical formulas of the permittivity and permeability tensors are proposed for arbitrarily shaped invisible cloaks. Such formulas can be easily implemented in the design of arbitrary cloaks. Full-wave simulations are given for heart-shaped invisible cloaks and perfectly electrical conducting (PEC) objects, in which we observe that the power-flow lines of incoming electromagnetic waves will be bent smoothly in the cloaks and will return to their original propagation directions after propagating around the object. We also show that the scattered field from the PEC object coated with the invisible cloak is much smaller than that from the PEC core. The application of NURBS in the design of arbitrary cloaks shows transformation optics to be a very general tool to interface with commercial softwares like 3D STUDIOMAX and MAYA.
TL;DR: In this paper, the authors proposed a metamaterial device that serves as a frequency-selective super-absorber, which consists of an absorbing core material coated with a shell of isotropic double negative metammaterial.
Abstract: Using the idea of transformation optics, we propose a metamaterial device that serves as a frequency-selective super-absorber, which consists of an absorbing core material coated with a shell of isotropic double negative metamaterial. For a fixed volume, the absorption cross section of the super-absorber can be made arbitrarily large at one frequency. The double negative shell serves to amplify the evanescent tail of the high order incident cylindrical waves, which induces strong scattering and absorption. Our conclusion is supported by both analytical Mie theory and numerical finite element simulation. Interesting applications of such a device are discussed.
TL;DR: The design of radially symmetric invisibility cloaks is extended through transformation optics to coated cylinders of an arbitrary cross section to implement a full-wave finite-element model for a cylindrical antenna radiating a p-polarized electric field in the presence of a F-shaped lossy object surrounded by the cloak.
Abstract: We extend the design of radially symmetric invisibility cloaks through transformation optics as proposed by Pendry et al. [Science 312, 1780 (2006)] to coated cylinders of an arbitrary cross section. The validity of our Fourier-based approach is confirmed by both analytical and numerical results for a cloak displaying a non-convex cross section of varying thickness. In the former case, we evaluate the Green's function of a line source in the transformed coordinates. In the latter case, we implement a full-wave finite-element model for a cylindrical antenna radiating a p-polarized electric field in the presence of a F-shaped lossy object surrounded by the cloak.
TL;DR: In this paper, isotropic and nonsingular parameters are constructed to give approximate cloaking to any desired degree of accuracy for electrostatic, acoustic, and quantum waves for the Helmholtz equation.
Abstract: Transformation optics constructions have allowed the design of electromagnetic, acoustic and quantum parameters that steer waves around a region without penetrating it, so that the region is hidden from external observations. The material parameters are anisotropic, and singular at the interface between the cloaked and uncloaked regions, making physical realization a challenge. We address this problem by showing how to construct isotropic and nonsingular parameters that give approximate cloaking to any desired degree of accuracy for electrostatic, acoustic and quantum waves. The techniques used here may be applicable to a wider range of transformation optics designs. For the Helmholtz equation, cloaking is possible outside a discrete set of frequencies or energies, namely the Neumann eigenvalues of the cloaked region. At these frequencies or energies the ideal cloak supports trapped states, vanishing outside of the cloaked region; near these energies, an approximate cloak supports almost trapped states. This is in fact a useful feature, and we conclude by giving several quantum mechanical applications.
TL;DR: This model elucidates the unique features of the resonant enhancement in "positive-to-negative transition" metamaterials for a broad frequency range from microwaves to optics.
Abstract: Resonant enhancement of electromagnetic waves propagating at oblique incidence in metamaterials, with dielectric permittivity and magnetic permeability linearly changing from positive to negative values, has been predicted and theoretically studied. This effect occurs for both TE and TM polarizations near the point where a refractive index changes its sign. Our model elucidates the unique features of the resonant enhancement in “positive-to-negative transition” metamaterials for a broad frequency range from microwaves to optics. © 2008 Optical Society of America OCIS codes: 160.3918, 160.2710, 260.5740.
TL;DR: It is demonstrated that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such meetamaterial can demonstrate various nonlinear properties.
Abstract: We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission.
TL;DR: A generalized transformation procedure to highly improve the flexibilities for the design of two-dimensional (2D) cloaks is established and the general expressions for the complex medium parameters are developed, which can be readily applied to design 2D cloaks with arbitrary geometries.
Abstract: Transformation optics opens an exciting gateway to design electromagnetic "invisibility" cloaks with anisotropic and inhomogeneous medium. In this paper, we establish a generalized transformation procedure to highly improve the flexibilities for the design of two-dimensional (2D) cloaks. The general expressions for the complex medium parameters are developed, which can be readily applied to design 2D cloaks with arbitrary geometries. An example of 2D cloak with irregular cross section is designed and studied by full-wave simulations. The Huygens' Principle is applied to quantitatively evaluate its unusual electromagnetic behaviors. All the theoretical and numerical results verify the effectiveness of the proposed approach. The generalization in this Paper makes a great step forward for the flexible design of electromagnetic cloaks with arbitrary shapes.
TL;DR: In this article, a method for eliminating a class of singularities in optical media where the refractive index goes to zero or infinity at one or more isolated points was proposed, where the permittivity and permeability tensors are discontinuous at one point.
Abstract: We propose a method for eliminating a class of singularities in optical media where the refractive index goes to zero or infinity at one or more isolated points. Employing transformation optics, we find a refractive index distribution equivalent to the original one that is nonsingular but shows a slight anisotropy. In this way, the original singularity is 'transmuted' into another, weaker type of singularity where the permittivity and permeability tensors are discontinuous at one point. The method is likely to find applications in designing and improving optical devices by making them easier to implement or to operate in a broad band of the spectrum.
TL;DR: The permittivity, permeability, wave vector, and refractive index are considered, and stability, refraction, gain, and fundamental limitations resulting from causality are discussed.
Abstract: Several results concerning active media or metamaterials are proved and discussed. In particular, we consider the permittivity, permeability, wave vector, and refractive index, and discuss stability, refraction, gain, and fundamental limitations resulting from causality.
TL;DR: A chiral optical negative-index metamaterial design of doubly periodic construction for the near-infrared spectrum is presented and an effective material parameter retrieval procedure is developed for general bi-isotropic meetamaterials.
Abstract: A chiral optical negative-index metamaterial design of doubly periodic construction for the near-infrared spectrum is presented. The chirality is realized by incorporating sub-wavelength planar silver-alumina-silver resonators and arranging them in a left-handed helical (i.e., stair-step) configuration as a wave propagates through the metamaterial. An effective material parameter retrieval procedure is developed for general bi-isotropic metamaterials. A numerical design example is presented and the retrieved effective material parameters exhibiting a negative index of refraction are provided.
TL;DR: In this article, an approach to broadband cloaking of light waves is analyzed for a simplified case of a scaling transformation for a general cylindrical coordinate system, which requires metamaterials with specifically engineered dispersion.
Abstract: An approach to broadband cloaking of light waves is analysed for a simplified case of a scaling transformation for a general cylindrical coordinate system. The proposed approach requires metamaterials with specifically engineered dispersion. The restriction on the signs of gradients in the dispersion dependencies of the dielectric permittivity and the magnetic permeability for different operational wavelengths is revealed and is shown to cause difficulties unless additional gain-assisted compensation for losses or electromagnetically induced transparency is introduced in the cloaking system.
TL;DR: By conformal transformation of the electromagnetic space, this work develops a methodology for realizing subwavelength ray optics with curved ray trajectories that enables deep-subwavelength-scale beams to flow through two- or three-dimensional spaces.
Abstract: We present a transformation optics approach for molding the light flow at the deep-subwavelength scale, using metamaterials with uniquely designed dispersion. By conformal transformation of the electromagnetic space, we develop a methodology for realizing subwavelength ray optics with curved ray trajectories. This enables deep-subwavelength-scale beams to flow through two- or three-dimensional spaces.
TL;DR: In this article, a review of the nonlinear left-handed metamaterials (LHMs) is presented, where the authors consider a model system that combines nonlinearity (dependence of the permittivity and permeability on the magnitude of the propagating field) with the anomalous dispersion exhibited by LHM.
Abstract: Metamaterials, exhibiting simultaneously negative permittivity e and permeability μ, more commonly referred to as left-handed metamaterials (LHMs) and also known as negative-index materials, have received substantial attention in the scientific and engineering communities [1]. Most studies of LHMs (and electromagnetic metamaterials in general) have been in the linear regime of wave propagation and have already inspired new types of microwave circuits and devices. The results of these studies have already been the subject of numerous reviews and books.This review covers a less explored but rapidly developing area of investigation involving media that combine nonlinearity (dependence of the permittivity and permeability on the magnitude of the propagating field) with the anomalous dispersion exhibited by LHM. The nonlinear phenomena in such media will be considered on the example of a model system: the nonlinear left-handed transmission line. These nonlinear phenomena include parametric generation and amplification, harmonic and subharmonic generation as well as modulational instabilities and envelope solitons.
TL;DR: In this paper, it was shown that higher-order Bloch modes can have considerable influence on the results for a periodically stacked metamaterial, and the authors derived criteria for the validity of the effective parameter approach.
Abstract: Effective material parameters for metamaterials are usually extracted for a single thin layer only. We show that, in general, these parameters cannot directly be assigned to a multilayered (bulk) metamaterial. The principal issue is the presence of higher-order Bloch modes. These modes are usually negligible for a single layer but can have considerable influence on the results for a periodically stacked structure. In particular, we show examples where a stack of single-layer negative refractive index metamaterials exhibits a positive index. Furthermore, on the basis of the dispersion relation of the respective Bloch modes, we derive criteria for the validity of the effective parameter approach.
TL;DR: In this article, the response of a cover formed by metallic plasmonic implants may be tailored at will so that at a given frequency, it possesses the plasmoric-type properties required for cloaking applications.
Abstract: In recent works, we have suggested that plasmonic covers may provide an interesting cloaking effect, dramatically reducing the overall visibility and scattering of a given object. While materials with the required properties may be directly available in nature at some specific infrared or optical frequencies, this is not necessarily the case for any given design frequency of interest. Here we discuss how such plasmonic covers may be specifically designed as metamaterials at terahertz, infrared, and optical frequencies using naturally available metals. Using full-wave simulations, we demonstrate that the response of a cover formed by metallic plasmonic implants may be tailored at will so that at a given frequency, it possesses the plasmonic-type properties required for cloaking applications.
TL;DR: The technique of source transformations are proposed as a powerful approach for antenna design, especially in relation to conformal antennas, using finite-element full-wave simulations.
Abstract: Transformation optics is a recently appreciated methodology for the design of complex media that control the propagation of electromagnetic and other types of waves. The transformation optical technique involves the use of coordinate transformations applied to some region of space, providing a conceptual means to redirect the flow of waves. Successfully designed devices to date have made use of transformations acting on passive space only; however, the technique can also be applied when source distributions (e.g., current and charge) are included within the space being transformed. In this paper we present examples of source transformations that illustrate the potential of these expanded transformation optical methods. In particular, using finite-element full-wave simulations, we confirm the restoration of dipole radiation patterns from both a distorted ‘pin-wheel’ antenna and a bent dipole partially occluded by a cylindrical scatterer. We propose the technique of source transformations as a powerful approach for antenna design, especially in relation to conformal antennas.
TL;DR: It is demonstrated that metamaterials represent model systems for longitudinal and transverse magnetic coupling in the optical domain and can lead to fully parallel or antiparallel alignment of the magnetic dipoles at the lowest frequency resonance.
Abstract: In this paper, we demonstrate that metamaterials represent model systems for longitudinal and transverse magnetic coupling in the optical domain. In particular, such coupling can lead to fully parallel or antiparallel alignment of the magnetic dipoles at the lowest frequency resonance. Also, we present the design scheme for constructing three-dimensional metamaterials with solely magnetic interaction. Our concept could pave the way for achieving rather complicated magnetic materials with desired arrangements of magnetic dipoles at optical frequencies.
TL;DR: In this paper, the authors describe the challenges and opportunities for creating magnetically active metamaterials in the optical part of the spectrum and describe several theoretical techniques used for calculating the effective parameters of plasmonic metammaterials: the effective dielectric permittivity eff(!) and magnetic permeability µeff(!).