Showing papers on "Metamaterial published in 2009"
TL;DR: This work investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice that is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.
Abstract: We investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice. These nanostructures are fabricated via an approach based on direct laser writing into a positive-tone photoresist followed by electrochemical deposition of gold. For propagation of light along the helix axis, the structure blocks the circular polarization with the same handedness as the helices, whereas it transmits the other, for a frequency range exceeding one octave. The structure is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.
2,252 citations
TL;DR: A nanoplasmonic analogue of EIT is experimentally demonstrated using a stacked optical metamaterial to achieve a very narrow transparency window with high modulation depth owing to nearly complete suppression of radiative losses.
Abstract: In atomic physics, the coherent coupling of a broad and a narrow resonance leads to quantum interference and provides the general recipe for electromagnetically induced transparency (EIT). A sharp resonance of nearly perfect transmission can arise within a broad absorption profile. These features show remarkable potential for slow light, novel sensors and low-loss metamaterials. In nanophotonics, plasmonic structures enable large field strengths within small mode volumes. Therefore, combining EIT with nanoplasmonics would pave the way towards ultracompact sensors with extremely high sensitivity. Here, we experimentally demonstrate a nanoplasmonic analogue of EIT using a stacked optical metamaterial. A dipole antenna with a large radiatively broadened linewidth is coupled to an underlying quadrupole antenna, of which the narrow linewidth is solely limited by the fundamental non-radiative Drude damping. In accordance with EIT theory, we achieve a very narrow transparency window with high modulation depth owing to nearly complete suppression of radiative losses. Plasmonic nanostructures enable the concentration of large electric fields into small spaces. The classical analogue of electromagnetically induced transparency has now been achieved in such devices, leading to a narrow resonance in their absorption spectrum. This combination of high electric-field concentration and sharp resonance offers a pathway to ultracompact sensors with extremely high sensitivity.
1,652 citations
TL;DR: This work demonstrates an improvement in biosensing technology using a plasmonic metamaterial that is capable of supporting a guided mode in a porous nanorod layer and provides an enhanced sensitivity to refractive-index variations of the medium between the rods.
Abstract: Label-free plasmonic biosensors rely either on surface plasmon polaritons or on localized surface plasmons on continuous or nanostructured noble-metal surfaces to detect molecular-binding events. Despite undisputed advantages, including spectral tunability, strong enhancement of the local electric field and much better adaptability to modern nanobiotechnology architectures, localized plasmons demonstrate orders of magnitude lower sensitivity compared with their guided counterparts. Here, we demonstrate an improvement in biosensing technology using a plasmonic metamaterial that is capable of supporting a guided mode in a porous nanorod layer. Benefiting from a substantial overlap between the probing field and the active biological substance incorporated between the nanorods and a strong plasmon-mediated energy confinement inside the layer, this metamaterial provides an enhanced sensitivity to refractive-index variations of the medium between the rods (more than 30,000 nm per refractive-index unit). We demonstrate the feasibility of our approach using a standard streptavidin-biotin affinity model and record considerable improvement in the detection limit of small analytes compared with conventional label-free plasmonic devices.
1,615 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: The optical 'carpet' cloak is designed using quasi-conformal mapping to conceal an object that is placed under a curved reflecting surface by imitating the reflection of a flat surface and enables broadband and low-loss invisibility at a wavelength range of 1,400-1,800 nm.
Abstract: Invisibility devices have captured the human imagination for many years. Recent theories have proposed schemes for cloaking devices using transformation optics and conformal mapping. Metamaterials, with spatially tailored properties, have provided the necessary medium by enabling precise control over the flow of electromagnetic waves. Using metamaterials, the first microwave cloaking has been achieved but the realization of cloaking at optical frequencies, a key step towards achieving actual invisibility, has remained elusive. Here, we report the first experimental demonstration of optical cloaking. The optical 'carpet' cloak is designed using quasi-conformal mapping to conceal an object that is placed under a curved reflecting surface by imitating the reflection of a flat surface. The cloak consists only of isotropic dielectric materials, which enables broadband and low-loss invisibility at a wavelength range of 1,400-1,800 nm.
1,318 citations
TL;DR: In this article, a dielectric optical cloak is designed using quasi-conformal mapping to conceal an object that is placed under a curved reflecting surface which imitates the reflection of a flat surface.
Abstract: Invisibility or cloaking has captured human's imagination for many years. With the recent advancement of metamaterials, several theoretical proposals show cloaking of objects is possible, however, so far there is a lack of an experimental demonstration at optical frequencies. Here, we report the first experimental realization of a dielectric optical cloak. The cloak is designed using quasi-conformal mapping to conceal an object that is placed under a curved reflecting surface which imitates the reflection of a flat surface. Our cloak consists only of isotropic dielectric materials which enables broadband and low-loss invisibility at a wavelength range of 1400-1800 nm.
955 citations
TL;DR: In this article, a single layer of electrically controlled metamaterial was used to achieve active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.
Abstract: Using a single layer of electrically controlled metamaterial, researchers have achieved active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.
935 citations
TL;DR: The presence of strong chirality in the terahertz metamaterial lifts the degeneracy for the two circularly polarized waves and allows for the achievement of negative refractive index without requiring simultaneously negative permittivity and negative permeability.
Abstract: We experimentally demonstrate a chiral metamaterial exhibiting negative refractive index at terahertz frequencies. The presence of strong chirality in the terahertz metamaterial lifts the degeneracy for the two circularly polarized waves and allows for the achievement of negative refractive index without requiring simultaneously negative permittivity and negative permeability. The realization of terahertz chiral negative index metamaterials offers opportunities for investigation of their novel electromagnetic properties, such as negative refraction and negative reflection, as well as important terahertz device applications.
905 citations
TL;DR: This work combined template stripping with precisely patterned silicon substrates to obtain ultrasmooth pure metal films with grooves, bumps, pyramids, ridges, and holes, and measured surface-plasmon–propagation lengths on the resulting surfaces approach theoretical values for perfectly flat films.
Abstract: Surface plasmons are electromagnetic waves that can exist at metal interfaces because of coupling between light and free electrons. Restricted to travel along the interface, these waves can be channeled, concentrated, or otherwise manipulated by surface patterning. However, because surface roughness and other inhomogeneities have so far limited surface-plasmon propagation in real plasmonic devices, simple high-throughput methods are needed to fabricate high-quality patterned metals. We combined template stripping with precisely patterned silicon substrates to obtain ultrasmooth pure metal films with grooves, bumps, pyramids, ridges, and holes. Measured surface-plasmon-propagation lengths on the resulting surfaces approach theoretical values for perfectly flat films. With the use of our method, we demonstrated structures that exhibit Raman scattering enhancements above 10(7) for sensing applications and multilayer films for optical metamaterials.
852 citations
TL;DR: In this paper, the authors review the recent progress of Mie resonance-based metamaterials by providing a description of the underlying mechanisms to realize negative permeability, negative permittivity and double negative media.
752 citations
TL;DR: The ridge gap waveguide as mentioned in this paper is a metamaterial-based waveguide that can be realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces.
Abstract: This letter presents a new metamaterial-based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub- millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high surface impedance (ideally a perfect magnetic conductor) in the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear either within the band of operation. The present letter introduces the gap waveguide and presents some initial simulated results.
TL;DR: In this paper, a negative index of refraction due to three-dimensional chirality is demonstrated for bilayered metamaterial based on pairs of mutually twisted planar metal patterns in parallel planes, which also shows negative electric and magnetic responses and exceptionally strong optical activity and circular dichroism.
Abstract: Recently it has been predicted that materials with exceptionally strong optical activity may also possess a negative refractive index, allowing the realization of superlenses for super-resolution imaging and data storage applications. Here we demonstrate experimentally and numerically that a chirality-induced negative index of refraction is possible. A negative index of refraction due to three-dimensional chirality is demonstrated for a bilayered metamaterial based on pairs of mutually twisted planar metal patterns in parallel planes, which also shows negative electric and magnetic responses and exceptionally strong optical activity and circular dichroism. Multilayered forms of the metamaterial are found to be suitable for use as ultrathin polarization rotators and circular polarizers for practical applications.
Book•
23 Nov 2009
TL;DR: In this paper, the authors provide an overview of optical cloaking with metamaterials and their applications in the field of transformation optics, including super resolution with meta-lenses, near-field superlens, and electric cloaking.
Abstract: Preface Chapter 1. Introduction What are metamaterials? Macroscopic effective parameters References Chapter 2. Optical Properties of Metal-Dielectric Composites Optical materials and electronic structures Optical properties of dielectric materials Optical properties of metals Metal-dielectric composites and mixing rules References Chapter 3. Experimental Techniques and Data Treatment Fabrication of two-dimensional optical metamaterials Approaching the third dimension Characterization of spectral properties Extraction of homogenized optical parameters References Chapter 4. Electric Metamaterials A brief overview of artificial dielectrics Optical properties of stratified metal-dielectric composites Periodic array of metallic wires Semicontinuous metal films References Chapter 5. Magnetic Metamaterials Negligible optical magnetism in nature Split-ring resonators Optical magnetic elements Magnetism in the visible spectrum Analytical model of magnetic nanostrips High-permittivity route to artificial magnetism References Chapter 6. Negative-Index Metamaterials A brief historical review Reversed phenomena in negative-index media Negative refraction in microwave frequencies The debut of optical negative-index materials General recipe for construction Alternative approaches References Chapter 7. Nonlinear Optics with Metamaterials Recent advances of nonlinear effects in metamaterials Second-harmonic generation and the Manley-Rowe relations in negative-index materials Optical parametric amplifications in negative-index materials References Chapter 8. Super Resolution with Meta-Lenses Perfect lens with subwavelength resolution Near-field superlens Tunable superlens using random composites Potential applications of the composite lens Far-field imaging with super-resolution References Chapter 9. Transformation Optics and Electromagnetic Cloak of Invisibility Invisibility and transformation optics: an overview Cloaking by coordinate transformation Towards experimental demonstrations Non-magnetic optical cloak Cloaking with high-order transformations Designs for high-order optical cloaking Alternative approaches for optical cloaking Concluding remarks on transformation optics References Index
TL;DR: In this article, a polarization-insensitive metamaterial absorber for terahertz frequencies is presented, which achieves an absorptivity of 77% at 1.145 THz.
Abstract: We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. Effective-medium theory is used to describe the absorptive properties of the metamaterial in terms of optical constants---a description that has been thus far lacking. From our theoretical approach, we construct a device that yields over 95% absorption in simulation. Our fabricated design consists of a planar single unit-cell layer of metamaterial and reaches an absorptivity of 77% at 1.145 THz.
TL;DR: In this article, a review of recent advances in the processing of microwave ferrites is presented, including self-bias magnetization, tunability of the magnetic anisotropy, low microwave loss, and volumetric and weight reduction.
TL;DR: The experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves and achieves deep-subwavelength resolution with low loss over a broad frequency bandwidth is reported.
Abstract: Like their optical counterparts, acoustic metamaterials are capable of manipulating sound waves in unusual ways. An acoustic hyperlens is now demonstrated that is capable of magnifying subwavelength acoustic waves, and could therefore find applications in medical imaging or underwater sonar. Acoustic metamaterials can manipulate sound waves in surprising ways, which include collimation, focusing, cloaking, sonic screening and extraordinary transmission1,2,3,4,5,6,7,8,9,10,11,12,13,14. Recent theories suggested that imaging below the diffraction limit using passive elements can be realized by acoustic superlenses or magnifying hyperlenses15,16. These could markedly enhance the capabilities in underwater sonar sensing, medical ultrasound imaging and non-destructive materials testing. However, these proposed approaches suffer narrow working frequency bands and significant resonance-induced loss, which hinders them from successful experimental realization. Here, we report the experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves. The fabricated acoustic hyperlens relies on straightforward cutoff-free propagation and achieves deep-subwavelength resolution with low loss over a broad frequency bandwidth.
TL;DR: It is demonstrated theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms, and these results are confirmed by accurate simulations of the electromagnetic field propagation in the meetamaterial.
Abstract: We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support a full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial.
TL;DR: In this article, the authors demonstrate the consequence of using different equivalent models to represent a lattice system consisting of mass-in-mass units and why negative mass is needed in the equivalent model.
TL;DR: In this paper, an Ag split ring resonator (SRR) is patterned with e-beam lithography onto planar VO_2 and etched via reactive ion etching to yield Ag/VO_2 hybrid SRRs.
Abstract: Engineering metamaterials with tunable resonances from mid-infrared to near-infrared wavelengths could have far-reaching consequences for chip based optical devices, active filters, modulators, and sensors. Utilizing the metal-insulator phase transition in vanadium oxide (VO_2), we demonstrate frequency-tunable metamaterials in the near-IR range, from 1.5 - 5 microns. Arrays of Ag split ring resonators (SRRs) are patterned with e-beam lithography onto planar VO_2 and etched via reactive ion etching to yield Ag/VO_2 hybrid SRRs. FTIR reflection data and FDTD simulation results show the resonant peak position red shifts upon heating above the phase transition temperature. We also show that, by including coupling elements in the design of these hybrid Ag/VO_2 bi-layer structures, we can achieve resonant peak position tuning of up to 110 nm.
TL;DR: The classical phenomenon of optical activity can be observed in artificial planar media which exhibit neither 3D nor 2D chirality in the form of strong circular dichroism and birefringence indistinguishable from those of chiral three-dimensional media.
Abstract: We report that the classical phenomenon of optical activity, which is traditionally associated with chirality (helicity) of organic molecules, proteins, and inorganic structures, can be observed in artificial planar media which exhibit neither 3D nor 2D chirality. We observe the effect in the microwave and optical parts of the spectrum at oblique incidence to regular arrays of nonchiral subwavelength metamolecules in the form of strong circular dichroism and birefringence indistinguishable from those of chiral three-dimensional media.
TL;DR: In this article, the effect of a tiny gap in a metal substrate on incident terahertz radiation in the regime where the gap's dimensions are smaller than the metal's skin-depth is investigated.
Abstract: The effect of a tiny gap in a metal substrate on incident terahertz radiation in the regime where the gap's dimensions are smaller than the metal's skin-depth are investigated. The results and theoretical analysis show that the gap acts as a capacitor charged by light-induced currents, and dramatically enhances the local electric field.
TL;DR: In this paper, the authors developed an approach to broad-band omnidirectional light absorption, based on light propagation in a metamaterial structure forming an effective "black hole".
Abstract: We develop an approach to broad-band omnidirectional light absorption, based on light propagation in a metamaterial structure forming an effective “black hole.” The proposed system does not rely on magnetic response, is nonresonant, and can be fabricated from existing materials.
TL;DR: The spectral tunability of these resonances from the visible to the mid-infrared is investigated, highlighting a potential for applications in surface enhanced spectroscopies.
Abstract: Plasmonic nanocavities consisting of the concentric arrangement of a disk and a ring sustain both subradiant and superradiant dipolar plasmon modes with large associated field enhancements and high refractive index sensitivities. In structures with broken symmetry, additionally a highly tunable Fano interference feature appears, which can be explained with a simple analytical harmonic oscillator model. The spectral tunability of these resonances from the visible to the mid-infrared is investigated, highlighting a potential for applications in surface enhanced spectroscopies.
TL;DR: This work demonstrates reconfigurable anisotropic metamaterials at terahertz frequencies where artificial "atoms" reorient within unit cells in response to an external stimulus and observes a marked tunability of the electric and magnetic response.
Abstract: We demonstrate reconfigurable anisotropic metamaterials at terahertz frequencies where artificial "atoms" reorient within unit cells in response to an external stimulus. This is accomplished by fabricating planar arrays of split ring resonators on bimaterial cantilevers designed to bend out of plane in response to a thermal stimulus. We observe a marked tunability of the electric and magnetic response as the split ring resonators reorient within their unit cells. Our results demonstrate that adaptive metamaterials offer significant potential to realize novel electromagnetic functionality ranging from thermal detection to reconfigurable cloaks or absorbers.
TL;DR: In this paper, a dual-band metamaterial absorber with two distinct and strong absorption points near 0.45 and 0.92 THz has been designed and analyzed.
Abstract: We report the design, simulation, and measurement of a dual-band metamaterial absorber in the terahertz region. Theoretical and experimental results show that the absorber has two distinct and strong absorption points near 0.45 and 0.92 THz, both which are related to the LC resonance of the metamaterial. The distributions of the power flow and the power loss indicate that the absorber is an excellent electromagnetic wave collector: the wave is first trapped and reinforced in certain specific locations and then completely consumed. This dual-band absorber has applications in many scientific and technological areas.
TL;DR: In this paper, the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators is presented.
Abstract: We present the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. We observed a tight focus of half-wavelength in width at 60.5 kHz by imaging a point source. This result is in excellent agreement with the numerical simulation by transmission line model in which we derived the effective mass density and compressibility. This metamaterial lens also displays variable focal length at different frequencies. Our experiment shows the promise of designing compact and lightweight ultrasound imaging elements.
TL;DR: In this article, the authors use scattering-type near-field microscopy to monitor the evolution of the near field oscillations of infrared gap antennas progressively loaded with metallic bridges of varying size.
Abstract: Optical and infrared antennas 1–6 enable a variety of cuttingedge applications ranging from nanoscale photodetectors 7 to highly sensitive biosensors 8 All these applications critically rely on the optical near-field interaction between the antenna and its ‘load’ (biomolecules or semiconductors) However, it is largely unexplored how antenna loading affects the near-field response Here, we use scattering-type near-field microscopy to monitor the evolution of the near-field oscillations of infrared gap antennas progressively loaded with metallic bridges of varying size Our results provide direct experimental evidence that the local near-field amplitude and phase can be controlled by antenna loading, in excellent agreement with numerical calculations By modelling the antenna loads as nanocapacitors and nanoinductors 9–11 , we show that the change of near-field patterns induced by the load can be understood within the framework of circuit theory Targeted antenna loading provides an excellent means of engineering complex antenna configurations in coherent control applications 12 , adaptive nano-optics 13 and metamaterials 14 Optical and infrared antennas based on metal nanostructures allow for efficient conversion of propagating light into nanoscale confined and strongly enhanced optical fields, and vice versa 1–5,15
Posted Content•
TL;DR: The first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators is presented, showing the promise of designing compact and lightweight ultrasound imaging elements.
Abstract: We present the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. We observed a tight focus of half-wavelength in width at 60.5 KHz by imaging a point source. This result is in excellent agreement with the numerical simulation by transmission line model in which we derived the effective mass density and compressibility. This metamaterial lens also displays variable focal length at different frequencies. Our experiment shows the promise of designing compact and light-weight ultrasound imaging elements.
TL;DR: Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light as mentioned in this paper, and combined with nonvolatility, multifunctional metamaterials might be formed.
Abstract: Magnetic nanostructures have long been in the focus of intense research in the magnetic storage industry. For data storage the nonvolatility of magnetic states is of utmost relevance. As information technology generates the need for higher and higher data-transfer rates, research efforts have moved to understand magnetization dynamics. Here, spin waves and their particle-like analog, magnons, are increasingly attracting interest. High-quality nanopatterned magnetic media now offer new ways to transmit and process information without moving electrical charges. This new functionality is enabled by spin waves. They are confined by novel functioning principles, which render them especially suitable to operate at the nanoscale. Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light. Combined with nonvolatility, multifunctional metamaterials might be formed. We report recent advances in this rapidly increasing research field called magnonics.
TL;DR: A design for a cloak to control bending waves propagating in isotropic heterogeneous thin plates is proposed, achieved through homogenization of a multilayered concentric coating filled with piecewise constant isotropIC elastic material.
Abstract: Control of waves with metamaterials is of great topical interest, and is fueled by rapid progress in broadband acoustic and electromagnetic cloaks. We propose a design for a cloak to control bending waves propagating in isotropic heterogeneous thin plates. This is achieved through homogenization of a multilayered concentric coating filled with piecewise constant isotropic elastic material. Significantly, our cloak displays no phase shift for both backward and forward scattering. To foster experimental efforts, we provide a simplified design of the cloak which is shown to work in a more than two-octave frequency range (30 Hz to 150 Hz) when it consists of 10 layers using only 6 different materials overall. This metamaterial should be easy to manufacture, with potential applications ranging from car industry to antiearthquake passive systems for smart buildings, depending upon the plate dimensions and wavelengths.