Direct calculation of permeability and permittivity for a left-handed metamaterial
TL;DR: In this article, an electromagnetic metamaterial was fabricated and demonstrated to exhibit a "left-handed" (LH) propagation band at microwave frequencies, a situation never observed in naturally occurring materials or composites.
Abstract: Recently, an electromagnetic metamaterial was fabricated and demonstrated to exhibit a “left-handed” (LH) propagation band at microwave frequencies. A LH metamaterial is one characterized by material constants—the permeability and permittivity—which are simultaneously negative, a situation never observed in naturally occurring materials or composites. While the presence of the propagation band was shown to be an inherent demonstration of left handedness, actual numerical values for the material constants were not obtained. In the present work, using appropriate averages to define the macroscopic fields, we extract quantitative values for the effective permeability and permittivity from finite-difference simulations using three different approaches.
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TL;DR: In this article, a current-driven homogenization (CDH) approach to calculate all 36 linear constitutive parameters of a metamaterial crystal is presented, where spatial dispersion is accounted for by evaluating the constitutive parameter as a function of frequency and wavenumber.
Abstract: A current-driven homogenization (CDH) approach to calculating all 36 linear constitutive parameters of a metamaterial crystal is presented. Spatial dispersion is accounted for by evaluating the constitutive parameters as a function of frequency and wavenumber. For two-dimensional centrosymmetric crystals spatial dispersion is shown to result in bianisotropy. The accuracy of the CDH constitutive parameters is verified by comparing the radiation efficiencies of a simple directional antenna embedded inside the homogenized and un-homogenized metamaterial slabs.
73 citations
Patent•
05 Apr 2002TL;DR: In this article, a system and method for imaging objects obscured by a covering layer of snow is described, which utilizes a continuous-wave radar generating short-wavelength radiofrequency (RF) signal beam scanned over angular displacements following a scanning pattern toward a target area.
Abstract: A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam scanned over angular displacements following a scanning pattern toward a target area. Reflections of the RF signal from objects buried beneath the snow are registered by an array of RF detectors whose signal magnitudes are summed and correlated with scan direction to generate a signal providing spatial object information, which by way of example, is visually displayed. The radio-frequency beam may be scanned over the scene electronically, or by either mechanically or electromechanically modulating antenna direction or the orientation of a beam deflector. The system is capable of generating multiple image frames per second, high-resolution imaging, registration of objects to a depth exceeding two meters, and can be implemented at low cost without complex signal processing hardware.
62 citations
TL;DR: The bottom-up fabrication of facile, lower-cost, larger areas optical metamaterials (OMMs) is expected to provide important benefits for applications in stealth technology and communication networks as mentioned in this paper.
Abstract: The bottom-up fabrication of facile, lower-cost, larger areas optical metamaterials (OMMs) is expected to provide important benefits for applications in stealth technology and communication networks. Currently available OMMs at optical wavelengths are all composed of periodic structures, and fabricated by top-down approaches of e-beam lithography or focused ion beam technique. Limited by the high cost and extremely small sample volumes size, the fabrication of visible OMMs is still quite challenging on the nanometer scale. The rapid maturation of synthetic methodology in the field of the nanometer scale has lead to the creation of new materials at an incredible rate. In this review, we regard a V-shaped core as an artificial atom and a dendritic cell as an artificial molecule, and address the bottom-up fabrication and performance of optical metamaterials, and with an outlook toward developing devices capable of operating in optical media.
57 citations
Patent•
15 Jan 2010TL;DR: In this paper, a broadband interface structure is arranged to provide electromagnetic energy characteristic of an apparent profile of the back surface region substantially different than an actual profile for electromagnetic energy received at the front surface region.
Abstract: Broadband metamateriai apparatus, methods, systems, and computer readable media are disclosed, as well as exemplary embodiments that provide cloaking, beam steering, and beam focusing. In one exemplary implementation, a broadband interface structure has a front surface region and a back surface region. The broadband interface structure is arranged to provide electromagnetic energy characteristic of an apparent profile of the back surface region substantially different than an actual profile of the back surface region for electromagnetic energy received at the front surface region.
55 citations
Patent•
22 Feb 2005TL;DR: In this paper, a 3D array of circuit elements and control lines is configured to transform from one circuit state to another circuit state in response to a change in a control signal received from one of the control lines.
Abstract: An apparatus includes a 3D array of circuit elements and control lines for coupling a remote control device to the circuit elements in the array. Each circuit element is configured to transform from one circuit state to another circuit state in response to a change in a control signal received from one of the control lines. The 3D array includes a region that behaves as a metamaterial in a selected frequency when the circuit elements of the region are in one set of circuit states and as a normal refractive medium in the selected frequency when the circuit elements of the region are another set of circuit states.
55 citations
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10,495 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
TL;DR: In this article, an effective description for a metalodielectric photonic bandgap (PBG) material was developed for a semi-infinite and slab observables.
Abstract: An effective description is developed for a metalodielectric photonic bandgap (PBG) material far beyond the quasi-static limit of traditional effective-medium theories. An analytic approach, recently presented by the authors, is further advanced to provide the complete effective permittivity and permeability functions. Reflection and transmission coefficients are presented for both TM and TE oblique plane-wave incidence, based on the determination of the equivalent impedance for each lattice plane in the crystal and the transfer-matrix method for reconstructing the effect of successive lattice planes. An analysis of the semi-infinite and slab observables yields the anisotropic effective refractive index, effective permittivity, and effective permeability, thus completing the macroscopic description of the interaction of electromagnetic waves with the medium. Among the novel aspects of the analysis is the equivalence of our PBG system with a physically dispersive system at ultraviolet frequencies and the derivation and explanation of the development of high dispersive magnetization (permeability) for these media, independently of the microscopic magnetic properties of the metallic implants.
44 citations