The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Minas H. Tanielian - One of the best experts on this subject based on the ideXlab platform.
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Microwave focusing and beam collimation using negative Index of Refraction lenses
IET Microwaves Antennas & Propagation, 2007Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, D. C. Vier, David R. Smith, S. Schultz, David SchurigAbstract:Negative Index of Refraction materials (NIMs) were first postulated by Veselago in 1968 and have recently been realised using structures formed with rings and wires deposited on printed circuit boards. The proof of the existence of negative Index of Refraction was established using a Snell's law experiment with a wedge. The predicted and measured Refraction angles were found to be consistent for a negative Index material and in excellent agreement with the theoretical expectations. For microwave lenses NIMs have the advantage of being lighter, having better focusing properties and potentially lower aberrations. Simulation and experimental results on NIM configurations including gradient Index of Refraction and spherical 3D lenses are presented. Both focusing and beam collimating applications will be considered. These results will be compared to normal positive Index of Refraction material lenses.
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Simulation and testing of a graded negative Index of Refraction lens
Applied Physics Letters, 2005Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, David R. SmithAbstract:A gradient Index (GRIN) lens using a negative Index of Refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable Index of Refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the Index of Refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the Index of Refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.
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Performance of a negative Index of Refraction lens
Applied Physics Letters, 2004Co-Authors: C. G. Parazzoli, R. B. Greegor, J. A. Nielsen, Matthew Thompson, A.m. Vetter, Minas H. Tanielian, D. C. VierAbstract:A plano-concave lens with negative Index of Refraction has been designed and fabricated. Such lenses have been postulated for many years, but only recently has their realization been made possible through improved simulation and fabrication procedures. We report here the simulation, fabrication, and performance of such a lens. The lens images the source field and reproduces the results of standard Gaussian optics. The curved lens with negative Index of Refraction in the microwave frequency region of the electromagnetic spectrum has been compared to a plano-convex Macor positive Index of Refraction lens having the same radius of curvature.
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Origin of dissipative losses in negative Index of Refraction materials
Applied Physics Letters, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10–16 GHz range. The origin of the dissipative losses has been identified and effective schemes to reduce them devised and implemented. Numerical simulation and experimental verification shows that losses in negative Index of Refraction materials can be significantly reduced by minimizing the underlying losses of the constituent materials.
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experimental determination and numerical simulation of the properties of negative Index of Refraction materials
Optics Express, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Benjamin E Koltenbah, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized and simulated several of these structures operating in the 10 - 15 GHz range. Our simulations using Maxwell's Equations solvers have included wire arrays, ring arrays and assemblies of unit cells comprised of rings and wires. We find good agreement between the numerical simulations and experimental measurements of the scattering parameters and Index of Refraction. The procedure was to first model ring and wire structures on the unit cell level to obtain scattering parameters from which effective a, i and n were retrieved. Next an assembled array of unit cells forming a 12 degrees wedge was used for the Snell's Law determination of the negative Index of Refraction. For the structure examined the computed value of n is within 20% of the one experimentally measured in the Snell's Law experiment from 13.6 to 14.8 GHz.
R. B. Greegor - One of the best experts on this subject based on the ideXlab platform.
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Microwave focusing and beam collimation using negative Index of Refraction lenses
IET Microwaves Antennas & Propagation, 2007Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, D. C. Vier, David R. Smith, S. Schultz, David SchurigAbstract:Negative Index of Refraction materials (NIMs) were first postulated by Veselago in 1968 and have recently been realised using structures formed with rings and wires deposited on printed circuit boards. The proof of the existence of negative Index of Refraction was established using a Snell's law experiment with a wedge. The predicted and measured Refraction angles were found to be consistent for a negative Index material and in excellent agreement with the theoretical expectations. For microwave lenses NIMs have the advantage of being lighter, having better focusing properties and potentially lower aberrations. Simulation and experimental results on NIM configurations including gradient Index of Refraction and spherical 3D lenses are presented. Both focusing and beam collimating applications will be considered. These results will be compared to normal positive Index of Refraction material lenses.
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Simulation and testing of a graded negative Index of Refraction lens
Applied Physics Letters, 2005Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, David R. SmithAbstract:A gradient Index (GRIN) lens using a negative Index of Refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable Index of Refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the Index of Refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the Index of Refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.
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Performance of a negative Index of Refraction lens
Applied Physics Letters, 2004Co-Authors: C. G. Parazzoli, R. B. Greegor, J. A. Nielsen, Matthew Thompson, A.m. Vetter, Minas H. Tanielian, D. C. VierAbstract:A plano-concave lens with negative Index of Refraction has been designed and fabricated. Such lenses have been postulated for many years, but only recently has their realization been made possible through improved simulation and fabrication procedures. We report here the simulation, fabrication, and performance of such a lens. The lens images the source field and reproduces the results of standard Gaussian optics. The curved lens with negative Index of Refraction in the microwave frequency region of the electromagnetic spectrum has been compared to a plano-convex Macor positive Index of Refraction lens having the same radius of curvature.
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Origin of dissipative losses in negative Index of Refraction materials
Applied Physics Letters, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10–16 GHz range. The origin of the dissipative losses has been identified and effective schemes to reduce them devised and implemented. Numerical simulation and experimental verification shows that losses in negative Index of Refraction materials can be significantly reduced by minimizing the underlying losses of the constituent materials.
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experimental determination and numerical simulation of the properties of negative Index of Refraction materials
Optics Express, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Benjamin E Koltenbah, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized and simulated several of these structures operating in the 10 - 15 GHz range. Our simulations using Maxwell's Equations solvers have included wire arrays, ring arrays and assemblies of unit cells comprised of rings and wires. We find good agreement between the numerical simulations and experimental measurements of the scattering parameters and Index of Refraction. The procedure was to first model ring and wire structures on the unit cell level to obtain scattering parameters from which effective a, i and n were retrieved. Next an assembled array of unit cells forming a 12 degrees wedge was used for the Snell's Law determination of the negative Index of Refraction. For the structure examined the computed value of n is within 20% of the one experimentally measured in the Snell's Law experiment from 13.6 to 14.8 GHz.
C. G. Parazzoli - One of the best experts on this subject based on the ideXlab platform.
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Microwave focusing and beam collimation using negative Index of Refraction lenses
IET Microwaves Antennas & Propagation, 2007Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, D. C. Vier, David R. Smith, S. Schultz, David SchurigAbstract:Negative Index of Refraction materials (NIMs) were first postulated by Veselago in 1968 and have recently been realised using structures formed with rings and wires deposited on printed circuit boards. The proof of the existence of negative Index of Refraction was established using a Snell's law experiment with a wedge. The predicted and measured Refraction angles were found to be consistent for a negative Index material and in excellent agreement with the theoretical expectations. For microwave lenses NIMs have the advantage of being lighter, having better focusing properties and potentially lower aberrations. Simulation and experimental results on NIM configurations including gradient Index of Refraction and spherical 3D lenses are presented. Both focusing and beam collimating applications will be considered. These results will be compared to normal positive Index of Refraction material lenses.
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Simulation and testing of a graded negative Index of Refraction lens
Applied Physics Letters, 2005Co-Authors: R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, Matthew Thompson, Minas H. Tanielian, David R. SmithAbstract:A gradient Index (GRIN) lens using a negative Index of Refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable Index of Refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the Index of Refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the Index of Refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.
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Performance of a negative Index of Refraction lens
Applied Physics Letters, 2004Co-Authors: C. G. Parazzoli, R. B. Greegor, J. A. Nielsen, Matthew Thompson, A.m. Vetter, Minas H. Tanielian, D. C. VierAbstract:A plano-concave lens with negative Index of Refraction has been designed and fabricated. Such lenses have been postulated for many years, but only recently has their realization been made possible through improved simulation and fabrication procedures. We report here the simulation, fabrication, and performance of such a lens. The lens images the source field and reproduces the results of standard Gaussian optics. The curved lens with negative Index of Refraction in the microwave frequency region of the electromagnetic spectrum has been compared to a plano-convex Macor positive Index of Refraction lens having the same radius of curvature.
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Origin of dissipative losses in negative Index of Refraction materials
Applied Physics Letters, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10–16 GHz range. The origin of the dissipative losses has been identified and effective schemes to reduce them devised and implemented. Numerical simulation and experimental verification shows that losses in negative Index of Refraction materials can be significantly reduced by minimizing the underlying losses of the constituent materials.
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experimental determination and numerical simulation of the properties of negative Index of Refraction materials
Optics Express, 2003Co-Authors: R. B. Greegor, C. G. Parazzoli, Benjamin E Koltenbah, Minas H. TanielianAbstract:Negative Index of Refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized and simulated several of these structures operating in the 10 - 15 GHz range. Our simulations using Maxwell's Equations solvers have included wire arrays, ring arrays and assemblies of unit cells comprised of rings and wires. We find good agreement between the numerical simulations and experimental measurements of the scattering parameters and Index of Refraction. The procedure was to first model ring and wire structures on the unit cell level to obtain scattering parameters from which effective a, i and n were retrieved. Next an assembled array of unit cells forming a 12 degrees wedge was used for the Snell's Law determination of the negative Index of Refraction. For the structure examined the computed value of n is within 20% of the one experimentally measured in the Snell's Law experiment from 13.6 to 14.8 GHz.
J H Scofield - One of the best experts on this subject based on the ideXlab platform.
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observation of a multiply ionized plasma with Index of Refraction greater than one
Physical Review Letters, 2005Co-Authors: Jorge Filevich, J Nilsen, J H Scofield, Mario C. Marconi, Jorge J. Rocca, James Dunn, S J Moon, R F Smith, R Keenan, J R HunterAbstract:We present clear experimental evidence showing that the contribution of bound electrons can dominate the Index of Refraction of laser created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms show that this results from the dominant contribution of low charge ions to the Index of Refraction. This usually neglected bound electron contribution can a.ect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.
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Plasmas with an Index of Refraction greater than 1
Optics letters, 2004Co-Authors: J Nilsen, J H ScofieldAbstract:Over the past decade, x-ray lasers in the wavelength range 14–47 nm have been used for interferometry of plasmas. As in optical interferometry of plasmas, the experimental analysis assumed that the Index of Refraction is due only to free electrons. This makes the Index of Refraction less than 1. Recent experiments in Al plasmas have shown fringe lines bending the wrong way as though the electron density were negative. We show how the bound electrons can dominate the Index of Refraction in many plasmas and make the Index greater than 1 or enhance the Index such that one would greatly overestimate the density of the plasma using interferometry.
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Plasmas with Index of Refraction greater than one
2004Co-Authors: J Nilsen, J H ScofieldAbstract:Over the last decade, X-ray lasers in the wavelength range14 - 47 nm have been used to do interferometry of plasmas. Just as for optical interferometry of plasmas, the experimental analysis assumed that the Index of Refraction is due only to the free electrons. This makes the Index of Refraction less then one. Recent experiments in Al plasmas have observed fringe lines bend the wrong way as though the electron density is negative. We show how the bound electrons can dominate the Index of Refraction in many plasmas and make the Index greater than one or enhance the Index such that one would greatly overestimate the density of the plasma using interferometry.
J Nilsen - One of the best experts on this subject based on the ideXlab platform.
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Multiply ionized carbon plasmas with Index of Refraction greater than one
Laser and Particle Beams, 2007Co-Authors: Jorge Filevich, J Nilsen, Jonathan Grava, Michael Purvis, Mario C. Marconi, Jorge J. Rocca, James Dunn, W. R. JohnsonAbstract:FordecadestheanalysisofinterferometryhavereliedontheapproximationthattheIndexofRefractioninplasmasisdue solelytothefreeelectrons.ThisgeneralassumptionmakestheIndexofRefractionalwayslessthanone.However,recent softx-raylaserinterferometryexperimentswithAluminumplasmasatwavelengthsof14.7nmand13.9nmhaveshown fringes that bend the opposite direction than would be expected when using that approximation. Analysis of the data demonstrated that this effect is due to bound electrons that contribute significantly to the Index of Refraction of multiply ionized plasmas, and that this should be encountered in other plasmas at different wavelengths. Recent studies of Silver and Tin plasmas using a 46.9 nm probe beam generated by a Ne-like Ar capillary discharge soft-ray laser identified plasmas with an Index of Refraction greater than one, as was predicted by computer calculations. In this paper we present newinterferometricresultsobtainedwithCarbonplasmasat46.9nmprobewavelengththatclearlyshowplasmaregions with an Index of Refraction greater than one. Computations suggest that in this case the phenomenon is due to the dominantcontributionofboundelectronsfromdoublyionizedcarbonionstotheIndexofRefraction.Theresultsreaffirm that bound electrons can strongly influence the Index of Refraction of numerous plasmas over a broad range of soft x-ray wavelengths.
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observation of a multiply ionized plasma with Index of Refraction greater than one
Physical Review Letters, 2005Co-Authors: Jorge Filevich, J Nilsen, J H Scofield, Mario C. Marconi, Jorge J. Rocca, James Dunn, S J Moon, R F Smith, R Keenan, J R HunterAbstract:We present clear experimental evidence showing that the contribution of bound electrons can dominate the Index of Refraction of laser created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms show that this results from the dominant contribution of low charge ions to the Index of Refraction. This usually neglected bound electron contribution can a.ect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.
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Plasmas with an Index of Refraction greater than 1
Optics letters, 2004Co-Authors: J Nilsen, J H ScofieldAbstract:Over the past decade, x-ray lasers in the wavelength range 14–47 nm have been used for interferometry of plasmas. As in optical interferometry of plasmas, the experimental analysis assumed that the Index of Refraction is due only to free electrons. This makes the Index of Refraction less than 1. Recent experiments in Al plasmas have shown fringe lines bending the wrong way as though the electron density were negative. We show how the bound electrons can dominate the Index of Refraction in many plasmas and make the Index greater than 1 or enhance the Index such that one would greatly overestimate the density of the plasma using interferometry.
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Plasmas with Index of Refraction greater than one
2004Co-Authors: J Nilsen, J H ScofieldAbstract:Over the last decade, X-ray lasers in the wavelength range14 - 47 nm have been used to do interferometry of plasmas. Just as for optical interferometry of plasmas, the experimental analysis assumed that the Index of Refraction is due only to the free electrons. This makes the Index of Refraction less then one. Recent experiments in Al plasmas have observed fringe lines bend the wrong way as though the electron density is negative. We show how the bound electrons can dominate the Index of Refraction in many plasmas and make the Index greater than one or enhance the Index such that one would greatly overestimate the density of the plasma using interferometry.
