The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Paul G Clem - One of the best experts on this subject based on the ideXlab platform.
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Optical Magnetic Mirrors without metals
Optica, 2014Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Michael B. Sinclair, Thomas S. Mahony, Young Chul Jun, Salvatore Campione, Daniel A. Bender, Joel R. Wendt, Paul G ClemAbstract:The reflection of an optical wave from metal, arising from strong interactions between the optical electric field and the free carriers of the metal, is accompanied by a phase reversal of the reflected electric field. A far less common route to achieving high reflectivity exploits strong interactions between the material and the optical Magnetic field to produce a “Magnetic mirror” that does not reverse the phase of the reflected electric field. At optical frequencies, the Magnetic properties required for strong interaction can be achieved only by using artificially tailored materials. Here, we experimentally demonstrate, for the first time to the best of our knowledge, the Magnetic mirror behavior of a low-loss all-dielectric metasurface at infrared optical frequencies through direct measurements of the phase and amplitude of the reflected optical wave. The enhanced absorption and emission of transverse-electric dipoles placed close to Magnetic Mirrors can lead to exciting new advances in sensors, photodetectors, and light sources.
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Optical Magnetic Mirrors using All Dielectric Metasurfaces
CLEO: 2014, 2014Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Michael B. Sinclair, Thomas S. Mahony, Young Chul Jun, Salvatore Campione, Daniel A. Bender, Joel R. Wendt, Paul G ClemAbstract:We experimentally demonstrate the Magnetic mirror behavior of all-dielectric metasurfaces at optical frequencies through phase measurements using time-domain-spectroscopy. The unique boundary conditions of Magnetic Mirrors can lead to advances in sensors, photodetectors and light sources.
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Demonstration of dielectric optical Magnetic Mirrors using phase-locked infrared time-domain spectroscopy
CLEO: 2013, 2013Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Paul G Clem, Thomas S. Mahony, Young Chul Jun, Daniel A. Bender, Joel R. Wendt, Jeremy B. Wright, Michael B. SinclairAbstract:We directly demonstrate a dielectric optical Magnetic mirror using phase-locked mid-infrared time-domain spectroscopy. This Magnetic mirror is formed by micron-sized cubes of tellurium fabricated on a dielectric substrate.
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realizing optical magnetism from dielectric metamaterials
Physical Review Letters, 2012Co-Authors: James C Ginn, Igal Brener, David W Peters, J R Wendt, Jeffrey Stevens, Paul Hines, Lorena I Basilio, L K Warne, Jon F Ihlefeld, Paul G ClemAbstract:We demonstrate, for the first time, an all-dielectric metamaterial composite in the midinfrared based on micron-sized, high-index tellurium dielectric resonators. Dielectric resonators are desirable compared to conventional metallodielectric metamaterials at optical frequencies as they are largely angular invariant, free of Ohmic loss, and easily integrated into three-dimensional volumes. Measurements and simulation provide evidence of optical magnetism, which could be used for infrared Magnetic Mirrors, hard or soft surfaces, and subwavelength cavities.
Russell M Kulsrud - One of the best experts on this subject based on the ideXlab platform.
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transport phenomena in stochastic Magnetic Mirrors
The Astrophysical Journal, 2001Co-Authors: Leonid Malyshkin, Russell M KulsrudAbstract:Parallel thermal conduction along stochastic Magnetic field lines may be reduced because the heat-conducting electrons become trapped and detrapped between regions of strong Magnetic field (Magnetic Mirrors). The problem reduces to a simple but realistic model for diffusion of monoenergetic electrons based on the fact that when there is a reduction of diffusion, it is controlled by a subset of the Mirrors, the principal Mirrors. The diffusion reduction can be considered as equivalent to an enhancement of the pitch angle scattering rate. Therefore, in deriving the collision integral, we modify the pitch angle scattering term. We take into account the full perturbed electron-electron collision integral, as well as the electron-proton collision term. Finally, we obtain the four plasma transport coefficients and the effective thermal conductivity. We express them as reductions from the classical values. We present these reductions as functions of the ratio of the Magnetic field decorrelation length to the electron mean free path at the thermal speed VT = 1/2. We briefly discuss an application of our results to clusters of galaxies.
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transport phenomena in stochastic Magnetic Mirrors
arXiv: Astrophysics, 2000Co-Authors: Leonid Malyshkin, Russell M KulsrudAbstract:Parallel thermal conduction along stochastic Magnetic field lines may be reduced because the heat conducting electrons become trapped and detrapped between regions of strong Magnetic field (Magnetic Mirrors). The problem reduces to a simple but realistic model for diffusion of mono-energetic electrons based on the fact that when there is a reduction of diffusion, it is controlled by a subset of the Mirrors, the principle Mirrors. The diffusion reduction can be considered as equivalent to an enhancement of the pitch angle scattering rate. Therefore, in deriving the collision integral, we modify the pitch angle scattering term. We take into account the full perturbed electron-electron collision integral, as well as the electron-proton collision term. Finally, we obtain the four plasma transport coefficients and the effective thermal conductivity. We express them as reductions from the classical values. We present these reductions as functions of the ratio of the Magnetic field decorrelation length to the electron mean free path at the thermal speed $V_T=\sqrt{2kT/m_e}$. We briefly discuss an application of our results to clusters of galaxies. Key words: Magnetic fields: conduction --- Magnetic fields: diffusion --- methods: analytical --- plasmas
Benjamin D G Chandran - One of the best experts on this subject based on the ideXlab platform.
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the importance of anisotropic interstellar turbulence and molecular cloud Magnetic Mirrors for galactic cosmic ray propagation
Space Science Reviews, 2001Co-Authors: Benjamin D G ChandranAbstract:Recent studies suggest that when magnetohydrodynamic (MHD) turbulence is excited by stirring a plasma at large scales, the cascade of energy from large to small scales is anisotropic, in the sense that small-scale fluctuations satisfy the inequality k ∥ k ⊥, where k ∥ and k ⊥ are, respectively, the components of a fluctuation’s wave vector ∥ and ⊥ to the background Magnetic field. Such anisotropic fluctuations are very inefficient at scattering cosmic rays. Results based on the quasilinear approximation for scattering of cosmic rays by anisotropic MHD turbulence are presented and explained. The important role played by molecular-cloud Magnetic Mirrors in confining and isotropizing cosmic rays when scattering is weak is also discussed.
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the importance of anisotropic interstellar turbulence and molecular cloud Magnetic Mirrors for galactic cosmic ray propagation
arXiv: Astrophysics, 2000Co-Authors: Benjamin D G ChandranAbstract:Recent studies suggest that when magnetohydrodynamic (MHD) turbulence is excited by stirring a plasma at large scales, the cascade of energy from large to small scales is anisotropic, in the sense that small-scale fluctuations satisfy the inequality k_parallel << k_perp, where k_parallel and k_perp are, respectively, the components of a fluctuation's wave vector parallel and perpendicular to the background Magnetic field. Such anisotropic fluctuations are very inefficient at scattering cosmic rays. Results based on the quasilinear approximation for scattering of cosmic rays by anisotropic MHD turbulence are presented and explained. The important role played by molecular-cloud Magnetic Mirrors in confining and isotropizing cosmic rays when scattering is weak is also discussed.
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confinement and isotropization of galactic cosmic rays by molecular cloud Magnetic Mirrors when turbulent scattering is weak
The Astrophysical Journal, 2000Co-Authors: Benjamin D G ChandranAbstract:Theoretical studies of magnetohydrodynamic (MHD) turbulence and observations of solar wind —uc- tuations suggest that MHD turbulence in the interstellar medium is anisotropic at small scales, with smooth variations along the background Magnetic —eld and sharp variations perpendicular to the back- ground —eld. Turbulence with this anisotropy is inefficient at scattering cosmic rays, and thus the scat- tering rate l may be smaller than has been traditionally assumed in diUusion models of Galactic cosmic-ray propagation, at least for cosmic-ray energies E above 1011¨1012 eV at which self-con—nement is not possible. In this paper, it is shown that Galactic cosmic rays can be eUectively con—ned through Magnetic re—ection by molecular clouds, even when turbulent scattering is weak. Elmegreens quasi- fractal model of molecular-cloud structure is used to argue that a typical Magnetic —eld line passes through a molecular cloud complex once every D300 pc. Once inside the complex, the —eld line will in most cases be focused into one or more dense clumps in which the Magnetic —eld can be much stronger than the average —eld in the intercloud medium (ICM). Cosmic rays following —eld lines into cloud com- plexes are most often Magnetically re—ected back into the ICM, since strong-—eld regions act as Magnetic Mirrors. For a broad range of cosmic-ray energies, a cosmic ray initially following some particular —eld line separates from that —eld line sufficiently slowly that the cosmic ray can be trapped between neigh- boring cloud complexes for long periods of time. The suppression of cosmic-ray diUusion due to mag- netic trapping is calculated in this paper with the use of phenomenological arguments, asymptotic analysis, and Monte Carlo particle simulations. Formulas for the coefficient of diUusion perpendicular to the Galactic disk are derived for several diUerent parameter regimes within the E-l plane. In one of these parameter regimes in which scattering is weak, it is shown that molecular-cloud Magnetic Mirrors strongly reduce cosmic-ray anisotropy in the ICM, and analytic formulas for the angular harmonics are derived. Subject headings: acceleration of particlescosmic raysISM: cloudsISM: Magnetic —elds ¨ turbulence
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heat transport along an inhomogeneous Magnetic field i periodic Magnetic Mirrors
The Astrophysical Journal, 1999Co-Authors: Benjamin D G Chandran, S C Cowley, Mariya Ivanushkina, R D SydoraAbstract:Thermal conduction plays a critical role in the evolution of galaxy-cluster gas, and an accurate determination of the thermal conductivity is important for determinations of mass accretion rates within clusters. Since clusters are believed to possess Magnetic fields with a dominant length scale lB that is much smaller than a typical cluster size, the calculation of the mean conductivity over cluster scales is extremely complicated. In this paper, we treat a small portion of the general problem: the effects of Magnetic Mirrors on the diffusion of charged particles along Magnetic field lines. For simplicity, we take the field strength to be periodic along field lines. We derive an analytic expression for the suppression factor as a function of the fractional variation in field strength (for arbitrarily large fractional variations), and verify our analytic findings with the use of Monte Carlo particle simulations.
James C Ginn - One of the best experts on this subject based on the ideXlab platform.
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Optical Magnetic Mirrors without metals
Optica, 2014Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Michael B. Sinclair, Thomas S. Mahony, Young Chul Jun, Salvatore Campione, Daniel A. Bender, Joel R. Wendt, Paul G ClemAbstract:The reflection of an optical wave from metal, arising from strong interactions between the optical electric field and the free carriers of the metal, is accompanied by a phase reversal of the reflected electric field. A far less common route to achieving high reflectivity exploits strong interactions between the material and the optical Magnetic field to produce a “Magnetic mirror” that does not reverse the phase of the reflected electric field. At optical frequencies, the Magnetic properties required for strong interaction can be achieved only by using artificially tailored materials. Here, we experimentally demonstrate, for the first time to the best of our knowledge, the Magnetic mirror behavior of a low-loss all-dielectric metasurface at infrared optical frequencies through direct measurements of the phase and amplitude of the reflected optical wave. The enhanced absorption and emission of transverse-electric dipoles placed close to Magnetic Mirrors can lead to exciting new advances in sensors, photodetectors, and light sources.
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Optical Magnetic Mirrors using All Dielectric Metasurfaces
CLEO: 2014, 2014Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Michael B. Sinclair, Thomas S. Mahony, Young Chul Jun, Salvatore Campione, Daniel A. Bender, Joel R. Wendt, Paul G ClemAbstract:We experimentally demonstrate the Magnetic mirror behavior of all-dielectric metasurfaces at optical frequencies through phase measurements using time-domain-spectroscopy. The unique boundary conditions of Magnetic Mirrors can lead to advances in sensors, photodetectors and light sources.
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Demonstration of dielectric optical Magnetic Mirrors using phase-locked infrared time-domain spectroscopy
CLEO: 2013, 2013Co-Authors: Sheng Liu, James C Ginn, Jon F Ihlefeld, Paul G Clem, Thomas S. Mahony, Young Chul Jun, Daniel A. Bender, Joel R. Wendt, Jeremy B. Wright, Michael B. SinclairAbstract:We directly demonstrate a dielectric optical Magnetic mirror using phase-locked mid-infrared time-domain spectroscopy. This Magnetic mirror is formed by micron-sized cubes of tellurium fabricated on a dielectric substrate.
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realizing optical magnetism from dielectric metamaterials
Physical Review Letters, 2012Co-Authors: James C Ginn, Igal Brener, David W Peters, J R Wendt, Jeffrey Stevens, Paul Hines, Lorena I Basilio, L K Warne, Jon F Ihlefeld, Paul G ClemAbstract:We demonstrate, for the first time, an all-dielectric metamaterial composite in the midinfrared based on micron-sized, high-index tellurium dielectric resonators. Dielectric resonators are desirable compared to conventional metallodielectric metamaterials at optical frequencies as they are largely angular invariant, free of Ohmic loss, and easily integrated into three-dimensional volumes. Measurements and simulation provide evidence of optical magnetism, which could be used for infrared Magnetic Mirrors, hard or soft surfaces, and subwavelength cavities.
Leonid Malyshkin - One of the best experts on this subject based on the ideXlab platform.
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transport phenomena in stochastic Magnetic Mirrors
The Astrophysical Journal, 2001Co-Authors: Leonid Malyshkin, Russell M KulsrudAbstract:Parallel thermal conduction along stochastic Magnetic field lines may be reduced because the heat-conducting electrons become trapped and detrapped between regions of strong Magnetic field (Magnetic Mirrors). The problem reduces to a simple but realistic model for diffusion of monoenergetic electrons based on the fact that when there is a reduction of diffusion, it is controlled by a subset of the Mirrors, the principal Mirrors. The diffusion reduction can be considered as equivalent to an enhancement of the pitch angle scattering rate. Therefore, in deriving the collision integral, we modify the pitch angle scattering term. We take into account the full perturbed electron-electron collision integral, as well as the electron-proton collision term. Finally, we obtain the four plasma transport coefficients and the effective thermal conductivity. We express them as reductions from the classical values. We present these reductions as functions of the ratio of the Magnetic field decorrelation length to the electron mean free path at the thermal speed VT = 1/2. We briefly discuss an application of our results to clusters of galaxies.
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transport phenomena in stochastic Magnetic Mirrors
Other Information: PBD: 31 Aug 2000, 2000Co-Authors: Leonid MalyshkinAbstract:Parallel thermal conduction along stochastic Magnetic field lines may be reduced because the heat conducting electrons become trapped and detrapped between regions of strong Magnetic field (Magnetic Mirrors). The problem reduces to a simple but realistic model for diffusion of mono-energetic electrons based on the fact that when there is a reduction of diffusion, it is controlled by a subset of the Mirrors, the principle Mirrors. The diffusion reduction can be considered as equivalent to an enhancement of the pitch angle scattering rate. Therefore, in deriving the collision integral, the authors modify the pitch angle scattering term. They take into account the full perturbed electron-electron collision integral, as well as the electron-proton collision term. Finally, they obtain the four plasma transport coefficients and the effective thermal conductivity. They express them as reductions from the classical values. They present these reductions as functions of the ratio of the Magnetic field decorrelation length to the electron mean free path at the thermal speed V{sub T} = {radical}2kT/m{sub e}. They briefly discuss an application of the results to clusters of galaxies.
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transport phenomena in stochastic Magnetic Mirrors
arXiv: Astrophysics, 2000Co-Authors: Leonid Malyshkin, Russell M KulsrudAbstract:Parallel thermal conduction along stochastic Magnetic field lines may be reduced because the heat conducting electrons become trapped and detrapped between regions of strong Magnetic field (Magnetic Mirrors). The problem reduces to a simple but realistic model for diffusion of mono-energetic electrons based on the fact that when there is a reduction of diffusion, it is controlled by a subset of the Mirrors, the principle Mirrors. The diffusion reduction can be considered as equivalent to an enhancement of the pitch angle scattering rate. Therefore, in deriving the collision integral, we modify the pitch angle scattering term. We take into account the full perturbed electron-electron collision integral, as well as the electron-proton collision term. Finally, we obtain the four plasma transport coefficients and the effective thermal conductivity. We express them as reductions from the classical values. We present these reductions as functions of the ratio of the Magnetic field decorrelation length to the electron mean free path at the thermal speed $V_T=\sqrt{2kT/m_e}$. We briefly discuss an application of our results to clusters of galaxies. Key words: Magnetic fields: conduction --- Magnetic fields: diffusion --- methods: analytical --- plasmas