Ari Sihvola - Academia.edu (original) (raw)
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Papers by Ari Sihvola
![Research paper thumbnail of Electromagnetic Chirality, Part 1: The Microscopic Perspective [Electromagnetic Perspectives]](https://attachments.academia-assets.com/120414936/thumbnails/1.jpg)
](IEEE Antennas and Propagation Magazine, Feb 1, 2020
![Research paper thumbnail of Electromagnetic Chirality, Part 2: The Macroscopic Perspective [Electromagnetic Perspectives]](https://attachments.academia-assets.com/120414934/thumbnails/1.jpg)
](IEEE Antennas and Propagation Magazine, Apr 1, 2020
arXiv (Cornell University), Mar 21, 2019
This contribution focuses on the scattering and extinction properties of homogeneous active diele... more This contribution focuses on the scattering and extinction properties of homogeneous active dielectric spheres. The permittivity ε = ε ′ − jε ′′ of active medium is complex such that ε ′′ < 0 (following the time-harmonic notation exp(jωt)). When such a sphere is exposed to an electromagnetic wave, it scatters energy. The amount of scattering is proportional to the scattering cross section of the particle [1]. An active scatterer is gainy and hence its absorption cross section is negative, leading to the conclusion that its extinction cross section (which is the sum of scattering and absorption cross sections) can be either positive, negative, or zero [2]. Figure 1 shows an example of a sphere which, depending on its size, displays all these three possibilities. The efficiencies Q sca , Q abs , Q ext (cross sections normalized by the geometric cross section) have been computed in two ways: directly from the Mie coefficients expansion, and also integrating the scattered and incident field interactions outside the scatterer.
We theoretically investigate whether a dielectric sphere can mimic the behavior of an equivalent ... more We theoretically investigate whether a dielectric sphere can mimic the behavior of an equivalent surface impedance sphere and we discuss some of the of emergent properties, such as cloaking (minimum scattering) and maximum absorption conditions.
2018 2nd URSI Atlantic Radio Science Meeting (AT-RASC), May 1, 2018
IEEE Transactions on Antennas and Propagation, May 1, 2021
A surface integral equation (SIE) method is developed to analyze electromagnetic scattering by th... more A surface integral equation (SIE) method is developed to analyze electromagnetic scattering by three-dimensional (3-D) objects with Soft-and-Hard/DB (SHDB) boundary condition. The SHDB boundary condition is a generalization of the Soft-and-hard (SH) and DB boundary conditions, which associate the normal and tangential field components on the boundary. In the developed method, the SHDB boundary condition is expressed in vector form which allows combining it with the tangential field integral equations. The obtained equations can be discretized with the standard method of moments (MoM) using the Rao-Wilton-Glisson (RWG) functions. Different combinations of the integral equations and boundary conditions are derived and their numerical performance are studied and compared. It is demonstrated with numerical experiments that much more stable system is obtained by considering the boundary conditions as extra equations, rather than integrating them to the surface integral equations. The solutions of the proposed non-square integral equation are verified with the physical optics approximations.
International Journal of Numerical Modelling-electronic Networks Devices and Fields, Jul 31, 2019
A discontinuous Galerkin (DG) surface integral equation method is proposed for electromagnetic sc... more A discontinuous Galerkin (DG) surface integral equation method is proposed for electromagnetic scattering from targets with the impedance boundary condition (IBC). We present electric field integral equation (EFIE), magnetic field integral equation (MFIE), and self-dual integral equation formulations for the problem, and study their numerical performance. Based on the results of these experiments, DG is developed for EFIE and MFIE (DG-EFIE and DG-MFIE). The convergence of the iterative solutions and the solution accuracy of DG-EFIE and DG-MFIE are further investigated for a wide range of surface impedances. The numerical performance of these formulations are found to be nearly complementary with respect to the surface impedance. The capability of the proposed DG solution strategy for calculating scattering from large multi-scale IBC targets is demonstrated.
Radio Science, Dec 1, 2017
STIN, Mar 1, 1991
Bi-isotropic heterogeneous media are analyzed. Bi-isotropic materials are characterized by four s... more Bi-isotropic heterogeneous media are analyzed. Bi-isotropic materials are characterized by four scalar parameters in the constitutive relations: permittivity, permeability, chirality, and nonreciprocity. The polarizabilities of general bi-isotropic spheres and elipsoids are derived, and these results are used consequently in the analysis of bi-isotropic mixtures. The generalized Maxwell-Garnett formulae are derived for mixtures with spherical or ellipsoidal inclusions in isotropic background medium. The ellipsoids are allowed also to have any orientation distribution. Rayleigh mixing rules are also presented and they are seen to be a natural extension of the Rayleigh rule in the dielectric case. Also, the relation of the results is discussed to the systems employing other sets of constitutive relations for bi-isotropic media. Numerical illustrations are performed that show the effect of shape, amount, and nature of inclusions on the bi-isotropic mixture parameters; this is essential information in the engineering problem of tailoring bi-isotropic composite materials.
2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), 2018
This presentation focuses on the electromagnetic scattering characteristics of spheres with surfa... more This presentation focuses on the electromagnetic scattering characteristics of spheres with surface defined by the impedance boundary condition. The results include resonances that are very strong and sharp for small subwavelength particles, and analogous to the localized surface plasmons.
IEEE Antennas and Propagation Magazine, Feb 1, 2020
IEEE Antennas and Propagation Magazine, Apr 1, 2020
arXiv (Cornell University), Mar 21, 2019
This contribution focuses on the scattering and extinction properties of homogeneous active diele... more This contribution focuses on the scattering and extinction properties of homogeneous active dielectric spheres. The permittivity ε = ε ′ − jε ′′ of active medium is complex such that ε ′′ < 0 (following the time-harmonic notation exp(jωt)). When such a sphere is exposed to an electromagnetic wave, it scatters energy. The amount of scattering is proportional to the scattering cross section of the particle [1]. An active scatterer is gainy and hence its absorption cross section is negative, leading to the conclusion that its extinction cross section (which is the sum of scattering and absorption cross sections) can be either positive, negative, or zero [2]. Figure 1 shows an example of a sphere which, depending on its size, displays all these three possibilities. The efficiencies Q sca , Q abs , Q ext (cross sections normalized by the geometric cross section) have been computed in two ways: directly from the Mie coefficients expansion, and also integrating the scattered and incident field interactions outside the scatterer.
We theoretically investigate whether a dielectric sphere can mimic the behavior of an equivalent ... more We theoretically investigate whether a dielectric sphere can mimic the behavior of an equivalent surface impedance sphere and we discuss some of the of emergent properties, such as cloaking (minimum scattering) and maximum absorption conditions.
2018 2nd URSI Atlantic Radio Science Meeting (AT-RASC), May 1, 2018
IEEE Transactions on Antennas and Propagation, May 1, 2021
A surface integral equation (SIE) method is developed to analyze electromagnetic scattering by th... more A surface integral equation (SIE) method is developed to analyze electromagnetic scattering by three-dimensional (3-D) objects with Soft-and-Hard/DB (SHDB) boundary condition. The SHDB boundary condition is a generalization of the Soft-and-hard (SH) and DB boundary conditions, which associate the normal and tangential field components on the boundary. In the developed method, the SHDB boundary condition is expressed in vector form which allows combining it with the tangential field integral equations. The obtained equations can be discretized with the standard method of moments (MoM) using the Rao-Wilton-Glisson (RWG) functions. Different combinations of the integral equations and boundary conditions are derived and their numerical performance are studied and compared. It is demonstrated with numerical experiments that much more stable system is obtained by considering the boundary conditions as extra equations, rather than integrating them to the surface integral equations. The solutions of the proposed non-square integral equation are verified with the physical optics approximations.
International Journal of Numerical Modelling-electronic Networks Devices and Fields, Jul 31, 2019
A discontinuous Galerkin (DG) surface integral equation method is proposed for electromagnetic sc... more A discontinuous Galerkin (DG) surface integral equation method is proposed for electromagnetic scattering from targets with the impedance boundary condition (IBC). We present electric field integral equation (EFIE), magnetic field integral equation (MFIE), and self-dual integral equation formulations for the problem, and study their numerical performance. Based on the results of these experiments, DG is developed for EFIE and MFIE (DG-EFIE and DG-MFIE). The convergence of the iterative solutions and the solution accuracy of DG-EFIE and DG-MFIE are further investigated for a wide range of surface impedances. The numerical performance of these formulations are found to be nearly complementary with respect to the surface impedance. The capability of the proposed DG solution strategy for calculating scattering from large multi-scale IBC targets is demonstrated.
Radio Science, Dec 1, 2017
STIN, Mar 1, 1991
Bi-isotropic heterogeneous media are analyzed. Bi-isotropic materials are characterized by four s... more Bi-isotropic heterogeneous media are analyzed. Bi-isotropic materials are characterized by four scalar parameters in the constitutive relations: permittivity, permeability, chirality, and nonreciprocity. The polarizabilities of general bi-isotropic spheres and elipsoids are derived, and these results are used consequently in the analysis of bi-isotropic mixtures. The generalized Maxwell-Garnett formulae are derived for mixtures with spherical or ellipsoidal inclusions in isotropic background medium. The ellipsoids are allowed also to have any orientation distribution. Rayleigh mixing rules are also presented and they are seen to be a natural extension of the Rayleigh rule in the dielectric case. Also, the relation of the results is discussed to the systems employing other sets of constitutive relations for bi-isotropic media. Numerical illustrations are performed that show the effect of shape, amount, and nature of inclusions on the bi-isotropic mixture parameters; this is essential information in the engineering problem of tailoring bi-isotropic composite materials.
2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), 2018
This presentation focuses on the electromagnetic scattering characteristics of spheres with surfa... more This presentation focuses on the electromagnetic scattering characteristics of spheres with surface defined by the impedance boundary condition. The results include resonances that are very strong and sharp for small subwavelength particles, and analogous to the localized surface plasmons.
Radio Science, 2013
1] Two wedges, one made of negative-permittivity material (primary) and another of an ordinary di... more 1] Two wedges, one made of negative-permittivity material (primary) and another of an ordinary dielectric (auxiliary/secondary), are posed nose-to-nose to form a "bowtie" configuration. This shape is very common and convenient for a number of real-world devices and constructions such as electron microscopes, optical superlenses, and nanotips. In all these structures, the efficient operation and functionality get strongly assisted by the increased electromagnetic power concentration in the vicinity of the edge. Such a field enhancement is attempted with proper choice of the characteristics of the dielectric wedge to increase the field intensity over the cross section of the metamaterial one. A slowly varying field assumption is adopted to formulate approximate solutions to similar structures (sharp and rounded corners). A quality factor has been defined based on the power carried by the supported modal waves, if they are excited by a suitable electric source, in the presence and in the absence of the auxiliary wedge. This quantity expresses the intensity enhancement that could be achieved and is represented in graphs with respect to the dielectric wedge parameters. The characteristics of the secondary component that lead to a maximization of the electric power into the primary one are identified and explained. In particular, periodic variations of the angular extent of the secondary wedge are observed, and the number of maxima is increased with the dielectric permittivity of the constituent material.
Physical Review B, 2021
Absorption and scattering of the impinging electromagnetic waves are the two fundamental operatio... more Absorption and scattering of the impinging electromagnetic waves are the two fundamental operations describing the energy exchange of any organic or inorganic particle with its environment. In the case of virion cells, substantial extinction power (counting both absorbing and scattering effects) is a prerequisite for performing a variety of coupling actions against the viral particles, and thus is a highly sought-after feature. By considering realistic dispersion for the dielectric permittivity of proteins and a core-shell modeling allowing for rigorous formulation via Mie theory, we report optical extinction resonances for corona virions at mid-infrared range that are not significantly perturbed by changes in the object's size or the background host. Our findings indicate the optimal regime for interaction of photonic radiation with viral particles, and may assist towards the development of equipment for thermal damage, disintegration, or neutralization of coronavirus cells.