Nonlinearities, Activity and Computational by Sergei Tretyakov
New Journal of Physics, 2021
Adding active components to a photonic device may dramatically enrich and improve its performance... more Adding active components to a photonic device may dramatically enrich and improve its performance but, at the same time, creates the risk of instability, namely, occurrence of unwanted self-oscillations. Stability considerations are not always given the attention they deserve when setups employing gain media are investigated; thus, the desired effects or reported regimes may not be achievable. In this work, a generic electromagnetic configuration comprising a pair of planar impedance metasurfaces is examined and analytical stability conditions for its operation are derived. The obtained results for the analyzed basic module can shed light on the stability conditions of more complex active systems that incorporate such components and serve a broad range of applications from imaging and polarization engineering to invisibility cloaking and wavefront transformations.
Papers by Sergei Tretyakov
We propose to use an antenna composed of two orthogonal helices as a low-scattering sensor. The v... more We propose to use an antenna composed of two orthogonal helices as a low-scattering sensor. The vector effective length is derived for the antenna using the small dipole approximation for the helices. The antenna can transmit and receive circular polarization in all directions with the Huygens' pattern. We observe that the antenna geometry does not backscatter, regardless of the polarization, when the incidence direction is normal to the plane of the helices. Scattered fields, scattered axial ratio, and the scattering cross section are presented. We show that the zero-backscattering property holds also for the antenna when it is capable to receive all the available power with conjugate loading. The approximate analytical model is validated with full-wave simulations.
We consider resonant patch antennas, implemented using loaded transmission-line networks and othe... more We consider resonant patch antennas, implemented using loaded transmission-line networks and other exotic structures having engineered dispersion. An analytical expression is derived for the ratio of radiation quality factors of such antennas and conventional patch antennas loaded with (reference) dielectrics. In the ideal case this ratio depends only on the propagation constant and wave impedance of the structure under test, and it can be conveniently used to study what kind of dispersion leads to improved impedance bandwidth. We illustrate the effect of dispersion by implementing a resonant patch antenna using a periodic network of LC elements. The analytical results predicting enhanced impedance bandwidth compared to the reference results are validated using a commercial circuit simulator. Discussion is conducted on the practical limitations for the use of the proposed expression.
Ieee Transactions on Antennas and Propagation, Oct 1, 2009
In this paper a planar electromagnetic absorber is introduced whose performance is maintained ove... more In this paper a planar electromagnetic absorber is introduced whose performance is maintained over a wide change of the incidence angle for both TE and TM polarization. The absorber comprises an array of patches over a grounded dielectric slab, with clear advantage in terms of manufacturability. It is shown that a high value of the relative permittivity of the substrate is essential for the operation of the absorber. The main contribution of the paper is to demonstrate and practically use the presence of an additional resonance of highimpedance surfaces when the plasma frequency of the wire medium comprising metallic vias in the dielectric substrate is close to the original resonance of the high-impedance surface. The presence of the vias between FSS and the ground plane is discussed both for the case of a high-permittivity absorber and for a low permittivity one. The radius of the vias influences the oblique incidence TM absorption, and when properly designed, the insertion of the vias result in bandwidth enlargement and higher absorption.
Journal of Electromagnetic Waves and Applications, 2003
... Abstract|New artifi cial reactive impedance surfaces have been re-cently suggested by Sievenp... more ... Abstract|New artifi cial reactive impedance surfaces have been re-cently suggested by Sievenpiper et al. ... 1. These novel artifi cial layers are also called 2D photonic (or electromagnetic, which is more appropriate for the frequency band of applications) bandgap structures. ...
Physical Review B Condensed Matter and Materials Physics, 2007
A concept of backward-wave bianisotropic composite medium matched to free space is suggested. It ... more A concept of backward-wave bianisotropic composite medium matched to free space is suggested. It is based on the use of a uniaxial bianisotropic structure embedded into a matrix with negative effective permittivity. Since bianisotropy is easier to achieve in the optical range than artificial magnetism, this concept is prospective for optical backward-wave metamaterials. As an example of possible realizations, a microwave Ω-composite combined with a wire lattice is analytically studied.
Physics Letters a, Apr 7, 2008
A backward-wave slab based on a capacitively and inductively loaded three-dimensional transmissio... more A backward-wave slab based on a capacitively and inductively loaded three-dimensional transmission-line network is designed in such a way that impedance-matching with free space is obtained. To enable field propagation from free space to the network and vice versa, the use of a transition layer is proposed. Matching of the designed network with free space and negative refraction occurring at the slab interfaces are confirmed with full-wave simulations.
Unknown, Jun 1, 1989
ABSTRACT
IEE Proceedings H Microwaves, Antennas and Propagation, 1991
The paper explores reflection and transmission characteristics of single and multilayer chiral sl... more The paper explores reflection and transmission characteristics of single and multilayer chiral slabs. The analysis is based on vector circuit modelling of chiral slabs in terms of transverse fields, dyadic impedance, admittance or transmission matrix components. Reflection and transmission coefficients for arbitrary angles of incidence and arbitrary polarisation states of the fields are derived. From these coefficients and to exemplify the method, reflected and transmitted fields of the co- and cross-polarised waves are calculated in single and multilayer chiral slabs for various electromagnetic and geometrical parameter values.
Eprint Arxiv Physics 0504123, Apr 18, 2005
An antenna prototype utilizing artificial impedance surfaces to control the near field distributi... more An antenna prototype utilizing artificial impedance surfaces to control the near field distribution is described. The antenna is a folded dipole placed above a finite-size artificial impedance surface. We have found that the field screening is most effective if the surface is a metal conductor. However, to achieve a reasonable value of the radiation resistance the dipole should be located far off the screen. If the surface is a magnetic wall, the antenna design is more compact, but the field behind the screen is large. Here we realize a compromise solution using an inductive surface of a moderate surface impedance, which allows realization of an effective near-field screen with still a reasonably low-profile design.
Abstract In this paper, two homogenization models are presented for the analysis of mushroom stru... more Abstract In this paper, two homogenization models are presented for the analysis of mushroom structures. The differences of these models rise from the different way of modeling the array of metallic vias connecting the metallic patches to the ground plane. It is shown that for electrically thin mushroom structures the results of these models concur with each other. Furthermore, it is shown in this paper that the use of metallic vias in mushroom structures results in additional resonances for the TM-polarized incident fields.
Nasa Sti Recon Technical Report N, Apr 1, 1989
The Silberstein wave-field decomposition of electromagnetic fields is applied to the problem of w... more The Silberstein wave-field decomposition of electromagnetic fields is applied to the problem of wave propagation in chiral medium. The problem involving a planar interface between two chiral media is considered and eigensolutions for the reflection and transmission problems are given. Numerical results are calculated for the eigenpolarizations and reflection coefficients with different incident field polarizations, for the problem involving an interface between isotropic and chiral media. Also, the limit cases of reflection from a half space with only small amount of chirality are studied and it is shown that the chirality gives a second-order effect on the co-polarized reflection coefficient and a first-order effect on cross-polarization.
Nasa Sti Recon Technical Report N, Dec 1, 1990
Cloaking using a volumetric structure composed of stacked two-dimensional transmission-line netwo... more Cloaking using a volumetric structure composed of stacked two-dimensional transmission-line networks is verified with measurements. The measurements are done in a waveguide, in which an array of metallic cylinders is inserted causing a short-circuit in the waveguide. The metal cylinders are cloaked using a previously designed and simulated cloak that hides the cylinders and thus enables wave propagation inside the waveguide.
Journal of Electromagnetic Waves and Applications, Apr 3, 2012
A model for a chiral material in which both the permittivity and permeability are equal to zero i... more A model for a chiral material in which both the permittivity and permeability are equal to zero is discussed. Such a material is referred by us as a "chiral nihility". It is shown that this exotic material can be realized as a mixture of small helical inclusions. Wave solutions and energy in such a medium are analyzed. It is shown that an extraordinary wave in chiral nihility is a backward wave. Wave reflection and refraction on a chiral nihility interface is also considered. It is shown that a linearly polarized wave normally incident onto this interface produces the wave of "standing phase" and the same wave in the case of oblique incidence causes two refracted waves, one of them with an anomalous refraction.
Proceedings of the 5th European Conference on Antennas and Propagation, Apr 11, 2011
ABSTRACT Electromagnetic cloaks based on volumetric transmission-line networks have been previous... more ABSTRACT Electromagnetic cloaks based on volumetric transmission-line networks have been previously proposed as candidates for simple, cheap, and broadband cloaking devices that can be used to hide mesh-like structures. In this paper we demonstrate, with numerical simulations, how a metallic object placed in the near-field of a horn antenna can be made “invisible” with such a cloak, thus restoring the antenna's radiation properties to resemble the case when the antenna is alone in free space.
2013 International Symposium on Electromagnetic Theory, 2013
ABSTRACT We study the occurrence of the so-called antiresonance in the material parameters (permi... more ABSTRACT We study the occurrence of the so-called antiresonance in the material parameters (permittivity, permeability) characterizing the electromagnetic response of a composite material slab. The material parameters are retrieved using the wellknown reflection/transmission method. As many previous works have either claimed or assumed that the antiresonance is an effect caused by the periodicity of the composite material, we study in this work both periodic and aperiodic material samples.
Proceedings of the Fourth European Conference on Antennas and Propagation, Apr 12, 2010
Combinations of electric and magnetic dipoles radiating circularly polarized waves are studied. T... more Combinations of electric and magnetic dipoles radiating circularly polarized waves are studied. The use of a chiral particle is introduced as a means to create a single radiating particle that combines an electric dipole and a magnetic dipole. It is shown both numerically and experimentally that a pair of two such particles, when fed with a 90 degree phase shift,
As was shown by N. Engheta, electromagnetic fields in two adjacent slabs bounded by two metal wal... more As was shown by N. Engheta, electromagnetic fields in two adjacent slabs bounded by two metal walls can satisfy the boundary conditions even if the distance between the two walls is much smaller than the wavelength. This is possible if one of the slabs has a negative permeability. Here we show that these subwavelength "resonators" resonate only if the permeability of at least one of the slabs is frequency dependent. Thus, there is no advantage of using these structures as frequency-selective devices. However, we have found that these systems can be in principle used as memory devices for evanescent fields, because the boundary conditions are identically satisfied for all plane evanescent waves inside the cavity. The physical meaning and practical limitations for possible realizations are discussed. The analysis is supported by FDTD simulations.
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Nonlinearities, Activity and Computational by Sergei Tretyakov
Papers by Sergei Tretyakov