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1.
Phys Rev Lett ; 125(26): 266102, 2020 Dec 31.
Article in English | MEDLINE | ID: mdl-33449712

ABSTRACT

Physical systems with material properties modulated in time provide versatile routes for designing magnetless nonreciprocal devices. Traditionally, nonreciprocity in such systems is achieved exploiting both temporal and spatial modulations, which inevitably requires a series of time-modulated elements distributed in space. In this Letter, we introduce a concept of bianisotropic time-modulated systems capable of nonreciprocal wave propagation at the fundamental frequency and based on uniform, solely temporal material modulations. In the absence of temporal modulations, the considered bianisotropic systems are reciprocal. We theoretically explain the nonreciprocal effect by analyzing wave propagation in an unbounded bianisotropic time-modulated medium. The effect stems from temporal modulation of spatial dispersion effects which to date were not taken into account in previous studies based on the local-permittivity description. We propose a circuit design of a bianisotropic metasurface that can provide phase-insensitive isolation and unidirectional amplification.

2.
Philos Trans A Math Phys Eng Sci ; 373(2049)2015 Aug 28.
Article in English | MEDLINE | ID: mdl-26217052

ABSTRACT

In this review paper I discuss electrically thin composite layers, designed to perform desired operations on applied electromagnetic fields. Starting from a historical overview and based on a general classification of metasurfaces, I give an overview of possible functionalities of the most general linear metasurfaces. The review is concluded with a short research outlook discussion.

3.
Phys Rev Lett ; 114(9): 095503, 2015 Mar 06.
Article in English | MEDLINE | ID: mdl-25793826

ABSTRACT

Conventional mirrors obey the simple reflection law that a plane wave is reflected as a plane wave, at the same angle. To engineer spatial distributions of fields reflected from a mirror, one can either shape the reflector or position some phase-correcting elements on top of a mirror surface. Here we show, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions. These proposed artificial surfaces, metamirrors, provide various functions of shaped or nonuniform reflectors without utilizing any mirror. This can be achieved only if the forward and backward scattering of the inclusions in the array can be engineered independently, and we prove that it is possible using electrically and magnetically polarizable inclusions. The proposed subwavelength inclusions possess desired reflecting properties at the operational frequency band, while at other frequencies the array is practically transparent. The metamirror concept leads to a variety of applications over the entire electromagnetic spectrum, such as optically transparent focusing antennas for satellites, multifrequency reflector antennas for radio astronomy, low-profile conformal antennas for telecommunications, and nanoreflectarray antennas for integrated optics.

4.
Sci Rep ; 4: 4484, 2014 Mar 27.
Article in English | MEDLINE | ID: mdl-24670919

ABSTRACT

Understanding the impact of order and disorder is of fundamental importance to perceive and to appreciate the functionality of modern photonic metasurfaces. Metasurfaces with disordered and amorphous inner arrangements promise to mitigate problems that arise for their counterparts with strictly periodic lattices of elementary unit cells such as, e.g., spatial dispersion, and allows the use of fabrication techniques that are suitable for large scale and cheap fabrication of metasurfaces. In this study, we analytically, numerically and experimentally investigate metasurfaces with different lattice arrangements and uncover the influence of lattice disorder on their electromagnetic properties. The considered metasurfaces are composed of metal-dielectric-metal elements that sustain both electric and magnetic resonances. Emphasis is placed on understanding the effect of the transition of the lattice symmetry from a periodic to an amorphous state and on studying oblique illumination. For this scenario, we develop a powerful analytical model that yields, for the first time, an adequate description of the scattering properties of amorphous metasurfaces, paving the way for their integration into future applications.

5.
Opt Express ; 19(7): 6699-704, 2011 Mar 28.
Article in English | MEDLINE | ID: mdl-21451696

ABSTRACT

Modified boundary conditions for composite material are suggested. The modified RT-retrieval procedure yields bulk values of effective impedance and refractive index, which are independent of system size and boundary realization, whereas the conductivities of the excess surface currents depend on the property of the interface. Simultaneous treatment of all the possible realizations of the system removes the dependence. The accuracy of the latter procedure is the same as the usage of static effective parameters, namely k(eff)d.


Subject(s)
Manufactured Materials/analysis , Models, Chemical , Refractometry/methods , Computer Simulation , Electric Impedance , Electromagnetic Fields , Light , Scattering, Radiation
6.
Phys Rev E Stat Nonlin Soft Matter Phys ; 71(4 Pt 2): 046612, 2005 Apr.
Article in English | MEDLINE | ID: mdl-15903811

ABSTRACT

Electromagnetic waves in an artificial medium formed by two mutually orthogonal lattices of thin ideally conducting straight wires (referred to as a two-dimensional wire medium) are considered. An effective medium approach and a full-wave method based on the dyadic Green's function and the method of moments are developed. Effects of spatial dispersion, such as the appearance of anisotropy in a square lattice and an additional extraordinary wave, as in crystal optics, are demonstrated. Evanescent waves with complex propagation constants are found. The case when both forward and backward extraordinary waves with respect to an interface exist simultaneously is observed and discussed. The effect of birefringence, so that one extraordinary wave has the wave vector making a positive angle to the interface and the other has the wave vector making a negative angle to the interface, is illustrated.

7.
Phys Rev E Stat Nonlin Soft Matter Phys ; 72(6 Pt 2): 066606, 2005 Dec.
Article in English | MEDLINE | ID: mdl-16486077

ABSTRACT

A transversal mode with zero group velocity and nonzero phase velocity that can exist in chains of silver nanospheres in the optical frequency range is theoretically studied. It is shown that the external source radiating a narrow-band nonmonochromatic signal can excite in the chain a mixture of standing and slowly traveling waves. The standing-wave component (named the resonator mode) is strongly dominating. The physical reason for such a regime is a sign-varying distribution of power flux over the cross section of the chain. A possible application of the resonator mode for evanescent-wave enhancement and for subwavelength imaging in the visible is discussed.

8.
Phys Rev E Stat Nonlin Soft Matter Phys ; 70(6 Pt 2): 068601; author reply 068602, 2004 Dec.
Article in English | MEDLINE | ID: mdl-15697567

ABSTRACT

It is shown that metamaterials considered by Phys. Rev. E 68, 026612 (2003)]] as media that support trans-vacuum-speed pulses must exhibit instantaneous response. Thus, they are not physically realizable as linear passive materials.

9.
Phys Rev E Stat Nonlin Soft Matter Phys ; 67(5 Pt 2): 056622, 2003 May.
Article in English | MEDLINE | ID: mdl-12786311

ABSTRACT

In this paper the electromagnetic properties of bianisotropic electromagnetic crystals are studied. The crystals are assumed to be rectangular lattices of perfectly conducting helicoidal spirals. The analytical theory of dispersion and plane-wave reflection refers to the case when the spiral step and the radius are small compared to the wavelengths in the host medium. The periods of the lattice can be arbitrary. Explicit closed-form expressions are derived for the effective material parameters of the medium in the low-frequency regime. The medium eigenmodes are elliptically polarized, and one of them propagates without interaction with the lattice. As to the other eigenmode, the lattice has strong spatial dispersion even at extremely low frequencies in the direction along the spiral axes. Numerical examples are given. An analogy between the spiral medium and the medium of loaded wires is indicated.

10.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(3 Pt 2B): 036610, 2002 Sep.
Article in English | MEDLINE | ID: mdl-12366283

ABSTRACT

Two-dimensional electromagnetic crystals formed by rectangular lattices of thin ideally conducting cylinders periodically loaded by bulk reactive impedances are considered. An analytical theory of dispersion and reflection from this medium is presented. The consideration is based on the local field approach. The transcendental dispersion equation is obtained in the closed form and solved numerically. Different types of the loads such as inductive, capacitive, serial, and parallel LC circuits are considered. Typical dispersion curves and reflection coefficients are calculated and analyzed.

11.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(1 Pt 2): 016608, 2002 Jul.
Article in English | MEDLINE | ID: mdl-12241501

ABSTRACT

An electrically controlled nonreciprocal electromagnetic band-gap material is proposed and studied. The new material is a periodic three-dimensional regular lattice of small magnetized ferrite spheres. In this paper, we consider plane electromagnetic waves in this medium and design an analytical model for the material parameters. An analytical solution for plane-wave reflection from a planar interface is also presented. In the proposed material, a new electrically controlled stop band appears for one of the two circularly polarized eigenwaves in a frequency band around the ferrimagnetic resonance frequency. This frequency can be well below the usual lattice band gap, which allows the realization of rather compact structures. The main properties of the material are outlined.

12.
J Opt Soc Am A Opt Image Sci Vis ; 17(10): 1791-7, 2000 Oct.
Article in English | MEDLINE | ID: mdl-11028527

ABSTRACT

A simple analytical theory for finding eigensolutions for plane electromagnetic waves propagating along an axis in infinite regular arrays of small dipole particles is presented. The spacing between dipoles in every plane is assumed to be smaller than the wavelength; separation between the planes is arbitrary. The influence of evanescent modes is taken into account. This theory gives a model for an effective propagation constant that can be applied in a wide frequency range from the quasi-static regime to the Bragg reflection (photonic bandgap) region.

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