Igor V. Bychkov

Transverse-electric plasmonic modes of cylindrical graphene-based waveguide at near-infrared and visible frequencies

Transverse-electric (TE) surface plasmons (SPs) are very unusual for plasmonics phenomenon. Graphene proposes a unique possibility to observe these plasmons. Due to transverse motion of carriers, TE SPs speed is usually close to bulk light one. In this work we discuss conditions of TE SPs propagation in cylindrical graphene-based waveguides. We found that the negativity of graphene conductivity’s imaginary part is not a sufficient condition. The structure supports TE SPs when the core radius of waveguide is larger than the critical value Rcr. Critical radius depends on the light frequency and the difference of permittivities inside and outside the waveguide. Minimum value of Rcr is comparable with the wavelength of volume wave and corresponds to interband carriers transition in graphene. We predict that use of multilayer graphene will lead to decrease of critical radius. TE SPs speed may differ more significantly from bulk light one in case of epsilon-near-zero core and shell of the waveguide. Results may open the door for practical applications of TE SPs in optics, including telecommunications.

Giant Faraday Rotation of High-Order Plasmonic Modes in Graphene-Covered Nanowires

Plasmonic Faraday rotation in nanowires manifests itself in the rotation of the spatial intensity distribution of high-order surface plasmon polariton (SPP) modes around the nanowire axis. Here we predict theoretically the giant Faraday rotation for SPPs propagating on graphene-coated magneto-optically active nanowires. Upon the reversal of the external magnetic field pointing along the nanowire axis some high-order plasmonic modes may be rotated by up to ∼100° on the length scale of about 500 nm at mid-infrared frequencies. Tuning the carrier concentration in graphene by chemical doping or gate voltage allows for controlling SPP-properties and notably the rotation angle of high-order azimuthal modes. Our results open the door to novel plasmonic applications ranging from nanowire-based Faraday isolators to the magnetic control in quantum-optical applications.

Topologically Induced Optical Activity in Graphene-Based Meta-Structures

Non-reciprocity and asymmetric transmission in optical and plasmonic systems is a key element for engineering the one-way propagation structures for light manipulation. Here we investigate topological nanostructures covered with graphene-based meta-surfaces, which consist of a periodic pattern of sub-wavelength stripes of graphene winding around the (meta-) tube or (meta-)torus. We establish the relation between the topological and plasmonic properties in these structures, as justified by simple theoretical expressions. Our results demonstrate how to use strong asymmetric and chiral plasmonic responses to tailor the electrodynamic properties in topological meta-structures. Cavity resonances formed by elliptical and hyperbolic plasmons in meta-structures are sensitive to the one-way propagation regime in a finite length (Fabry-Perot-like) meta-tube and display the giant mode splitting in a (Mach-Zehnder-like) meta-torus.

Magnetoelectric susceptibility tensor of multiferroic TbMnO3 with cycloidal antiferromagnetic structure in external field

Magnetoelectric, dielectric, and magnetic susceptibility tensors of multiferroic TbMnO3 with cycloidal antiferromagnetic structure in external electric and magnetic fields have been investigated with taking into account dynamics of spin, electro-dipole, and acoustic subsystems. All components of tensors depend on values of external electric and magnetic fields. The possibility of control of electrodynamic properties of multiferroic TbMnO3 with cycloidal antiferromagnetic structure by external electric and magnetic fields has been shown. The resonant interaction of spin, electro-dipole, electromagnetic, and acoustic waves in such material is observed.

Plasmonics of magnetic and topological graphene-based nanostructures

Abstract Graphene is a unique material in the study of the fundamental limits of plasmonics. Apart from the ultimate single-layer thickness, its carrier concentration can be tuned by chemical doping or applying an electric field. In this manner, the electrodynamic properties of graphene can be varied from highly conductive to dielectric. Graphene supports strongly confined, propagating surface plasmon polaritons (SPPs) in a broad spectral range from terahertz to mid-infrared frequencies. It also possesses a strong magneto-optical response and thus provides complimentary architectures to conventional magneto-plasmonics based on magneto-optically active metals or dielectrics. Despite a large number of review articles devoted to plasmonic properties and applications of graphene, little is known about graphene magneto-plasmonics and topological effects in graphene-based nanostructures, which represent the main subject of this review. We discuss several strategies to enhance plasmonic effects in topologically distinct closed surface landscapes, i.e. graphene nanotubes, cylindrical nanocavities and toroidal nanostructures. A novel phenomenon of the strongly asymmetric SPP propagation on chiral meta-structures and the fundamental relations between structural and plasmonic topological indices are reviewed.

Core-shell biochar-bearing iron ore powder model for calculation of effective electrodynamic parameters

The simplified model of biochar-bearing iron ore with binder was studied. It was considered to be a mixture of two types of core-shell particles, iron ore - binder particles and biochar - binder particles. The expressions to calculate complex effective permittivity and permeability was derived by effective medium approximation (EMA). The corresponding dependencies on volume fraction of iron ore in the mixture are provided.

Negative group velocity waves in rectilinear thin wires array

A well-known metamaterial consisting of rectilinear thin wires array forming a 2D-square lattice within the non-conductive matrix was theoretically investigated in this paper. The frequency dependencies of wavelength of smoothed electromagnetic field distributions inside the wired structure, show that this material has a wide band in which there are negative group velocity waves. This effect is clearly observed in the case when the wavelength of the smoothed distribution of the electromagnetic field is much longer than the distance between the wires. For this case, also figures of field distribution from point source were modeled. They show that negative refraction and focusing of electromagnetic radiation observed, ie. the studied material is left-handed. Unlike most of the left-handed metamaterials that are composed of two separate inter-elements (typically, a split ring and a rod), in this paper it is proposed to use only one type of inclusion, namely the conductive rod.

Magneto‐Plasmonics and Optical Activity in Graphene‐Based Nanowires

Nowadays, graphene plasmonics shows a great number of features unusual for traditional (metal-based) plasmonics from high localization and large propagation distance of surface plasmon-polaritons (SPPs) through the existence of both TEand TM-polarized SPPs to the possibility of controlled SPPs by graphene chemical potential (or, equivalently, by gate voltage or chemical doping). Cylindrical graphene-based plasmonic structures have some advantages in contrast to planar geometry: absence of edge losses, existence of high-order azimuthal modes, etc. In this work, we discuss some ways to obtain an optical activity in cylindrical graphene-based plasmonic structures and its possible applications to SPPs manipulation.

Dependencies of dynamical magnetic losses in conductor-coated dielectric particles on radius of dielectric core, thickness and conductivity of conductive shell

In this work, we modeled dielectric spherical particles covered by metallic layer. We obtained dependencies of real and imaginary parts of the effective permittivity and permeability of powders from metalized dielectric particles on the frequency, radius and permittivity of the particle, thickness and conductivity of the metallic layer. We used finite element method for calculation of the electromagnetic fields in the investigated model and combination of impedance lows for ideal conductor and ideal magnetic mirror to calculate effective electrodynamics parameters. Novel technique for calculation of effective permittivity and permeability from results of direct calculations of electromagnetic fields in the model is provided in this paper. The imaginary part of the effective permeability is large enough compared with imaginary part of the effective permittivity and reaches its maximum values at the thickness of the metallic layer less than the skin depth. Therefore, microwave heating of such particles is d...

Radiation and Propagation of Waves in Magnetic Materials with Helicoidal Magnetic Structure

In this chapter, we are shortly reviewing some problems of electromagnetic and acoustic wave propagation and radiation in the magnets with helicoidal spin structure. We show the band structure of the coupled wave spectrum in the materials. The band gap width depends on the spiral angle (or, equivalently, on external magnetic field value). Interaction of spin and electromagnetic waves leads to opening the gap in spinelectromagnetic dispersion. This gap leads to opacity window in reflection spectrum of spiral magnet plate. The opacity window closes at phase transition into collinear ferromagnetic state and reaches a maximum at simple spiral state. At the frequencies near band gap boundaries, the rotation of polarization plane of propagating electro‐ magnetic wave is observed. Account of interaction of spin and electromagnetic waves with acoustic subsystem leads to opening the gap in spin-acoustic spectrum. This gap leads to some features in electromagnetic reflectance spectrum and to rotation of acoustic wave polarization plane, i.e. to acoustic Faraday effect. We also show the possibility of acoustic and electromagnetic wave radiation by helicoidal magnets at phase transition into collinear ferromagnetic state. Some features of electromagnetic waves generation by spiral magnets placed in homogeneous magnetic field with harmonical time-dependence are also discussed.