Optical Radiation Trapping by Current in Gyrotropic Liquid Metacrystals

It is shown that direct electric current passing through a suspension of gyrotropic nanoparticles with residual magnetization (gyrotropic liquid metacrystal) forms a unidirectional waveguide for optical radiation so that trapped light can propagate only in the direction opposite to the direction of current. The localization of electromagnetic radiation is associated with the emergence of nonuniform gyrotropy of the medium as a result of reorientation of magnetic nanoparticles in the nonuniform magnetic field of the current. By way of examples, we consider the trapping of the radiation by a plane current sheet and by a cylindrical current-carrying filament. The dispersion equations of trapped modes are derived and analyzed. The analogy with topologically protected edge photon states is considered.     

Sign inversion of the rotatory power and topology of the surface of gyration of αNiSO4·6H2O

The sign inversion point of the rotatory power of the gyrotropic crystals α-NiSO₄·6H₂O (λ _l=503 nm at 300 K) has been established. The topology of the gyration surface varies greatly in the vicinity of λ _l. We have demonstrated the possibility of using this method of spectrophotometric polarimetry for precise monitoring of the mounting of a gyrotropic crystal in the system “polarizer-crystal-analyzer.” Fiz. Tverd. Tela (St. Petersburg) 40, 1608–1609 (September 1998)     

Theory of gyrotropic ring resonators with counterpropagating modes coupling

The Faraday effect in ring resonators leads to the resonance splitting of clockwise and counter-clockwise propagating modes. In this work we investigate how this resonance splitting influences the ring resonator's behavior if both modes are coupled by a sidewall corrugation of the resonator. Coupled mode theory is used to evaluate the transmission and reflection characteristics of a ring resonator coupled to a waveguide. Based on these evaluations, we characterize a novel ring resonator switch. The resonance of the corrugated gyrotropic resonator coupled to a waveguide can be switched off by the application of the external magnetic field. In this case, the resonance is not shifted, as what typically occurs at small perturbations, but suppressed.     

Natural electromagnetic waves in round inhomogeneous layered waveguides

A general theory of gyrotropic waveguide is considered. The theory allows the entire spectrum of natural electromagnetic waves and oscillations in regular waveguide structures discretely inhomogeneous in their cross sections to be obtained. A mathematical model is discussed that enables the propagation constants to be calculated for an arbitrary number of bigyrotropic layers of the structure based on an informal algorithmic formulation of the dispersion equation. Examples of numerical analysis of electrodynamic structures are given. They provide the basis for the development of gyromagnetic microwave devices and measuring cutoff converters intended for monitoring of the electrophysical characteristics of various materials and fluid media. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 15–19, September, 2006.     

The field distributions and dispersion characteristics in chiroferrite central-loaded waveguide

The field distributions and dispersion characteristics of hybrid modes in circular chiro ferrite central-loaded waveguide are investigated numerically in this paper. Especially, the effects of constitutive parameters of chiro ferrite material on the propagation behaviour of hybrid modes are examined in detail, and some novel features are pointed out. The results show that, as reciprocal chiral and gyrotropic media, nonreciprocal chiroferrite materials have potential applications for the design of microwave, millimeter wave and integrated optical devices.     

Comparative study of asymmetric versus symmetric planar slab dielectric optical waveguides

In this paper we have studied the asymmetric versus symmetric planar waveguide in terms of their usefulness in optical fiber communication systems. We have explored the thin waveguide versus thick waveguide first. Later on usefulness of asymmetric versus symmetric waveguide is carried out to target for WDM optical network application. All kinds of optical network components are fabricated on Si substrate with the point of view of their application. Here asymmetric planar structure may be more useful compared to symmetric waveguide in terms of their non-uniform power confinement properties. However, the symmetric waveguide structure may be more useful for their high power confinement properties. It is well known that the thin symmetric waveguide supports at least one mode. However the thick waveguide may support many even as well as odd modes. We study the power confinement properties for symmetric as well as asymmetric waveguide structure. We conclude that higher order modes show the nonlinear power variations. Mode field profile for various cases is discussed as well. Comparative study between asymmetric versus symmetric waveguide has a lot of significance in optical network area. It has been shown through analysis that in asymmetric waveguide, the power flows more through film region in the case of fundamental mode. Power confinement properties for asymmetric waveguide versus symmetric waveguide have been studied.     

Photocurrent in gyrotropic Weyl semimetals

Photocurrents in the Weyl semimetals belonging to the gyrotropic symmetry classes have been theoretically studied. It has been shown that the circular photocurrent transverse to the direction of light incidence appears in weakly gyrotropic crystals with the C _nv (n = 3, 4, 6) symmetry only when spin-dependent terms both linear and quadratic or cubic in the quasimomentum, as well as a spin-independent term resulting in the tilt of the cone dispersion, are taken into account in the electron effective Hamiltonian. A polarization-independent magnetic-field-induced photocurrent, which is allowed only in gyrotropic systems, has been predicted. For crystals with the C_2v symmetry, a microscopic mechanism of the photocurrent in a quantized magnetic field, which is generated in direct optical transitions between the ground and first excited magnetic subbands, has been considered. It has been shown that this photocurrent becomes nonzero in the presence of the anisotropic tilt of dispersion cones.     

Multilayer gyrotropic waveguide structures with azimuthal magnetization

An algorithm to obtain the dispersion equation and to determine the field configuration in the case of an arbitrary number of layers is developed by the successive joining of tangential components of the eigenwave electromagnetic field of a regular waveguide with concentric azimuthally magnetized gyrotropic layers. The electrical and magnetic field components in each layer are represented in the form of a linear combination of four particular analytic solutions of the system of generalized wave equations. By using an electronic computer the phase and dissipation characteristics of circular and coaxial waveguides with azimuthally magnetized ferrite-dielectric layers are computed for variations in their material and geometric parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 24–28, April, 1981.     

Modeling of a bimetallic eccentric cylindrical plasma waveguide based on a transmission line for TEM-mode

In this paper, a plasma waveguide made of two eccentric cylindrical metallic walls have been studied according to the theory of transmission lines. The inductance per unit length L, the capacitance per unit length C, the resistance per unit length R and the shunt conductance per unit length G are obtained. The graphs of variations of the mentioned parameters vs. geometrical dimensions of waveguide are investigated. This investigations have been done for two different types of plasma waveguide. At first stage, plasma region will be considered in cold and collisional approximation and in second stage, a drift plasma in cold collisionless approximation will be considered. Also, graphs of phase velocity variation vs. the main parameters of the waveguide are presented.     

Amplitude-Phase Effects in Acousto-Optical Interaction in Gyrotropic Cubic Crystals

The amplitude-phase features of an intermediate regime of light diffraction on ultrasound in gyrotropic cubic crystals have been investigated. It is established that in the gyrotropic medium excited by ultrasound two coupled phase lattices of photoelasticity appear as a result of the rotation of the polarization planes of interacting waves. These lattices determine the polarization and energy characteristics of a diffracted light. For a gyrotropic cubic crystal of bismuth germanate, good agreement between the theoretical and experimental dependences of the efficiency of diffraction on the ultrasonic intensity in the intermediate regime close to the Bragg regime of diffraction is obtained.     

Dynamics of Magnetic Skyrmions in Nanodots

Bloch and Neel magnetic skyrmions have been studied in systems of confined geometry (nanodots, a linear array of nanodots). The spectra of low- and high-frequency excitation modes of a skyrmion state have been calculated. It has been shown that skyrmion spectrum asymmetry, namely, the characteristic difference between the frequencies of the azimuthal modes of the azimuthal skyrmion modes rotating clockwise and counterclockwise, is associated with asymmetry in the magnetization profiles of high-frequency spin waves propagating on the background of a skyrmion state in a nanodot. The low-frequency spectrum contains the only gyrotropic mode localized near the center of a nanodot. The gyrotropic frequency depends on the material parameters of a nanodot and the size of a skyrmion. The eigenfrequency of the gyrotropic mode of an isolated skyrmion in a nanodot in ultrathin films (L ~ 1 nm) does not depend on the internal structure of a skyrmion and is the same for Bloch and Neel skyrmions. The interaction of skyrmions, in particular, in a linear chain of nanodots with the ground skyrmion state, leads to distinctions in low-frequency spectra. The structure of a skyrmion (of Bloch or Neel type) is exhibited as a shift of dispersion curves and a difference between the frequencies of ferromagnetic resonance in a system of interacting skyrmions.     

Contribution to the theory of longitudinal instability of an electron beam in a waveguide with a magnetoactive dielectric

Conclusions Thus, our investigation shows that the character of the instability of an electron beam in a waveguide depends significantly on the state of the magnetization of the ferrite. Thus, in the case of an unsaturated ferrite the spectrum of the excited oscillations is unbounded, in contrast to the case of a longitudinally magnetized ferrite, when the spectrum of the waveguide harmonics is bounded by the frequency In the case of gyrotropic ferrite waveguide, the frequencies of the excited oscillations increase with increasing longitudinal magnetic field [see formula (21)], as is well confirmed by measurement results [8].The development of instability leads to a redistribution of the energy over the length of the beam (this effect was observed in experiment [8]), so that ferrite waveguides can be used for self-acceleration of intense electron beams.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 20, No. 3, pp. 444–450, March, 1977     

The influence of magnetic impurities in the vortex core dynamics in magnetic nano-disks

In this work we have used spin dynamics simulations to study the gyrotropic frequency behavior in nano-disks of Permalloy with magnetic impurities. We consider the effect of attractive impurity and repulsive impurity placed near the vortex core gyrotropic trajectory. We observed that the gyrotropic frequency is affected by the presence of impurity. The gyrotropic frequency shift depends on the relative position between the impurity and the vortex core gyrotropic trajectory and if impurity is attractive or repulsive. Our results agree with the analytical model and with experimental behavior for the gyrotropic frequency shown in the literature.     

Collinear Acousto–Optic Interaction of Light Beams near the Optical Axes of Biaxial Crystals

Collinear acousto–optic interaction of light beams near the optical axes of biaxial crystals, including gyrotropic ones, is considered. Efficient acousto–optic transformation of fast and slow light beams under the conditions of internal conical refraction has been revealed. It is shown that the width of the transmission band and the central frequency of ultrasound in collinear acousto–optic filtration in a nongyrotropic crystal are determined by the angle at the apex of the cone of wave vectors (by the anisotropy of the crystal) and in a gyrotropic one by the projection of the gyration vector onto the direction of the optical axis.     

Generalization of a scattering theorem for plane-stratified gyrotropic media

A previously derived eigenmode scattering theorem for plane-stratified gyrotropic media established that the scattering matricesS andS′, defined, respectively, in terms of a given and a conjugate set of eigenmode amplitudes, are mutually transposed, i.e. , the theorem being valid specifically for the incoming and outgoing eigenmodes ofgyrotropic bounding media. In this paper the theorem is extended to include linearly and circularly polarized base-modes in theisotropic media which may bound the multilayered, gyrotropic structure. Transformation of the eigenmode scattering matrix leads to a generalization of the scattering theorem to include base modes which are not necessarily eigenmodes of the medium. In the important special case in which the ambient magnetic field is parallel to the plane of the stratification, the scattering matrix is shown to have a special symmetry whose form depends on the base modes chosen (eigenmodes, linear modes or circular modes).     

Research on spectral domain immittance approach

In this paper, we have obtained the equations of electrodynamics for a gyrotropic medium using the Maxwell's equations. Through the Fourier Transforms (FT), the admittances of TM and TE modes in the electrically gyrotropic substrate and the magnetically gyrotropic substrate are given. Then we can use the spectral domain immittance approach to analyse the finline structures with a gyrotropic medium. The propating characteristics of the dominant mode in magnetized-ferrite-loaded double-layered finlines are studied, numerical results are presented which could be used in designing a finline displacement isolator.     

High-Frequency Backward Waves in Longitudinally Magnetized Gyrotropic Waveguides

Backward waves in waveguides completely filled with magnetoactive plasma (gaseous or semiconductor plasma) have been investigated numerically. It is shown that two types of backward waves exist in such waveguides: cyclotron backward waves and waveguide HE-modes. While the cyclotron modes are backward waves at arbitrary system parameters (plasma density, magnetic field and waveguide radius), the waveguide backward waves appear only at certain values of there parameters. In addition the cyclotron backward waves can propagate at arbitrary wave-number k_z and at arbitrary phase velocity. The backward waveguide modes exist only at limited values of k_z and of phase velocities.     

Optimal conditions of the acousto-optic interaction in crystals with gyrotropy

The conditions of the acousto-optic interaction in the crystals with gyrotropy are considered. The optimal length of the acousto-optic interaction and the diffraction efficiency in the gyrotropic direction are calculated. The diffraction efficiency is determined by the coupled wave method which allows calculation of the field interaction in the gyrotropic crystal [1]. It is theoretically shown and experimentally confirmed that the diffraction efficiency in the gyrotropic direction is independent of incident light polarization, when the polarization plane rotates by 45° along the interaction length.     

Novel properties of wave propagation in biaxially anisotropic left‐handed materials

Some physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left‐handed materials are investigated in this paper: (i) we show that in the biaxially gyrotropic left‐handed material, the left‐right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media; (ii) it is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left‐handed media we will present a different geometric phase that is independent of the cone angles; (iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left‐ and right‐handed (LRH) media is also studied in detail by using the Lewis‐Riesenfeld invariant theory. Some interesting applications (e.g., controllable position‐dependent frequency shift, detection of quantum‐vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left‐handed media is briefly discussed.     

Anomalies in second order elastic constants and gyrotropic constants of triglycine sulphate near phase transition

The anomalies in second order elastic constants and gyrotropic constants have been considered for the phase transition of triglycine sulphate. Expressions have been derived for the equilibrium values of order parameter and strain variables in both phases. Using Landau-Khalatnikov equation the fluctuation in order parameter is expressed in terms of fluctuations in strain variables. Substitution of these in free energy gives anomalies arising from Landau and coupling energies in second order elastic constants. The real part of the anomalies decreases steeply across the transition temperature and thereafter flatly tend to ferroelectric values. The anomalies in the components of the gyrotropic tensor have been derived and their temperature variation discussed.