Wave nonreciprocity in inhomogeneous gyrotropic media and multilayer systems: I. Inhomogeneous gyrotropic media

The propagation of electromagnetic waves in naturally (or structurally) gyrotropic inhomogeneous media is considered. A new mechanism of wave nonreciprocity is found, which is caused by the simultaneous presence of a gradient of one of the parameters of a medium and natural (or structural) gyrotropy. The problem of light transmission through a layer of a naturally gyrotropic inhomogeneous medium of finite thickness is solved by the method of addition of layers. Specific features of this nonreciprocity are considered. It is shown that such a system can operate as a one-sided reflector at certain angles of incidence of light. The mechanisms of enhancement of the nonreciprocity effects are investigated. It is shown that multiple reflections in a layer of finite thickness and diffraction of light by periodic inhomogeneities of a medium increase the nonreciprocity effects by several (from 2 to 5) orders of magnitude. This phenomenon, in turn, opens new fields of application of the nonreciprocity effects. Another interesting manifestation of wave nonreciprocity is revealed, which consists in asymmetry of the curve R(?):R(?)≠R(??) (R is the reflectance and ? is the angle of incidence).     

Accumulation and transmission of the light energy in nonreciprocal multilayer systems

The specific features of light energy distribution within a multiplayer optical system are calculated by using the effective layer addition method. Various mechanisms of nonreciprocity are discussed, and Jones matrices of systems with different mechanisms of nonreciprocity are considered and compared. Accumulation of polarized light energy and resonance light diode transmission (due to the asymmetric character of interaction between the light and nonreciprocal anisotropic system) in multilayer systems with cholesteric liquid crystal layer(s) in presence of small absorption are predicted in certain range of the light spectrum and polarization. The accumulation of light in the multilayer optical systems with the defects, based on realistic solid materials with periodical structure, are also discussed, aiming at their applications in the liquid or gas-heaters and solar energy and fiber optics converters.     

Inversionless amplification of light by a two-level medium as a result of mechanical-to-electromagnetic atomic energy conversion

Nonreciprocal effects in the acousto-optical interaction in gyrotropic cubic crystals with electroinduced anisotropy are studied. It is shown that the presence of optical gyrotropy leads to the doubling of the number of peaks of amplitude nonreciprocity, whereas an external electric field causes their shift and enhancement. It is found that the direction of lasing in a ring laser can be reversed by changing the direction of the control field. The results obtained can be used for the development and optimization of polarization-and electro-controlled acousto-optical nonreciprocal elements on the basis of cubic gyrotropic crystals.     

Optical energy accumulation by a system comprising an optical diode,insulating layer,and mirror

The optical properties of a multilayer system comprising an optical diode, insulating layer, and mirror are studied. The distribution of the electromagnetic wave energy in the system is considered. It is shown that the energy of the wave is accumulated within certain spectral intervals. Two mechanisms underlying this observation are discussed. One is due to the diode effect (i.e., nonreciprocal transmission or reflection); the other is associated with periodic layers existing in the system. Multilayer structures based on the phenomenon discovered may find application in water or gas heaters and in optical-to-electric energy converters.     

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.     

Eigenmode scattering relations for plane-stratified gyrotropic media

We consider the 4×4 scattering matrixS for a plane wave incident on a plane-stratified gyrotropic multilayer slab, which is assumed to have a single symmetry axis (the magnetisation vector in a ferrite sheet, or the external magnetic field direction in a plane-stratified magnetoplasma). In the given (original) problem the plane of incidence is at an azimuthal angle ϕ with respect to the magnetic meridian plane (the plane containing the normal to the stratification, and the gyrotropic symmetry axis), and there is a corresponding “conjugate” set of wave fields, in which the plane of incidence is at an azimuthal angle (π−ϕ), with a corresponding conjugate scattering matrixS′. Adjoint wave fields, obtained by reversing the magnetic symmetry vector, are used to yield the eigenmode amplitudes required in the definition of the scattering matrices. At an interface between two adjacent layers the scattering matrices are shown to be uniquely determined by the characteristic wave polarisations, and this is used to prove that the given and conjugate scattering matrices,S andS′, for the overall multilayer system are mutually transposed, i.e. .     

Multilayered open dielectric waveguide with a gyrotropic layer

Open dielectric waveguides with a gyrotropic layer have been studied with a view to find structures in which the nonreciprocity in the propagation constant is maximized. A prediction based on a qualitative analysis and numerical studies for confirming the theory are included.This work was supported by a contract N00014-79-C-0553 from the Office of Naval Research.     

Optical diode based on a highly anisotropic layer of a helical periodic medium subjected to a magnetic field

The effect of an applied magnetic field on the optical properties of a layer of a helical periodic medium is studied in view of magnetooptic activity. The case when the radiation is normally incident on the layer and the magnetic field is aligned with the axis of the medium is considered. Irreversibility (nonreciprocity) effects in such a system are discussed. The situations with weak and high anisotropy are investigated. It is shown that the system can function as an optical shutter, optical diode, or one-side reflector. Reasons for the high irreversibility of transmission (reflection) are found.     

Diffraction enhancement and suppression of rotation of plane of polarization in chiral photonic crystals

The oblique propagation of light through a gyrotropic crystal layer placed in an ultrasonic field is considered. The problem is solved using the Ambartsumyan method of addition of layers. The wavelength dependences of the amplitude and polarization characteristics are studied for different values of the problem parameters. Application of such systems is discussed.     

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.     

Brewster’s angle polarizer design based on a gyrotropic double-periodic perforated layer

This paper is devoted to the study of the features of artificial gyrotropic magneto-dielectric layer with two-dimensional periodicity. Such a layer can be used in the development of the polarizers operating in the microwave and optical ranges. Analytical solution of a plane wave scattering from a double-periodic gyrotropic layer is obtained by the Method of Integral Functionals in the quasi-static approximation. The numerical results allow to realize the TE- and TM-pass Brewster’s angle polarizers.     

Optical transmission through metal/dielectric multilayer films perforated with periodic subwavelength slits

The transmission of p-polarized plane wave through Ag/SiO₂ multilayer films perforated with periodic subwavelength air slits is investigated by using the finite-difference time-domain (FDTD) method. The results show that the optical transmission property is mediated by the interference among the propagating coupled-SPP modes along the lateral direction inside the SiO₂ layers and the conditions of Fabry-Pérot-like resonance along the longitudinal direction together. When some geometric parameters are suitably initialized, the high transmission peaks can split into more peaks as the functional layer (metal/dielectric/metal sandwich stack) number increases, and the wavelength of the same-order transmission peak exhibits a red shift as the grating period increases.     

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.     

Nonreciprocity of the optical properties of a multilayer structure with a noncollinear orientation of the magnetization of layers

Optics and Spectroscopy - The nonreciprocity effects that occur both upon the transmission of light through a multilayer ferromagnetic film structure with magnetization vectors of layers lying in...     

X波段叠层片式微带铁氧体环行器的设计

采用叠层片式化设计有望实现微波环形器与低温共烧陶瓷(LTCC)技术的结合。借助三维电磁仿真手段设计了一种X波段微带铁氧体环行器,基片采用具有不同饱和磁化强度的旋磁材料构成叠层片式结构。研究结果表明,叠片数目及其饱和磁化强度的搭配对环形器的回波损耗和隔离度特性影响显著,这与叠层结构引入的界面及叠片变化的饱和磁化强度影响了环形器的等效输入电路参数有关。通过优化设计,可以获得具有高回波损耗、高隔离度及低插入损耗等优良性能的器件,但带宽受叠片数目及其饱和磁化强度的搭配影响较小,难以通过优化进行拓展。     

Magnetoelastic interaction in a shear wave propagating in a one-dimensional acoustically gyrotropic magnetic phononic crystal

The specific features of the localization and propagation of a shear wave caused by magnetoelastic interaction are studied using the example of a finite one-dimensional magnetic superlattice consisting of acoustically gyrotropic and acoustically nongyrotropic layers. The case where the wavelength of the elastic wave is commensurate with the period of the superlattice is considered.     

Optical sum-frequency emission from langmuir-blodgett films of variable thickness: effects of the substrate and polar orientation of fatty acids in the films

The nonlinear optical response arising from a model multilayer structure, i.e., Langmuir-Blodgett (LB) films comprised of different numbers of per-protonated (H) and per-deuterated (D) fatty acid layers on solid substrates, has been evaluated by sum-frequency generation (SFG) spectroscopy. The SFG signals depend significantly on the absolute polar orientation of the fatty acids in the individual layers and on the nonlinear optical response of the substrate. The SFG spectra on gold and fused quartz substrates demonstrate a totally different dependence on the number of the contributing H layers, which it is possible to analyze quantitatively. The results provide important information for understanding the origin of the nonlinear optical responses from ordered systems composed of multiple interfaces and therefore for extracting exact structural information about each interface from the observed SFG signals.     

Theoretical study of optical characteristics of multilayer coatings ZnO/CdS/CdTe using first-principles calculations

A new method for predicting optical characteristics of multilayer coatings based on calculated material properties is presented. This method combines the use of the full potential linear-augmented plane wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) and the optical matrix approach for modeling the multilayer assembly. The simulation process is applied to thin films of the II–VI semiconductors compounds. The optical constants of each thin film are determined by using the first principle calculations. Each layer is represented by the square Abeles matrix, including all necessary data in the calculation of the optical characteristics (as transmittance, reflectance and absorbance). The simulation of multilayer optical response includes the effect of thickness, light polarization and incident angle. The obtained results are helpful in the design of the multilayer systems with required properties.     

Group Representation of Waves in Gyrotropic Crystals

A new group (linear) representation of the propagation of waves in properly and naturally gyrotropic crystals in the general case where the nonreciprocity effect takes place has been developed. Simple expressions of the dependence of ray (group) velocities and polarization vectors of isonormal waves on the complex vector of principal velocities dual to the unitary tensor by which the optical properties of crystals are directly characterized have been obtained. The relationship between gyrotropy and anisotropy and the dipole moment and displacement current induced by the radiation in the crystal has been established. It is shown that the presence of gyrotropy and nonlinear polarization of radiation together with the elimination of conical points entails a phase ambiguity of the ray velocity of the quantummechanical type and a smearing and layering of the wave surface, as well as a discreteness of the spectrum of velocity values of isonormal waves.     

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.