Polarization Plane Research Articles

Generation of the CMB cosmic birefringence through axion-like particles, sterile and active neutrinos

The cosmic birefringence (CB) angle refers to the rotation of the linear polarization plane of Cosmic Microwave Background (CMB) radiations when parity-violating theories are considered. We analyzed the Quantum Boltzmann equation for an ensemble of CMB photons interacting with the right-handed sterile neutrino dark matter (DM) and axion-like particles (ALPs) DM in the presence of the scalar metric perturbation. We used the birefringence angle of CMB to study those probable candidates of DM. It is shown that the CB angle contribution of sterile neutrino is much less that two other sources considered here. Next, we combined the results of the cosmic neutrinos’ contribution and the contribution of the ALPs to producing the CMB birefringence and discussed the uncertainty on the parameter space of axions caused by the share of CMB-cosmic neutrino interaction in generating this effect. Finally, we plotted the EB power spectrum of the CMB and showed that this spectrum behaves differently in the presence of cosmic neutrinos and ALPs interactions in small l. Hence, future observed data for CEBl,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C^{l}_{EB},$$\\end{document} will help us to distinguish the CB angle value due to the various sources of its production.

Few-layer bifunctional metasurfaces enabling asymmetric and symmetric polarization-plane rotation at the subwavelength scale

We introduce and numerically validate the concept of few-layer bifunctional metasurfaces comprising two arrays of quasiplanar subwavelength resonators and a middle grid (array of rectangular holes) that offer both symmetric and asymmetric transmissions connected, respectively, with symmetric and asymmetric polarization-plane rotation functionalities. The proposed structures are thinner than λ/7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda /7$$\\end{document} and free of diffractions. Usually, the structure’s symmetry or asymmetry, i.e. unbroken or broken spatial inversion symmetries, are considered for metasurfaces as prerequisites of the capability of symmetric or asymmetric conversion of linearly polarized waves, respectively. Due to the achieved adjustment of the resonances enabling the rotation of the polarization plane simultaneously for both orthogonal polarizations of the incident wave, the symmetric polarization-plane rotation functionality can be obtained within one subwavelength band, whereas the asymmetric polarization-plane rotation functionality associated with the asymmetric transmission is obtained within another subwavelength band. This combination of the functionalities in one subdiffraction structure is possible due to the optimal choice of the grid parameters, since they may strongly affect the coupling between the two resonator arrays. Although normal incidence is required for the targeted bifunctionality, the variations of the incidence angle can also be exploited for the enrichment of the overall functional capability. Variations of the polarization angle give another important degree of freedom. The connection between the polarization-angle dependence of cross-polarized transmission and capability of symmetric and asymmetric polarization-plane rotation functionalities is highlighted. The feasible designs of the bifunctional metasurfaces are discussed.

Gravitational waves effects in a Lorentz–violating scenario

This paper focuses on how the production and polarization of gravitational waves are affected by spontaneous Lorentz symmetry breaking, which is driven by a self–interacting vector field. Specifically, we examine the impact of a smooth quadratic potential and a non–minimal coupling, discussing the constraints and causality features of the linearized Einstein equation. To analyze the polarization states of a plane wave, we consider a fixed vacuum expectation value (VEV) of the vector field. Remarkably, we verify that a space–like background vector field modifies the polarization plane and introduces a longitudinal degree of freedom. In order to investigate the Lorentz violation effect on the quadrupole formula, we use the modified Green function. Finally, we show that the space–like component of the background field leads to a third–order time derivative of the quadrupole moment, and the bounds for the Lorentz–breaking coefficients are estimated as well.

Study of the reflection of a plane electromagnetic wave from a layer of chiral metamaterial located on a conducting plane, taking into account the inhomogeneity and dispersion of material parameters

To reduce the radar signature of moving objects, such as cars, boats, manned and unmanned aircraft systems, technologies for creating broadband radio-absorbing materials are being actively developed and improved. Among such materials are composites and chiral metamaterials, which have unique characteristics that make it possible to effectively control the reflection and rotation of the plane of polarization of electromagnetic waves. In addition, devices included in the structure of infocommunication systems are subject to electromagnetic radiation, which can cause undesirable effects and interference. Radio-absorbing coatings based on metamaterials can significantly reduce the reflection of electromagnetic waves and effectively counteract the effects of electromagnetic radiation. The purpose of this study is to solve the scientific and technical problem of determining the reflection coefficients of electromagnetic waves from a radio-absorbing material consisting of a chiral metamaterial located on a conducting surface. The main objective of the work is to study the interaction of a plane electromagnetic wave with the specified layer of metamaterial located on a conducting plane, taking into account the inhomogeneity and dispersion of material parameters.

Research on measuring method of self-mixing interference magnetic field based on Faraday effect

In this paper, the magnetic field measurement method of laser self-mixing interference based on the Faraday effect is proposed. The polarization plane of the linearly polarized light is changed by the terbium gallium garnet crystal with the influence of the magnetic field. The light modulated by the magnetic field reentered into the laser cavity through the Brewster window and formed the self-mixing effect. The theoretical analysis of the self-mixing interference model based on the Faraday effect is conducted, which explains essential features of the experimental results. The magnetic field is measured by the peak-to-peak value of self-mixing interference signal. The experimental results show that the relative error of the magnetic field measurement is within ±1.6%. The measurement method has the advantage of simple and compact structure with strong anti-interference ability.

Magnetic properties of Sohncke-type Pb(TiO) Cu4(PO4)4 exposed by resonant x-ray Bragg diffraction

The enantiomorphous (chiral) crystal class of Sohncke-type Pb(TiO)Cu4(PO4)4 permits the rotation of the plane of polarization of light (optical activity). Copper ions participate in noncollinear antiferromagnetic order below a temperature ≈ 7 K, with magnetoelectric and piezomagnetic effects permitted. Crystal and magnetic symmetries of Pb(TiO)Cu4(PO4)4 are fully incorporated in calculated resonant x-ray Bragg diffraction patterns that are successfully compared with existing limited experimental data [Misawa , ]. Specifically, there is additional intensity of a Bragg spot (a chiral signature) from circular polarization (helicity) in the primary beam of x rays. The chiral signature is shown to arise from Cu axial magnetic dipoles, with the prospect of future experiments revealing interference between magnetic dipoles and (Templeton-Templeton) chargelike quadrupoles. An expression for the additional intensity used by Misawa does not respect magnetic symmetry, and our symmetry-informed answer overturns their principal conclusions about chirality and magnetic order. Dirac quadrupoles and octupoles are potentially strong sources of diffraction when the reflection vector is parallel to the unique direction in the tetragonal lattice. Notably, a Dirac quadrupole is a parity- and time-odd atomic multipole unlike a multisite spin entity previously mentioned in the context of Pb(TiO)Cu4(PO4)4 [Kimura , ]. Published by the American Physical Society 2024

Stimulated magneto-optics with different detunings for plasma local diagnostics

The polarization plane stimulated rotation angle of a probe signal in an intense laser field in plasma is calculated for arbitrary detunings of intense and weak laser waves compared with the resonant transition frequency of the medium. Estimates of the residual gas local density in a cesium plasma have been found based on the Faraday, Cotton–Mouton effects and on the effect of stimulated rotation of the polarization plane of the probe signal in an intense laser field. It is shown that the rotation in the medium has a complex structure consisting of the sum of only the influence of the magnetic field, only the influence of the intense laser field and the interfering part of the magnetic and intense laser fields.

Dead-zone-free atomic magnetometer based on hybrid Poincaré beams

In this paper, we present the experiment and the theory scheme of light-atom interaction in atomic magnetometers by using a hybrid Poincaré beam (HPB) to solve an annoying problem, named “dead zone.” This kind of magnetometer can be sensitive to arbitrary directions of external magnetic fields. The HPB has a complex polarization distribution, consisting of a vector radially polarized beam and a scalar circularly polarized beam in our experiment. These two kinds of beams have different directions of dead zones of external magnetic fields; thereby, the atomic magnetometer with an HPB can avoid the non-signal area when the direction of the external magnetic field is in the plane perpendicular to the light polarization plane. Furthermore, the optical magnetic resonance (OMR) signal using an HPB still has no dead zones even when the direction of the external magnetic field is in the plane parallel to the polarization plane in our scheme. Our work has the potential to simplify and optimize dead-zone-free atomic magnetometers.

Planck constraints on cosmic birefringence and its cross-correlation with the CMB

Cosmic birefringence is the in-vacuo, frequency independent rotation of the polarization plane of linearly polarized radiation, induced by a parity-violating term in the electromagnetic Lagrangian. We implement a harmonic estimator for the birefringence field that only relies on the CMB E to B mode cross-correlation, thus suppressing the effect of cosmic variance from the temperature field. We derive constraints from Planck public releases 3 and 4, revealing a cosmic birefringence power spectrum consistent with zero at about 2σ up to multipole L = 1500. Moreover, we find that the cross-correlations of cosmic birefringence with the CMB T-, E- and B-fields are also well compatible with null. The latter two cross-correlations are provided here for the first time up to L = 1500.

Giant Faraday rotation in atomically thin semiconductors

Faraday rotation is a fundamental effect in the magneto-optical response of solids, liquids and gases. Materials with a large Verdet constant find applications in optical modulators, sensors and non-reciprocal devices, such as optical isolators. Here, we demonstrate that the plane of polarization of light exhibits a giant Faraday rotation of several degrees around the A exciton transition in hBN-encapsulated monolayers of WSe2 and MoSe2 under moderate magnetic fields. This results in the highest known Verdet constant of -1.9 × 107 deg T−1 cm−1 for any material in the visible regime. Additionally, interlayer excitons in hBN-encapsulated bilayer MoS2 exhibit a large Verdet constant (VIL ≈ +2 × 105 deg T−1 cm−2) of opposite sign compared to A excitons in monolayers. The giant Faraday rotation is due to the giant oscillator strength and high g-factor of the excitons in atomically thin semiconducting transition metal dichalcogenides. We deduce the complete in-plane complex dielectric tensor of hBN-encapsulated WSe2 and MoSe2 monolayers, which is vital for the prediction of Kerr, Faraday and magneto-circular dichroism spectra of 2D heterostructures. Our results pose a crucial advance in the potential usage of two-dimensional materials in ultrathin optical polarization devices.

Development of manufacturing technology of polarization parabolic antenna reflectors for antennas of millimeter wave band

Structurally antenna with rotation of the polarization plane consists of three main elements: an irradiator, a parabolic transreflector and a flat twist-reflector. A common problem for such antennas is complexity of the manufacture of the main element – parabolic transreflector. The purpose of the article is search for unreinforced foiled material, research the possibility of manufacturing parabolic transreflector by the photochemical method of making printed boards, as well as forming blanks for parabolic forming them. The article considers a new method of manufacturing of a parabolic transreflector for an antenna made of foil-fluoroplastic with a rotation of polarization plane. The technology of forming conductors with a width of 75 microns with a step of 225 microns by the photochemical method (according to the technology of manufacturing printed circuit boards) with subsequent molding of the workpiece to obtain a given parabolic form, has been developed. The main technological operations of manufacturing a parabolic transreflector have been described. The proposed solutions indicate the prospects of the developed technology manufacturing of polarization parabolic antenna reflectors for millimeter wave antennas.

Polarized signatures of orbiting hot spots: Special relativity impact and probe of spacetime curvature

Context. The Galactic Center supermassive black hole is well known to exhibit transient peaks of flux density on a daily basis across the spectrum. Recent infrared and millimeter observations have strengthened the case for the association between these flares and circular orbital motion in the vicinity of the event horizon. The strongly polarized synchrotron radiation associated with these events leads to specific observables called QU loops, that is, looping motion in the Stokes QU plane of linear polarization. These patterns have been observed by the Submillimeter Array, VLTI/GRAVITY, and ALMA. Aims. We want to deepen the understanding of the QU loops associated with orbiting hot spots. To this end, we computed such loops in Minkowski and Schwarzschild spacetimes in order to determine which aspects of the observed patterns are due to special- or general-relativistic phenomena. Methods. We considered a parcel of energized plasma in circular motion in Minkowski spacetime and in Keplerian orbit in the Schwarzschild spacetime. We computed, using the GYOTO ray-tracing code, the polarized radiative transfer associated with this orbiting hot spot and derived the evolution of the flux density, astrometry, and Stokes Q and U parameters. Results. We show that QU loops in Minkowski spacetime at low or moderate inclination i ≲ 45° (where i = 0° is a face-on view) share all the qualitative features of Schwarzschild QU loops. There exist QU loops for all setups considered (including for the face-on view and vertical magnetic field), there may be one or two QU loops per orbital period for a vertical magnetic field configuration, and there are always two QU loops in case of a toroidal magnetic field. The simplicity of Minkowski spacetime is a key asset for allowing us to provide analytical formulas that explain the details of this behavior. Moreover, we analyzed the flux variation of the hot spot and show that it is dictated either by the angular dependence of the radiative transfer coefficients or by relativistic beaming. In the former case, this can lead to extreme flux ratios, even at a moderate inclination. Finally, we highlight the increasing mirror asymmetry of the Schwarzschild QU track with increasing inclination and show that this behavior is a specific Schwarzschild feature caused by light bending. Conclusions. Although special-relativistic effects have not been extensively discussed in this context, they are a crucial part in generating the observed QU loops. However, general-relativistic light bending leads to a specific observable feature encoded in the asymmetry of the observed loops, and this feature might allow the spacetime curvature to be quantified.

INFLUENCE OF SURFACTANT CONCENTRATION ON CHANGES IN THE PLANE OF POLARIZATION OF LIGHT WHEN PASSING THROUGH THE LCD MEDIUM

The effect of surfactants in the form of cetyltrimethyl ammonium bromide (CTAB) in nematic liquid crystal cells of type 5CB have been studied by the polarization-optical method. The relationship between the concentrations of the introduced surfactant and the angle of rotation of the polarization plane is established. The clear boundaries of the linear and elliptical polarization of the light transmitted through the cell are indicated, depending on the concentration of surface-active substances (surfactants). Possible applications of such materials in semiconductor and solid-state laser technology and display technologies are proposed.

A clinical 3D pointing test differentiates spatial memory deficits in dementia and bilateral vestibular failure

BackgroundDeficits in spatial memory, orientation, and navigation are often neglected early signs of cognitive impairment or loss of vestibular function. Real-world navigation tests require complex setups. In contrast, simple pointing at targets in a three-dimensional environment is a basic sensorimotor ability which provides an alternative measure of spatial orientation and memory at bedside. The aim of this study was to test the reliability of a previously established 3D-Real-World Pointing Test (3D-RWPT) in patients with cognitive impairment due to different neurodegenerative disorders, bilateral vestibulopathy, or a combination of both compared to healthy participants.MethodsThe 3D-RWPT was performed using a static array of targets in front of the seated participant before and, as a transformation task, after a 90-degree body rotation around the yaw-axis. Three groups of patients were enrolled: (1) chronic bilateral vestibulopathy (BVP) with normal cognition (n = 32), (2) cognitive impairment with normal vestibular function (n = 28), and (3) combined BVP and cognitive impairment (n = 9). The control group consisted of age-matched participants (HP) without cognitive and vestibular deficits (n = 67). Analyses focused on paradigm-specific mean angular deviation of pointing in the azimuth (horizontal) and polar (vertical) spatial planes, of the preferred pointing strategy (egocentric or allocentric), and the resulting shape configuration of the pointing array relative to the stimulus array. Statistical analysis was performed using age-corrected ANCOVA-testing with Bonferroni correction and correlation analysis using Spearman’s rho.ResultsPatients with cognitive impairment employed more egocentric pointing strategies while patients with BVP but normal cognition and HP used more world-based solutions (pBonf 5.78 × 10-3**). Differences in pointing accuracy were only found in the azimuth plane, unveiling unique patterns where patients with cognitive impairment showed decreased accuracy in the transformation tasks of the 3D-RWPT (pBonf < 0.001***) while patients with BVP struggled in the post-rotation tasks (pBonf < 0.001***). Overall azimuth pointing performance was still adequate in some patients with BVP but significantly decreased when combined with a cognitive deficit.ConclusionThe 3D-RWPT provides a simple and fast measure of spatial orientation and memory. Cognitive impairment often led to a shift from world-based allocentric pointing strategy to an egocentric performance with less azimuth accuracy compared to age-matched controls. This supports the view that cognitive deficits hinder the mental buildup of the stimulus pattern represented as a geometrical form. Vestibular hypofunction negatively affected spatial memory and pointing performance in the azimuth plane. The most severe spatial impairments (angular deviation, figure frame configuration) were found in patients with combined cognitive and vestibular deficits.

Magnetochiroptical nanocavities in hyperbolic metamaterials enable sensing down to the few-molecule level.

In this work, we combine the concepts of magnetic circular dichroism, nanocavities, and magneto-optical hyperbolic metamaterials (MO-HMMs) to demonstrate an approach for sensing down to a few molecules. Our proposal comprises a multilayer MO-HMM with a square, two-dimensional arrangement of nanocavities. The magnetization of the system is considered in polar configuration, i.e., in the plane of polarization and perpendicular to the plane of the multilayer structure. This allows for magneto-optical chirality to be induced through the polar magneto-optical Kerr effect, which is exhibited by reflected light from the nanostructure. Numerical analyses under the magnetization saturation condition indicate that magnetic circular dichroism peaks can be used instead of reflectance dips to monitor refractive index changes in the analyte region. Significantly, we obtained a relatively high sensitivity value of S = 40 nm/RIU for the case where refractive index changes are limited to the volume inside nanocavities, i.e., in the limit of a few molecules (or ultralow concentrations), while a very large sensitivity of S = 532 nm/RIU is calculated for the analyte region distributed along the entire superstrate layer.

Circular polarizer based on twisted double [formula omitted] thin film

We unveil a highly efficient circular polarizer based on twisted double Td − WTe2 thin film in the transmissive and reflective modes. This polarizer can transform a linearly polarized incident wave into a circularly polarized one with extremely high extinction ratios by simply adjusting the orientation of the incident polarization plane. The proposed structure provides switching between the right-handed and left-handed circular polarizations (RCP and LCP) in the output wave by tuning the frequency and, in particular, the polarization direction of the incident wave. Furthermore, the twist angle of the thin films can control the handedness of the converted wave to be either LCP or RCP. Owing to the high efficiency of the polarization conversion and accessibility of the realization of the proposed structure, it may have potential applications as a polarization manipulator in the optical sensing, communication, and defense industry.

Instability of a Kerr-type naked singularity due to light and matter accretion and its shadow

We study null and timelike constant radii geodesics in the environment of an over-spinning putative Kerr-type naked singularity. We are particularly interested in two topics: first, the differences of the shadows of the naked rotating singularity and the Kerr black hole; and second, the spinning down effect of the particles falling from the accretion disk. Around the naked singularity, the non-equatorial prograde orbits in the Kerr black hole remain intact up to a critical rotation parameter ( α=63−9 ) and cease to exist above this value (Charbulák and Stuchlík 2018 Eur. Phys. J. C 78 879). This has an important consequence in the shadow of the naked singularity if the shadow is registered by an observer on the polar plane or close to it as the shadow cannot be distinguished from that of a Kerr black hole viewed from the same angle considering only the light emanating from the unstable photon orbits. We show that the timelike retrograde orbits in the equatorial plane immediately (after about an 8% increase in mass for the case of initial α = 1.5) reduce the spin parameter of the naked singularity from larger values to α = 1 at which an event horizon appears. This happens because the retrograde orbits have a larger capture cross-section than the prograde ones. So if a naked singularity happens to have an accretion disk, it will not remain naked for long, an event horizon forms.

Polarization state conversion achieved by chiral mechanical metamaterial

Recently, metamaterials have driven advancements in wave propagation and polarization control. Chiral elastic metamaterials, in particular, have attracted considerable attention due to their distinctive properties, such as acoustical activity and auxeticity. Such characteristics arise from the additional degrees of freedom for tuning the embedded micro- and macro-rotations. In this study, we demonstrate an unusual energy exchange between longitudinal and in-plane shear waves in a 3D chiral mechanical metamaterial. The structural design is capable of inducing up to a 90∘ rotation in the plane of polarization. Additionally, this capacity for conversion is achieved by employing both an arrangement of chiral cells and a single meta-atom. This peculiar behavior enables a seamless switch between the three polarization states existing within a solid material, namely, the longitudinal state, the shear horizontal state, and the shear vertical state. Furthermore, a 2D discrete mono-atomic mass-spring model featuring inclined connectors is used to characterize the distinctive energy exchange between modes. This characterization is based on the retrieval of the pertinent elastic coefficients. The engineered chiral metamaterial polarization converter stands as a promising device for momentum conservation conversions and applications in elasto-dynamic polarimetry.

The Domain and Structural Characteristics of Ferroelectric Copolymers Based on Vinylidene Fluoride Copolymer with Tetrafluoroethylene Composition (94/6).

This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer-Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound and quasi-free (impurity) charges. It was shown that an "abnormal" decrease in conductivity was observed in fields near the coercive fields. This could be associated with the appearance of deep traps of the impurity charge carriers formed by the polar planes of β-phase crystals. The conductivity data obtained from the charge and current responses differed. It was concluded that chain segments contributing to polarization with sufficiently low fields were present in the amorphous phase. A comparison showed that the average size of β-phase crystals (crystals of X-ray diffraction reflection width) was almost one order of magnitude lower than the domain size obtained using piezoresponse force microscopy (PFM). The analysis of the fast-stage dielectric response before and after polarization indicated that as the external polarizing field increased in the ferroelectric polymer chains, conformational transitions occurred according to the T3GT3G- → (-TT-)n и TGTG → (-TT-)n types. This was accompanied by an increase in the effective dipole moment in the amorphous phase chains. The analysis of the IR spectroscopy data obtained in transmission and ATR modes revealed a difference in the conformational states of the chains in the core and surface parts of the film.

ВЛАСНІ КОЛИВАННЯ В ПЛАНАРНО-КІРАЛЬНИХ ДВОШАРОВИХ ОБ’ЄКТАХ ПОРОДЖУЮТЬ ШТУЧНУ ОПТИЧНУ АКТИВНІСТЬ

Subject and Purpose. The research focuses on how the resonance frequencies, the Q-factor of resonances, and the polarization plane rotation ability are influenced by the topology of individual components of a planar-chiral double-layer object consisting of a pair of con- jugated irises having rectangular slots and accommodated in a circular waveguide. Methods and Methodology. All the numerical results are obtained by the mode-matching technique (MMT) and the transverse reso- nance method on the basis of our own proprietary MWD-03 software package. Results. By the waveguide example, it has been shown that the internal structure of individual components and dihedral symmetry of the conjugated bilayer allow all the conclusions of the spectral theory (theory of eigen-oscillations) to be carried over to all the objects of the type. On the other hand, these objects behave as symmetric two-port waveguide components with conventionally "symmetric" and "antisymmetric" eigen-oscillations. The mutual coupling of these eigen-oscillations depends on the bilayer parameters. Where the frequen- cies of these eigen-oscillations are close enough, the polarization plane rotation and the transmission bandwidth reach their highest. It has been demonstrated that as a slot number increases, the resonance frequency decreases. The theoretical results have been confirmed by the measurements at the X range of frequencies for pairs of conjugated irises with various numbers of rectangular slots. Conclusions. A pair of conjugated chiral irises can rotate the polarization plane. The iris topology, iris spacing, and the mutual ro- tation angle alter resonance frequencies. The resonance frequencies can be reduced by increasing the rectangular slot length and/or slot number. Even though they have not longitudinal symmetry, such objects have properties of two-port waveguide components. In particular, the phase shift of their reflection and transmission coefficients is modulo 90. Besides, a possibility exists to divide eigen-oscillations into conventionally "symmetric" and "antisymmetric" based on the proximity of their fields to those whose type of symmetry is known before- hand. This makes it possible to approximate the reflection and transmission coefficients through corresponding eigenfrequencies.