Rotation Of Polarization Plane Research Articles

Two wavelength Mueller matrix reconstruction of blood plasma films polycrystalline structure in diagnostics of breast cancer.

The model of a Mueller matrix description of mechanisms of optical anisotropy typical for polycrystalline films of blood plasma--optical activity, birefringence, as well as linear and circular dichroism--is suggested. On this basis, the algorithms of reconstruction of parameters distribution (polarization plane rotations, phase shifts, coefficients of linear and circular dichroism) of the indicated types of anisotropy were found for different spectrally selective ranges. Within the statistical analysis of such distributions, the objective criteria of differentiation of films of blood plasma taken from healthy women and breast cancer patients were determined. From the point of view of probative medicine, the operational characteristics (sensitivity, specificity and accuracy) of the method of Mueller matrix reconstruction of optical anisotropy parameters were found, and its efficiency in diagnostics of breast cancer was demonstrated.

Systematic study of magnetic linear dichroism and birefringence in (Ga,Mn)As

Magnetic linear dichroism and birefringence in (Ga,Mn)As epitaxial layers is investigated by measuring the polarization plane rotation of reflected linearly polarized light when magnetization lies in the plane of the sample. We report on the spectral dependence of the rotation and ellipticity angles in a broad energy range of $0.12--2.7\phantom{\rule{4pt}{0ex}}\mathrm{eV}$ for a series of optimized samples covering a wide range on Mn dopings and Curie temperatures and find a clear blueshift of the dominant peak at energy exceeding the host material band gap. These results are discussed within the framework of the $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ and mean-field kinetic-exchange model of the (Ga,Mn)As band structure. We infer that disorder-induced nondirect transitions significantly influence magneto-optical properties of (Ga,Mn)As.

Temperature measurement of photovoltaic cells surface

In this work a method of measuring the temperature of photocells is considered. A series of works are analyzed in which noted that temperature fluctuations of environment and photocell significantly affect output characteristics of photovoltaic cells. Temperature measurements are used in maximum power point tracking algorithms, for calculating the thermal coefficients of photocells. The described method uses yttrium iron garnet crystal placed in a constant magnetic field and magnetized to saturation as a sensing element of the device. To measure the temperature change the polarization plane rotation angle of transmitted light in the crystal dependence on temperature is used

Malus’ law for X-ray radiation

Light propagation through a polarizer-analyzer system is investigated on the basis of quantum concepts about the nature of light. It is shown that Malus’ law, which is based on principles of classical electrodynamics, does not fully take into account all effects that can arise under light propagation through a polarizer-analyzer system. In particular, the phenomenon of a possible change in the light frequency is not considered, e.g., in the case of X-ray radiation. The derivation of Malus’ law based on quantum principles is presented. For comparison, the differential effective cross section of the interaction between a photon and an electron is found taking into account rotation of the photon polarization plane in the Compton effect.

Domain non-reciprocity of electromagnetic waves in a centrosymmetric TbMnO3

The polariton spectrum in a centrosymmetric TbMnO3 is considered at low temperatures in a commensurate antiferromagnetic state after the spin-flop transition in a magnetic field. It is shown that a linear dependence of the electric polarization P on a magnetic field H, observed in this state, is caused by ordering spins of the terbium ions. The magnetoelectric energy PGH (G is the antiferromagnetic vector of terbium) induces in a centrosymmetric TbMnO3 without a linear magnetoelectric effect the non-reciprocal spectrum of TM and TE polaritons. In antiferromagnetic 180° terbium domains, the speed of electromagnetic waves turns out to be different, and directions of the electric field precession and the polarization plane rotation have opposite signs. The order of these effects were found to be 10−3.

Resonant features of planar Faraday metamaterial with high structural symmetry

The transmission of electromagnetic wave through a planar chiral structure, loaded with the gyrotropic medium being under an action of the longitudinal magnetic field, is studied. The frequency dependence of the metamaterial resonance and the angle of rotation of the polarization plane are obtained. We demonstrate both theoretically and experimentally a resonant enhancement of the Faraday rotation. The ranges of frequency and magnetic field strength are defined, where the angle of polarization plane rotation for the metamaterial is substantially higher than that one for a single ferrite slab.

The enhanced magneto-optical Kerr effect in Co/TiO2 multilayer films

Spectral dependences of the polarization plane rotation angle (θk) in the polar Kerr effect in Co/TiO2 multilayer nanocomposite films have been studied in the 400–1000 nm wavelength range. It is established that the sign, magnitude, and shape of the magneto-optical spectrum depend on the dielectric spacer thickness and the number of layers in the structure. The Kerr rotation angle in Co/TiO2 multilayers is significantly greater than that in homogeneous Co films of the same thickness. The angle of rotation of the polarization plane reaches a record high value of 2θk = 7.3° in the Co(5 nm)/TiO2(17 nm) multilayer structure with number of layers n = 8 at a wavelength of 540 nm.

Determination of polarization relaxation times of atomic levels

Rotation of polarization plane of a probe signal under influence of a time-advanced intense pulse is investigated taking into account optical pumping of atoms in a resonant medium. A formula is derived for the angle of rotation of polarization plane of the probe signal. It follows from this formula that modification of the polarization plane is caused by two processes: radiative decay of atoms and collision-induced redistribution of atoms over magnetic sublevels. It is shown that this method enables direct measuring long times of atomic collisions on the background of short times of the radiation decay.

The problem of equivalence of two formulations of material equations for natural gyrotropic media

We study the behavior of rotation of polarization plane when passing from positive to negative dielectric and magnetic susceptibilities of a gyrotropic medium for two formulations of material equations in such media.

편파면 회전을 위한 도파관 아이리스 편파기 설계 분석

본 논문은 정방형 도파관을 이용하여 편파면을 회전시키는 편파기의 단순화된 설계법을 제안하였다. Ku 밴드 주파수인 14.3GHz~14.8GHz에서 동작하는 <TEX>$180^{\circ}$</TEX> 편파기의 특성을 최적화하기 위하여, 개선된 모드정합법과 구분적 멱보간법을 편파기 설계에 적용하였다. 최적화 결과는 VSWR<2 인 범위의 Ku 밴드 주파수 대역에서 500MHz의 대역폭을 나타내었고, 직교모드 <TEX>$TE_{10}$</TEX>와 <TEX>$TE_{01}$</TEX> 간에 위상차는 14.2GHz~14.8GHz 주파수 대역에서 <TEX>$180^{\circ}{\pm}1^{\circ}$</TEX> 를 갖는다. 그리고 교차편파 손실은 40dB 이하이고, 통과대역의 삽입손실은 0.1dB 이다. 따라서 제안한 편파기는 낮은 VSWR과 소형의 크기가 요구되는 실질적인 Ku 밴드 시스템에 적용이 가능하다. In this paper, the simplified design methodology for rotation of polarization plane using a square waveguide is proposed. In order to optimize the characteristics of <TEX>$180^{\circ}$</TEX> polarizer operating from 14.3GHz to 14.8GHz in Ku-band, the modified mode matching method and piecewise power tower interpolation are applied to the polarizer design. The optimized results show that the frequency bandwidth in VSWR<2 has covered 500MHz in the Ku-band and phase difference between two orthogonal modes <TEX>$TE_{10}$</TEX>and <TEX>$TE_{01}$</TEX> is <TEX>$180^{\circ}{\pm}1^{\circ}$</TEX> in the range of 14.3GHz~14.8GHz. The cross polarization loss has obtained below 40dB and the insertion loss has 0.1dB in the passband. Therefore, the proposed polarizer is suitable for practical Ku-band system requiring the low VSWR and compact size.

Experimental Investigation of the Polarization Plane Rotation of Light in Cholesteric Liquid-Crystalline Film with an Anisotropic Defect Layer

This paper experimentally demonstrated that in the cholesteric liquid-crystalline films it is possible to induce defect, which can be controlled by external electric field. Three cases of induced defects were examined and the main result of the experiment is that the rotation of polarization plane has maximum value when light first propagates through chiral liquid-crystalline photonic structure and then falls to the anisotropic layer. We have also supporting calculations, showing an agreement between experimental results and theoretical calculations. We present a new liquid crystal device configuration that performs as a tunable linear polarizer for both polarized and unpolarized lights.

Multicolor Reflection from Chiral Photonic Crystals on the Base of Alternate Right- and Left-Handed Cholesteric Liquid Crystal Layers

In this paper, we investigated the optical properties of stacked right- and left-hand chiral photonic crystal layers. The reflection spectra peculiarities of this system were investigated showing that, in contrast to a single CLC layer, there are multiple PBGs. The Eigen polarizations (EP) of the system are degenerated and the polarization plane rotation decreases if the system thickness is increased; the rotation sign depends on the first sublayer chirality sign. We also investigated the influence of sublayer thicknesses, sublayer local dielectric anisotropies, and sublayer helix pitches on the reflection peculiarities of the system.

Topology of magnetic field and polarization in accretion discs of AGN

In this paper we demonstrate that the wavelength dependence of polarization degree and position angle allows us to derive the distribution of magnetic field in accretion disc. The polarized radiation arises due to scattering of emission light by electrons in a magnetized optically thick accretion disc. Faraday rotation of polarization plane is taken into consideration. Through wavelength dependence of polarization it is possible to derive the value of the magnetic Prandtl number in the accretion disc plasma. The power law index of the polarization wavelength dependence is related with the radial distribution of magnetic field in an accretion disc. This allows us to test the various models of an accretion disc around the central black hole.

Chirality in nonlinear-optical response of planar G-shaped nanostructures

Chirality effects in optical second harmonic generation (SHG) are studied in periodic planar arrays of gold G-shaped nanostructures. We show that G-shaped structures of different handedness demonstrate different SHG efficiency for the left and right circular polarizations, as well as the opposite directions of the SHG polarization plane rotation. The observed effects are interpreted as the appearance of chirality in the SHG response which allows clear distinguishing of two enantiomers.

Photonic band gaps from a stack of right- and left-hand chiral photonic crystal layers

In the present paper we investigated the optical properties of a stack of right- and left- hand chiral photonic crystal layers. The problem is solved by Ambartsumian's layer addition modified method. We investigated the reflection spectra peculiarities of this system and showed that in contrast to a single cholesteric liquid crystal (CLC) layer this system has multiple photonic band gaps (PBGs) (at light normal incidence). We showed that this system has unique polarization properties, particularly the eigenpolarizations (EPs) of the system are degenerated (i.e., the two EPs coincide) for an even number of layers and, in contrast to ordinary gyrotropic systems, the polarization plane rotation decreases if the system thickness is increased, the rotation sign depends on the first sublayer chirality sign, the system is very sensitive to the change of the sublayer number in the system, etc. We also investigated the influence of sublayer thicknesses, incidence angle, the sublayer local dielectric anisotropies, the sublayer helix pitches on the reflection peculiarities, and other optical parameters of the system.

Photonic density and nonreciprocal optical properties in chiral liquid crystals

Nonreciprocal optical properties of anisotropic (nano-film) heterostructures made of a cholesteric and nematic liquid crystal (CLC-NLC) layers are studied. Namely, a NLC-CLC (and CLC-NLC) structures are considered in which the NLC layer is a quarter-wave plate. The problem is exactly solvable by Ambartsumians’ modified layer addition and Mullers’ transfer-matrix methods. The peculiarities of the polarization dependent properties, such as the photonic density of states, reflection spectra, the polarization plane rotation and ellipticity spectra are investigated. It is shown that such a system canwork as a light modulator, an element for obtaining linearly polarized light with an electrically tunable polarization plane rotation, or a transformer of non-polarized source into linearly polarized light. The analysis of the optical properties in investigated structures can be used for design of perspective optical diodes, microlasers and multifunctional elements on chiral liquid crystals with electrically tunable polarization plane rotation and field controlled light polarization.

Cholesteric liquid crystals with tunable defect inside as polarization azimuth rotation amplifiers and polarization azimuth stabilizers

In the present paper, we investigate the polarization properties of the cholesteric liquid crystals (CLCs) with an isotropic/anisotropic defect inside them, and possibilities of amplification of the polarization plane rotation and stabilization of the light polarization azimuth by these systems are investigated.

Coherent spin dynamics of electrons and excitons in nanostructures (a review)

The studies of spin phenomena in semiconductor low-dimensional systems have grown into the rapidly developing area of the condensed matter physics: spintronics. The most urgent problems in this area, both fundamental and applied, are the creation of charge carrier spin polarization and its detection, as well as electron spin control by nonmagnetic methods. Here, we present a review of recent achievements in the studies of spin dynamics of electrons, holes, and their complexes in the pump-probe method. The microscopic mechanisms of spin orientation of charge carriers and their complexes by short circularly polarized optical pulses and the formation processes of the spin signals of Faraday and Kerr rotation of the probe pulse polarization plane as well as induced ellipticity are discussed. A special attention is paid to the comparison of theoretical concepts with experimental data obtained on the n-type quantum well and quantum dot array samples.

Enhanced form birefringence of metal nanoparticles with anisotropic shell mediated by localized surface plasmon resonance

We have prepared optically birefringence materials consisting of an isotropic core of metal nanoparticle and an anisotropic shell of amorphous oxide. The sample shows an enhanced optical birefringence in a wavelength-selective way. The sample was prepared by depositing amorphous iron oxide thin films on top of the silver nanoparticles using the oblique deposition technique. This results in ellipsoidal shell of amorphous iron oxide surrounding a silver nanoparticle. The form birefringence appears because of the anisotropic shape of shells; the refractive index for the light polarized parallel to the elongation direction of ellipsoid is different from that for the light polarized perpendicularly. Moreover, the rotation of polarization plane is significantly enhanced at around the wavelength of localized surface plasmon resonance (LSPR). The difference in refractive index between two optical axes is as large as 0.34 for a 600 nm light, which is more than twice of typical birefringence crystal calcite (0.14 for visible light). It is speculated that the anisotropic shell induces the dependence of LSPR wavelength on the polarization direction of the incident light, which causes the polarization dependence of refractive index through the Kramers-Kronig relation.

Magnetic Field Effect on the Localized Plasmon Resonance in Patterned Noble Metal Nanostructures

Sizable rotation of light polarization plane induced by magnetic field when transmitting through gold nanostructures was observed which was characterized by Faraday rotation and ellipticity. The dependence of disk diameter and disk to disk distance were investigated. The plot of Faraday effect versus disk diameter showed resonant features which were associated with the excitation of localized surface plasmon (LSPR). The magnitude of Faraday rotation or ellipticity from gold nanodisks was found to be at the order of 0.01 degree at magnetic field of 1 Tesla. The MO activity was modeled by the effective medium model, resonant behavior was observed around LSPR resonance and the magnitude of experimental MO activities show good correspondence with the calculation. The results suggest active control on the plasmonic modes by external magnetic field.