Rotation Of Optical Indicatrix Research Articles

Elasto-optic effect anisotropy in gallium phosphide crystals

Elasto-optic coefficients of gallium phosphide (GaP) crystals were calculated on the basis of their piezo-optic and elastic coefficients. Surfaces of the spatial distribution of piezo- and elasto-optic effects in these crystals were built. The maxima of the surfaces of the elasto-optic effect and the geometries of acousto-optic interaction that correspond to these maxima were found. Ratios that describe the rotation of optical indicatrix, depending on direction of the action of uniaxial pressure or deformation on cubic crystal, were recorded. It was shown that such rotations induced by mechanical stress do not exceed 1.5° in GaP, but in some cubic crystals they can reach tens of degrees.

Topological defects of optical anisotropy parameters caused by the screw dislocations of crystalline structure

We have analyzed spatial distributions of optical birefringence and angle of optical indicatrix rotation caused by inhomogeneous mechanical stresses appearing...

Study of piezo-optic effect of calcium tungstate crystals by the conoscopic method

Conoscopic method for piezo-optic effect study in optically uniaxial crystals related to 4, 4¯, 4/m symmetry class was described. Ratio for determination of difference between principal piezo-optic coefficients π11–π12 and rotating coefficient π61 on the basis of change of the angle between optical axes and optical indicatrix rotation under uniaxial pressure loading along X1 crystal physics axis was presented. The method was tested on CaWO4 crystals (4/m symmetry class). It was shown that the error of π61 coefficient determination by conoscopic method is less by a factor of ten that the one obtained by interferometry method.

Topological defects of optical indicatrix orientation in stressed glasses: spatial distribution of optical anisotropy parameters

We have revealed topological defects (TDs) of the angle of optical indicatrix (OI) orientation in a glass Li2B4O7 sample, which originate from the specific spatial distribution of optical birefringence caused by residual mechanical stresses. It has been found that the strength of TDs of the OI rotation angle is equal to ±1/2. Following from the experimental results, we have shown that the regions around the TDs of OI orientation are those of a 3D stressed state. We have formulated criteria for determining whether 2D or 3D distributions of the optical anisotropy parameters appear, based on the TDs of OI orientation. It has been shown that, in some particular cases, the regions with the TDs can testify the availability of a 2D stressed state. Besides, we have demonstrated experimentally that the TDs can appear for more than one projection in the case of 3D distributions of the OI parameters, which appear under bending of glass plates by a distributed load.

Reinvestigation of piezooptic anisotropy appearing in a crystalline disk loaded along its diameter

In order to correct the errors present in our recent study (Savaryn V. et al. Ukr. J. Phys. Opt. 13 (2012) 82), we have rederived the main phenomenological relations describing the changes in optical anisotropy of crystalline disks loaded along their diameters. Basing on the analysis of these relations, we have developed an improved technique for determining the piezooptic coefficients 44  , 55  and 66  for the crystals of almost all of the point symmetry groups. The technique is based on studying the spatial distributions of optical birefringence and optical indicatrix rotation angle induced along the chords and diameters of a crystalline disk compressed along its diameter.

Polarised single crystal infra-red spectra and optical indicatrix rotation in an organic charge transfer molecule

Polarised infrared reflectance spectra have been obtained for oriented single crystals of the polar organic nonlinear optical material 2-(α-methylbenzylamino)-5-nitropyridine (MBANP). The strong charge transfer electronic absorption was measured in several solvents and as a thin solid film. DFT calculations of vibrational frequencies and eigenvectors were used to assign relevant vibrational features and to derive useful information about the molecular structure. The intensities of the bands associated with the donor and acceptor groups are increased by electron phonon coupling with the strong charge transfer transition. This results in unusually strong NO2 and N–H stretching vibrations. The spectra are consistent with a large rotation of the optical indicatrix with increasing wavelength due to the bent shape and strong electron-phonon coupling in the molecule.

Induction of optical vortex in the crystals subjected to bending stresses

We describe a method for generation of optical vortices that relies on bending of transparent parallelepiped-shaped samples fabricated from either glass or crystalline solid materials. It is shown that the induced singularity of optical indicatrix rotation leads in general to appearance of a mixed screw-edge dislocation of the phase front of outgoing optical beam. At the same time, some specified geometrical parameters of the sample can ensure generation of a purely screw dislocation of the phase front and, as a result, a singly charged canonical optical vortex.

On the tricritical behaviour of the Sn2P2S6 crystals

Based on the results for temperature dependences of optical birefringence and optical indicatrix rotation derived for Sn2P2S6 crystals, we show that at the atmospheric pressure, those crystals are under the conditions of tricritical point, with the critical exponent of the order parameter . At the same time, we have found that the temperature behaviour of the rotation angle of spontaneous electric polarization obeys the law . The action of hydrostatic pressure leads to only small changes in the critical exponent β, thus suggesting that the tricritical point on the P, T-diagram of Sn2P2S6 should occur in the pressure range .

Temperature dependence of the crystal-optics characteristics of [N(CH3)4]2ZnCl4:Ni2+ crystals with correlated motion of tetrahedral groups

The optical birefringence, optical indicatrix rotation, and residual intensity have been experimentally investigated in the parent and incommensurate phases of [N(CH3)4]2ZnCl4 crystals doped with Ni2+. The temperature dependences obtained are nonlinear in a wide temperature range (T i − 360 K). It is shown that the nature of this nonlinearity is related to the presence of local spatial regions of the correlated motion of tetrahedral groups. It is established that the deformation of tetrahedral groups increases the temperature range of existence of these regions.

Thermal Expansion and Phase Transformation Observation in Cs2BX4 Crystals

The results of studies for thermal expansion and optical indicatrix rotation at the ferroelastic phase transition, along with the domain structure observations for Cs2HgCl4, Cs2HgBr4 and Cs2CdBr4 crystals are presented. On the basis of the literature data and the results of our studies for the heterophase structure, domain structure and thermal expansion, the phase diagram common for Cs2HgCl4, Cs2HgBr4 and Cs2CdBr4 crystals is proposed.

Temperature-dependent optical anisotropy of L-arginine phosphate single crystal

The optical anisotropy at different temperatures (birefringence, complete optical gyration tensor, and optical indicatrix rotation) for a monoclinic crystal of L-arginine phosphate has been determined by using the high-accuracy universal polarimeter (HAUP) method at a wavelength of 632.8 nm. The thermal variation coefficients of the birefringence along the (010), (101), (100), and (-201) planes were found to be -25.9×10-6 K-1, 11.1×10-6 K-1, 6.4×10-6 K-1, and -10.7×10-6 K-1, respectively. The tensor components in terms of rotatory power were found to be ϱ11=-6.6°/mm, ϱ22=19°/mm-1, ϱ33=49.7°/mm, and ϱ13=-43.7°/mm at room temperature.

Optical anisotropy and EO properties of ferroelectrics TGS and LHP single crystals using a HAUP technique

Triglycine sulphate, (NH 2 CH 2 CO 2 H) 3 H 2 SO 4 (TGS), is a ferroelectric crystal widely used in optical properties studies, phase transitions theory as well as test for experimental techniques. Lead monohydrogen phosphate, PbHPO 4 (LHP), is a typical representative of the family of ferroelectric schultenites, suitable in testing microscopic theories of ferroelectricity. In this work the so-called high-accuracy universal polarimeter (HAUP) has been used to determine the natural anisotropy in the birefringent crystalline sections (010), obtaining the temperature dependence of optical anisotropy magnitudes of the crystal: gyrotropy, birefringence and optical indicatrix rotation. Our HAUP technique also permits to investigate the electro-optic (EO) coefficients associated to the phases above and below phase transition temperatures.

Crystal optical studies of lithium tetraborate

Using the HAUP-type universal polarimeter and the Senarmont technique, detailed crystal optical studies of Li2B4O7, lithium tetraborate, are carried out. It is shown that the optical indicatrix rotation and the optical activity are absent from the crystal, in accordance with symmetry considerations. Measurements of optical birefringence reveal the existence of a regular staircase-like temperature behaviour in the whole range under investigation (290-480 K), a hysteresis character of the birefringence under cycling temperature and a pronounced thermooptical memory effect. The origins of the above phenomena are analysed, in particular the possible influence of the pyroelectric effect and systematic errors of the optical equipment. A conclusion is drawn that the main features of the birefringence are well explained by an incommensurately modulated super-structure which is at present a matter of debate. The peculiarities of the optical properties of lithium tetraborate are compared with those of incommensurate crystals known from the literature.

Crystal optics of magnetoelectrics

Abstract The presence in magnetoelecttics of the specific space-time symmetry operation 1′ allows the existence of several new optical phenomena that may occur in transmission and reflection. Among those are the nonreciprocal gyrotropic birefringence, the rotation of optical indicatrix, the nonreciprocal reflection, the electric field induced nonreciprocal rotation. Theoretical aspects and experimental observations of some of these effects in Cr2O3 are discussed. Nonlinear optical phenomena that can occur due to magnetoelectric interaction are also discussed (BiFeO3, magnetic garnet films). At the end we discuss unusual electromagnetooptical phenomena, observed experimentally in noncentrosymmetric crystals in the presence of magnetic field (CsCuCl3, LIIO3, Pb5Ge3O11, Cd1–xMnxTe, Te).

Gyrotropic and birefringent properties of ferroelectric TGS

Abstract A new polarimetric method for measuring all the components of optical activity, linear birefringence and optical indicatrix rotation is applied to TGS ferroelectrics. The temperature dependencies of the above optical parameters for a and c axis directions are obtained in both ferroelectric and paraelectric phases. Induced and spontaneous electrooptic and electrogyration effects are studied. The results are considered within a framework of a phenomenological approach to TGS as a gyroelectric crystal. A small anomalous gyration and rotation of the optical indicatrix in a multidomain state are explained by the influence of a distorted layered domain structure.

Optical study of the ferroelastic phase transition of (N(CH3)4)2ZnBr4

Abstract (N(CH3)4)2ZnBr4 undergoes a ferroelastic phase transition from an orthorhombic mmm structure to a monoclinic 2/m phase. Birefringence and optical indicatrix rotation about the monoclinic axis have been measured in the ferroelastic phase and their temperature dependences have been related to the order parameter of the transition. The spontaneous strain has also been determined by means of X-ray diffraction. It is shown that in the temperature range covered, this quantity is proportional to the optical polarization coefficient B6, which becomes spontaneous at the transition. This fact has allowed us to obtain a numerical estimate of the p66 elastooptic coefficient at the transition point.

Optical study of the ferroelastic phase transition in CsLiSO4

Abstract The piezooptic behaviour of CsLiSO4 corresponds to the phenomenological model of a pseudoproper ferroelastic transition in a wide temperature region of the paraelastic phase but is violated in the vicinity of the phase transition. Log-log analysis of spontaneous values of birefringence, optical indicatrix rotation and shear strain indicates that the transition is very near (0.2°) the tricritical point.

X-ray and optic investigations of phase transition in CsLiCrO4crystal

Abstract The study of optical properties and X-ray investigations were carried out in CsLiCrO4crystal. It was found (is discussed) an unusual 4 temperature dependence of optical indicatrix rotation and monoclinic angles.

Optical, dielectric and magnetic studies of phase transitions in BaMnF4

Abstract Temperature variations of the index of refraction, birefringence, rotation of optical indicatrix and optical activity have been studied below and above the phase transition at TI=251K. The transition was found to be of the slight first order with critical exponent of the order parameter β = 0,28 ± 0,02. Anomalous decrease of dielectric permeability e2 was observed at temperatures 50K and below and was interpreted as a consequence of magnetic ordering. Near TN a small peak of e2 was detected, its amplitude and position on the temperature scale being dependent upon magnetic field along b-axis.

Successive Phase Transitions in Cs2CdBr4

X-ray and dielectric measurements were made on Cs 2 CdBr 4 (CCB) crystals, and optical observation was also made. CCB undergoes successive phase transitions at T 1 =-21°C, T 2 =-36°C and T 3 =-65°C. The space groups in all phases have been determined: I: Pnam, II: P Pnam 1ss , III: P2 1 /n and IV: P\bar1. The space group for the incommensurate II-phase is determined on the basis of four-dimensional space group concept. Temperature dependence of the position and the intensity of satellite reflections in the incommensurate phase was measured. Rotation of optical indicatrix was found in III- and IV-phases and its temperature dependence was measured. Ferroelastic activities in III- and IV-phases were found.