Showing papers on "Birefringence published in 1976"
TL;DR: KxRb1−xTiOPO4, a nonlinear optical material with coefficients comparable to BaNa2Nb5O15, has been prepared as optically perfect single crystals which are transparent from 350 to 4500 nm.
Abstract: KxRb1−xTiOPO4, a new nonlinear optical material with coefficients comparable to BaNa2Nb5O15, has been prepared as optically perfect single crystals which are transparent from 350 to 4500 nm. We have shown that the material is phase matchable over its entire transparency range and that 1060‐nm radiation can be doubled with minimal beam walk‐off. The material is free from optical damage for power densities at least as large as 150 MW/cm2. Also, it is chemically stable and easily polished.
580 citations
TL;DR: In this article, the refractive indices and optical birefringence of congruently grown lithium niobate (LiNbO3) have been measured at 0.633 μm and 3.39 μm in the temperature range 20° to 600°C.
187 citations
TL;DR: In this article, a hybrid aligned nematic (HAN) cell with either positive or negative dielectric anisotropy is studied, lying perpendicular to one substrate and parallel to the other.
Abstract: Electric field‐induced deformation is studied in a unique hybrid‐aligned nematic (HAN) cell, in which the director of a nematic liquid crystal (LC) with either positive or negative dielectric anisotropy is varied continuously, lying perpendicular to one substrate and parallel to the other. The experimental results show the absence of threshold field in the birefringence–vs–applied voltage relationship as well as the slow variation of birefringence with voltage; these phenomena are analyzed in terms of the Frank‐Oseen continuum theory. Also, the above characteristics of HAN are demonstrated to have such advantages in multicolor LC display applications as low operating voltage and fairly good color separation together with uniform and bright color generation.
90 citations
Patent•
20 Apr 1976
TL;DR: A liquid crystal color display as mentioned in this paper consists of a first electrode, a first substrate whose surface has a property of orientating the molecules of a nematic liquid crystal parallel with the surface, a second electrode, and at least one polarizer.
Abstract: A liquid crystal color display device which comprises a first electrode; a first substrate whose surface has a property of orientating the molecules of a nematic liquid crystal parallel with said surface; a second electrode; a second substrate whose surface has a property of orientating the molecules of the nematic liquid crystal perpendicular to said surface; a nematic liquid crystal interposed between the first and second substrates; at least one polarizer; and a means whereby the birefringence of the liquid crystal cell is changed to display various colors.
72 citations
Patent•
08 Mar 1976
TL;DR: In this paper, a reflective mode liquid crystal light valve was proposed for general image processing and projection and particularly suited for application to real-time coherent optical data processing, which utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to creating the bright on-state.
Abstract: There is disclosed a high performance reflective mode liquid crystal light valve suitable for general image processing and projection and particularly suited for application to real-time coherent optical data processing. A preferred example of the device uses a CdS photoconductor, a CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent light image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the AC voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal thus modulates the polarization of the coherent read-out or projection light responsively to the non-coherent image. An analyzer is used to create an intensity modulated output beam.
69 citations
TL;DR: In this article, the authors evaluated the refractive index change in a collisionless gas from the Stark shifts of the rotational energy levels that arise from the polarizability anisotropy.
Abstract: The refractive index change in a collisionless gas is evaluated from the Stark shifts of the rotational energy levels that arise from the polarizability anisotropy. For the limit of an extremely short-duration excitation, a multilevel coherent effect resulted in delayed refractive index bursts. Both stationary and transient responses of this birefringence to an optical field were considered for symmetric top molecules, with particular emphasis on the special case of linear molecules.
63 citations
TL;DR: The measured birefringence of the refractive indices of GaAs•AlAs multilayers grown by molecular beam epitaxy was found to vary from 0.056 at 0.9 μm to 0.042 at 1.1 μm.
Abstract: The measured birefringence of the refractive indices of GaAs‐AlAs multilayers grown by molecular beam epitaxy is found to vary from 0.056 at 0.9 μm to 0.042 at 1.1 μm.
57 citations
TL;DR: In this paper, the vacuum polarization tensor in the presence of a static homogeneous magnetic field is calculated exactly as a function of both the magnetic field and the wave vector, and is regularized explicitly by using Shabad's diagonalization with respect to tensor indices.
Abstract: The vacuum polarization tensor in the presence of a static homogeneous magnetic field is calculated exactly as a function of both the magnetic field and the wave vector, and is regularized explicitly by using Shabad’s diagonalization with respect to tensor indices The wave properties for the two electromagnetic modes in the birefringent vacuum are calculated exactly using a technique from plasma physics The strongfield limit is considered explicitly and it is shown that the two modes reduce to forms equivalent to the magnetoacoustic and shear Alfven modes in a plasma with Alfven speed much greater than the speed of light
54 citations
TL;DR: In this paper, superconvergence techniques are applied to dispersion relations for the index of refraction in optically active systems to find sum rules applicable to the optical constants for circularly polarized electromagnetic waves.
Abstract: Superconvergence techniques are systematically applied to dispersion relations for the index of refraction in optically active systems to find sum rules applicable to the optical constants for circularly polarized electromagnetic waves. New results include the theorems that (i) the zeroth moment of the circular dichroism and (ii) the first moment of the circular birefringence are zero. The latter theorem yields the simple rule that the rotation of the plane of polarization of linear light caused by an optically active medium averages to zero when integrated over all energies. Generalizations of the $f$ and inertial sum rules to circularly polarized modes are given, as well as a new rule relating the second moment of the circular dichroism to the cyclotron frequency in magneto-optics or to the rotatory strengths in natural optical activity.
38 citations
TL;DR: In this article, a sign reversal of the Kerr effect between direct current and optical frequency fields is reported both for the pure isotropic phase and for the material in solution, when conducted over a limited temperature range.
Abstract: The Kerr effect has been studied in the nematic liquid crystal M.B.B.A. both for its isotropic phase and in solutions in CCl4. Electric and high frequency laser fields were used and both Static and Optical Kerr constants evaluated. The laser-induced birefringence has been studied as a function of temperature, time and equivalent field strength. A sign reversal of the Kerr effect between direct current and optical frequency fields is reported both for the pure isotropic phase and for the material in solution. In addition the static field studies indicated that a sign reversal in d.c. fields might be obtainable as a function of solution concentration. The studies in the isotropic phase, when conducted over a limited temperature range, indicated that the short-range-order theory proposed by de Gennes is appropriate to this system.
37 citations
TL;DR: The second harmonic coefficient d 36 of HgGa 2 S 4 has been measured to be 5 times larger than d 36 (LiNbO 3 ), and the birefringence is usefully large as discussed by the authors.
Abstract: The second harmonic coefficient d 36 of HgGa 2 S 4 has been measured to be 5 times larger than d 36 (LiNbO 3 ). The birefringence is usefully large.
TL;DR: Equations are derived for the refractive indices, birefringence, absorption coefficients and dichroic ratios, of photoreceptors of the vertebrate type composed of a stack of discs and the common invertebrate type of parallel microvilli that show that the net bireFringence may be separated into a form (structure dependent) and an intrinsic (membrane anisotropy dependent) bire fringence component of similar magnitude.
TL;DR: Experiments and calculations are presented that show that the sensitivity and accuracy of the traditional transient electric birefringence technique can be enhanced by several orders of magnitude through the use of a low‐powered laser and crystal polarizing optics, signal averaging, and digital data processing.
Abstract: Transient electric birefringence experiments have been performed on well-characterized highly monodisperse samples of tobacco mosaic virus (TMV) Experiments and calculations are presented that show that the sensitivity and accuracy of the traditional transient electric birefringence technique can be enhanced by several orders of magnitude through the use of a low-powered laser and crystal polarizing optics, signal averaging, and digital data processing Measurements of the field-free decay of the birefringence yield for the rotational diffusion coefficient, DR = 318 ± 3 sec−1 The length of the rodlike virion, calculated from the Broersma equation with this value of DR and a rod diameter of 15 nm, is 2925 ± 10 nm Measurements of the growth of the birefringence when an electric field is applied across the sample yield μ2/kT(α∥ − α⊥) = 047 ± 007, where μ is the permanent dipole moment (assumed parallel to the symmetry axis of the virus) and α∥ − α⊥ is the electrical polarizability anistropy of the virus Using the value of α∥ − α⊥ measured by O'Konski et al, we then obtain μ = 25 × 10−14 esu cm
TL;DR: The changes in birefringence in the rigor to relax transition of single triton-extracted rabbit psoas muscle fibers have been investigated with quantitative polarized light techniques and the results are compatible with the view that the subfragment-2 moieties of myosin angle away from theMyosin aggregates (light meromyosin) to permit the attachment of theSubfragments-1 moieties to actin.
Abstract: The changes in birefringence in the rigor to relax transition of single triton-extracted rabbit psoas muscle fibers have been investigated with quantitative polarized light techniques. The total birefringence of rest lenght fibers in rigor was (1.46 +/- 0.08) x 10(-3) and increased to (1.67 +/- 0.05) x 10(-3) after Mg-ATP relaxation. Pyrophosphate relaxation increased the total birefringence only slightly, whereas subsequent Mg-ATP relaxation elicited the maximum increase in birefringence. Changes in lattice spacing did not account for the total increase in birefrigence during relaxation. Moreover, the increase in total birefringence was attributable to increases in intrinsic birefringence as well as form birefringence. No change in birefringence was exhibited upon exposure to a relaxation solution after myosin extraction. Synthetic myosin filaments were prepared and treated with relaxation and rigor solutions. The negatively stained filaments treated with a rigor solution had gross irregular projections at either end, while the filaments treated with a relaxing solution were more spindle shaped. The results are compatible with the view that the subfragment-2 moieties of myosin angle away from the myosin aggregates (light meromyosin) to permit the attachment of the subfragment-1 moieties to actin.
TL;DR: In this article, anisotropic glasses were obtained by uniaxial stretching of phase-separated borosilicate glasses in the transformation temperature range, and the sign inversion of the birefringence, induced by subsequent heat treatments, was correlated with microstructure.
Abstract: Optically anisotropic glasses were obtained by the uniaxial stretching of phase-separated borosilicate glasses in the transformation temperature range. The sign inversion of the birefringence, induced by subsequent heat treatments, was correlated with microstructure. The positive birefringence is attributed to form birefringence and the negative birefringence to “distribution birefringence” caused by the anisotropic distribution of the separated phase.
TL;DR: The magnetooptical Faraday rotation of a guided He-Ne laser beam in index-gradient fibers was measured and the proportionality between the rotation of the polarization vector and the length of the light path in an applied homogeneous longitudinal magnetic field is disturbed.
Abstract: The magnetooptical Faraday rotation of a guided He–Ne laser beam in index-gradient fibers was measured. The proportionality between the rotation of the polarization vector and the length of the light path in an applied homogeneous longitudinal magnetic field is disturbed. The measuring results can be explained by means of a theoretical model combining the Faraday effect with birefringence.
TL;DR: In this article, a study of the anisotropic swelling behavior of single crystal samples of Kraton K102 copolymer on imbibing a selective swelling agent is presented.
Abstract: A study is reported of the anisotropic swelling behavior of “single crystal” samples of an S–B–S two-phase copolymer, Kraton K102, on imbibing a selective swelling agent. This material consists of a hexagonal array of polystyrene cylinders in a matrix of polybutadiene. Initially the material expands reversibly, perpendicular to the cylinders. Low-angle x-ray studies show that this corresponds to expansion of the hexagonal lattice and indicates lateral expansion of the matrix material. Birefringence changes can be broadly ascribed to the changes in form birefringence.
Subsequently, irreversible expansion occurs along the rod direction. x-ray diffraction studies combined with electron microscopy indicate a transformation of the cylindrical microstructure into a more complex arrangement. This often appears to be an arrangement of spheres, packed on a hexagonal or square lattice, but this cannot completely account for the x-ray results. Some micrographs suggest the existence of a more complex network of the polystyrene microphase units.
TL;DR: In this article, a coaxial cylinder was used for the measurement of flow birefringence of polymer melts at extremely low shear rates (10−3 s−1) under transient conditions.
Abstract: A description is given of a coaxial cylinder apparatus, suitable for the measurement of the flow birefringence of polymer melts at extremely low shear rates (~10−3 s−1) and, in particular, under transient conditions.
TL;DR: In this article, a polarization modulated birefringence scheme allowing continuous measurements on single domains at phase transitions has been developed, which reveals the initial first order nature of the transition and yields improved values for the critical exponent and transition parameters.
Abstract: A polarization modulated birefringence scheme allowing continuous measurements on single domains at phase transitions has been developed. Measurements on the 184 K transition in KMnF3 clearly revealed the initial first order nature of the transition and yielded improved values for the critical exponent and transition parameters.
TL;DR: It is shown that the smaller fly photoreceptors have pronounced waveguide effects for wavelengths greater than 400 nm, and V is determined by measuring their birefringence by means of a direct measurement of V.
TL;DR: Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response.
Abstract: The optical birefringence induced in DNA solutions by both oscillating hydrodynamic fields (flow birefringence) and oscillating electric fields (Kerr effect) is measured over a wide frequency range. The observed frequency response of the birefrigence is compared with theories for rigid ellipsoidal particles and for Gaussian chains. DNA at 6 × 105 molecular weight is found to exhibit rigid particle hydrodynamic behavior, while DNA at 5 × 106 molecular weight behaves like a flexible chain. Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response. The dielectric model for DNA contains both permanent and dispersionless induced dipole moments. The dielectric behavior of DNA has the character of a permanent dipole but with anomalous low-frequency dispersion in the Kerr effect. The existing theories do not adequately describe this dispersion. A fluctuation dipole mechanism with relaxation times comparable to those associated with the hydrodynamic motion could possibly demonstrate the observed polar behavior.
TL;DR: Formulae are derived which give the refractive indices and birefringence of arrays of parallel cylinders or cylindrical shells, and of spheres and ellipsoids, lying in a plane.
TL;DR: In this article, the authors studied the relaxation of stress and birefringence in simple extension for two samples of 1,2-polybutadiene with 95% and 88% vinyl content and weight-average molecular weight 1.9 and 2.9 × 105, respectively.
Abstract: Relaxation of stress and birefringence in simple extension has been studied for two samples of 1,2-polybutadiene with 95% and 88% vinyl content and weight-average molecular weight 1.9 and 2.9 × 105, respectively. The extension ratio, λ, ranged from 1.14 to 2.08, temperatures from 0 to 15°C, and times, reduced to 0°C, up to 3 × 105 sec. The stress-optical coefficient C was negative and positive, respectively, for the two samples, the difference being attributable to opposite signs and very different magnitudes of the contributions of the 1,2 and 1,4 moieties to the birefringence. For each polymer, C was independent of time but increased (algebraically) with temperature. For one polymer a very minor dependence of C on λ was observed. At any instant of time, the dependence of both stress and birefringence on λ could be described by equations of the Mooney–Rivlin form with coefficients C1,C2 and B1,B2, respectively. At short times the contributions of the C1 and C2 terms to the stress and of the B1 and B2 terms to the birefringence are roughly equal. With increasing time, C1 and B1 decrease gradually while C2 and B2 remain constant over several decades in time. Finally, C2 and B2 decrease rather rapidly. A tentative interpretation of these phenomena in terms of motions of entanglements is given.
TL;DR: In this paper, the change in birefringence and stress during the crystallization of a polymer above its Tg and from a calculation of the intrinsic bireringence of a polycrystalline crystal was calculated, which was illustrated for several polymers and gave values in reasonable agreement with other methods for the study of crystallinity.
Abstract: Stress-induced crystallization may be studied by the birefringence technique and by low-angle light scattering. From measurements of the change in birefringence and stress during the crystallization of a polymer above its Tg and from a calculation of the intrinsic birefringence of a polymer crystal, the change in volume fraction crystallinity may be calculated. The technique is illustrated for several polymers and found to give values in reasonable agreement with other methods for the study of crystallinity. Crystallization is also accompanied by the development of a low-angle light scattering pattern, the size and shape of which is indicative of the amount, size and morphology of the crystalline superstructure.
TL;DR: In this paper, it was found that, in as-grown crystals, an internal biasing field of 20 ∼ 30 kV/cm exists and this can be removed by annealing crystals at 250°C for 12 hours.
Abstract: Temperature dependence of spontaneous polarization, dielectric constant, optical rotatory power and birefringence of ferroelectric Ca2Pb(C2H5CO2)6 have been measured in a wide temperature region including the I-II phase transition point. It was found that, in as-grown crystals, an internal biasing field of 20 ∼ 30 kV/cm exists and this can be removed by annealing crystals at 250°C for 12 hours. Effects of annealing on dielectric and optical properties were also investigated. Below about 0°C, the spontaneous polarization decreased with decreasing temperature in contrast to that of the isomorphous ferroelectric Ca2Sr(C2H5CO2)6. Except for this point, temperature dependence of the other quantities are very similar to those of Ca2Sr(C2H5CO2)6.
TL;DR: In this article, an approximate analytical expression for the transmission of thin twisted nematic layers between a polarizer/analyzer pair was derived for the case of a thin twisted nematic layer, where the direction of the incident light was assumed to be parallel to the normal of the electrode.
Abstract: An approximate analytical expression is calculated for the transmission of thin twisted nematic layers situated between a polarizer/analyzer pair. The approximation assumes that the twist angle of the nematic liquid crystal is smaller than the maximum retardation of the cell. The direction of the incident light is assumed to be parallel to the normal of the electrode. This configuration is analyzed for a general arrangement of polarizer and analyzer; the general result is evaluated for the case of the polarizer parallel and analyzer perpendicular to the liquid-crystal optical axis on the input and output electrodes, respectively. The results show that in the case of a thin twisted nematic layer the transmission depends on the thickness of the layer, on the birefringence of the liquid crystal, and on the wavelength of the light. This is a departure from the well-known independence of the transmission on these parameters for a thick twisted nematic layer.
Patent•
08 Mar 1976
TL;DR: In this article, a real-time coherent optical data processing system using a reflective mode liquid crystal light valve is described, which is particularly suited for application to real time coherent data processing.
Abstract: There is disclosed a high performance coherent optical data processing system using a reflective mode liquid crystal light valve which is particularly suited for application to real-time coherent optical data processing. A preferred example of the system uses a reflective light valve comprising a CdS photoconductor, a CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent light image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the AC voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal thus modulates the polarization of the coherent read-out or projection light responsively to the non-coherent image. An analyzer is used to create an intensity modulated output beam which is projected through a Fourier transform lens onto a screen or other detector means.
TL;DR: Among the known ferroelectrics, only a few, Gd2(MoO4)3, boracites, Bi4Ti3O12, BaTiO3 and PLZT, come close to meet the requirements for alphanumeric displays as mentioned in this paper.
Abstract: Among optical field effect phenomena of known solid state materials, only three are suitable for alphanumeric displays: (i) electric field switching of the spontaneous birefringence, (ii) electric field induced birefringence and (iii) electric field switching of the spontaneous optical rotatory power (electrogyration). The birefringence effects are necessarily coupled with mechanical deformations, whereas electrogyration is not. Among the known ferroelectrics, only a few, Gd2(MoO4)3, boracites, Bi4Ti3O12, BaTiO3 and PLZT come close to meet the requirements for alphanumeric displays. For large scale production, the development of shear free or very low shear compositions-for single crystals, layers and ceramics-appears mandatory. Possibilities will be discussed. Some PLZT compositions are in an advanced development state.
TL;DR: If the applied electric field is sufficiently high, the steady‐state birefringence becomes becomes positive even at a very high concentration of TMV, it was found that the TMV behaves as if it possesses a permanent dipole perpendicular to its long axis.
Abstract: A tentative and phenomenological analysis of negative electric birefringence, which has often been observed as an anomalous birefringence phenomenon in a concentrated solution of rodlike macromolecules, is presented. Tobacco mosaic virus (TMV) was used as a typical example for the investigation. It was found that if the applied electric field is sufficiently high, the steady-state birefringence becomes becomes positive even at a very high concentration of TMV. From this finding and analysis of the time course of birefringence transients, it was suggested that the TMV (common strain, OM type), which originally has no inherent permanent dipole, behaves as if it possesses a permanent dipole perpendicular to its long axis. Supporting evidence was also obtained from birefringence experiments on concentrated solutions of the HR strain of TMV, which has an inherent permanent dipole along its long axis. Other possibilities, for example, the effects of the walls of electrodes or of polymerization of TMV molecules, were excluded.