Showing papers on "Birefringence published in 1985"
TL;DR: In this article, the anchoring energy function at the interface between 5CB(pentylcyanobiphenyl) and an obliquely evaporated SiO was determined by measuring the birefringence and the capacitance of a 56μm-thick cell up to 150 V rms at 0.23°C below the clearing temperature.
Abstract: We show that the anchoring energy function, i.e., the anisotropic part of the interfacial free energy, at a nematic liquid crystal‐wall interface can be determined uniquely without a numerical fitting procedure, when the integrated birefringence of a liquid crystal cell with a thickness much larger than the extrapolation length is measured as a function of an electric or magnetic field well above the Freedericksz threshold. The precision of the present method is closely argued, showing that the resulting anchoring energy function is reasonably insensitive to the uncertainties in the material parameters and in the cell thickness. As an example, the anchoring energy function at the interface between 5CB(pentylcyanobiphenyl) and an obliquely evaporated SiO was determined for the first time, by measuring the birefringence and the capacitance of a 56‐μm‐thick cell up to 150 V rms at 0.23 °C below the clearing temperature. A saturation of the field‐induced distortion was clearly observed at about 100 V rms. The...
281 citations
TL;DR: In this article, a system which shows a relatively large blue-phase range is investigated, and the response times are a few tens of microseconds below 10°C. But due to the small value of the cholesteric pitch, the blue phase shows no Bragg-reflections in visible light.
Abstract: A system which shows a relatively large blue-phase range is investigated. Owing to the small value of the cholesteric pitch the blue-phase shows no Bragg-reflections in visible light. Nevertheless, electric-field induced birefringence shows quite large values. The response times are a few tens of microseconds below 10°C. Crude estimates of the effects lead to values reasonably close to the experimental ones. Zero voltage birefringence effects are encountered, field induced and slowly decaying at higher temperatures and surface induced at lower temperatures where a uniaxial phase appears to be stable.
183 citations
TL;DR: In this article, exact solutions for the intensity-dependent polarization state of a light wave in a birefringent optical fiber are presented for the operation of fiber-optic logic gates, pulse shapers, and intensity discriminators.
Abstract: Exact solutions are presented for the intensity‐dependent polarization state of a light wave in a birefringent optical fiber. The theory takes into account both the linear polarization evolution and the nonlinear ellipse rotation. It is shown that, contrary to current belief, self‐induced polarization changes are possible even with equal excitation of the fiber’s principal axes. The theory is applicable to the operation of recently demonstrated fiber‐optic logic gates, pulse shapers, and intensity discriminators.
163 citations
TL;DR: In this paper, the alternating sign of the effective nonlinear optical (nlo) coefficient enables efficient frequency mixing independent of the constraints of birefringence for periodic laminar ferroelectric domain superstructures in chromium-doped LiNbO3.
Abstract: Periodic laminar ferroelectric domain superstructures in chromium‐doped LiNbO3 have been grown by modulating the bias current during Czochralski growth. Periodic domain patterns stacked along the y axis with domain thicknesses as low as 8 μm have been prepared. The alternating sign of the effective nonlinear optical (nlo) coefficient enables efficient frequency mixing independent of the constraints of birefringence. This is demonstrated by realizing frequency doubling of 1.06‐μm YAG : Nd laser radiation using the largest nlo coefficient, d33. For domain thicknesses equal to an odd multiple of the coherence length, d=(2m+1)lc, the second harmonic intensity varies as the square of the domain number. For the optimum case, d=lc, an improvement of the nlo efficiency, as compared to the 90° phase‐matched process, by the factor [(2/π)d33/d31]2=15 is inferred.
134 citations
Patent•
16 May 1985
TL;DR: In this paper, the authors proposed a method for compensating the birefringence of the liquid crystal layer in its homeotropic structure, so that the cell has a high contrast for said structure, in the case of an oblique observation made in a given observation plane.
Abstract: Liquid crystal cell having a homeotropic structure, with compensated birefringence for said structure. The cell comprises a liquid crystal layer which can have a hometropic structure and electrodes located on either side of the layer and whereof at least one is transparent. It also comprises means for compensating the birefringence of the liquid crystal layer in its homeotropic structure, so that the cell has a high contrast for said structure, in the case of an oblique observation made in a given observation plane. Application to the construction of data display means.
126 citations
TL;DR: In this article, optical observations of a number of main-chain thermotropic liquid-crystal polymers were carried out at elevated temperatures using an apparatus that is capable of providing a controlled translational oscillatory shearing motion to samples of typically 1-10 µm thickness.
Abstract: We report optical observations of a number of main-chain thermotropic liquid-crystal polymers. In situ measurements were carried out at elevated temperatures using an apparatus that is capable of providing a controlled translational oscillatory shearing motion to samples of typically 1–10 µm thickness. In static samples we observe either a general birefringence with local scattering from line defects which we believe to be disclinations, or in thicker samples a texture dominated by light scattering due to the presence of dence disclinations. Superimposed shearing appears to result in both the multiplication of disclinations and the progressive decrease in the distance between individual disclinations. At high shear rates pure birefringence in the direction of flow is observed. Finally we report on the optical relaxation behaviour of oriented samples together with an explanation for the skin core effect observed when thermotropic liquid-crystal polymers are extruded through dies.
89 citations
TL;DR: In this paper, a new apparatus for in vivo retinal-scattering experiments incorporating Mueller-matrix ellipsometry is described, where the state of polarization of the entrance beam is modulated, after which the Stokes vector of the exit beam is assessed.
Abstract: A new apparatus for in vivo retinal-scattering experiments incorporating Mueller-matrix ellipsometry is described. The basic principle is that the state of polarization of the entrance beam is modulated, after which the Stokes vector of the exit beam is assessed. Results show that nearly 90% of the degree of polarization of the entrance beam is preserved after double passage of the ocular media and retinal scattering. Changes in the state of polarization are studied in terms of a rotation around an eigenvector on the Poincare sphere. These studies show that the type of change in the state of polarization of the totally polarized component is probably caused by a linearly birefringent process.
74 citations
TL;DR: In this paper, the PMMA and polyvinylidene fluoride (PVDF) were combined in the form of a compatible, amorphous blend to reduce birefringence.
72 citations
TL;DR: The elastic constants k11, k22, k33, the bulk and rotational viscosities, the birefringence, the static dielectric and electro-optical properties in TN-LCDs of new, positive dielectrics and electro...
Abstract: The elastic constants k11, k22, k33 , the bulk and rotational viscosities, the birefringence, the static dielectric and electro-optical properties in TN-LCDs of new, positive dielectric and electro...
72 citations
TL;DR: In this article, the three principal indices of birefringent optical thin films are deduced from measurements made on narrow-band interference filters, including 2.688, 2.429, and 2.452.
Abstract: Shadowing causes form birefringence in optical thin films that are deposited at oblique incidence. For light incident in the plane containing the direction of deposition and the substrate normal, the TE and TM polarizations in the film are decoupled, and field transfer can be described using 2×2 matrices. The three principal indices of birefringent films are deduced from measurements made on narrow-band interference filters. In one example refractive indices of 2.688, 2.429, and 2.452 were computed for TiO2 deposited at 27° to the substrate normal. Both TiO2 and ZrO2 behave as positive biaxial media.
67 citations
Patent•
13 Sep 1985
TL;DR: In this article, the optical multiplexer/demultiplexer provides arbitrarily closely spaced wavelength channels, the spacing and locations thereof being determined by the thickness of birefringent crystals such as, for example, quartz.
Abstract: An optical multiplexer/demultiplexer provides for arbitrarily closely spaced wavelength channels, the spacing and locations thereof being determined by the thickness of birefringent crystals such as, for example, quartz. Such a device can also be used for duplexing bidirectional signals. Methods for mechanically tuning the devices to given laser wavelengths are described, as well as simplified constructions which can be used with polarized light sources such as lasers.
TL;DR: A new method for precisely measuring the wavelength dependence of modal birefringence in highly bireFringent fibers is presented using an incoherent light source such as a fiber Raman laser.
Abstract: Modal birefringence of highly birefringent fibers can be measured nondestructively by the elastooptic modulation method. Based on this modulation method, a new method for precisely measuring the wavelength dependence of modal birefringence in highly birefringent fibers is presented using an incoherent light source such as a fiber Raman laser.
TL;DR: In this article, the Mueller matrix approach is used to analyze the problems associated with the calibration of a modern CD spectropolarimeter constructed on the basis of a modulation technique in polarization spectroscopy.
Abstract: The Mueller matrix approach is used to analyze the problems associated with the calibration of a modern CD spectropolarimeter constructed on the basis of a modulation technique in polarization spectroscopy. As a result, the performance of the CD spectropolarimeter is found to be determined by the characteristics of the photomultiplier as a partial polarizer, the residual static strain birefringence of the modulator, and the first harmonic response of a lock‐in amplifier. Furthermore, the CD signal is greatly affected by the circular birefringence of a sample in addition to the above three factors. Thus, the necessity of checking these factors before the calibration is carried out using a standard sample is pointed out.
TL;DR: In this paper, the operation of a fiber-optic logic gate is demonstrated for the first time, and the principle of operation is based upon the intensity-dependent polarization rotation in birefringent fibers.
Abstract: Operation of a fiber‐optic logic gate is demonstrated for the first time. The principle of operation is based upon the intensity‐dependent polarization rotation in birefringent fibers. Using a birefringent fiber combined with polarizers in the crossed state, the ON/OFF state of an AND operation is clearly observed with an extinction ratio of approximately 10 dB. The fiber‐optic logic gate would be a promising device for optical information processing in the future because of the feasibility of compact configuration and very fast‐speed operation.
TL;DR: In this article, a hybrid aligned nematic liquid crystal sample presented a bulk flexo-electric polarization P. The coupling of P with an external electric field normal to the bounding plates allows, for weak anchoring, a texture distortion.
Abstract: A hybrid aligned nematic liquid crystal sample presents a bulk flexo-electric polarization P. The coupling of P with an external electric field normal to the bounding plates allows, for weak anchoring, a texture distortion. We report a new linear flexo-electro-optic effect in such a cell with a weak anchoring, which presents an electrically controlled birefringence. The results also indicate that the sin2 θs form of the surface anchoring energy is inadequate when the surface angle θ s is large. Low voltage screening by counterions is also discussed.
TL;DR: It is concluded that the photosensitization process is not uniform over a cross section of the fiber; and periodic modification of the refractive index is anisotropic and therefore a small photoinduced birefringence exists and gives more weight to the hypothesis that the photoinduced filters are essentially phase gratings.
Abstract: Reflecting Bragg filters having some polarizing properties can be photoinduced in monomode optical fibers exposed to a linearly polarized laser beam. Their reflectivity does indeed reach a maximum when the polarization direction of a reading beam is parallel to the polarization direction of the writing beam. This behavior is independent of the relative angle between the polarization direction of the writing beam and the birefringence axes of the fiber. These polarizing properties disappear for long exposure times of the fiber to the writing beam. From these results we conclude that the photosensitization process is not uniform over a cross section of the fiber; and periodic modification of the refractive index is anisotropic and therefore a small photoinduced birefringence exists. We have verified that effect; this result gives more weight to the hypothesis that the photoinduced filters are essentially phase gratings.
TL;DR: In this paper, a new experimental technique is presented for the study of the dynamics of dilute colloidal suspensions in transient shear flow, based on the polarization modulation of light, the experiment permits simultaneous determinations of linear dichroism, linear birefringence (Δn′), the orientation angle of the principal axis of Δn″, and the orientation angles of the primary axis of δn′.
TL;DR: In this paper, the depolarization ratios of the Raman bands of isotropic samples are in good agreement with those obtained with the use of conventional instruments, provided that the reflection or transmission factor of the beamsplitter is introduced as a correction.
Abstract: Polarized Raman spectra of the reference materials carbon tetrachloride and α-quartz are obtained with the Raman microprobe MOLE with the use of different high-numerical-aperture objectives. The depolarization ratios of the Raman bands of isotropic samples are in good agreement with those obtained with the use of conventional instruments, provided that the reflection or transmission factor of the beamsplitter is introduced as a correction. Even with the very wide-aperture objectives used, the depolarization effect is not large and can be evaluated theoretically. Correct polarized spectra of anisotropic samples can also be obtained with a Raman microspectrometer. Here again, the depolarization effect induced by the wide-aperture objective is not large and can be evaluated theoretically if the birefringence of the crystal does not play a significant role. The depolarization induced by the birefringence is especially important when incident and scattered light propagate in a direction close to the optical axis of the crystal, but can be minimized by a reduction of the optical path within the sample.
TL;DR: In this article, the authors measured the acoustoelastic birefringence of an aluminum beam by transmitting ultrasonic shear waves at two perpendicular polarizations through the thickness of the beam.
Abstract: Acoustoelastic birefringence is measured by transmitting ultrasonic shear waves at two perpendicular polarizations through the thickness of an aluminum beam. From the data obtained before bending, after bending, and after the beam has been sectioned to relieve the residual stresses, the acoustoelastic birefringence induced by residual stress is separated from that induced by texture change. Supplemented with strain‐gauge data at all these states, the texture‐induced anisotropy is shown to be related to plastic (permanent) strains in the beam. A nearly linear relationship is observed in compressional deformation of 6061‐T6 aluminum up to −0.6% plastic strain in the beam, whereas the birefringence is almost independent of tensile plastic strain.
TL;DR: In this article, an analysis of multiple-beam Fizeau fringes crossing fibres with irregular transverse sections is given, where the area enclosed under the fringe shift is considered to represent the path difference integrated across the fibre.
Abstract: An analysis of multiple-beam Fizeau fringes crossing fibres with irregular transverse sections is given. The area enclosed under the fringe shift is considered to represent the path difference integrated across the fibre. The method is applied to the determination of refractive indicies and birefringence of dralon fibres. Microinterferograms are given for illustration.
TL;DR: In this article, the source of optical artifacts in circularly polarized luminescence was examined by application of the method of Mueller matrices, and it was shown that the artifacts in most cases are due to the small inherent birefringence in the photoelastic modulator employed in the experimental measurement.
Abstract: The source of optical artifacts in circularly polarized luminescence is examined by application of the method of Mueller matrices. Expressions for the circularly polarized luminescence intensity are developed that illustrate that the source of the artifact in most cases is due to the small inherent birefringence in the photoelastic modulator employed in the experimental measurement. Experimental results are presented that are consistent with this conclusion.
TL;DR: In this paper, a thin-film waveguide Faraday rotator with non-reciprocal polarization rotation of ±45° for light of wavelength 1.45 μm with an extinction ratio of 500:1 has been demonstrated.
Abstract: A thin‐film waveguide Faraday rotator which provides nonreciprocal polarization rotation of ±45° for light of wavelength 1.45 μm with an extinction ratio of 500:1 has been demonstrated. This isolator structure makes use of laser annealing to reverse the sublattice magnetization and hence the sign of the Faraday effect in localized regions of a (Bi, Ga) yttrium iron garnet film. A novel geometrical pattern was designed for these regions to overcome the effects of the inherent thin‐film birefringence.
TL;DR: In this paper, an external electric field induces birefringence in a solution of polydiacetylene (poly‐4BCMU) in toluene due to orientation of the macromolecules.
Abstract: Application of an external electric field induces birefringence in a solution of polydiacetylene (poly‐4BCMU) in toluene due to orientation of the macromolecules. The field induced orientation in the red phase indicates an anisotropic polarizibility tensor characteristic of a rod‐like conformation. The birefringence due to the polymer in its coil conformation (yellow phase) is extremely weak. The transient response of the anisotropic light scattering was studied in the red phase after switching the electric field on or off. We find a free rotational relaxation time of ∼0.1 s, consistent with the rotational diffusion constant expected for rod‐like polydiacetylene macromolecules. These results rule out the large aggregate interpretation proposed to explain the color change transition. The field induced birefringence data independently demonstrate the existence of the rod‐coil conformational transition for polydiacetylene 4BCMU macromolecules in solution.
TL;DR: The use of surface-impedance and surface-admittance concepts for analyzing reflection and refraction at an isotropic dielectric interface (first developed about 1938) is extended to include an interface between uniaxial birefringent dielectrics as discussed by the authors.
Abstract: The use of surface-impedance and surface-admittance concepts for analyzing reflection and refraction at an isotropic dielectric interface (first developed about 1938) is extended to include an interface between uniaxial birefringent dielectrics. Total internal reflection and the polarizing (Brewster) angle at an anisotropic interface are shown to be naturally explainable in terms of surface impedance (for TM polarization) and surface admittance (for TE polarization). The allowable modes in an integrated optical uniaxial asymmetric dielectric slab waveguide are also shown to be directly obtainable using the surface impedance/admittance approach. Numerical examples are presented.
TL;DR: D devices were made for cabled and uncabled fiber which provide complete polarization control by adjusting the angles of two such coils by inducing linear birefringence induced by coiling the fiber in a loop.
Abstract: Single-mode fiber-optic quarterwave plates utilizing linear birefringence induced by coiling the fiber in a loop are described. Optimal quarterwave plates are obtained by one turn of 1.0-cm radius for 0.6328-μm light for a single-mode fiber with an outer diameter of 81 μm. For single-mode fiber with a diameter of 120 μm, optimal quarterwave plates consist of one turn of 0.95-cm radius for 1.30-μm wavelength or two turns of 1.3-cm radius for 1.55-μm wavelength. Devices were made for cabled and uncabled fiber which provide complete polarization control by adjusting the angles of two such coils.
TL;DR: In this article, a photo-elastic birefringence modulator was proposed for single-mode optical fibers using a single-input single-output (SISO) modulator.
Abstract: A new birefringence measurement technique for single-mode optical fibers using a photo-elastic birefringence modulator is described. The method is compared to an existing static measurement method to illustrate the sensitivity, accuracy, and speed made available. Experimental results on both low- and high-birefringence fibers are presented.
TL;DR: In this article, the supertwisted birefringence effect for highly multiplexed liquid-crystal displays was investigated for normal and oblique incidence of light assuming a 1/100 duty cycle.
Abstract: Numerical results are presented on transmission, reflection, and color of the recently described, supertwisted birefringence effect for highly multiplexed liquid‐crystal displays. The electro‐optical properties, which are investigated for normal and oblique incidence of light assuming a multiplexed duty cycle of 1/100, are compared to those of a 270° layer operating in the Mauguin mode and to 270° twisted Heilmeier and White–Taylor guest‐host schemes.
TL;DR: Optical birefringence in liquid phase-epitaxial-grown (LPE) bi-substituted iron garnet films was investigated with annealing as mentioned in this paper.
Abstract: Optical birefringence in liquid‐phase‐epitaxial‐grown (LPE) Bi‐substituted iron garnet films was investigated with annealing The optical birefringence was found to be composed of a stress‐induced part and a growth‐induced part The growth‐induced optical birefringence Δng was about 5×10−4 at λ=115 μm Δng and the growth‐induced magnetic anisotropy Kg disappeared after the annealing Time constants for changes of Δng and Kg by the annealing were nearly the same and orders of a few hours at 1100–1150 °C A deformation of the microscopic structure around bismuth ions seems to be responsible for both Δng and Kg The large growth‐induced optical birefringence in Bi‐substituted iron garnet films plays an important role to achieve high efficiency TE‐TM mode conversion in magneto‐optical waveguides
Patent•
17 Apr 1985
TL;DR: In this paper, a frequency doubler for a laser is disclosed in which a Type II SHG crystal is oriented to generate a second harmonic frequency beam in response to the orthogonal components of a fundamental beam.
Abstract: A frequency doubler for a laser is disclosed in which a Type II SHG crystal is oriented to generate a second harmonic frequency beam in response to the orthogonal components of a fundamental beam. After the fundamental beam makes a round trip through the SHG crystal, any differential phase delays between the orthogonal components due to birefringence are eliminated to improve the efficiency of the cavity.
TL;DR: In this article, a binary ferroelectric liquid-crystal mixture with room-temperature Ferroelectricity and a large spontaneous polarization has been developed and a guest-host-type device was fabricated using the mixture, and some potential problems in the application of the materials to electro-optical switching devices are pointed out on the basis of the optical properties of this device.
Abstract: A binary ferroelectric liquid-crystal mixture having both room-temperature ferroelectricity and a large spontaneous polarization has been developed. The temperature range is from 20°C to 34°C. The spontaneous polarization is almost the same value, 4 nC/cm2, as that in DOBAMBC. Five material constants for the mixture; the transition temperature, spontaneous polarization, helical pitch, tilt angle and birefringence, are reported. A guest-host-type device was fabricated using the mixture, and some potential problems in the application of the materials to electro-optical switching devices are pointed out on the basis of the optical properties of this device.