Showing papers on "Birefringence published in 1990"

Physics and Chemistry of Crystalline Lithium Niobate

Abstract: Introduction Physico-chemical properties of lithium metaniobate: Phase diagram for the Li^O2-0-Nb^O 2O^O5 system Crystal structure of lithium metaniobate Crystal-chemical features of metaniobates of alkali metals Phase formation in LN Crystals Methods of obtaining single crystals of lithium niobate Peculiarities of growth of LN single crystals Synthesis of the charge and preparation of the melt Choice of the optimum conditions for growth Growth conditions for LN crystals of a constant radius High-temperature annealing and formation of single-domains in crystal The Stepanov technique Electric phenomena arising in crystallization of LN Defect structure of single-crystal lithium niobate: Morphology and macro-defects Point defects in LN Formation of F centres in LN crystals Twinning in LN crystals The domain structure of lithium metaniobate crystals: Ferroelectric domains in lithium metaniobate Selective etching of LN crystals Growth domain structure Formation of a stationary domain structure Depolarisation mechanisms of lithium metaniobate crystals The influence of temperature gradients on domain formation in the process of crystal growth and annealing The effect of annealing on the near-surface domain structure The regular domain structure in LN crystals Electrical properties of lithium metaniobate: Electric conductivity Dielectric properties Thermal diffusion in lithium niobate crystals Relaxation phenomena in lithium niobate crystals Electric fields in lithium niobate crystals Electric effect and relaxation polarization of lithium niobate Thermionic emission of lithium niobate single crystals Effective ion charges and spontaneous electric moment of lithium niobate Optical and electro-optical properties of lithium metaniobate single crystals Optical properties of lithium metaniobate Electro-optical effect in dielectric crystals Phenomenological theory of the electro-optical effect Establishment of electro-optic coefficients Specific features of lithium niobate crystals applications in electro-optical devices Nonlinear optical properties of lithium niobate: Elements of nonlinear optics Methods used to establish nonlinear coefficients Relationship of birefringence and phase-matching temperature to lithium niobate crystal composition Criteria for nonlinear-optical quality of crystals Enhancement of SHG in lithium niobate crystals with periodic laminar ferroelectric domains Photoelectrical and photo-refractive properties: Model representations of the photo-refractive effect Occurrence of optical distortion in lithium niobate crystals exposed to cw laser radiation Occurence of optical distortion in lithium niobate exposed to pulsed laser radiation Laser-induced physical effects in lithium niobate Photo-induced distortion of the crystal structure in lithium niobate Optical inhomogeneity of crystals and methods of its investigation Nature of optical inhomogeneity Electrically induced optical inhomogeneity of crystals Doping and heat treatment effects on crystal optical inhomogeneity Methods used to observe optical inhomogeneities in lithium niobate crystals Conclusions References Index

Polarization control for coherent communications

Abstract: Two practical implementations of endless polarization control are described. The first approach uses polarization maintaining fiber transducer, while the second uses an integrated optic lithium niobate device. In order to characterize the lithium niobate device in detail, a technique for analyzing the birefringence as a function of the applied voltages was developed, and the measured performance of the devices is presented. Fractional-wave controllers for both static and endless control applications are considered, and design rules for maximum wavelength-window and minimum loss fiber-loop polarization adjusters are given. Endless control using various configurations of the three types of transducers is discussed, and it is shown how apparently different schemes are closely related. >

Analysis of multilayer thin-film structures containing magneto-optic and anisotropic media at oblique incidence using 2×2 matrices

Abstract: A complete analysis of multilayer structures containing an arbitrary number of dielectric, metal, magnetic, and birefringent/dichroic layers is presented. An algorithm, based on simple 2×2 matrices, is derived which allows reflection, transmission, absorption, magneto‐optic conversion, birefringence, and dichroism of the structure to be computed on a personal computer. The incident beam is assumed to be plane monochromatic with arbitrary angle of incidence. There are no approximations involved, and the results are direct consequences of Maxwell’s equations.

Optical properties of lithium-rich lithium niobate fabricated by vapor transport equilibration

Abstract: Lithium-rich lithium niobate of excellent optical homogeneity can be fabricated by a vapor transport equilibration (VTE) technique The high-optical-quality, uniformly birefringent crystals noncritically phase match for second-harmonic generation of 532-nm radiation from 1064-nm Nd:YAG radiation at 238 degrees C The refractive indexes and their temperature dependence have been measured and used to derive temperature-dependent Sellmeier equations, which predict noncritical phase matching for wavelengths as short as 976 nm to generate blue at 488 nm at room temperature The Sellmeier equations accurately predict experimental phase-matching temperatures over a wide temperature range >

Polarization independent optical isolator

Abstract: A polarization independent optical isolator is disclosed which uses a single birefringent plate. A pair of stacked reciprocal rotators, a Faraday rotator, and reflector are positioned in tandem adjacent to the birefringent plate. In the forward (transmitting) direction, a lightwave signal exiting an optical fiber is split into a pair of orthogonal rays by the birefringent plate. The orthogonal rays then pass through a first reciprocal rotator and the Faraday rotator. The rotated rays are then redirected by the reflector back through the Faraday rotator. After passing through the second reciprocal rotator, the orthogonal rays re-enter the same birefringent plate where they are recombined and launched in an output fiber. Since a Faraday rotator is a non-reciprocal device, any signal traveling through the isolator in the reverse (isolation) direction will be split on both passes through the birefringent plate such that neither will intercept the input fiber.

The simultaneous measurement of optical activity and circular dichroism in birefringent linearly dichroic crystal sections. I. Introduction and description of the method

Abstract: The 'HAUP' method, described by Kobayashi and Uesu (1983-85), for the measurement of optical activity in birefringent crystals is extended to include dichroic effects and analysed qualitatively in a novel way using intensity contour maps. The elimination of the parasitic ellipticities of the polariser and analyser is achieved by repeating the measurement in a second crystal setting, rather than physically exchanging the prisms, which has been reported as unworkable.

Liquid crystal display device with a birefringent compensator

Abstract: Disclosed herein is a liquid crystal display device comprising (1) a liquid crystal cell having a structure in which liquid crystal molecules in the liquid crystal layer sandwiched between substrates are oriented substantially in parallel to the surface of the substrate and twisted at an angle of from 120° to 360° in the thickness direction of the liquid crystal layer when the voltage is not applied, (2) a pair of polarizers disposed so as to sandwich the liquid crystal cell therebetween and (3) a birefringence layer disposed between the liquid crystal layer and at least one of the polarizers. The liquid crystal display device can provide black and white display of excellent visual angle characteristic and of excellent quality. Furthermore, the maximum, minimum, and perpendicular refractive indexes, n x , n y , and n z , respectively, of the birefringence layer satisfy the following relationship: n.sub.y

Liquid crystal display with compensator having two films with positive and negative intrinsic birefringence, respectively

Abstract: A liquid crystal display comprising a liquid crystal element, at least two birefringent films and a pair of polarizing sheets so arranged that said element and said films are held therebetween, said liquid crystal element comprising a cell composed of two sheets of substrates and a twisted nematic liquid crystal, each substrate being provided with an electrode on one surface thereof, said substrates being arranged so that the electrodes are opposed to each other and said twisted nematic liquid crystal being held between said electrodes, characterized in that said birefringent films are composed of at least one uniaxially stretched film of a polymer having a positive intrinsic birefringence and light transmission properties and at least one uniaxially stretched film of a polymer having a negative intrinsic birefringence and light transmission properties.

Rocking filter formation in photosensitive high birefringence optical fibres

Abstract: Parent et al. observed that the refractive index changes induced in optical fibres by Hill grating formation (at 488 and 514.5 nm) were birefringent. A wavelength filter, formed in a simple and novel way by exposing high birefringence fibre to linearly polarised 488nm light, is reported. Narrow bandwidth operation and high conversion efficiencies are achieved experimentally between the two orthogonal polarisation states of the fibre.

LCD system having improved contrast ratio

Abstract: An LCD display system is formed by stacking two or more independently operated LCD elements. By exploiting the birefringent effect of STN nematic liquid crystals a full range of colors may be displayed. Display rows in the stacked panels are preferably interlaced to achieve high display resolution. Optics are desirably included to collimate light, illuminating the stacked elements, to reduce parallax effects and to disperse light exiting the stacked elements to permit wide angle viewing. The contrast between a pixel in the dark state and in the white state of the high resolution display system may be increased by modifying the Δnd product of the liquid crystal in the passive regions to compensate for the natural birefringence of the liquid crystal in optically aligned active regions.

Measurement of the nonlinear refractive index of single‐crystal polydiacetylene channel waveguides

Abstract: We have measured the nonlinear refractive index (n2) of single crystalline poly(bis(p‐toluene sulfonate) of 2,4‐hexadiyn‐1,6‐diol) (PTS) polydiacetylene channel waveguides at 1.06 μm using two different techniques. The first method employs a Mach–Zehnder interferometer to determine the intensity‐induced phase shift in the waveguide. In the second case n2 is derived from the intensity‐dependent birefringence, which is measured with a Babinet–Soleil compensator. With both measurements the value of n2 in the direction of the PTS polymer chain axis is found to be ∼3×10−11 cm2/W. Such a large value of n2 would allow all‐optical device applications of this material at low‐power levels.

Birefringent filter with tilted optic axis for tuning dye lasers: theory and design.

Abstract: The dependence of the tuning behavior of a birefringent filter on the orientation of the optic axis to the surface of the plate is studied The Jones matrix representing a tilted birefringent plate is reduced to practical form, and this leads to simplifying the theoretical operation of tuning a birefringent filter in a laser resonator The principles of proper determination of the filter parameters are given A design method, which takes into consideration the bandwidth, rejection and tuning range of the filter, and design examples, is provided

Electro-optic sampling of high-speed devices and integrated circuits

Abstract: The operating speeds of the fastest electronic devices and integrated circuits (ICs) have surpassed the capabilities of conventional electronic measurement instrumentation. Electro-optic sampling is an optical probing technique which has ultrashort temporal resolution and is capable of noninvasively probing ICs at internal nodes. This technique is voltage-sensitive because it relies upon the electric field produced by the signal voltage on the device under test (DUT). The electric field (and hence the voltage) can be sampled because it produces birefringence in an electro-optic crystal which changes the state of polarization of an ultrashort-duration optical probe pulse that propagates through the electro-optic crystal. The electro-optic crystal is the substrate of the DUT for direct probing, is a crystal on a separate test structure for hybrid probing, and is a separate crystal placed above the DUT for external probing. Temporal resolution below 1 ps and a sensitivity below 0.1 mV/√Hz have been demonstrated (though not in the same experiment). The principles of electro-optic sampling are reviewed in this paper. Selected applications for measurement of high-speed waveforms in discrete devices and in ICs are presented.

Soliton stability in birefringent optical fibers: analytical approach

Abstract: Propagation of short pulses in birefringent optical fibers is considered in the framework of two coupled nonlinear Schrodinger equations. When the amplitudes of the pulses belonging to different polarizations are equal, we propose a simple analytical explanation of the amplitude threshold for the capture of two partial pulses into a coupled two-component pulse. Our approach is based on a soliton phenomenology. The analytical dependence of the amplitude threshold on linear birefringence is in good agreement with numerical results of Menyuk [ J. Opt. Soc. Am. B5, 392 ( 1988)]. The influence of small dissipative losses on the effect is also discussed.

Light Propagation in Cubic and other Anisotropic Crystals

Abstract: A consistent multipole theory is presented to describe light propagation in non-absorbing non-magnetic crystals. Although valid for the 32 crystal classes, the theory is applied here to all except the five members of the triclinic and monoclinic systems. To account for the birefringence that has been observed in certain cubic crystals and also for the predicted Jones birefringence, the theory has to allow for electric octopoles and magnetic quadrupoles induced by the light wave. At the earlier stage of electric quadrupoles and magnetic dipoles, it is able to describe optical activity in crystals. An expression for this is derived which, when electric quadrupole contributions are omitted, yields the familiar Nye result. As a criterion for the correct inclusion in the theory of all relevant induced multipole moments, tensor expressions for observables are shown to be independent of the choice of origin. Finally, the concepts of O-ray and E-ray are found to break down beyond the electric dipole approximation and alternatives are proposed.

Novel Polarization-Rotating Fiber Resonator For Rotation Sensing Applications

Abstract: A novel fiber resonator architecture is presented, employing a 90 deg rotation of the polarization within the birefringent fiber ring. In principle, this concept provides a temperature-independent separation of the resonance dips corresponding to the two resonant polarization states in the ring. The technique thus avoids gross thermally driven errors encountered in the use of ordinary polarization-maintaining rings for resonator fiber-optic gyros. Data from an experimental polarization-rotating ring at 1.3 μm wavelength demonstrates greatly improved thermal stability in the presence of typical imperfections of a practical device.

Liquid crystal display device having biaxial birefringent plates at each side of the liquid crystal layer

Abstract: The liquid crystal display device of the present invention comprises a liquid crystal layer of a nematic liquid crystal having positive dielectric anisotropy and including a chiral material, the liquid crystal layer being interposed between a pair of substrates with transparent electrodes each having an aligning layer which are arranged substantially in parallel to provide a twist angle of 160°-300°, a driving means to apply a voltage across the electrodes attached to the substrates which interpose the liquid crystal layer, a pair of polarizing plates arranged outside the liquid crystal layer, and at least one birefringent plate provided between the liquid crystal layer and the polarizing plate at at least one side of the liquid crystal layer, wherein the product Δn 1 ·d, of the anisotropy of refractive index Δn, of liquid crystal molecules in the liquid crystal layer and the thickness d, of the liquid crystal layer is in a range of 0.4-1.5 μm, and three main refractive indices n x , n y and n z of the birefringent plate are in a relation of n x ≧n z >n y where n x and n y respectively represent the refractive indices in the direction of film plane of the birefringent plate (provided n x >n y ) and n z represents the refractive index in the direction of film thickness of the birefringent plate.

4-(N,N-Dimethylamino)-3-acetamidonitrobenzene single crystals for nonlinear-optical applications

Abstract: High-quality single crystals of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) were grown from dimethylsulfoxide solutions Crystal platelets with dimensions as large as 10 mm × 5 mm × 2 mm were produced and optically characterized An interferometric method for the measurement of refractive indices of platelike samples was developed and used for platelet surfaces parallel to one principal axis of the indicatrix Dispersion data of the refractive indices and the birefringence were used to calculate the optical angle and the propagation directions for phase-matched frequency doubling of Nd:YAG laser radiation as well as the dependence of phase-matching angles in the x–z plane on different wavelengths Loci of directions for type I and type II collinear phase-matched second-harmonic generation were predicted and experimentally verified By measuring the effective nonlinear-optical susceptibilities in several phase-matched configurations we were able to evaluate all different nonlinear-optical susceptibility coefficients allowed by Kleinman’s symmetry, the highest one being d23 = (50 ± 15) pm/V with Miller’s coefficient δ23 = (049 ± 01) m2/As

Quasi-Phase-Matched Interactions In Lithium Niobate

Abstract: Phase-matching nonlinear interactions by periodic variations in the nonlinear susceptibility, quasi-phase-matching, offers advantages in accessible tuning range and in choice of nonlinear coefficients over the conventional birefringent technique. Periodically reversed ferroelectric domains can be used to create monolithic structures with the necessary high-spatial-frequency variations in the nonlinear susceptibility. We present two techniques for the fabrication of periodically-poled lithium niobate crystals, and results for bulk and guided-wave second harmonic generation of blue and green light.

Wave propagation through a medium with static and dynamic birefringence: theory of the photoelastic modulator

Abstract: A theoretical analysis is given of the propagation of a linearly polarized electromagnetic wave through a medium with a harmonically oscillating birefringence and a static birefringence whose principal axis is inclined to the oscillation axis. The theory is applied to the photoelastic modulator (PEM) to predict the transmitted light flux in experimental configurations of particular spectroscopic and polarimetric importance. Included is the general configuration of a modulator between two polarizers (applicable to nearly all PEM-based light-transmission experiments) and the single-polarizer configuration (characteristic of recent experiments to measure natural optical activity by light reflection). Good agreement between observed results not only provides a test of the theory but accounts for recently observed anomalies that are not explicable on the basis of the standard description of the photoelastic modulator.

Interferometric optical-time-domain reflectometer to determine backscattering characterization of silica-based glass waveguides

Abstract: An interferometric optical-time-domain reflectometer (OTDR) system with high spatial resolution has been developed for diagnosis of optical waveguides and hybrid optical circuits. A spatial resolution as short as 14 μm is obtained by using a newly developed 1.3-μm-wavelength superluminescent diode, and a minimum detectable reflectivity of −100 dB is achieved. Scattering centers that are produced by waveguide irregularities are clearly observed in silica-based glass optical waveguides, and the loss origin of the waveguides is discussed. Also, evaluation of other waveguide characteristics, such as modal birefringence and facet reflectivity, can successfully be made by the OTDR system.

Picosecond circular dichroism spectroscopy: a Jones matrix analysis

Abstract: Measurement of time-resolved circular dichroism signals can be complicated by transient linear dichroism and birefringence effects. These signals arise from using a polarized light beam for excitation and from imperfect modulation of the circularly polarized probe beam. In a polarization-modulation experiment designed to measure the time dependence of circular dichroism, a small amount of pump-induced linear dichroism coupled with birefringence of optics would dominate the observed signals, rendering an accurate measurement virtually impossible. We examine these effects within the Jones matrix formalism. These calculations demonstrate how one can experimentally eliminate transient linear polarization signals, permitting accurate measurement of the transient circular dichoism of a sample with picosecond resolution. Theory and experiment are compared for time-dependent data on myoglobin following the photoelimination of CO from carbonmonoxy myoglobin.

Optical fiber sensor

Abstract: The disclosed optical fiber sensor uses the effect of variation in the birefringence in a birefringent optical fiber as a function of the stresses and of the temperature. It has a linearly polarized, wide-spectrum source coupled to a polarizing-preserving single-mode optical fiber, along one of its neutral axes, devices capable of inducing coupling points being distributed along this fiber. A polarizer at 45° with respect to the neutral axes of the fiber is placed at output of this sensor fiber. The output radiation is analyzed by spectroscopy, for example in a scanning Michelson interferometer associated with a detector. The detection by the interferometer enables the identification of the devices that are subjected to stresses. The same type of device may be used for the simultaneous detection of the stresses and/or the temperatures. The disclosed device can be applied notably to the monitoring and supervision of any installation in which strains have to be detected.

Detection of high-frequency ultrasound with a polarization-maintaining fiber

Abstract: The effect of a high-frequency ultrasound wave incident normally upon a polarization-maintaining optical fiber is investigated theoretically and experimentally. Two different mechanisms accounting for the birefringence change in the fiber resulting from radial strain produced by the ultrasonic wave are identified and studied. A polarization-maintaining fiber can respond to lower frequencies than a single-mode fiber in the polarimetric mode. Moreover, it does so with better sensitivity and requires no real-time control of the polarization state of the input light. The frequency separating the ranges of significance of the two mechanisms is experimentally found to be about 1 MHz (in water). The principle and the realization of a polarimetric ultrasonic sensor using a polarization-maintaining fiber are also described. >

Electrooptic voltage sensor: birefringence effects and compensation methods.

Abstract: Crystals of Bi(4)Ge(3)O(12)from two different sources exhibited linear birefringences of 1.7 x 10(-5)-5.4 x 10(-5)5 (or, phase retardations of 1.3-4.1 degrees /cm) at a wavelength of 830 nm. These birefringences, however, are sensitive to temperature. The temperature variation of the birefringence dB/(B(0)dT) normalized by the room temperature birefringence B(0) was -1 to -7 x 10(-3)/ degrees C. The effects of the temperature dependent birefringence and the birefringence induced by pressure on an electrooptic voltage sensor were measured and quantitatively compared to the predictions. To remove the temperature dependent birefringences, the crystals were annealed over two days. The birefringences were reduced to about half of their original values after a first annealing process, but the values remained unchanged after a second annealing process. To eliminate the effects of the birefringences, a compensation method was used. After applying this compensation method to an electrooptic voltage sensor, the temperature stability of the sensor was improved to +/-0.75% from +/-7.0% in the temperature range between -2 and 65 degrees C, and the pressure stability was improved to +/-0.2% from +/-2% under pressure as high as 1 x 10(5) N/M(2).

Compensator for liquid crystal display

Abstract: A compensator for an active matrix type liquid crystal display using a thin film transistor is provided The compensator is made by a film of a liquid crystalline polymer which exhibits a twisted nematic orientation in a liquid crystal state and assumes a glassy state at temperatures below a liquid crystal transition point thereof, the constituent molecules of the liquid crystalline polymer film having a helical structure with a helical axis wherein the twist angle is in the range of 70 to 150 degrees, and the product Δn·d of birefringence Δn of the liquid crystalline polymer film and film thickness,d, being in the range of 02 to 30 μm