Showing papers on "Birefringence published in 1993"

Electrooptic Effects in Liquid Crystal Materials

Abstract: 1 Liquid Crystalline State.- 1.1 Structure of Liquid Crystal Phases.- 1.1.1 Molecules.- 1.1.2 Thermotropic Mesophases Formed by Achiral Rod-Like Molecules.- 1.1.3 Thermotropic Chiral Mesophases.- 1.1.4 Mesophases of Disc-Like and Lath-Like Molecules.- 1.1.5 Polymer Liquid Crystals.- 1.1.6 Lyotropic Liquid Crystals.- 1.2 Mixtures.- 1.2.1 Nematic Eutectics.- 1.2.2 Reentrant Phases.- 1.2.3 Mixtures of Smectics.- 1.2.4 Nemato-Cholesteric Compositions.- 1.2.5 Ferroelectric Mixtures.- 1.3 Liquid Crystalline Materials.- 1.3.1 Chemical Classes.- 1.3.2 Chemical Structure and Transition Temperatures.- 1.3.3 Material.- 1.4 Direct Influence of an Electric Field on the Structure of Liquid Crystals.- 1.4.1 Field-Induced Shifts of the Phase Transition Temperatures.- 1.4.2 Influence of the Field on the Order Parameters.- 1.4.3 Field-Induced Changes in Symmetry.- References.- 2 Properties of the Materials.- 2.1 Dielectric Permittivity.- 2.1.1 Isotropic Liquids.- 2.1.2 Dielectric Anisotropy of Nematics.- 2.1.3 Nematic Mixtures.- 2.1.4 Other Phases.- 2.2 Electrical Conductivity.- 2.2.1 Dependence on Impurity Concentration.- 2.2.2 Conductivity Anisotropy.- 2.3 Optical Anisotropy and Dichroism.- 2.3.1 Optical Anisotropy.- 2.3.2 Dichroism.- 2.4 Viscoelastic Properties.- 2.4.1 Elasticity.- 2.4.2 Viscosity.- 2.4.3 Diffusion Coefficients.- References.- 3 Surface Phenomena.- 3.1 Structure of Surface Layers.- 3.1.1 Surface-Induced Changes in the Orientational Order Parameter.- 3.1.2 Surface-Induced Smectic Ordering.- 3.1.3 Polar Surface Order and Surface Polarization.- 3.2 Surface Energy.- 3.2.1 Wetting of a Solid Substrate.- 3.2.2 Surface Energy and Anchorage of a Nematic Liquid Crystal.- 3.2.3 Techniques for Measuring Anchoring Energies.- 3.3 Cells and Orientation.- 3.3.1 Electrooptical Cells.- 3.3.2 Liquid Crystal Orientation.- 3.3.3 Anchoring Transitions.- References.- 4 Electrooptical Effects Due to the Uniform Distortion of Nematic Liquid Crystals.- 4.1 Electrically Controlled Birefringence.- 4.1.1 Director Distribution.- 4.1.2 Tilted Directors at the Boundaries.- 4.1.3 Different Geometries. Simultaneous Action of Electric and Magnetic Fields.- 4.1.4 Effect of Electrical Conductivity.- 4.1.5 The Frederiks Transition for a Weak Anchoring at the Boundaries.- 4.1.6 Dynamics of the Frederiks Transition.- 4.1.7 The Frederiks Transition in Ferronematic Liquid Crystals.- 4.1.8 Optical Characteristics of the Electrically Controlled Birefringence Effect.- 4.2 Twist-Effect.- 4.2.1 Preparation of Twist Cells, Optical Properties at Zero Field.- 4.2.2 Transmission-Voltage Curve for Normal Light Incidence.- 4.2.3 Electrooptics of the Twist Cell for Oblique Incidence.- 4.2.4 Matrix Addressed Displays and Multiplexing Capability of Twist-Effect Materials.- 4.2.5 Dynamics of the Twist Effect.- 4.2.6 New Possibilities.- 4.3 Supertwist Effects.- 4.4 "Guest-Host" Effect.- 4.4.1 Change in Intensity of the Coloring.- 4.4.2 Colorimetry of "Guest-Host" Displays.- 4.4.3 Color Switching.- 4.4.4 Change in Fluorescence.- 4.5 The Flexoelectric Effect.- 4.5.1 Physical Reasons.- 4.5.2 Static Flexoelectric Distortion in Different Geometries Determination of Flexoelectric Moduli.- 4.5.3 Dynamics of the Flexoelectric Effect.- 4.5.4 Microscopic Approach to Determination of the Flexoelectric Coefficients.- 4.6 Reflectivity in an Electric Field.- 4.6.1 Optical Properties of Nontwisted Nematic Layers.- 4.6.2 Various Techniques.- 4.7 Field Behavior of the Isotropic Phase.- 4.7.1 The Kerr Effect in the Isotropic Phase.- 4.7.2 Reorientation of Surface Quasi-Nematic Layers.- 4.8 Electric Field Effects in Nematic Polymers.- 4.8.1 Thermotropic Mesophases.- 4.8.2 Lyotropic Polymers 212.- 4.9 Electrooptical Properties of Polymer Dispersed Liquid Crystal Films.- References.- 5 Modulated and Nonuniform Structures in Nematic Liquid Crystals.- 5.1 Orientational Modulated Structures.- 5.1.1 Flexoelectric Domains.- 5.1.2 Dielectric Two-Dimensional Structure in the Frederiks Transition.- 5.1.3 Other Types of Modulated Structures.- 5.2 Electrohydrodynamic Modulated Structures.- 5.2.1 Low-Frequency Limit The Kapustin-Williams Domains.- 5.2.2 Different Types of Low-Frequency Electrohydrodynamics.- 5.2.3 Electrohydrodynamic Instability in Nematics with Oblique Director Orientation at the Boundaries.- 5.2.4 Electrohydrodynamic Instability: "Chevron" Mode.- 5.2.5 Anisotropic Instabilities for Different Field and Cell Configurations.- 5.2.6 Allowance for Flexoelectricity in Anisotropic Domain Structures.- 5.2.7 High-Frequency Inertia Anisotropic Mode.- 5.2.8 Modulated Structures with Large Periods in Homeotropic Nematics.- 5.2.9 "Isotropic" Mechanism of the Excitation of Electrohydrodynamic Domains.- 5.2.10 Instabilities in Homeotropic Nematics with ?? >0.- 5.2.11 Classification of Threshold Conditions for Different Instabilities in Nematics.- 5.2.12 Electrohydrodynamic Instabilities in Polymer Nematics.- 5.2.13 The Instabilities above the Threshold Voltage. Dynamic Scattering of Light.- 5.3 Nematics in Spatially Nonuniform Fields.- 5.3.1 Homeotropic Orientation.- 5.3.2 Homogeneous Alignment.- 5.3.3 Twist Cells.- References.- 6 Electrooptical Properties of Cholesterics and Nonferroelectric Smectics.- 6.1 The Pitch of Helix and the Optical Properties of Cholesterics.- 6.1.1 Textures.- 6.1.2 Methods of Measuring the Pitch.- 6.1.3 Optical Properties of Planar Cholesteric Textures.- 6.1.4 Diffraction on the Focal-Conic Texture.- 6.1.5 Pitch Dependence on Cell Thickness.- 6.2 Field-Induced Dielectric Instabilities of Cholesterics.- 6.2.1 Texture Transitions.- 6.2.2 Instability of the Planar Cholesteric Texture.- 6.2.3 Field Untwisting of a Cholesteric Helix.- 6.2.4 Electrically Switched Bistable Structures.- 6.3 Electrohydrodynamic Instabilities in Cholesterics.- 6.4 Flexoelectric Effects.- 6.4.1 Fast Linear-in-Field Rotation of the Cholesteric Helix.- 6.4.2 Flexoelectric Domains.- 6.5 Electrooptical Effects in Blue Phases.- 6.5.1 Optical Features.- 6.5.2 Field Behavior.- 6.6 Electric Field Behavior of Nonferroelectric Smectics.- 6.6.1 The Frederiks Transition in a Smectic A.- 6.6.2 Dielectrically Induced Texture Transitions.- 6.6.3 The Frederiks Transition in a Smectic C.- 6.6.4 Electrohydrodynamic Instabilities in Smectics A and C.- References.- 7 Ferroelectric Liquid Crystals.- 7.1 The Physical Properties of Ferroelectric Liquid Crystals. Methods of Measurement.- 7.1.1 The Symmetry.- 7.1.2 The Microscopic Approach. Ferroelectric Mixtures.- 7.1.3 Physical Parameters.- 7.1.4 Tilt Angle.- 7.1.5 Spontaneous Polarization.- 7.1.6 Flexoelectric Polarization.- 7.1.7 Rotational Viscosity.- 7.1.8 Helix Pitch.- 7.1.9 Dielectric Properties.- 7.1.10 Optical Properties.- 7.1.11 Total Free Energy with Allowance for Anchoring.- 7.2 Electrooptical Effects in Ferroelectric Liquid Crystals.- 7.2.1 The Clark-Lagerwall Effect.- 7.2.2 Deformed Helix Ferroelectric Effect.- 7.2.3 Electroclinic Effect Near the Smectic A ? C* Phase Transition.- 7.2.4 Other Electrooptical Effects.- 7.2.5 Orientation of Samples.- 7.2.6 Problems of Bistability Realization.- 7.3 Ferroelectric Liquid Crystal Polymers.- 7.3.1 Introductory Remarks.- 7.3.2 Chemical Structures.- 7.3.3 Ferroelectricity.- 7.3.4 Electrooptical Switching.- References.- 8 Applications of Electrooptical Liquid Crystalline Materials.- 8.1 Displays.- 8.1.1 Active Matrix Addressed Displays.- 8.1.2 Supertwist Displays for Personal Computers.- 8.1.3 Projection Displays.- 8.1.4 Guest-Host Large Area Information Boards.- 8.1.5 General Trends in Display Applications.- 8.2 Optical Data Processing Devices.- 8.2.1 Light Valves.- 8.2.2 Modulators, Shutters.- 8.2.3 Deflectors of Light.- 8.2.4 Integrated Optical Devices.- 8.2.5 Matrix Spatial Light Modulators or Controlled Transparencies.- 8.2.6 Liquid Crystal Logic Elements.- 8.2.7 Optical Filtration.- 8.2.8 Application of Polymer Liquid Crystals in Optoelectronics.- 8.3 Other Applications.- 8.3.1 Storage Devices.- 8.3.2 Stereoscopic Liquid Crystal Sytems.- 8.3.3 Nondestructive Testing.- 8.3.4 Large Area Glass Light Shutters on Polymer Dispersed Liquid Crystal Films.- References.

Two-dimensional femtosecond vibrational spectroscopy of liquids

Abstract: The nonlinear optical response of liquids subjected to a series of N femtosecond laser pulses is calculated using a multimode harmonic model for nuclear motions, with nonlinear coupling to the radiation field through the coordinate dependence of the electronic polarizability. Using electronically off‐resonant optical fields, this multidimensional spectroscopy is shown to provide direct information regarding the homogeneous or the inhomogeneous nature of the spectral density obtained from optical birefringence measurements. Complementary information can be obtained using infrared pulses where the multiple time correlation functions of the nuclear dipole moment (rather than the electronic polarizability) are being probed.

Off-resonant transient birefringence in liquids

Abstract: Off‐resonant transient birefringence measurements are analyzed using a reduced equation of motion for the ground state density matrix, which is expanded using an effective Hamiltonian. Assuming that the pump field is weak, we express the polarization relevant for the birefringence signal in terms of a convolution of the tensorial polarizability response function with the external fields. The homodyne‐detected birefringence signal is directly compared with the coherent Raman signal. The relationship between off‐resonant birefringence and spontaneous Raman experiments is discussed. By expanding the polarizability in powers of the nuclear coordinates and applying the Brownian oscillator model to the coordinate response function, we separate the birefringence signal into intra‐ and intermolecular coordinate response functions. Off‐resonant transient birefringences of acetonitrile, chloroform, dimethylsulfoxide, and a series of alcohols were measured. The data are transformed to the frequency domain by using a model independent analysis method. The spectra are discussed in the context of various models for the distribution of intermolecular modes (spectral density) in liquids.

More than 100-wavelength-channel picosecond optical pulse generation from single laser source using supercontinuum in optical fibres

Abstract: A novel method for generating multiwavelength-channel picosecond optical pulses from a single laser source is proposed using supercontinuum in optical fibres combined with an all-fibre birefringent periodic filter. More than 100-wavelength-channel, 10 ps optical pulses are generated simultaneously over a 1.224–1.394 μm spectral range with a 1.9 nm spacing using a 7.6 ps Nd : YLF laser pulse source.

Method and apparatus for performing optical measurements

Abstract: A method and apparatus for performing various optical measurements is provided utilizing an optical coherence domain refrectometer (OCDR). A short coherence optical radiation source applies optical radiation through like optical paths to a sample and an optical reflector. The optical reflector is movable in accordance with a predetermined velocity profile to permit interferometric scanning of the sample, the resulting output having a Doppler shift frequency modulation. This output may be demodulated and detected to obtain desired measurements and other information. Additional information may be obtained by applying radiation from two or more sources at different wavelengths to the sample and reflector and by separately demodulating the resulting outputs before processing. Birefringent information may be obtained by polarizing the optical radiation used, by suitably modifying the polarization in the sample and reference paths and by dividing the output into orthogonal polarization outputs which are separately demodulated before processing.

Polarel panel for stereoscopic displays

Abstract: A polarel panel includes a sheet polarizer in intimate juxtaposition with a layer made up of regions of isotropic material interspersed with regions of liquid crystal material. In one embodiment, optical activity of the liquid crystal material rotates the electric vector of incoming linearly polarized light through 90° in selected areas. In another embodiment, birefringence causes rotation of the electric vector of incoming linearly polarized light through 90° in selected areas.

Extended Jones matrix method. II

Abstract: We derive an extended Jones matrix method to treat the transmission of light through birefringent networks, where the incident angle of light and the optical axis of the birefringent media are arbitrary. As an example, we employ the method to analyze the leakage problem of a twisted nematic liquid-crystal display and to suggest its possible solutions. A generalization of the method covers all dielectric media, including uniaxial and biaxial crystals and also gyrotropic materials that exhibit optical rotation and Faraday rotation.

Liquid crystal light valve projector with improved contrast ratio and with 0.27 wavelength compensation for birefringence in the liquid crystal light valve

Abstract: In a liquid crystal light valve projector, a quarter-wave compensator plate is disposed between a polarization plate and a liquid crystal light valve to compensate for polarization irregularities induced by the off-incident reflections in the cone of light projected onto the LCLV. The quarter-wave compensation plate reverses the phase of the P component of said illumination light with respect to said compensator plate by 180° thereby eliminating P-polarization leakage during the dark state of an LCLV projector. The invention also combines the compensator plate with a heat shield and a low stress-optical coefficient counter electrode substrate to reduce the birefringence of the LCLV thereby also minimizing leakage of P-polarized light onto the projection screen during the dark state of the projector.

Liquid crystal millimeter wave electronic phase shifter

Abstract: The birefringence of two common nematic liquid crystals were measured in the millimeter wave range, and were found to be in the range of 0.19–0.22 at room temperature. Using liquid crystal electro‐ and magneto‐optical effects, we present the first experimental data of a novel liquid crystal millimeter wave electronic phase shifter. Our experiments show that liquid crystals could play an important role in future millimeter wave device technologies.

Liquid crystal microwave phase shifter

Abstract: We experimentally demonstrate the phase shift of a microwave signal using the electrically controlled birefringence of a liquid crystal. A phase shift of 20° at 10.5 GHz for an interaction length of 4 cm and an applied voltage of 16 V (electric field : 0.3 V/μm) is obtained.

Determination of the Li/Nb ratio in lithium niobate by means of birefringence and Raman measurements

Abstract: Two optical methods for the determination of the Li/Nb ratio in lithium niobate (LiNbO3) are discussed. Data for the optical birefringence method are presented, they cover the entire composition range in which LiNbO3 can be fabricated and a wide spectral region. The line-widths of lattice modes have been measured by means of Raman scattering as a function of the Li/Nb ratio for single crystals with polished and rough surfaces.

Polarization properties of Rayleigh backscattering in single-mode fibers

Abstract: The state and degree of polarization (SOP, DOP) of Rayleigh backscattered light in low birefringent optical fibers was calculated using Stokes calculus. It was found that the SOP of Rayleigh backscattered light in low birefringent fiber is constant, viz. the same as the SOP of the incoming light. The DOP of Rayleigh backscattered light is one-third of the DOP of the incoming light, and not just anywhere between 0 and 100% as often mentioned in the literature. The experimental results agree with the calculations. >

Polarization-insensitive arrayed-waveguide wavelength multiplexer with birefringence compensating film

Abstract: An integrated-optic polarization-insensitive wavelength multiplexer that is based on an arrayed-waveguide grating is described. Polarization dependence due to thermal stress was eliminated by depositing an a-Si birefringence compensation film on the arrayed-waveguide. The multiplexing operation of 16 wavelength channels with a 0.8 nm spacing was confirmed to be independent of the polarization state. >

Refractive index dispersions of liquid crystals

Abstract: Refractive indices of two nematic liquid crystals, 5CB and 5PCH, were measured from the 400- to 800-nm region at various temperatures. Results fit the three-band model well. Through comparisons, the contributions of σ and π electrons to the refractive indices and birefringence of uniaxial liquid crystals are evaluated quantitatively. These physical insights are useful for tailoring liquid crystal molecules with proper refractive indices.

Alignment Control of a Liquid Crystal on a Photosensitive Polyvinylalcohol Film

Abstract: The photoinduced optical anisotropy of an azo dye-doped polyvinylalcohol film has been utilized for controlling the azimuthal alignment of a liquid crystal. The dynamic behaviors of the optical transmission of the film and of a liquid crystal layer aligned on the film are studied using linearly polarized pumping (Ar+ laser) and probing (He-Ne laser) beams. The results show that the azo dye-doped polyvinylalcohol film memorizes the information on the polarization direction of the exciting laser beam and the resulting anisotropy induced in the film causes adjacent liquid crystal molecules on the film to rotate azimuthally.

Temperature and strain sensitivity measurements of high-birefringent polarization-maintaining fibers.

Abstract: The strain and temperature sensitivities of three common commercial high-birefringent polarization-maintaining fibers (bow-tie, polarization-maintaining and absorption-reducing, and elliptical core fibers) have been measured by using a dynamic polarimetric method. The experimental setup and measuring process are described in detail. Where possible, the measuring data are compared with published data, and good agreement is obtained.

A 1.3 mu m directional coupler polarization splitter by ion exchange

Abstract: A glass waveguide polarization splitter for operation in the 1.3 mu m wavelength region is reported. The device, which has a symmetric directional coupler configuration, exploits the stress-induced birefringence in K/sup +/-Na/sup +/, ion-exchanged waveguides, giving rise to an adequate difference in the coupling lengths for the two polarizations. Starting from the measured potassium concentration (refractive index) profile of the structure and utilizing a combination of the multilayer stack theory and the effective-index method, the normal mode propagation constants and mode field profiles are calculated to determine the polarization splitting length and the extinction ratio, and the results are compared with the experimental data. It is shown that in a given coupler, the splitting occurs at several wavelengths in the 1.0-1.45 mu m range. A 25 mm-long coupler, fabricated by thermal diffusion of K/sup +/ ions in BK7 glass, exhibits an extinction ratio of 18.2 dB at 1.32 mu m, in excellent agreement with the simulation results. >

Twisted nematic liquid crystal display devices with optical axis of birefringent layer inclined with respect to birefringent layer normal

Abstract: The disclosure relates to electrically controlled display devices that use the polarization rotation properties of twisted nematic liquid crystal layers. A display device comprises an optical cavity formed by two polarizers enclosing a layer of twisted nematic liquid crystal with which uniaxial birefringent means are associated in order to compensate for the residual birefringence of the liquid crystal layer which tends to reduce the contrast ratio of the display device. Thus, the homogeneity of the angular distribution of the contrast ratio is improved in relation to a device having no compensating means. The disclosed device can be applied in particular to data display devices for computers and to the display of television pictures directly or by projection.

Thin, flexible waveplate of fluorinated polyimide

Abstract: A thin optical half-waveplate at 1.55μm, only 14.5μm thick, which is 6.3 times as thin as a zeroth order quartz waveplate, is prepared using fluorinated polyimide. This material has good flexibility, thickness controllability, and high thermal stability. The retardation of the waveplate was retained after annealing at 350°C for 1 h.

Optical switch employing first and second ferroelectric cells with alignment layers having alignment directions offset by 45

Abstract: A liquid-crystal optical beam switch comprising: a first birefringent layer (14) which divides an input beam (24) into its two polarization components; a first segmented twisted nematic liquid-crystal polarization modulator (16), the segments (30,32) of which rotate one of the polarization beams by 90° but not the other so they both have the same polarization state and which polarization state depends on the biasing state of a two-state biasing source (33); a second birefringent layer 18 which displaces the beams in a direction perpendicular to that produced by the first birefringent layer if they are of one polarization but do not displacement them if they are of the other polarization dependent upon the biasing state; a second segmented twisted nematic liquid-crystal polarization modulator (20) the segments (50,52) of which are oppositely biased from the segments of the first liquid-crystal modulator to thereby restore the original polarization difference; and a third birefringent layer (22) which, acting conversely to the first birefringent layer, recombines the beams into one of two output beams (58,64) dependent on the biasing state. A further stage of switching is provided by a fourth birefringent layer (104) having twice the thickness of and the same displacement direction as the second birefringent layer and by a separately switched associated unsegmented liquid-crystal polarization modulator (92).

Properties of doped and undoped crystals of single domain KTiOAsO4

Abstract: Large single crystals of KTiOAsO4 (KTA) measuring up to 35×31×58 mm3 (along abc) are grown from the pure potassium arsenate self-fluxes and from the tungstate flux using the seeded high-temperature solution growth technique. Small amounts of Fe2O3, Sc2O3, or In2O3 (∼0.2–0.4 wt %) are added to the melt to promote single-domain formation in the flux-grown crystals. We report here the linear optical and nonlinear optical properties of these crystals. We observed an unusually strong optical birefringence increase with Fe2O3 dopant concentration [δ(nz−nx)∼0.017/wt % Fe]. This increase leads to a blue shift in the second-harmonic generation cutoff wavelength of as much as 37 nm for a ∼0.47 wt % Fe-dopant level in KTA.

Molecular alignment of polymer liquid crystals in shear flows. 1. Spectrographic birefringence technique, steady-state orientation, and normal stress behavior in poly(benzyl glutamate) solutions

Abstract: The orientation state of liquid crystalline solutions of poly(benzyl glutamate) under shear flow was investigated and the relationship between the microscopic structure and the macroscopic mechanical rheological behavior is discussed. The flow birefringence observed in textured solutions under shear flow is always less than that measured in quiescent, defect-free monodomains of the solutions. At low shear rates, the birefringence is roughly constant and in the range of 53-63% of that observed in a monodomain; there is no evidence of a low-orientation , piled-polydomin structure

Refractive indices of wurtzite and zincblende GaN

Abstract: Refractive index measurements on both wurtzite and zincblende CaN films grown by plasma-enhanced molecular beam epitaxy are reported. For birefringent uniaxial wurtzite GaN samples the index of refraction was measured along the c crystalline axis. In this direction the index is 2.78 at 3.4eV. For cubic GaN films grown on GaAs substrates, the refractive index is 2.91 at 3.2eV. Estimation of the confinement factor for optimised waveguides based a combination of III–V nitrides indicates very favourable values for laser operation.

Polarization-selective computer-generated holograms

Abstract: We demonstrate polarization-selective computer-generated holograms with independent phase profiles for the two orthogonal linear polarizations The holograms are made of two surface-relief-etched birefringent substrates joined face to face We describe their design and fabrication and present experimental results for dual binary-phase computer-generated holograms fabricated in lithium niobate The first-order diffraction efficiency varied from 6% to 25%, with as much as 40:1 contrast between polarizations Such elements can be used in compact optoelectronic systems or combined with electro-optic polarization rotators to make electrically controlled optical elements

Refractive indices of lithium niobate as a function of wavelength and composition

Abstract: An interferometric method is applied to determine the refractive indices of lithium niobate single crystals over a wide wavelength and composition range. A generalized two term Sellmeier equation is proposed that describes the refractive indices as a function of wavelength and stoichiometry. On the basis of this generalized Sellmeier equation the parameters of nearly all optical characterization methods for LiNbO3 can be calculated. By means of a Kramers–Kronig analysis the shift in the UV absorption edge and the change in the extraordinary refractive index with the composition can be referred to each other. Excellent agreement is found with the respective experimental values.

Azo polymers for reversible optical storage. III. Effect of film thickness on net phase retardation and writing speed

Abstract: The optical writing phenomenon observed on azoaromatic-containing polymer thin films exhibits a writing rate proportional to the intensity of the writing beam. This property of the mechanism for optically inducing dichroism and birefringence results directly in nonlinear optical behavior in the thin film. The net phase retardation obtainable and the writing rates are functions of the thin-film thickness that reflect this nonlinear behavior.

Wave-front control using liquid-crystal devices.

Abstract: We report on complete wave-front control with amplitude- and phase-modulation liquid-crystal devices (LCD’s) A twisted nematic device is used for amplitude modulation, and an electrically controlled birefringent device is used for phase modulation Because the LCD’s are optically coupled with afocal optics and are driven by individual LCD driver circuits, the amplitude and the phase can be controlled two dimensionally and independently Complex amplitude data are calculated, and on-axis computer-generated holograms are directly recorded Furthermore, we discuss LCD performance requirements for high-quality reconstruction

Measurement of polarization mode dispersion and modal birefringence in highly birefringent fibers by means of electronically scanned shearing-type interferometry.

Abstract: A method for measuring modal birefringence and polarization mode dispersion in highly birefringent fibers is presented. It employs a white-light interference phenomenon arising between polarization modes as a result of mode coupling induced by a pointlike lateral force applied in approximately one half the length of the tested fiber. This permits the use of a Wollaston prism without a delay line as an analyzing interferometer. Results of measurements of modal birefringence and polarization mode dispersion at λ(0)= 826 nm are reported for four commercially available fibers: the York Bow-Tie, the Fujikura Panda, the Andrew E-type, and the Andrew D-type.