Showing papers on "Birefringence published in 2003"
TL;DR: In this article, a model based on Rayleigh-Gans-Debye light scattering theory has been developed to describe the light transmission properties of fine-grained, fully dense polycrystalline ceramics consisting of birefringent crystals.
Abstract: A model based on Rayleigh-Gans-Debye light scattering theory has been developed to describe the light transmission properties of fine-grained, fully dense polycrystalline ceramics consisting of birefringent crystals. This model extends light transmission models based on geometrical optics, which are only valid for coarse-grained microstructures, to smaller crystal sizes. We verify our model by measuringthe light transmission properties of fully dense (>99.99%) polycrystalline alpha-alumina (PCA) with mean crystal sizes ranging from 60 mm down to 0.3 mm. The remarkable transparency exhibited by PCA samples with small crystal sizes (< 2 mm) is very well explained by thismodel.
802 citations
TL;DR: In this article, the authors proposed image processing algorithms for measuring two-dimensional distributions of linear birefringence using a pair of variable retarders and obtained the lowest noise level of 0.036 nm.
Abstract: We propose image processing algorithms for measuring two-dimensional distributions of linear birefringence using a pair of variable retarders. Several algorithms that use between two and five recorded frames allow us to optimize measurements for speed, sensitivity, and accuracy. We show images of asters, which consist of radial arrays of microtubule polymers recorded with a polarized light microscope equipped with a universal compensator. Our experimental results confirm our theoretical expectations. The lowest noise level of 0.036 nm was obtained when we used the five-frame technique and four-frame algorithm without extinction setting. The two-frame technique allows us to increase the speed of measurement with acceptable image quality.
398 citations
TL;DR: In this article, explicit formulae are obtained for the two refractive indices and polarizations in optically anisotropic crystals that are both dichroic (absorbing) and chiral (optically active).
Abstract: Using a new formalism involving projection from the sphere of directions to the stereographic plane, and associated complex variables, explicit formulae are obtained for the two refractive indices and polarizations in optically anisotropic crystals that are both dichroic (absorbing) and chiral (optically active). This enables three types of polarization singularity to be classified and explored: singular axes, which are degeneracies where the two refractive indices are equal, and which for a transparent non–chiral crystal condense pairwise onto the optic axes; C points, where the polarization is purely circular (right– or left–handed), with topological index +1, +½ or +¼ and whose positions are independent of the chirality; and L lines, where the polarization is purely linear, dividing direction space into regions with right– and left–handedness. A local model captures essential features of the general theory. Interference figures generated by slabs of crystal viewed directly or through a polarizer and/or analyser enable the singularities to be displayed directly.
204 citations
TL;DR: In this paper, the photo-elastic relation and wave equations for inhomogeneous and anisotropic waveguides are reviewed and the effective refractive indexes and mode shapes of planar waveguide under different stress states are obtained analytically.
198 citations
TL;DR: No mechanical or active elements for analyzing polarization are used, and all the parameters related to the spatially-dependent monochromatic Stokes parameters corresponding to azimuth and ellipticity angles can be determined from a single frame.
Abstract: This paper describes a method for the mapping of spatially distributed states-of-polarization of light with a simple and compact configuration. A tiny block of polarization-analyzing optics, consisting of four thin birefringent wedge prisms and a sheet analyzer, are incorporated into an imaging polarimeter, such that mesh-like multiple fringes are generated over a CCD image sensor of a video camera. Fourier analysis of the obtained fringes provides information for determining the two-dimensional distribution of the state-of-polarization. No mechanical or active elements for analyzing polarization are used, and all the parameters related to the spatially-dependent monochromatic Stokes parameters corresponding to azimuth and ellipticity angles can be determined from a single frame. The effectiveness of this method is demonstrated by a prototype incorporating calcite wedge prisms.
197 citations
TL;DR: In this article, a number of optical elements with subwavelength structured surfaces have been developed, where the structures are equivalent to refractive index materials with form birefringence, and many new optical elements are realized using the artificial refractive indices of these sub-wavelength structures.
Abstract: Various optical elements with subwavelength structured surfaces have been developed. The periods of the subwavelength structures are too short to generate diffracted light waves. But the structures are equivalent to refractive index materials with form birefringence. Many new optical elements are realized using the artificial refractive indices of these subwavelength structures. Some typical elements are described here in the passive element regime, and fabrication methods of the elements are explained.
186 citations
Patent•
09 Apr 2003TL;DR: A phase-resolved functional optical coherence tomography system simultaneously obtains the Stokes vectors, structure, blood flow velocity, standard deviation, and birefringence images in human skin this article.
Abstract: A phase-resolved functional optical coherence tomography system simultaneously obtains the Stokes vectors, structure, blood flow velocity, standard deviation, and birefringence images in human skin. The multifunctional images were obtained by processing the analytical interference fringe signals derived from the two perpendicular polarization detection channels. The blood flow velocity and standard deviation images were obtained by comparing the phase from the pairs of analytical signals in the neighboring A-lines in the same polarization state. The Stokes vectors were obtained by processing the analytical signals from two polarization diversity detection channels for the same reference polarization state. From the four Stokes vectors, the birefringence image, which is insensitive to the orientations of the optical axis in the sample, was obtained. Multifunctional images of a port wine stain birthmark in human skin are demonstrated.
168 citations
TL;DR: In this paper, the phase transition temperatures, birefringence and visco-elastic coefficient of several high birerringence isothiocyanato-to-lane compounds were evaluated.
Abstract: The phase transition temperatures, birefringence and visco-elastic coefficient of several high birefringence isothiocyanato tolane compounds were evaluated. The polarizability of these compounds was calculated by the Austin Model 1 (AM1) and Modified Neglect of Diatomic Overlap (MNDO) methods. Using these compounds, we have formulated a eutectic mixture exhibiting a wide nematic range and high figure of merit.
165 citations
01 Jan 2003
TL;DR: In this article, Raman Gap Solitons Experiments within the bandgap of a nonlinear fiber Bragg Grating were conducted in order to investigate the effect of pulse propagation in fiber Gratings with quadratic nonlinearity.
Abstract: 1 Introduction- 2 Theory of Nonlinear Pulse Propagation in Periodic Structures- 3 Polarization Effects in Birefringent, Nonlinear, Periodic Media- 4 Raman Gap Solitons in Nonlinear Photonic Crystals- 5 Self-transparency and Localization in Gratings with Quadratic Nonlinearity- 6 Photonic Band Edge Effects in Finite Structures and Applications to x(2) Interactions- 7 Theory of Parametric Photonic Crystals- 8 Nonlinear Propagation in Fiber Gratings- 9 Gap Solitons Experiments within the Bandgap of a Nonlinear Bragg Grating- 10 Pulsed Interactions in Nonlinear Fiber Bragg Gratings- 11 Chalcogenide Glasses- 12 Optical Properties of Microstructure Optical Fibers- 13 Semiconductor Optical Amplifiers with Bragg Gratings- 14 Atomic Solitons in Optical Lattices- 15 Discrete Solitons- 16 Nonlinear Localized Modes in 2D Photonic Crystals and Waveguides
158 citations
TL;DR: A new kind of polarization splitter based on dual-core photonic crystal fibers with a symmetric directional coupler configuration that gives rise to an adequate difference in the coupling lengths for the two orthogonal polarizations is reported.
Abstract: We report a new kind of polarization splitter based on dual-core photonic crystal fibers. The polarization splitter has a symmetric directional coupler configuration. Each core exhibits high birefringence, which gives rise to an adequate difference in the coupling lengths for the two orthogonal polarizations. A 1.7-mm-long splitter is obtained with the splitting ratio better than -11 dB and a bandwidth of 40 nm. The relationship between the length of the polarization splitter and the diameter of the air hole in the middle of the two cores is discussed.
158 citations
TL;DR: In this article, the birefringence properties of glass-fibre-enforced epoxy resin compounds were measured using optical coherence tomography (OCT) with polarisation-sensitive (PS) imaging.
Abstract: Optical coherence tomography (OCT) is a relatively new imaging technique capable of recording cross-sectional images of transparent and turbid structures with micrometer-scale resolution. Originally developed for biomedical imaging applications, this technique also has a great potential for non-destructive material characterisation and testing. Polarisation-sensitive (PS) OCT is a recent extension of classical OCT that measures and images birefringence properties of a sample, which, however, has not yet been applied to materials science. We present imaging of glass-fibre-enforced epoxy resin compounds and the detection of dry spots, where the epoxy did not properly penetrate the glass-fibre structure. Furthermore, we demonstrate PS-OCT imaging of the birefringence properties of different materials. The mapping of strain fields of samples under uniaxial and non-uniform external stress and the detection of flow patterns in injection-moulded plastic parts could be demonstrated with this technique for the first time.
TL;DR: Based on the different focusing between radially and tangentially polarized light in thermally stressed isotropic laser rods, Nd:YAG laser oscillators were developed to produce low-loss stable oscillation in a single polarization.
Abstract: Production and amplification of radially and azimuthally (tangentially) polarized laser beams are demonstrated. Based on the different focusing between radially and tangentially polarized light in thermally stressed isotropic laser rods, Nd:YAG laser oscillators were developed to produce low-loss stable oscillation in a single polarization. Pure radially polarized light at 70 W with M2=2 and on-axis impure radially polarized light at 150 W with M2=2.5 were achieved. The radially polarized beams were then amplified while good beam quality and polarization purity were retained. Complete elimination of thermal-birefringence-induced aberrations was demonstrated. This should allow much better beam quality from rod-based high-power lasers.
06 Oct 2003
TL;DR: In this article, a polarization-maintaining fiber-based reflectometer for depth resolved birefringence measurement is presented, where linear bireringence of a sample may be measured from data recorded in a single A-Scan.
Abstract: Generally, and in one form of the present invention, is a polarization-maintaining fiber-based polarization sensitive optical low coherence reflectometer for depth resolved birefringence measurement. With the present invention, linear birefringence of a sample may be measured from data recorded in a single A-Scan. In addition, the present invention provides for the simultaneous measurement of retardation and orientation of birefringent axes, wherein measured retardation is insensitive to sample rotation in the plane perpendicular to ranging.
TL;DR: A polarization-maintaining fiber-based polarization-sensitive optical low-coherence reflectometer for measurement of depth-resolved birefringence, where the linear bireFringence of a sample can be measured from data recorded in a single A scan.
Abstract: We describe a polarization-maintaining fiber-based polarization-sensitive optical low-coherence reflectometer for measurement of depth-resolved birefringence. Unlike for other fiber-based polarization-sensitive optical low-coherence reflectometers, here the linear birefringence of a sample can be measured from data recorded in a single A scan. Simultaneous measurement of retardation and orientation of birefringent axes with mica wave plates is demonstrated. The measured retardation is insensitive to sample rotation in the plane perpendicular to ranging.
TL;DR: In this article, the use of magnetically controlled birefringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves in the range of terahertz frequencies was presented.
Abstract: We present the use of magnetically controlled birefringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves in the range of terahertz frequencies. This device can be operated at room temperature. A maximum phase shift of 141° has been demonstrated at 1.025 THz and the results are in good agreement with theoretical predictions.
TL;DR: In this article, an optical torque can be induced on microscopic birefringent particles of calcite held by optical tweezers, which can either become aligned with the plane of polarization or spin with constant rotation frequency.
Abstract: Light-induced rotation of absorbing microscopic particles by transfer of angular momentum from light to the material raises the possibility of optically driven micromachines. The phenomenon has been observed using elliptically polarized laser beams or beams with helical phase structure. But it is difficult to develop high power in such experiments because of overheating and unwanted axial forces, limiting the achievable rotation rates to a few hertz. This problem can in principle be overcome by using transparent particles, transferring angular momentum by a mechanism first observed by Beth in 1936, when he reported a tiny torque developed in a quartz waveplate due to the change in polarization of transmitted light. Here we show that an optical torque can be induced on microscopic birefringent particles of calcite held by optical tweezers. Depending on the polarization of the incident beam, the particles either become aligned with the plane of polarization (and thus can be rotated through specified angles) or spin with constant rotation frequency. Because these microscopic particles are transparent, they can be held in three-dimensional optical traps at very high power without heating. We have observed rotation rates in excess of 350 Hz.
TL;DR: In this paper, the authors report the results of a recent investigation on the properties of a highly birefringent photonic crystal fiber including modal bireringence, mode field diameter, divergence angle and polarization mode dispersion, which are important for sensing and communication applications.
Abstract: We report the results of our recent investigation on the properties of a highly birefringent photonic crystal fiber including modal birefringence, mode field diameter, divergence angle, and polarization mode dispersion, which are important for sensing and communication applications.
TL;DR: The Stokes parameters determined from two orthogonal polarization components of the backscattered light allow the internal stress to be identified in terms of its magnitude and principal direction based on a birefringence light scattering model of glass/epoxy composites.
Abstract: We measure the spatial distribution of the mechanical stress induced inside translucent glass/epoxy composites by means of polarization-sensitive optical coherence tomography. The Stokes parameters determined from two orthogonal polarization components of the backscattered light allow the internal stress to be identified in terms of its magnitude and principal direction based on a birefringence light scattering model of glass/epoxy composites. Measurement examples show the particular case of stress concentration near a through hole and the internal structural damages caused by excessive tensile loading.
TL;DR: In this article, a free-standing microcavity structure, with different layer designs, has been fabricated and it has been shown that the cavity structure can show transmission resonances in the technologically relevant wavelength region of 1.55 μm with quality factors up to 3380.
Abstract: Porous silicon free-standing microcavity structures, with different layer designs, have been fabricated. Single microcavities show transmission resonances in the technologically relevant wavelength region of 1.55 μm with quality factors up to 3380. High-order cavities show sub-nm transmission peaks over the whole stop band. Coupled microcavity structures, where splitting of the degenerate cavity mode occurs, lead to multiple transmission peaks in a limited region of the stop band. We also report incident angle-dependent measurements, where transmission peak blueshift and splitting of transverse electric and transverse magnetic polarized modes due to porous silicon birefringence were observed.
TL;DR: A novel polarization-sensitive optical coherence tomography (PS-OCT) system was developed using polarization maintaining (PM) optical fibers and fiber coupler to measure birefringence properties of samples and has been applied to image biological sample.
Abstract: A novel polarization-sensitive optical coherence tomography (PS-OCT) system was developed using polarization maintaining (PM) optical fibers and fiber coupler to measure birefringence properties of samples. Polarization distortion due to PM fibers and coupler can be calibrated with different polarization states during two consecutive A-scans. By processing the analytical interference fringe signals derived from two orthogonal polarization detection channels, the system can be used to measure phase retardation and optic axis orientation. Standard wave plates with different orientation and retardation were used as samples to test the system and calibrating method. We have also applied this system to image biological sample such as beef tendon.
TL;DR: A method for measuring birefringence by use of thermal-light polarization-sensitive optical coherence tomography is presented and the detection scheme is described, together with a discussion of the validity domain of the equations used to evaluate the bireFringence in the presence of white-light illumination.
Abstract: A method for measuring birefringence by use of thermal-light polarization-sensitive optical coherence tomography is presented. The use of thermal light brings to polarization-sensitive optical coherence tomography a resolution in the micrometer range in three dimensions. The instrument is based on a Linnik interference microscope and makes use of achromatic quarter-wave plates. A mathematical representation of the instrument is presented here, and the detection scheme is described, together with a discussion of the validity domain of the equations used to evaluate the birefringence in the presence of white-light illumination.
TL;DR: Birefringence is minimized in various polymer optical devices by adjusting process conditions, because it degrades the performance of devices and this method minimizes it, independent of process conditions.
Abstract: We report a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to that of the polymer and has rod-shaped crystals that are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Birefringence is minimized in various polymer optical devices by adjusting process conditions, because it degrades the performance of devices. This method minimizes it, independent of process conditions, which potentially improves the productivity of devices.
TL;DR: It was found that x-ray diffraction is insensitive to the orientational distribution function's precise form, and the measured angular intensity distribution is described equally well by both Onsager's trial function and a Gaussian.
Abstract: The orientational distribution function of the nematic phase of suspensions of the semiflexible rodlike virus fd is measured by x-ray diffraction as a function of concentration and ionic strength. X-ray diffraction from a single-domain nematic phase of fd is influenced by interparticle correlations at low angle, while only intraparticle scatter contributes at high angle. Consequently, the angular distribution of the scattered intensity arises from only the single-particle orientational distribution function at high angle but it also includes spatial and orientational correlations at low angle. Experimental measurements of the orientational distribution function from both the interparticle ~structure factor! and intraparticle ~form factor! scattering were made to test whether the correlations present in interparticle scatter influence the measurement of the single-particle orientational distribution function. It was found that the two types of scatter yield consistent values for the nematic order parameter. It was also found that x-ray diffraction is insensitive to the orientational distribution function’s precise form, and the measured angular intensity distribution is described equally well by both Onsager’s trial function and a Gaussian. At high ionic strength, the order parameter S of the nematic phase coexisting with the isotropic phase approaches theoretical predictions for long semiflexible rods S50.55, but deviations from theory increase with decreasing ionic strength. The concentration dependence of the nematic order parameter also better agrees with theoretical predictions at high ionic strength indicating that electrostatic interactions have a measurable effect on the nematic order parameter. The x-ray order parameters are shown to be proportional to the measured birefringence, and the saturation birefringence of fd is determined enabling a simple, inexpensive way to measure the order parameter. Additionally, the spatial ordering of nematic fd was probed. Measurements of the nematic structure factor revealed a single large peak in contrast to nematics of rigid rods.
TL;DR: An instrument for measuring the magnitude of birefringence of tomographic images and the principal directions of axes that use thermal-light polarization-sensitive optical coherence tomography is described and typical results obtained with optical samples are presented.
Abstract: We describe an instrument for measuring the magnitude of birefringence of tomographic images and the principal directions of axes that uses thermal-light polarization-sensitive optical coherence tomography. The instrument permits full-field measurements with an axial resolution of 1.5 μm and a transverse resolution limited by diffraction. We obtained a sensitivity of 84 dB, limited by shot noise, when we integrated the signal for 1 s. We verified the validity of the measurement by measuring the birefringence of a variable phase shifter. We present typical results obtained with optical samples.
TL;DR: In this article, the authors used two orthogonally polarized He-Cd laser beams and subsequent annealing to obtain high thermal stability up to 150 °C diffracting the beam and converting the polarization state at the same time according to the theoretical expectation.
Abstract: Highly stable polarization gratings have been prepared in photocrosslinkable polymer liquid-crystal films by the use of two orthogonally polarized He–Cd laser beams and subsequent annealing. The resulting pure polarization gratings exhibiting thermal stability up to 150 °C diffract the beam and convert the polarization state at the same time according to the theoretical expectation.
TL;DR: This work has applied a retrogressive solution: mechanical light modulation by rotating a linear polarizer with respect to a quarter wave plate continuously tuned by tilting to the operating wavelength to anomalously birefringent crystals of 1,8-dihydroxyanthraquinone.
Abstract: A microscope was constructed for imaging circular dichroism of heterogeneous anisotropic media. To avoid linear biases that are common with electronic circular polarization modulation, we chose a retrogressive solution: mechanical light modulation by rotating a linear polarizer with respect to a quarter wave plate continuously tuned by tilting to the operating wavelength. Our comparatively slow technique succeeds with near-perfect circular input and signal averaging using a CCD camera. We have applied the method to anomalously birefringent crystals of 1,8-dihydroxyanthraquinone that are shown to have intergrown mirror image domains, undetected by X-ray diffraction because the twinning complexity renders differences in anomalous dispersion, already small, unreliable. The origin of the anomalous birefringence and the assignment of the absolute configuration are discussed.
TL;DR: In this article, a pig tendon was studied by the use of the conventional fibre-based optical coherence tomography (OCT) systems. And the results demonstrate that conventional OCT can be used to monitor the tissue birefringence.
Abstract: This paper addresses whether conventional fibre-based optical coherence tomography (OCT) is capable of obtaining birefringence information of well-organized tissues. For this purpose, a highly organized tissue, pig tendon, is studied by the use of the conventional fibre-based OCT systems. It is found that the tendons result in well-defined banded OCT images. The observed bands in the OCT images are sensitive to the wavelength of light source applied and phase retardation. The results demonstrate that conventional OCT can be used to monitor the tissue birefringence.
TL;DR: In this article, first principles of the linear and nonlinear optical properties of KDP and CO(NH2)2 are presented for two crystals considered, the resulting indices of refraction, birefringence, and non-linear optical coefficients are in good agreement with experiments.
Abstract: First-principles calculations of the linear and nonlinear optical properties of KH2PO4 (KDP) and CO(NH2)2 are presented. The calculations are an extension of methods we developed earlier and applied to borate crystals. Electronic band structure obtained from a pseudopotential method is input to the calculation. For two crystals considered, the resulting indices of refraction, birefringence, and nonlinear optical coefficients are in good agreement with experiments. The origin of nonlinear effects has been explained through real-space atom-cutting analysis. For KDP, the contributions of PO4 groups to second-harmonic generation effect are dominant, and the hydrogen bonds contribute much more to birefringence. For both KDP and urea, the contributions from the virtual electron process to nonlinear optical responses are dominant.
TL;DR: What is believed to be the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber is reported, which is highly compact and expected to be temperature stable.
Abstract: We report what we believe is the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber. Very high coupling efficiencies (as much as -23.5‐dB suppression of the input polarization) and loss of <0.02 dB were achieved for fibers as short as 11 mm. The filters, which we prepared by periodic mechanical twisting and heating with a scanned CO2 laser beam, are highly compact, and they are expected to be temperature stable.
TL;DR: A white-light spectral interferometric technique employing a low-resolution spectrometer for measurement of the dispersion of the group and phase modal birefringence in an elliptical-core optical system over a wide spectral range is presented.
Abstract: We present a white-light spectral interferometric technique employing a low-resolution spectrometer for measurement of the dispersion of the group and phase modal birefringence in an elliptical-core optical fiber over a wide spectral range. The technique utilizes a tandem configuration of a Michelson interferometer and the optical fiber to record a series of spectral interferograms and to measure the equalization wavelengths as a function of the optical path difference in the Michelson interferometer, or equivalently, the wavelength dependence of the group modal birefringence in the optical fiber. Applying a polynomial fit to the measured data, the wavelength dependence of the phase modal birefringence can also be determined.