Showing papers on "Birefringence published in 2002"
TL;DR: The theory and calculation of the Stokes vector of light reflected from turbid media is described, application of PS-OCT to contemporary biomedical imaging problems is given and effect of multiple scattering and speckle on the accuracy and noise of the computed Stokes parameters is discussed.
Abstract: Polarization sensitive optical coherence tomography (PS-OCT) provides depth resolved measurements of the polarization state of light reflected from turbid media such as tissue. The theory and calculation of the Stokes vector of light reflected from turbid media is described and application of PS-OCT to contemporary biomedical imaging problems is given. Measurement of the depth resolved Stokes parameters allows determination of the degree of polarization and optical axis orientation in turbid media that can be modeled as a linear retarder. Effect of multiple scattering and speckle on the accuracy and noise of the computed Stokes parameters is discussed. Future directions for development of PS-OCT instrumentation for biological and medical applications is given.
536 citations
Patent•
05 Mar 2002
TL;DR: In this article, an optical coherence tomography (OCT) device was proposed, which irradiates a biological tissue with low coherence light, obtains a high resolution tomogram of the inside of the tissue by low-coherent interference with scattered light from the tissue, and is provided with an optical probe which includes an optical fiber having a flexible and thin insertion part for introducing the low coherent light.
Abstract: An Optical Coherence Tomography (OCT) device irradiates a biological tissue with low coherence light, obtains a high resolution tomogram of the inside of the tissue by low-coherent interference with scattered light from the tissue, and is provided with an optical probe which includes an optical fiber having a flexible and thin insertion part for introducing the low coherent light. When the optical probe is inserted into a blood vessel or a patient's body cavity, the OCT enables the doctor to observe a high resolution tomogram. In a optical probe, generally, a fluctuation of a birefringence occurs depending on a bend of the optical fiber, and this an interference contrast varies depending on the condition of the insertion. The OCT of the present invention is provided with polarization compensation means such as a Faraday rotator on the side of the light emission of the optical probe, so that the OCT can obtain the stabilized interference output regardless of the state of the bend.
453 citations
TL;DR: The ability to discriminate among different patterns of fibrillar orientation, as exemplified by tendon, fascia, cornea, and successive lamellar rings in an intervertebral disc, is demonstrated.
377 citations
TL;DR: The OCT system successfully reveals the birefringent nature of human skin tissue through the measurement of the distribution of each element of the Müller matrix of a measured object from 16 OCT images.
Abstract: We have developed a spectral interferometric optical coherence tomography (OCT) system with polarization sensitivity that is able to measure a two-dimensional tomographic image by means of one-dimensional mechanical scanning. Our system, which has an axial resolution of 32 mum , calculates the distribution of each element of the Muller matrix of a measured object from 16 OCT images. The OCT system successfully reveals the birefringent nature of human skin tissue.
289 citations
TL;DR: D Degree of polarization, Stokes parameters, and diffuse reflectance as functions of linearly birefringent parameters based on numerical results and theoretical analysis are discussed and compared in an effort to understand the essential physical processes of polarized light propagation in fibrous tissues.
Abstract: A detailed study, based on a Monte Carlo algorithm, of polarized light propagation in birefringent turbid media is presented in this paper. Linear birefringence, which results from the fibrous structures, changes the single scattering matrix and alters the polarization states of photons propagating in biological tissues. Some Mueller matrix elements of light backscattered from birefringent anisotropic turbid media present unusual intensity patterns compared with those for nonbirefringent isotropic turbid media. This result is in good agreement with the analytic results based on the double-scattering model. Degree of polarization, Stokes parameters, and diffuse reflectance as functions of linearly birefringent parameters based on numerical results and theoretical analysis are discussed and compared in an effort to understand the essential physical processes of polarized light propagation in fibrous tissues.
287 citations
Journal Article•
TL;DR: In eyes with a normal macula, the magnitude and axis of anterior segment birefringence can be determined from a polarimetry image of the Henle fiber layer and individualized anterior segment compensation can be achieved.
Abstract: Purpose To describe a method for assessment and individualized compensation of anterior segment birefringence with scanning laser polarimetry. Methods A scanning laser polarimeter (GDx Nerve Fiber Analyzer; Laser Diagnostic Technologies, Inc., San Diego, CA) was modified to accommodate a variable compensator. The magnitude and axis of anterior segment birefringence of normal eyes were determined from a polarimetry image of the Henle fiber layer. The variable compensator was then adjusted to minimize anterior segment birefringence. Retinal nerve fiber layer (RNFL) and macular measurements were then obtained. Macular images with individualized compensation served to verify the effectiveness of the compensation. To demonstrate individualized compensation, two sets of three images each were obtained from four eyes of four normal subjects. One set was obtained with individualized compensation and another with fixed compensation, as used in the commercial polarimetry system. Results In the tested eyes, the magnitude of anterior segment birefringence ranged from 21.7 to 86.3 nm, and the slow axis ranged from 5.7 degrees nasally upward to 54.3 degrees nasally downward. The maximum residual retardation resulting from compensation was 70 nm for fixed compensation and 11.5 nm for individualized compensation. The compensation residual directly affected the assessment of the RNFL by scanning laser polarimetry. RNFL images obtained with individualized compensation were more consistent with the expected anatomy of the eye. In the eyes measured, the range of RNFL thicknesses appeared to be narrower with the variable corneal and lens compensator (VCC) compared with the fixed corneal compensator (FCC). Conclusions In eyes with a normal macula, the magnitude and axis of anterior segment birefringence can be determined from a polarimetry image of the Henle fiber layer. Individualized anterior segment compensation can be achieved with the described method so that the measured birefringence largely reflects the RNFL birefringence. Whether and how macular diseases affect this method remain to be investigated.
281 citations
TL;DR: This work built a fiber-based PS-OCT setup that produces quasi-real-time images of the human retina in vivo and preliminary measurements showed that the double-pass phase retardation per unit depth of the RNFL near the optic nerve head is 39±6°/100 µm.
Abstract: To our knowledge, this is the first demonstration of in vivo depth-resolved birefringence measurements of the human retinal nerve fiber layer (RNFL) by use of polarization-sensitive optical coherence tomography (PS-OCT). Because glaucoma causes nerve fiber layer damage, which may cause loss of retinal birefringence, PS-OCT is a potentially useful technique for the early detection of glaucoma. We built a fiber-based PS-OCT setup that produces quasi-real-time images of the human retina in vivo. Preliminary measurements of a healthy volunteer showed that the double-pass phase retardation per unit depth of the RNFL near the optic nerve head is 39±6°/100 µm.
278 citations
TL;DR: The experimental results show that this OCT system can be effectively applied to the measurement of soft tissues, which are less stable than hard tissues, and Polarization parameters such as diattenuation, birefringence, and orientation of the fast axis can be extracted through decomposition of the measured Jones matrix.
Abstract: Two-dimensional depth-resolved Jones-matrix images of scattering biological tissues were measured with novel double-source double-detector polarization-sensitive optical coherence tomography (OCT). The Jones matrix can be determined in a single scan with this OCT system. The experimental results show that this system can be effectively applied to the measurement of soft tissues, which are less stable than hard tissues. Polarization parameters such as diattenuation, birefringence, and orientation of the fast axis can be extracted through decomposition of the measured Jones matrix. The Jones matrix of thermally treated porcine tendon showed a reduction of birefringence from thermal damage. The Jones matrices of porcine skin and bovine cartilage also revealed that the density and orientation of the collagen fibers in porcine skin and bovine cartilage are not distributed as uniformly as in porcine tendon. Birefringence is sensitive to changes in tissue because it is based on phase contrast.
242 citations
01 Nov 2002
TL;DR: In this article, the authors present a general description of wave propagation in nonlinear media, including high-resolution nonlinear optical spectroscopy, and four-wave mixing and mixing.
Abstract: Introduction. Nonlinear Optical Susceptibilities. General Description of Wave Propagation in Nonlinear Media. Electrooptical and Magnetooptical Effects. Optical Rectification and Optical Field-Induced Magnetization. Sum-Frequency Generation. Harmonic Generation. Difference Frequency Generation. Parametric Amplification and Oscillation. Stimulated Raman Scattering. Stimulated Light Scattering. Two-Photon Absorption. High-Resolution Nonlinear Optical Spectroscopy. Four-Wave Mixing. Four-Wave Mixing Spectroscopy. Optical-Field-Induced Birefringence. Self-Focusing. Multiphoton Spectroscopy. Detection of Rare Atoms and Molecules. Laser Manipulation of Particles. Transient Coherent Optical Effects. Strong Interaction of Light with Atoms. Infrared Multiphoton Excitation and Dissociation of Molecules. Laser Isotope Separation. Surface Nonlinear Optics. Nonlinear Optics in Optical Waveguides. Optical Breakdown. Nonlinear Optical Effects in Plasmas. Index.
229 citations
TL;DR: In this article, a weak probe beam was used to analyze the birefringence induced in a room temperature vapour by a strong counter-propagating circularly polarized pump beam.
Abstract: We study polarization spectroscopy of Rb vapour. A weak probe beam analyses the birefringence induced in a room temperature vapour by a strong counterpropagating circularly polarized pump beam. In contrast to most other work on polarization spectroscopy, we use a polarization beam splitting cube and two detectors (rather than a polarizer and one detector) to analyse the probe beam. The signal is in the form of a derivative of a Lorentzian. For theoretical analysis we study the closed atomic transition 5 2S1/2 (F = 3) → 5 2P3/2 (F' = 4) in the D2 line of 85Rb. We study the time needed to redistribute population among the mF states, derive an expression for the expected lineshape and present experimental data in excellent agreement with theory. The polarization spectrum provides an ideal error signal for frequency stabilization of a laser. We describe the geometry and parameters for optimizing the error signal.
222 citations
TL;DR: It is demonstrated that tissue structure, birefringence, and blood flow can be imaged simultaneously by use of techniques of polarization-sensitive optical coherence tomography and phase-resolved optical Doppler tomography.
Abstract: We demonstrate that tissue structure, birefringence, and blood flow can be imaged simultaneously by use of techniques of polarization-sensitive optical coherence tomography and phase-resolved optical Doppler tomography An efficient data-acquisition procedure is implemented that optimizes the concurrent processing and display of all three image types Images of in vivo human skin acquired with a high-speed fiber-based system are presented
ETSI1
TL;DR: In this paper, the authors demonstrate theoretically and experimentally how fiber Bragg gratings can be valuable tools for monitoring composite structures in service, and for obtaining the internal stress and strain states in laminates.
TL;DR: A phase-resolved functional optical coherence tomography system that can simultaneously yield in situ images of tissue structure, blood flow velocity, standard deviation, birefringence, and the Stokes vectors in human skin is described.
Abstract: We describe a phase-resolved functional optical coherence tomography system that can simultaneously yieldin situ images of tissue structure, blood flow velocity, standard deviation, birefringence, and the Stokes vectors in human skin. Multifunctional images were obtained by processing of analytical interference fringe signals derived from two perpendicular polarization-detection channels. The blood flow velocity and standard deviation images were obtained by comparison of the phases from pairs of analytical signals in neighboring A-lines in the same polarization state. The analytical signals from two polarization-diversity detection channels were used to determine the four Stokes vectors for four reference polarization states. From the four Stokes vectors, the birefringence image, which is not sensitive to the orientation of the optical axis in the sample, was obtained. Multifunctional in situ images of a port wine stain birthmark in human skin are presented.
TL;DR: M maskless, single-step fabrication of strongly birefringent Fresnel zone plates by focusing of femtosecond laser pulses deep within silica substrates is demonstrated.
Abstract: We demonstrate maskless, single-step fabrication of strongly birefringent Fresnel zone plates by focusing of femtosecond laser pulses deep within silica substrates. The process allows us to produce alternate zone rings directly by inducing a local refractive-index modification of the order of n~10-2 . The embedded zone plates shown in this Letter exhibit efficiencies that vary by as much as a factor of ~6 for orthogonal polarizations. Focal lengths of primary and secondary foci are shown to compare well with theory.
TL;DR: It is shown that this method can be used to image and measure the distribution of the polarization state at the surface of a specimen, and the obtained results indicate that precise quantitative measurements of the polarized state can be achieved.
Abstract: We present what we believe to be a new digital holographic imaging method that is able to determine simultaneously the distributions of intensity, phase, and polarization state at the surface of a specimen on the basis of a single image acquisition. Two reference waves with orthogonal polarization states interfere with the object wave to create a hologram that is recorded on a CCD camera. Two wave fronts, one for each perpendicular polarization state, are numerically reconstructed in intensity and phase. Combining the intensity and the phase distributions of these two wave fronts permits the determination of all the components of the Jones vector of the object-wave front. We show that this method can be used to image and measure the distribution of the polarization state at the surface of a specimen, and the obtained results indicate that precise quantitative measurements of the polarization state can be achieved. An application of the method to image the birefringence of a stressed polymethyl methacrylate sample is presented.
TL;DR: In this article, the Fourier transform spectral densities of these responses are presented for each liquid and are interpreted in terms of the molecular and interaction-induced contributions to the many-body polarizability.
Abstract: Spatially masked optical Kerr effect (SM-OKE) spectroscopy is a nonresonant femtosecond pump–probe technique capable of measuring isotropic contributions to the transient birefringence of molecular liquids. In conjunction with traditional optical-heterodyne-detected optical Kerr effect spectroscopy, polarization-selective SM-OKE measurements are used to experimentally measure the anisotropic and isotropic third-order nonlinear response of CS2, acetonitrile, methanol, and water. These two responses, which allow the intermolecular dynamics to be separated by symmetry, form a complete and independent basis for describing the polarization dependence of nonresonant third-order experiments. The Fourier transform spectral densities of these responses are presented for each liquid and are interpreted in terms of the molecular and interaction-induced contributions to the many-body polarizability. The molecular contributions are suppressed in the isotropic response for all liquids, while the line shape in the inter...
Patent•
04 Oct 2002
TL;DR: An electroactive lens (100, 200, 300) as discussed by the authors can include first (110, 115, 120, 122, 125) and second (135, 137, 140, 145, 150) electroactive cells, having controlled birefringence (e.g. a Nematic liquid crystal) the cells being adjacent to and stacked upon each other and, when in a resting state, oriented orthogonal to each other to reduce birerringence.
Abstract: An electro-active lens (100, 200, 300) that may include first (110, 115, 120, 122, 125) and second (135, 137, 140, 145, 150) electro-active cells, having controlled birefringence (e.g. a Nematic liquid crystal) the cells being adjacent to and stacked upon each other and, when in a resting state, oriented orthogonal to each other to reduce birefringence.
TL;DR: In this paper, polarization beam-splitters and optical switches based on subwavelength quasi-periodic structures are presented. And they show experimental results for infra-red radiation at a wavelength of 10.6 μm.
Patent•
30 Apr 2002
TL;DR: In this paper, an optical film is provided, which displays a positive wavelength dependency across the entire wavelength region from 400 to 800 nm, and is capable of imparting a specified retardation to transmitted light with a single sheet of film.
Abstract: An optical film is provided, which displays a positive wavelength dependency across the entire wavelength region from 400 to 800 nm, and is capable of imparting a specified retardation to transmitted light with a single sheet of film. The optical film particularly, includes a thermoplastic norbornene-based resin with a specified structure formed of a structural unit (I) which imparts a positive birefringence and a structural unit (II) which imparts a negative birefringence, and which satisfies particular conditions with respect to ΔNI(λ), ΔNII(λ), ΔNI(800) and ΔNII(800) wherein ΔNI(λ) and ΔNII(λ) represent the difference between a refractive index Nx(λ) in an x axis direction at a wavelength λ, and a refractive index Ny(λ) in a y axis direction, and ΔNI(800) and ΔNII(800) represent the difference in refractive indexes at a wavelength of 800 nm, and the x axis represents the stretching direction and the y axis represents the in-plane direction perpendicular to the x direction.
TL;DR: A simple model of SLP suggests an algorithm for calculating birefringence that, unlike previous methods, uses all of the data available in the images to achieve better signal-to-noise ratio and lower sensitivity to depolarization.
Abstract: Scanning laser polarimetry (SLP), a technology for glaucoma diagnosis, uses imaging polarimetry to detect the birefringence of the retinal nerve fiber layer. A simple model of SLP suggests an algorithm for calculating birefringence that, unlike previous methods, uses all of the data available in the images to achieve better signal-to-noise ratio and lower sensitivity to depolarization. The uncertainty of the calculated retardance is estimated and an appropriate averaging strategy to reduce uncertainty is demonstrated. Averaging over a large area of the macula of the eye is used in a new method for determining anterior segment birefringence.
TL;DR: The first observation of a new optical phenomenon, magnetoelectric directional anisotropy (MEA), which occurs in crossed electric field E and magnetic field B perpendicular to the wave vector k of the light is reported.
Abstract: We report the first observation of a new optical phenomenon, magnetoelectric directional anisotropy (MEA). MEA is a polarization-independent anisotropy which occurs in crossed electric field E and magnetic field B perpendicular to the wave vector k of the light. It is described by a contribution to the refractive index of the form (delta)n=(gamma)k x E x B. Our experiment was performed on a Er(1.5)Y(1.5)Al(5)O(12) crystal, but MEA should exist in all media. The relation of this new effect with recently discovered magnetoelectric birefringence is discussed.
TL;DR: It is shown that laser tweezers stably trap thin coinlike microdisks in 3D with an edge-on orientation and measures its harmonically bound Brownian rotation over 5 decades in time.
Abstract: Nonspherical particles can uniquely probe soft system dynamics. We show that laser tweezers stably trap thin coinlike microdisks in 3D with an edge-on orientation. Scattered light forms a streak that we track using a fast camera to measure the disk's angular displacement. Linearly polarized tweezers rotationally trap a birefringent disk, and we measure its harmonically bound Brownian rotation over 5 decades in time. Near a surface, the disk exhibits a translational-orientational switchback oscillation. Circularly polarized tweezers rotate the disk and streak, yielding a colloidal lighthouse.
TL;DR: In this paper, the performance of various polarizer designs using α-barium borate has been compared with the experimental investigation of a manufactured device, and the results are presented that compare theory with experimental investigation.
Abstract: Until recently, the construction of polarizers for operation below ∼260 nm were limited to materials such as magnesium fluoride and crystalline quartz. These materials have a much smaller birefringence than calcite, but unlike calcite they have good transmission below 200 nm. These materials are, however, not well suited for Glan-Taylor-type polarizer designs, as they do not produce a large angular separation of the polarized components. A new material, α-barium borate, has recently become available, which transmits to just below 200 nm and has a birefringence that approaches that of calcite. We analyze the performance of various polarizer designs that use this material. Results are presented that compare theory with experimental investigation of a manufactured device.
TL;DR: In this paper, a cavity ring-down polarimetry (RSDP) was proposed for probing circular birefringence (nonresonant rotatory dispersion) and circular dichroism with unprecedented sensitivity.
Abstract: Detailed theoretical analyses are presented for cavity ring-down polarimetry, a recently developed scheme for probing circular birefringence (nonresonant rotatory dispersion) and circular dichroism (resonant differential absorption) with unprecedented sensitivity. Aside from elucidating the nature of time-resolved signals generated by various modes of operation, the influence of instrumental imperfections on polarimetric response is examined. The unique ability of cavity ring-down polarimetry to interrogate nonresonant optical activity in low-pressure chiral vapors is demonstrated by extracting specific rotation parameters at two complementary excitation wavelengths (355 nm and 633 nm) for gaseous samples of α-pinene, β-pinene, and cis-pinane. The resulting isolated-molecule properties are contrasted with those derived from conventional solution-phase experiments and state-of-the-art ab initio calculations.
TL;DR: In this paper, it was shown that the closure of the effective constitutive tensor is necessary and sufficient for the absence of birefringence, i.e., for the existence of a unique light cone structure.
Abstract: We study wave propagation in local nonlinear electrodynamical models. Particular attention is paid to the derivation and the analysis of the Fresnel equation for the wave covectors. For the class of local nonlinear Lagrangian nondispersive models, we demonstrate how the originally quartic Fresnel equation factorizes, yielding the generic birefringence effect. We show that the closure of the effective constitutive (or jump) tensor is necessary and sufficient for the absence of birefringence, i.e., for the existence of a unique light cone structure. As another application of the Fresnel approach, we analyze the light propagation in a moving isotropic nonlinear medium. The corresponding effective constitutive tensor contains nontrivial skewon and axion pieces. For nonmagnetic matter, we find that birefringence is induced by the nonlinearity, and derive the corresponding optical metrics.
TL;DR: Detailed experimental and numerical results for birefringence tuning in microstructured optical fibers are presented and the symmetry properties of the modes for different waveguide structures are studied.
Abstract: We present detailed experimental and numerical results for birefringence tuning in microstructured optical fibers. Index tunable polymer is infused into specific air-holes to obtain birefringence whose tunability is achieved by temperature tuning the polymer index. We also study the symmetry properties of the modes for different waveguide structures.
TL;DR: In this paper, the autocloning technique is used to fabricate photonic crystals for the visible range by the "autocloning" technique, in which multilayers are stacked by an appropriate combination of sputter deposition and sputter etching.
Abstract: We fabricate photonic crystals for the visible range by the ‘autocloning’ technique, in which multilayers are stacked by an appropriate combination of sputter deposition and sputter etching. TiO2/SiO2 and Ta2O5/SiO2 are chosen as materials since they are transparent in the range and give a high contrast of refractive indices. The fabrication technique has flexibility regarding materials and size and is very reliable and reproducible even if the pitch is less than 0.2 μm. We also study the application of photonic crystals to birefringent elements such as waveplates and polarization selective gratings and experimentally verify that they are useful for optical pick-up systems.
TL;DR: In this paper, two s-polarized (s+s) writing beams in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) were studied by means of photoinduced change in alignment of PLCs.
Abstract: Formation of intensity gratings was studied with two s-polarized (s+s) writing beams in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) by means of photoinduced change in alignment of PLCs. Remarkable differences were observed between these two PLCs. T-AB showed higher values of the diffraction efficiency (η) and a faster response than CB-AB. In photoinduced alignment behavior of the PLCs, T-AB exhibited a faster change in alignment than CB-AB with the value of η about 30% in the Raman−Nath regime and the maximum value for modulation of the refractive index (Δn‘) of about 0.08. It was revealed that η and Δn‘ are dependent on the structure of the mesogenic unit. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the T-AB films. The 3-D object was reconstructed with high resolution (>5000 lines/mm).
TL;DR: A simple correspondence between the paraxial propagation formulas along the optical axis of a uniaxial crystal and inside an isotropic medium is found in the case of beams with linearly polarized circularly symmetric boundary distributions.
Abstract: A simple correspondence between the paraxial propagation formulas along the optical axis of a uniaxial crystal and inside an isotropic medium is found in the case of beams with linearly polarized circularly symmetric boundary distributions. The electric fields of the ordinary and the extraordinary beams are related to the corresponding expressions in a medium with refractive index no and ne2/no, where no and ne are the ordinary and the extraordinary refractive indexes, respectively. Closed-form expressions for Laguerre–Gauss and Bessel–Gauss beams propagating through an anisotropic crystal are given.
Patent•
11 Jan 2002TL;DR: In this article, a dual channel optical reflectometer composed of four separate paths (100, 102, 104 and 106) interconnected through a path coupler (108) is presented.
Abstract: One form of the present invention is a dual channel optical reflectometer composed of four separate paths (100, 102, 104 and 106), interconnected through a path coupler (108). The source path (100), optically connected to the path coupler (108), is comprised of a light source (110) that is optically coupled to a birefringent optical fiber (112). A depolarizer (114) is placed in-line in the optical fiber (112) and is of sufficient length (116) to insure complete decorrelation with independent phase components that are separated by virtue of the birefringent nature of the optical fiber (112). The reference path (102) is comprised of another birefringent optical fiber (118) that is optically connected to the path coupler (108) on one end, and has the other end optically aligned with a collimating lens (120) that collimates the light emitted from the second end of optical fiber (118) into a scanning delay line (122).