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Showing papers on "Birefringence published in 1992"


Journal ArticleDOI
TL;DR: In this article, a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample is presented.
Abstract: We present a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample. The device is insensitive to the rotation of the sample in the plane perpendicular to ranging. Phase measurement accuracy is ±0.86°, but the reflectometer can distinguish local variations in birefringence as small as 0.05° with a distance resolution of 10.8 μm and a dynamic range of 90 dB. Birefringence-sensitive ranging in a wave plate, an electro-optic modulator, and a calf coronary artery is demonstrated.

621 citations


Journal ArticleDOI
TL;DR: In this paper, nonlinear birefringence effects in a fiber ring laser cavity have been exploited to produce selfstarting, passive mode-locking to give 1.5 ps soliton pulses.
Abstract: Nonlinear birefringence effects in a fibre ring laser cavity have been exploited to produce selfstarting, passive mode-locking to give 1.5 ps soliton pulses.

451 citations


Journal ArticleDOI
TL;DR: In this paper, optically induced reorientation of the azoaromatic molecules will have wide applications in image recording and in electro-optical devices, and the resulting polarization information is easily detected and exhibits long-term stability.
Abstract: Dichroism and birefringence are shown to be optically induced and erased in high‐glass‐transition azoaromatic polymers. The resulting polarization information is easily detected and exhibits long‐term stability. This optically induced reorientation of the azoaromatic molecules will have wide applications in image recording and in electro‐optical devices.

306 citations


Journal ArticleDOI
TL;DR: In this article, the scaling limits of diode-end-pumped Nd:YAG laser are analyzed by pumping geometry, thermal distortion, birefringence, and fracture.
Abstract: The authors analyze the scaling limits of diode-end-pumped Nd:YAG lasers imposed by pumping geometry, thermal distortion, birefringence, and fracture. A scalable 15-W output power diode-end-pumped laser which achieves a 60% slope efficiency is demonstrated. Thermal distortion in this laser is reduced from 2.6 waves to less than 0.15 waves with an aspheric laser rod. Depolarization is reduced by 40 times to less than 0.2% per pass using optical rotators. Modeling results, which accurately predict thermal distortion and birefringence, imply a thermal fracture-limited output power for short end-pumped rods less than 45 W. A dual rod design for an 80-W device is described. One of the four modules in this device has been assembled and tested, producing a CW output of 22.5 W. >

280 citations


Journal ArticleDOI
TL;DR: The hypothesis that the thickness of the form birefringent retinal nerve fiber layer can be assessed by ellipsometric methods is supported.
Abstract: A retinal laser ellipsometer has been developed by coupling a Fourier ellipsometer to a laser scanning system. The instrument has been used to assess the origin and the amount of change in the state of polarization of a laser beam that has double passed the retina around the optic nerve head of postmortemhuman eyes. Eight eyes with no history of glaucoma were studied. At 200 points around the optic nerve head of each eye the Mueller matrices of the retina were examined for the amount of retardation, the orientation of the optic axis, and the amount of dichroism. The degree of polarization preservation of the detected light varied between 50% and 87%. Little dichroism was found, and there was no obvious correlation to the physical arrangement of any retinal structure. However, there was a substantial amount of linear uniaxial birefringence with the optic axis perpendicular to the incident laser beam. Furthermore the calculated optic axis direction showed a strong correlation with the physical orientation of the radial symmetrically arranged retinal nerve fiber axons around the optic nerve head. The local distribution of the corresponding retardation values showed two maxima that coincided with the areas of the thickest retinal nerve fiber layer. These results support the hypothesis that the thickness of the form birefringent retinal nerve fiber layer can be assessed by ellipsometric methods.

242 citations


Journal ArticleDOI
TL;DR: A wavelength-division multiplexer with no polarization dependence is demonstrated, based on an arrayed-waveguide grating fabricated with silica-based optical waveguides on a silicon substrate, designed to operate in the 115th order for high wavelength resolution.
Abstract: A wavelength-division multiplexer with no polarization dependence is demonstrated. It is based on an arrayed-waveguide grating fabricated with silica-based optical waveguides on a silicon substrate. The polarization dependence that is due to the birefringence of the waveguide is eliminated by inserting a quartz λ/2 plate in the middle of the arrayed waveguide. Moreover the grating is designed to operate in the 115th order for high wavelength resolution. The polarization insensitivity and the high resolution lead to the successful multiplexing of 13 wavelength channels with 1-nm spacing. A passband width of 0.3 nm and a cross-talk level of −30 dB are achieved.

166 citations


Journal ArticleDOI
TL;DR: In this paper, nonlinear birefringence effects in an all-fibre ring laser cavity have been exploited to produce self-starting passive mode-locking with pulse durations lying in the nanosecond region.

123 citations


Journal ArticleDOI
TL;DR: In this paper, two ways of analyzing the polarization mode dispersion with random coupling in standard single-mode fibers are presented, one based on principal polarization states and the other based on unpolarized short pulses split by local birefringence.

121 citations


Journal ArticleDOI
D. Boese1, H. Lee1, Do Y. Yoon1, Jerome D. Swalen1, J. F. Rabolt1 
TL;DR: In this article, the in-plane and out-of-plane dielectric properties of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) were investigated by optical waveguide, ultraviolet-visible (UV-VIS), infrared (IR), and dielectrics spectroscopy.
Abstract: Thin films of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, ultraviolet-visible (UV-VIS), infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n∥ = 1.806 and the out-of-plane index n⊥ = 1.589 at 1064 nm wavelength. No discernible effect of the film thickness on this optical anisotropy is found between films of ca. 2.1 and ca. 7.8 μm thickness. This large birefringence is attributed to the preferential orientation of the biphenyltetracarboximide moieties with their planes parallel to the film surface, coupled with the strong preference of BPDA-PDA chains to align along the film plane. The frequency dispersion of the in-plane refractive index n∥ is consistent with the results calculated by the Lorentz–Lorenz equation from the UV-visible spectrum exhibiting several absorption bands in the 170–500 nm region. The contribution from the IR absorption in the range 7000–400 cm,−1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.046 to the in-plane refractive index n∥. Tilt-angle–dependent polarized IR results indicate nearly the same increase for the out-of-plane index n⊥. Application of the Maxwell relation then leads to the out-of-plane dielectric constant e⊥ ≃ 2.7 at 1.2 × 1013 Hz, as compared with the measured value of ca. 3.0 at 106 Hz. Assuming this small difference to remain the same for the in-plane dielectric constants e∥, we obtain a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant e∥ ≃ 3.4 at 1.2 × 1013 Hz, and e∥ ≃ 3.7 at 106 Hz. © 1992 John Wiley & Sons, Inc.

118 citations


Patent
15 May 1992
TL;DR: In this article, discretely and continuously tunable single and multiple-stage polarization interference filters employing chiral smectic liquid crystal cells as electronically rotatable retarders are provided.
Abstract: Discretely and continuously tunable single and multiple-stage polarization interference filters employing chiral smectic liquid crystal cells as electronically rotatable retarders are provided. Discretely tunable filters of this invention include those which employ bistable surface-stabilized ferroelectric liquid crystal cells. Continuously tunable filters of this invention include those that employ chiral smectic A ferroelectric liquid crystal cells. Single stage filters include fixed birefringent elements in combination with chiral smectic liquid crystal cells and multiple stage filters can include only chiral smectic liquid crystal cells or can include chiral smectic liquid crystal cells in combination with fixed birefringent elements. Blocking filters useful for color generation and color displays are also provided. The FLC filters provided can be temporally multiplexed.

114 citations


Journal ArticleDOI
TL;DR: The study reveals that Hi-Bi fibers are insensitive to light polarized along the fast axis, in contrast to Lo- bi fibers, which are photosensitive along both axes, and the significance of the results to models based on stress and/or glass defects is briefly discussed.
Abstract: A study of photoinduced birefringence in bow-tie (stress-induced) high-birefringence (Hi-Bi) and low-birefringence (Lo-Bi) germanosilicate optical fibers is conducted by using 532-nm light. The study reveals that Hi-Bi fibers are insensitive to light polarized along the fast axis, in contrast to Lo-Bi fibers, which are photosensitive along both axes. The induced birefringence in Lo-Bi fibers is reversible, whereas the change in Hi-Bi fibers is permanent. The sign of the induced birefringence is established experimentally for the first time to our knowledge, and the significance of the results to models based on stress and/or glass defects is briefly discussed.

Journal ArticleDOI
TL;DR: In this article, it was shown that the optical damage resistance of undoped LiNbO3 is increased with an increase in the Nb content of the crystal, and that the crystal quality, as represented by x-ray rocking curve peak width, has no correlation with the Optical damage resistance.
Abstract: Lithium niobate single crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varying between 45.5–58 mol % Li2O. Their optical damage resistance was characterized by measurement of the photoinduced birefringence change. Their crystal quality was characterized by x‐ray topography and x‐ray rocking curves. The photoinduced birefringence change increased with an increase in the Li content of the crystal. The Li‐poor crystals, which were richer in Nb content than the crystal with the congruent composition, showed the smallest birefringence change, in spite of the fact that the x‐ray rocking curve width of these Li‐poor crystals was much wider than the congruent crystal. It is concluded that the optical damage resistance of undoped LiNbO3 is increased with an increase in the Nb content of the crystal, and that the crystal quality, as represented by x‐ray rocking curve peak width, has no correlation with the optical damage resistance.

Journal ArticleDOI
TL;DR: In this article, the order-to-disorder transition (ODT) in a concentrated solution of a polystyrene-polyiso- prene diblock copolymer (molecular weights of the poly styrene and polyisoprene blocks are 1.2 X l(r and 1.9 x lo4, respectively) in bis(2-ethylhexyl) phthalate is identified by a discontinuous decrease in the static birefringence of the sample upon heating.
Abstract: The order-to-disorder transition (ODT) in a concentrated solution of a polystyrene-polyiso- prene diblock copolymer (molecular weights of the polystyrene and polyisoprene blocks are 1.2 X l(r and 1.9 x lo4, respectively) in bis(2-ethylhexyl) phthalate is identified by a discontinuous decrease in the static birefringence of the sample upon heating. The location of the ODTis confirmed by rheologicalmeasurements; both the storage and loss moduli of the solution show a sharp decrease at the same temperature. Solutions with concentrations ranging from 48 to 61 wt 95 polymer were examined with the birefringence technique. The measured ODT temperatures for these solutions range from 27 to 178 "C. Small-angle X-ray scattering measurements at temperatures well below the ODT indicate that the ordered solutions have a lamellar microstructure.

Journal ArticleDOI
TL;DR: In this article, the use of a Faraday mirror in a double-pass design yields optical gain with high efficiency, without spatial hole burning and independent of gain-fibre birefringence.
Abstract: A novel single-polarisation fibre amplifier design is presented. The use of a Faraday mirror in a double-pass design yields optical gain with high efficiency, without spatial hole burning and independent of gain-fibre birefringence. An amplifier, tunable polarised laser, and a high-power polarised super-fluorescent source are demonstrated.

Journal ArticleDOI
TL;DR: In this paper, the authors derived the gain for mixed Stokes and anti-Stokes waves propagating in a birefringent fiber under the combined action of parametric four-photon mixing and Raman scattering, for different types of phase matching.
Abstract: We derive the gain for mixed Stokes and anti-Stokes waves propagating in a birefringent fiber in the presence of an intense pump wave, under the combined action of parametric four-photon mixing and Raman scattering, for different types of phase matching. We discuss the conditions for the suppression or the enhancement of the Raman gain as a function of the linear mismatch and of the sideband detuning, owing to coupling between Stokes and anti-Stokes components of the growing wave. We confirm the analytical predictions of the linearized analysis with the numerical solution of the coupled nonlinear Schrodinger equations, including the contribution of the tensorial Raman response of the fiber.

Journal ArticleDOI
TL;DR: In this paper, a source or detector of visible light having dimensions much smaller than the wavelength, λ, in the near-field of the sample was placed to increase the resolution of optical microscopy.
Abstract: The resolution of optical microscopy can be extended beyond the diffraction limit by placing a source or detector of visible light having dimensions much smaller than the wavelength, λ, in the near‐field of the sample (<λ/10). This technique, near‐field scanning optical microscopy, is sensitive to a variety of important sample properties including optical density, refractive index, luminescence, and birefringence. Although image contrast based on certain sample characteristics is similar to that observed in traditional optical microscopy, strong coupling between the probe and sample often produces contrast unique to the near‐field.

Patent
10 Jan 1992
TL;DR: In this paper, a method for preparing a polymer-dispersed liquid crystal (PDLC) device in general is also disclosed, which displays a variable grey scale which has a uniform optical transmission.
Abstract: A polymer-dispersed liquid crystal device comprises a multiplicity of droplets of a birefringent, functionally nematic liquid crystal material dispersed in a matrix comprising the reaction product of ultraviolet radiation polymerizable materials. The device specularly transmits incident light as a function of the magnitude of an electric field applied across the device. The difference between a first applied voltage corresponding to a first percentage of the total incident light transmitted by the device as specular light and a second applied voltage corresponding to a second percentage of the total incident light transmitted by the device as specular light is greater than or equal to 15 volts. As a result, a polymer-dispersed liquid crystal device according to the invention displays a variable grey scale which has a uniform optical transmission. A method for preparing a PDLC device in general is also disclosed.

Patent
17 Jun 1992
TL;DR: In this paper, a waveguide optical device having a guide member for propagation of light in a longitudinal direction is described. And the guide path has an effective index of refraction greater than the effective indexes of refractive index of the isolation zones.
Abstract: A waveguide optical device having a guide member for propagation of light in a longitudinal direction. The guide member has upper and lower boundaries. A mass of birefringent material is disposed proximal to the guide member. The birefringent material has molecular dipoles subject to alignment by an imposed electrical field. The birefringent mass is overlapped by the optical field of the propagated light. An upper electrode is disposed in spaced relation to the birefringent mass. A lower electrode is disposed in spaced relation to the guide member. The electrodes have the capability of imposing an alternating current voltage across the birefringent mass to rotate the molecular dipoles of the birefringent mass in a plane defined by the normal to the guide member and the propagation vector of the light. The boundaries and the electrodes define an upper isolation zone between the upper electrode and the upper boundary, a guide path between the boundaries, and a lower isolation zone between the lower boundary and the lower electrode. The guide path has an effective index of refraction greater than the effective indexes of refraction of the isolation zones.

Journal ArticleDOI
TL;DR: In this article, the development of crystallinity of polyethylene terephthalate (PET) is discussed in relation to the rate of crystallization, the residual degree of orientation, and stress relaxation.
Abstract: The fabrication of poly(ethylene terephthalate), PET, into fibers, films, and containers usually involves molecular orientation caused by molecular strain, which may lead to stress- or strain-induced crystallization (SIC). The SIC of PET was studied by the methods of birefringence, density, thermal analysis, light scattering, and wide-angle X-ray. The development of crystallinity is discussed in relation to the rate of crystallization, the residual degree of orientation, and stress relaxation. The experimental procedure involves stretching samples at temperatures above the glass transition temperature, Tg, to a given extension ratio and at a specific strain rate of an Instron machine. At the end of stretching, the sample is annealed in the stretched state and at the stretching temperature for various periods of time, after which the sample is quickly quenched to room temperature for subsequent measurements. During stretching, the stress strain and the stress relaxation curves are recorded. The results indicate that the SIC of annealed, stretched PET can proceed in three different paths depending on the residual degree of orientation. At a low degree of residual orientation, as indicated by the birefringence value, annealing of stretched PET leads only to molecular relaxation, resulting in a decrease of birefringence. At intermediate orientation levels, annealing causes an initial decrease in birefringence followed by a gradual increase and finally a leveling off of birefringence after a fairly long period of time. At higher orientation levels, annealing causes a rapid increase in birefringence before leveling off. The interpretation of the above results is made using the measurements of light scattering, differential scanning calorimetry, and wide-angle X-ray. The rate of the SIC of PET is also discussed in terms of specific data analysis.

Journal ArticleDOI
TL;DR: In this article, a semivectorial beam-propagation method was proposed to determine the form birefringence in rib or channel waveguides by using the alternating-implicit method to simulate the propagation of the optical beam.
Abstract: The authors report a semivectorial beam-propagation method which can determine the form birefringence in rib or channel waveguides. In this approach, a finite-difference equation is solved by using the alternating-implicit method to simulate the propagation of the optical beam. Since boundary conditions are incorporated into the finite-difference equation, polarized modes can be simulated. Numerical results on three well-known rib waveguides are presented with comparisons to published data. >

Patent
30 Mar 1992
TL;DR: In this paper, a haze-free light modulating polymer dispersed liquid crystal (PDLC) material is disclosed which comprises a polymer which is birefringent and possesses anisotropic optical properties similar to those of the dispersed liquid crystals such that the PDLC material in its transparent state exhibits a refractive index that is matched for all directions of incident light providing for an optically clear, scatter-free film for all angles of view.
Abstract: A haze-free light modulating polymer dispersed liquid crystal (PDLC) material is disclosed which comprises a polymer which is birefringent and possesses anisotropic optical properties similar to those of the dispersed liquid crystal such that the PDLC material in its transparent state exhibits a refractive index that is matched for all directions of incident light providing for an optically clear, scatter-free film for all angles of view. Electrooptic light shutters are possible from this material which are transparent in the field OFF-state and opaque in the field ON-state or vice versa, depending upon the liquid crystal phase structure and configuration of the light shutter device.

Journal ArticleDOI
TL;DR: Under certain conditions, birefringence leads to polarization sensitivity in the nonlinear regime, which is likely to be contributing to instabilities that have been observed recently in mode-locked fiber lasers.
Abstract: The switching characteristic of a nonlinear-optical loop mirror can be inverted by a birefringent bias element. The device reflectance is insensitive to polarization in the linear regime for arbitrary birefringence in the loop. Under certain conditions, birefringence leads to polarization sensitivity in the nonlinear regime, which is likely to be contributing to instabilities that have been observed recently in mode-locked fiber lasers.

Journal ArticleDOI
TL;DR: In this article, a Lyot depolarizer was added to the gyro coil to remove all birefringence-induced effects and to provide a constant scale factor for pi-bias phase shifts in fiber gyros.
Abstract: Experimental observations of pi -bias phase shifts causing an inverted interference fringe have been made in fiber gyros using depolarized light and ordinary fiber. These observations are accounted for by a four-parameter birefringence model representing the gyro coil which explicitly accounts for polarization mode mixing in the interior of the coil. The addition of a Lyot depolarizer to the coil is shown to remove all birefringence-induced effects and to provide a constant scale factor. >

Journal ArticleDOI
TL;DR: An expression relating birefringence and the structure of ordered block copolymer materials formed under quiescent conditions has been derived in this article, where the intensity of the light exciting the sample held between perfectly crossed polarizers is found to be directly proportional to the average grain size.
Abstract: An expression relating birefringence and the structure of ordered block copolymer materials formed under quiescent conditions has been derived. The intensity of the light exciting the sample held between perfectly crossed polarizers is found to be directly proportional to the average grain size. The constant of proportionality depends only on material properties that can be obtained independently. Preliminary experiments support the validity of the simplifying assumptions invoked

Journal ArticleDOI
TL;DR: In this paper, a birefringent filter was proposed for femtosecond (F2C) laser with a steeply diving optic axis, which achieved two-octave tunability with negligible deterioration of the stopband rejection.
Abstract: A design for a birefringent filter is described, which is suitable for tunable femtosecond lasers. Using a single plate, which has a steeply diving optic axis, two-octave tunability is attained with negligible deterioration of the stopband rejection. For a specific wavelength region, it means that the filter's bandwidth can be changed by a factor of four. Another characteristic of the design is that, for the same bandwidth, the proposed plate is five times thicker than a conventional plate in which the optic axis is parallel to the surface. Thus, etalon effects can be avoided. Tuning characteristics of color center lasers utilizing the new filter are also presented. >

Journal ArticleDOI
TL;DR: In this article, the antiferroelectric phase transition in titanite was investigated using linear optical birefringence and X-ray diffraction techniques, and the critical exponent of the macroscopic order parameter was found to be β = 0.14 ± 0.02 and the transformation was interpreted in terms of a two-dimensional quasi-spin model.
Abstract: The antiferroelectric phase transition in titanite characterised by a collinear displacement of Ti-atoms from their central octahedral position is investigated using linear optical birefringence and X-ray diffraction techniques. Both methods indicate a continuous transition near 496 K and extra contributions to δΔn and X-ray intensity signals at higher temperatures. The critical exponent of the macroscopic order parameter is found to be β = 0.14 ± 0.02 and the transformation is interpreted in terms of a two-dimensional quasi-spin model. Topological features of the structure agree well with the spatial distribution of the diffuse scattering of the superstructure reflection 40 $$\bar 3$$ .

Journal ArticleDOI
TL;DR: Transmission formulas and transmission curves of birefringent filters when the optic axis is not in the plane of the filter plates are given and discussed in detail and this is the first design in a tunable laser pumped by a quasi-cw source.
Abstract: Transmission formulas and transmission curves of birefringent filters when the optic axis is not in the plane of the filter plates are given and discussed in detail. The optimum parameters of birefringent filters, such as the most suitable ratio of thicknesses, tuning angles, and plate thicknesses, are obtained. As far as we know this is the first design of birefringent filters used in a tunable laser pumped by a quasi-cw source.

Journal ArticleDOI
TL;DR: In this article, the existence of new kinds of travelling periodical waves due to cross-phase modulation in single mode fibers with weak birefringence was shown, and it was shown that the cross phase modulation can be used to obtain a new kind of traveling periodical wave.

Patent
24 Sep 1992
TL;DR: In this article, a class of light modulating materials comprising microdomains of ferroelectric smectic liquid crystal dispersed in a light-transmissive polymer medium is described.
Abstract: Disclosed is a class of light modulating materials comprising microdomains of ferroelectric smectic liquid crystal dispersed in a light-transmissive polymer medium. The microdomains are formed by phase separation of the liquid crystal from solution with the polymer as the polymer is solidified. The switching of the liquid crystal may be either monostable or multistable (e.g., bistable), depending on the liquid crystal and polymer. The material modulates light in either a scattering-transmissive mode or a birefringence mode. Materials operating in the scattering-transmissive mode do not require polarizers. Advantages of the materials include switching times down to the order of microseconds or less, multistable optical states, wide viewing angles and high contrast.

Patent
06 Jan 1992
TL;DR: In this article, a birefringent liquid crystal interspersed in isotropic polymer is used for light modulating devices, and a polarizer disposed on a surface of the liquid crystal device produces haze-free viewing for all viewing angles in the plane orthogonal to the polarization direction of the light passed by the polarizer.
Abstract: The invention provides an improvement in light modulating devices employing birefringent liquid crystal interspersed in isotropic polymer. A polarizer disposed on a surface of the liquid crystal device produces haze-free viewing for all viewing angles in the plane orthogonal to the polarization direction of the light passed by the polarizer.