Showing papers on "Optical polarization published in 1991"
TL;DR: Property and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.
Abstract: The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.
839 citations
TL;DR: In this paper, an analytical characterization of polarization dispersion measurements is presented, where the authors report the solution of Poole's stochastic dynamical equation for the evolution of the dispersion vector with fiber length.
Abstract: An analytical characterization of polarization dispersion measurements is presented. The authors report the solution of Poole's stochastic dynamical equation for the evolution of the polarization dispersion vector with fiber length. The authors extend this to a more complete description by considering small, second-order dispersion effects through the frequency derivative of the dispersion vector. The complete analytical solution is seen to accord with what were originally empirically derived features of the joint probability distribution of the polarization dispersion vector and its frequency derivatives. Among the analytically determined properties are the Gaussian probability densities of the three components of the dispersion vector, and the hyperbolic secant (soliton shaped) probability densities of the components of the derivative of the dispersion vector. >
526 citations
TL;DR: The authors present a polarization reflectance model that uses the Fresnel reflection coefficients, which accurately predicts the magnitudes of polarization components of reflected light, and all the polarization-based methods presented follow from this model.
Abstract: The authors present a polarization reflectance model that uses the Fresnel reflection coefficients. This reflectance model accurately predicts the magnitudes of polarization components of reflected light, and all the polarization-based methods presented follow from this model. The authors demonstrate the capability of polarization-based methods to segment material surfaces according to varying levels of relative electrical conductivity, in particular distinguishing dielectrics, which are nonconducting, and metals, which are highly conductive. Polarization-based methods can provide cues for distinguishing different intensity-edge types arising from intrinsic light-dark or color variations, intensity edges caused by specularities, and intensity edges caused by occluding contours where the viewing direction becomes nearly orthogonal to surface normals. Analysis of reflected polarization components is also shown to enable the separation of diffuse and specular components of reflection, unobscuring intrinsic surface detail saturated by specular glare. Polarization-based methods used for constraining surface normals are discussed. >
450 citations
TL;DR: In this article, high linear polarization (up to 5-8%) discovered in the deep minima of isolated AE-Herbig stars is discussed in the framework of the model of "zodiacal light" produced by scattering matter in a circumstellar dust envelope (probably in protoplanetary discs).
Abstract: High linear polarization (up to 5–8%) discovered by our group in the deep minima of isolated AE-Herbig stars is discussed in the framework of the model of ‘zodiacal light’ produced by scattering matter in a circumstellar dust envelope (probably in protoplanetary discs). The numerical simulations of polarizational and colourimetrical properties of the scattered light based on the Mie theory permit to obtain from the observations some important parameters of circumstellar dust: the size distribution of grains, their rough chemical composition (silicate/graphite), the flatness of the dust envelope.
182 citations
TL;DR: In this paper, a polarization independent interferometric optical-time-domain reflectometer is proposed and demonstrated, which is composed of a superluminescent diode and a fiber coupler which combines a polarization-maintaining fiber and a conventional singlemode fiber to achieve a polarizationindependent spatial profile of the reflectance in a single-mode fiber or waveguide sample.
Abstract: A polarization-independent interferometric optical-time-domain reflectometer is proposed and demonstrated. The experimental setup is composed of a superluminescent diode and a fiber coupler which combines a polarization-maintaining fiber and a conventional single-mode fiber to achieve a polarization-independent spatial profile of the reflectance in a single-mode fiber or waveguide sample. The polarization independence and the reliability of the measured reflectivity, were confirmed, and the measurement of loss and birefringence in an optical waveguide from its reflectance profile is demonstrated. The influence of dispersion in the fibers on the spatial resolution of the reflectometer is also discussed. >
159 citations
01 Jan 1991
TL;DR: In situ measurements made by the three spacecraft that passed within 10,000 km of the nucleus provided the first opportunity to investigate both the full size-range of particles and the complete process of dust production as discussed by the authors.
Abstract: Prior to the 1986 apparition of comet Halley, all attempts to determine the physical properties of cometary dust were limited to remote observations and the analysis of various particles captured by the Earth’s atmosphere. The in situ measurements made by the three spacecraft that passed within 10,000 km of the nucleus provided the first opportunity to investigate both the full size-range of particles and the complete process of dust production. Information on composition is derived through mass spectra and the scattering and emission of light from the grains, whilst the dynamics of the dust coma can be modeled from the three separate sets of measurements made over a period of eight days.
127 citations
TL;DR: This work hypothesizes that the roughly elliptical cross-sectioned double-cone inner segment acts as a birefringent, polarization-sensitive dielectric waveguide, and that the double cone mosaic generates a 'polarization contrast' neural image, and confirms three predictions derived from these hypotheses.
Abstract: Many invertebrates and vertebrates are sensitive to the polarization of light. The biophysical basis of invertebrate polarization sensitivity is an intrinsic dichroism, the alignment of chromophores along the photoreceptor microvilli. But such dichroism to axially propagating light is not present in vertebrate photoreceptors, whose chromophores are free to rotate in the plane of the outer-segment disc membranes, and a biophysical mechanism responsible for vertebrate polarization sensitivity has not been established. We hypothesize that the roughly elliptical cross-sectioned double-cone inner segment acts as a birefringent, polarization-sensitive dielectric waveguide, and that the double cone mosaic generates a 'polarization contrast' neural image. Here we confirm three predictions derived from these hypotheses: (1) 90 degrees periodicity for polarization sensitivity; (2) polarization sensitivity maxima corresponding to the absolute orientation of the axes of the double-cone inner-segment cross-sections; and (3) action spectrum for polarization sensitivity corresponding to the absorption spectrum of the double cones. We also present evidence for a polarization-opponent neural encoding in vertebrates.
126 citations
TL;DR: In this paper, a general method for calculating the radar cross section (RCS) from a three-dimensional target is described, where the target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package.
Abstract: A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data. >
121 citations
TL;DR: The spatial distribution of polarization angle is summarized for 15 dark clouds that lack prominent star formation, for four star clusters embedded in dark clouds, for one evolved cluster with little associated extinction, and for six dark cloud complexes as discussed by the authors.
Abstract: The spatial distribution of polarization angle is summarized for 15 dark clouds that lack prominent star formation, for four star clusters embedded in dark clouds, for one evolved cluster with little associated extinction, and for six dark cloud complexes. Most clouds have either one well-defined mean direction over their spatial extent or two or three spatial zones having noticeably different mean directions. Nearly all regions have a single local maximum in their number distribution of polarization angle. Clouds with embedded clusters have a more complex distribution of polarization direction than do clouds without clusters. It is proposed that the enhanced dispersion of polarization angle in clusters may be more closely associated with young stars and/or with dense gas, than simply with the number of stars in the cluster. The greatest dispersion in direction among clouds without clusters, 0.7 radians, occurs in L1689 in Ophiuchus. 54 refs.
112 citations
TL;DR: In this paper, a simple model based upon the hypothesis that leaves specularly reflect light according to the Fresnel equations relates the observed bidirectional effects to the architectural and phenological conditions of the canopy.
112 citations
TL;DR: Using vector diffraction theory and an exact method for computing reflection coefficients for multilayer structures, the effects of high-numerical-aperture focusing on the state of polarization in optical data storage systems are analyzed.
Abstract: Using vector diffraction theory and an exact method for computing reflection coefficients for multilayer structures, we analyze the effects of high-numerical-aperture focusing on the state of polarization in optical data storage systems. The focused incident beam is decomposed into a spectrum of plane waves, and the reflected beam is obtained by the superposition of these plane waves after they are independently reflected from the multilayer. Plots of polarization rotation angle and ellipticity for several disk structures are presented.
TL;DR: In this article, a narrowband rocking filter was made in polarisation-maintaining monomode optical fiber by photoinducing periodic birefringent gratings along the length of the fibre.
Abstract: Efficient, narrowband rocking filters have been made in polarisation-maintaining monomode optical fibre by photoinducing periodic birefringent gratings along the length of the fibre. These gratings, fabricated with a period chosen to provide synchronous coupling between the two principal states of polarisation of the LP01 mode at a preselected wavelength, gently rock to and fro along the principal polarisation axes of the fibre. To photoinduce the grating, the fibre is exposed periodically along its length to a UV light beam which is incident at right angles to the geometrical axis of the fibre and is directed π/A rad with respect to the principal polarisation axes. Efficient polarisation mode conversion at 1.3 μm with the birefringent fibre grating is demonstrated.
TL;DR: In this article, the authors used polarization images of several star-forming regions with mass outflows (GSS 30, S255, GL 5180, GL 2591, GGD 27, and NGC 7538) to establish the universality of bipolarity and of shell or cavity structure in the IRN consistent with that of CO outflow.
Abstract: The inefficiency of the stellar formation process leads rather generally to high residual dust densities, and so to the existence of infrared reflection nebulosity (IRN), in regions of star formation. Polarization images of several star-forming regions with mass outflows (GSS 30, S255, GL 5180, GL 2591, GGD 27, and NGC 7538) presented here: (1) establish the universality of bipolarity and of shell or cavity structure in the IRN consistent with that of CO outflow; (2) identify the source of the mass outflow in each case; (3) show that the opening angle near this central source is large; and (4) demonstrate several instances of multiple shells, probably arising from episodic mass loss. Astrometry of 2.2-micron sources with arcsecond accuracy identifies the illuminating source of each IRN uniquely with a compact H II region or a bright IR source. The polarization images provide strong evidence for large-scale dust toroids around each of these sources. The density and mass of these disks are estimated from the extinction through the disk.
TL;DR: In this article, a planar four-channel wavelength demultiplexer with weak polarization dependence is proposed and demonstrated, which operates in the wavelength range 776.5-781.2 nm, with a channel spacing of 1.55 nm.
Abstract: A planar four-channel wavelength demultiplexer with weak polarization dependence is proposed and demonstrated. This demultiplexer is based on an optical-phased array. An experimental device with dimensions 4.5*3.2 mm/sup 2/ was designed and fabricated, using conventional (high-quality) optical lithography. The demultiplexer operates in the wavelength range 776.5-781.2 nm, with a channel spacing of 1.55 nm. Insertion loss was 0.6 dB for the central channels and 1.2 dB for the outer channels for transverse-electric (TE) polarization, excluding 1.3-dB waveguide propagation loss. Crosstalk values measured 15.4-29.7 dB for the TE and 13.4-22.2 dB for the transverse-magnetic (TM) polarization. >
TL;DR: This method of quantitative orientation measurement has wide application for the many birefringent tissues such as bone, smooth and striated muscle and elastin enabling comparison among tissues of varied physical circumstances and function.
TL;DR: In this article, nonlinear polarisation switching of picosecond pulses from the linear polarisation eigenstates of a 200 m-long low-birefringence spun fiber is reported.
Abstract: Nonlinear polarisation switching of picosecond pulses from the linear polarisation eigenstates of a 200 m-long low-birefringence spun fibre is reported. The relatively low switching peak power of 20 W is promising for applications to all-optical processing and intensity discrimination of ultra-short pulses.
Patent•
06 Sep 1991TL;DR: In this article, the distortion of the light beam polarization caused by a single-mode optical fiber is corrected by introducing two different linearly polarized light beams and measuring Stokes parameters which are used to construct a calibration matrix that is inverted and multiplied times measured Stokes parameter of subsequent measurements to yield true stokes parameters.
Abstract: An instrument includes a polarized optical source for producing three sequential predetermined states of polarization of a light beam and an optical polarization meter for measuring the polarization of a portion of the light beam transmitted by or reflected from an optical network by splitting it into four beams, passing three of the beams through optical elements, measuring the transmitted intensity of all four beams, and calculating Stokes parameters. The light beam enters the optical polarization meter through a single-mode optical fiber that acts as a spatial filter for controlling the position and alignment of the beam with respect to the optical elements. The distortion of the light beam polarization caused by this optical fiber is corrected by introducing two different linearly polarized light beams and measuring Stokes parameters which are used to construct a calibration matrix that is inverted and multiplied times measured Stokes parameters of subsequent measurements to yield true Stokes parameters. The three sequential predetermined states of polarization yield three corresponding Jones input vectors, and the Stokes parameters for the responses of the optical network are converted to three Jones output vectors. A Jones matrix for the optical network to within a complex constant is then computed from the Jones input and output vectors. Relative polarization sensitivity can be determined from this matrix for the optical network. The relative distortion caused by the optical network can be corrected by multiplying by the inverse of the matrix during later measurements through the optical network. Additionally, power measurements on the optical network and a substituted optical through enable absolute determinations and corrections.
TL;DR: In this article, a near threshold, highly linearly polarised TEMoo mode whose direction varies randomly from one laser to the other was obtained, and at higher currents, high order modes lase in a linear polarisation orthogonal to the fundamental mode.
Abstract: The polarisation properties of quantum well vertical cavity surface emitting lasers are observed to be significantly different from their edge emitting counterparts. A near threshold, highly linearly polarised TEMoo mode whose direction varies randomly from one laser to the other is obtained. At higher currents, high order modes lase in a linear polarisation orthogonal to the fundamental mode. No polarisation selection rule is observed.
TL;DR: In this paper, the intensity noise characteristics of GaAlAs-GaAs vertical cavity surface emitting (SE) lasers have been investigated and a low-intensity noise of -145 dB/Hz was obtained with an output power of 2.2 mW.
Abstract: The intensity noise characteristics of GaAlAs-GaAs vertical cavity surface emitting (SE) lasers have been investigated. A low-intensity noise of -145 dB/Hz was obtained with an output power of 2.2 mW. The spontaneous emission factor is estimated to be 2*10/sup -5/, both from the bias dependence of the intensity noise and from the relative mode intensity below threshold. This is in good agreement with theoretical expectation. The possibility of low-noise operation of a microcavity SE laser with an extremely low output power of less than approximately 100 mu W is shown. The polarization stability of the surface emitting laser is demonstrated by measuring the intensity fluctuations of an individual polarization state. >
TL;DR: In this article, a singlemode fused biconical coupler for polarization beamforming is described and a usable spectral window as broad as 17 nm with an extinction ratio smaller than -15 dB for both output fibers is obtained.
Abstract: A single-mode fused biconical coupler for polarization beamsplitting is described. In the coupling region, standard communication fibers are used. The output fibers are polarization-maintaining. To stop the coupler drawing process accurately, the degree of polarization is measured during the drawing and is used as a criterion. Losses of 0.2 dB are typical, and a minimum extinction ratio of -27 dB is achieved. A usable spectral window as broad as 17 nm with an extinction ratio smaller than -15 dB for both output fibers is obtained. Any specified wavelength for the minimum of the extinction ratio is reached within +or-3 nm. >
TL;DR: In this paper, the radio and optical properties of a complete 5 GHz sample of strong radio sources are studied, and the detection rate of radio galaxies containing optical cores with high polarization is consistent with the hypothesis that all radio sources contain optically polarized cores, with strength proportional to the core radio flux density.
Abstract: The radio and optical properties of a complete 5 GHz sample of strong radio sources are studied. High polarization is strongly correlated with the fraction of the total 5 GHz flux density found in a milliarcsec core. The detection rate of radio galaxies containing optical cores with high polarization is consistent with the hypothesis that all radio sources contain optically polarized cores, with strength proportional to the core radio flux density. High optical polarization, optical power-law fraction, line-to-continuum ratio, emission lines of small equivalent widths, and large amplitude flux variability are all strongly correlated with the fraction of the 5 GHz radio flux density that is unresolved on VLBI scales. The distributions of these properties are well matched by a model where radio and optical radiation have the same beaming geometry and with Doppler boosting of a factor of 10-100 in the optical. A striking alignment of the position angle of the VLBI structure axis and the position angle of optical polarization in highly polarized sources is confirmed.
TL;DR: The theoretical results based on this model match the experimental measurements and allow us to optimize the operation of the LCLV as an intensity or phase-only spatial light modulator.
Abstract: The complex amplitude reflectance of the liquid crystal light valve (LCLV) is determined as a function of the writing intensity and applied voltage using an approximate model. The input and output polarizers are assumed to have arbitrary directions. The theoretical results based on this model match our experimental measurements. This theory allows us to optimize the operation of the LCLV as an intensity or phase-only spatial light modulator. When the polarizers are orthogonal and the input polarizer is at -34 degrees with the front liquid crystal director, the intensity reflectance reaches 100% (compared to 81% for the conventional configuration). Phase-only modulation is realizable by use of appropriate applied voltage bias and configuration of polarizers.
TL;DR: A method based on Kerr ellipsometry in which analysis of the polarization state of transmitted light between a nearly crossed polarizer and an analyzer allows separation of pump-induced dichroism and birefringence provides a natural measurement of nonlinear phase retardations in angle units.
Abstract: We report on a method aimed at measuring both the real and imaginary parts of the third-order Kerr-type nonlinear-optical susceptibility of isotropic materials. It is based on Kerr ellipsometry in which analysis of the polarization state of transmitted light between a nearly crossed polarizer and an analyzer allows separation of pump-induced dichroism and birefringence. The method provides a natural measurement of nonlinear phase retardations in angle units, without any calibration procedure. By using a white-light continuum as a probe, this property is used to get a simultaneous measurement of the nonlinear dispersion in the whole visible spectrum. It is illustrated in tetramethylsilane, where stimulated Stokes and anti-Stokes Raman contributions to the nonlinearity are observed.
TL;DR: In this article, Uchida et al. suggested that the Orion molecular cloud complex formed through the Parker instability (the buoyancy of a magnetic field entrained in matter), and that the helical filament is the result of spinning gas falling along the magnetic field and twisting it.
Abstract: USING the Nagoya telescope1, Uchida et al.2 found an unusual helical filamentary structure, spinning about its long axis, in the L1641 cloud in the Orion cloud complex. Noting that this structure is consistent with a helically twisted magnetic field inferred from optical polarization observations3,4, they argued that the helical filament is a manifestation of torsional magnetohydrodynamic (Alfven) waves draining angular momentum from a nearby massive cloud, thus promoting collapse and star formation. Here we present an alternative interpretation. We suggest that the Orion molecular cloud complex formed through the Parker instability5 (the buoyancy of a magnetic field entrained in matter), and that the helical filament is the result of spinning gas falling along the magnetic field and twisting it. The twisted magnetic field, unlike a purely planar field, suppresses the Parker instability on small scales, allowing the generation of finite clouds rather than general turbulence.
TL;DR: In this article, the nonlinear spectra of absorption and dispersion near the band edge are calculated for quantum well wires with one subband, taking into account phase space filling, plasma screening and band gap renormalization due to an optically excited thermal electron-hole plasma.
Abstract: The nonlinear spectra of absorption and dispersion near the band edge are calculated for quantum well wires with one subband The calculations take into account phase space filling, plasma screening and band gap renormalization due to an optically excited electron-hole plasma Large optical nonlinearities are obtained around the exciton ground state mainly due to state-filling by the optically excited thermal electron-hole plasma, while the plasma screening effects are found to have relatively little influence For all plasma densities n (including n = 0), the free-carrier transition spectra differ strongly from those calculated with Coulomb interaction
TL;DR: In this paper, a new polarization splitter which utilizes artificial anisotropic dielectrics is presented, which is composed of layers of periodically laminated SiO2/TiO2 thin films.
Abstract: Experimental verification is made of a new polarization splitter which utilizes artificial anisotropic dielectrics. The splitter is composed of layers of periodically laminated SiO2/TiO2 thin films. The SiO2 and TiO2 films are alternately deposited by rf sputtering and reactive dc sputtering, respectively. The thickness of each layer is 50 nm, while the total number of the layers amounts to 2000. The measured polarization split angles are 5.7° (λ=0.63 μm) and 5.1° (λ=1.3 μm), being roughly the same as those predicted.
TL;DR: In this article, a novel polarization splitter is proposed for use in integrated optical circuits on lithium niobate, which is based on the mode sorting effect with no external control, while its fabrication requires only a single technology: the diffusion of titanium.
Abstract: A novel polarization splitter is proposed for use in integrated optical circuits on lithium niobate. In contrast to previously reported devices, its operation is based on the mode sorting effect with no external control, while its fabrication requires only a single technology: the diffusion of titanium. The splitter is formed by a Y junction. The polarization splitting can be achieved by making the output waveguides from two titanium strips with different dimensions. A realistic design of these output guides is presented, and some technological aspects are discussed. The operation of the polarization splitter is investigated with the beam propagation method. The results show that a 15-dB extinction ratio is obtained with branching angles larger than 0.2 degrees . The extinction ratio can be as high as 30 dB with a branching angle of 0.1 degrees . The excess losses are below 0.05 dB. >
TL;DR: Polarization lidar data are used to demonstrate that clouds composed of hexagonal ice crystals can generate multiple-ringed colored coronas in mid-latitude cirrus clouds, and these displays are associated with unusual cloud conditions that appear to be effective in generating the displays.
Abstract: Polarization lidar data are used to demonstrate that clouds composed of hexagonal ice crystals can generate multiple-ringed colored coronas. Although relatively uncommon in the mid-latitude cirrus sample, the coronas are associated with unusual cloud conditions that appear to be effective in generating the displays. Invariably, the cirrus cloud tops are located at or slightly above elevated tropopauses at temperatures between -60 and -70 C. The cloud top region also generates relatively strong laser backscattering and unusually high 0.5-0.7 linear depolarization ratios. Color photograph analysis of corona ring angles indicates crystals with mean diameters of from 12 to 30 microns. The cirrus cloud types were mainly subvisual to thin cirrostratus, but also included fibrous cirrus. Estimated cloud optical thicknesses at the 0.694-micron laser wavelength ranged from about 0.001 to 0.2, where the upper limit reflects the effects of multiple scattering and/or unfavorable changes in particle characteristics in deep cirrus clouds.
TL;DR: In this paper, a guided-wave Mach-Zehnder interferometer structure, based on the use of a four-port hybrid optical coupler consisting of symmetric and nonsymmetric y junctions, is proposed for wavelength division multiplexing application.
Abstract: A guided-wave Mach-Zehnder interferometer structure, based on the use of a four-port hybrid optical coupler consisting of symmetric and nonsymmetric y junctions, is proposed for wavelength-division multiplexing application. This structure provides less sensitivity to fabrication parameters and optical polarization, and can also be applied to a wide-wavelength spacing operation. Interferometers for wavelength splitting in the 1.3- and 1.55- mu m windows were designed and fabricated into a glass substrate with a dry silver ion exchange process. The measured crosstalk was -30 dB with nonpolarized light. >
IBM1
TL;DR: In this article, a finite-difference beam propagation method is derived directly from the vectorial Maxwell equations, which allows the analysis of coupling between various components of the electric field vector for optical beams propagating in dielectric waveguides as well as corresponding changes in the beam-polarisation state.
Abstract: A finite-difference beam-propagation method is derived directly from the vectorial Maxwell equations The new approach allows the analysis of coupling between various components of the electric-field vector for optical beams propagating in dielectric waveguides as well as corresponding changes in the beam-polarisation state