Birefringence Polarization Research Articles

Spectral signal processing in intrinsic interferometric sensors based on birefringent polarization-maintaining optical fibers

The straightforward spectral signal processing technique is applied in intrinsic strain, temperature and distributed linear position interferometric fiber optic sensors based on birefringent polarization maintaining fibers. The method provides nonincremental absolute measurements of external physical parameter affecting the sensing fiber. Simultaneous interrogation of sensors in a network is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Theory of birefringence and spontaneous polarization in the tetragonal phase of PbTiO3 due to lattice deformation caused by the change of temperature

The microscopic mechanism of birefringence in the tetragonal phase of PbTiO3 is discussed taking account of the dipole-dipole interaction (dipole-dipole effect) due to the ionic and electronic polarizations of the crystal and the spontaneous Kerr effect as a cause of the strong local field acting on the constituent ions, where the lattice deformation due to the change of temperature is also considered. For the spontaneous polarization we use only the first effect. It is found that the birefringence and the spontaneous polarization are in good agreement with the experimental data.

The size distribution of interstellar dust particles as determined from polarization: Spheroids

view Abstract Citations (147) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Size Distribution of Interstellar Dust Particles as Determined from Polarization: Spheroids Kim, Sang-Hee ; Martin, P. G. Abstract We have determined the size distribution of polarizing interstellar dust grains based on electromagnetic scattering by spheroidal particles, extending our original work based on infinite cylinders. Shapes and alignment variants included the following: perfectly aligned oblate particles with axial ratios 1.414:1, 2:1, 4:1, and 6:1, picket fence prolate particles with axial ratios 2:1 and 4:1, and 2:1 prolate particles with perfect spinning alignment. Our analysis is based on bare silicate grains. The size distributions found are qualitatively similar to those derived using infinite cylinders. When expressed as contributions to the total mass, the distributions peak at mean size approximately 0.2 microns and are skewed, with the relative rate of decrease to larger and smaller sizes depending on lambda max. Using infinite cylinders, the specific requirement of a reasonable fit in the infrared produces a substantial dip in the mass distribution at approximately 0.4 microns, hinting at a bimodal mass distribution. But this dip is not present when oblate and prolate particles are used. This confirms that the dip is related to the incorrect behavior of scattering for infinite cylinders in the long wavelength limit. Fitting HST ultraviolet polarization data beyond 6 microns -1 introduces an additional bump at the small size end (approximately 0.01 microns) of the distribution. This unusual feature can be traced to the sudden rise in the imaginary part of the refractive index of 'astronomical silicate.' When a 'modified astronomical silicate' is used, the size of the additional bump is much reduced, if not absent. Based both on the smoothness of the mass distribution and on the fit to the polarization curve, oblate shapes are preferred to prolate. Among the oblates, the 6:1 oblate shape gives the most satisfactory result, simply because the width of the calculated polarization curve of single-sized 6:1 oblate particles is the narrowest. Mass distributions from fitting extinction curves using aligned spheroids have been determined. They resemble closely those based on spheres. Polarization to extinction ratios are large enough to match the maximum interstellar value for all axial ratios and shapes studied, though the most spherical (1.4:1 oblate and 2:1 spinning prolate) particles would have to be nearly perfectly aligned. The birefringence and interstellar circular polarization in the ultraviolet are predicted. Publication: The Astrophysical Journal Pub Date: May 1995 DOI: 10.1086/175604 Bibcode: 1995ApJ...444..293K Keywords: Cosmic Dust; Interstellar Matter; Particle Size Distribution; Polarization (Waves); Spheroids; Electromagnetic Scattering; Interstellar Extinction; Mass Distribution; Maximum Entropy Method; Astrophysics; ISM: DUST; EXTINCTION; POLARIZATION full text sources ADS | data products SIMBAD (5) MAST (1) ESA (1) Related Materials (2) Described in: 1979ApJ...228..450R Source Software: 2013ascl.soft11005M

Theoretical analysis of birefringence and form-induced polarization mode dispersion in birefringent optical fibers: A full-vectorial approach

A new numerical method for analyzing birefringence and dispersion characteristics of birefringent optical fibers is presented. A major advantage of the method, based on the solution of full-vectorial Maxwell equations, is its high accuracy no matter how great the geometrical anisotropy of the optical fiber. To verify the reliability of our numerical procedure, the modal birefringence and the form-induced polarization mode dispersion in elliptical core fibers with different eccentricities are investigated and their values compared with some theoretical and experimental results.

A highly birefringent fibre polarization modulation scheme for ellipsometry: system analysis and performance

An investigation of the polarization modulation performance of a highly birefringent fibre was carried out. The performance of the system and aspects such as the modulation method and the properties of the highly birefringent fibre were analysed in order to enhance performance. An important application of such a polarization modulation technique is in a novel ellipsometer, and the use of the fibre-based system to make ellipsometric measurements to determine the refractive index of a bulk sample is described.

Pyroelectric, pressureelectric and optical properties of potassium pentaborate tetrahydrate crystals

Abstract Results of studies of pyroelectric properties, the influence of hydrostatic pressure on spontaneous polarization, electrooptic effect and spontaneous birefringence of potassium pentaborate tetrahydrate crystals are presented. It is shown that potassium pentaborate crystals are linear pyroelectric with no phase transitions in temperature of 4.2–430 K. Obtained temperature dependence of pyroelectric coefficient has been described with the help of Einstein and Debye functions.

Self-mode-locking of cw solid-state lasers with a nonlinear birefringent polarisation modulator

A fluctuation model is used to show that effective self-mode-locking can be achieved in cw solid-state lasers with nonlinear birefringent polarisation modulators of two types. The discriminating action of modulators is based on the rotation and distortion of the polarisation ellipse, which depends on the intensity of the radiation propagating in the birefringent medium and is related to self-phase-modulation of two polarisation components. The linear phase shift of these components and the angular orientations of the modulator parts are determined to ensure that the modulator acts as a discriminator. An analysis is made of the regions of efficient self-mode-locking of cw lasers with nonlinear birefringent modulators as a function of the laser parameters.

Antiferroelectric behavior in a liquid crystalline polymer

AbstractElectro‐optic and polarization reversal measurements were performed on a side‐chain polymer exhibiting a chiral smectic phase. Based on the observed electro‐optic and current responses, we discuss the possibility of an antiferroelectric structure in the polymer. In order to establish a model for the observed behavior, a detailed comparison with the properties of the low molar mass antiferroelectric substance MHPOBC was made. The birefringence modulation in the chiral smectic polymer, originating from the field‐induced antiferroelectric‐to‐ferroelectric transition, is analyzed for the case of a randomly oriented sample. The result shows that the coincidence of birefringence modulation and polarization current peaks is strong evidence for the existence of antiferroelectric order in the smectic layers. Such coincidence was observed both for MHPOBC and the chiral side‐chain polyacrylate.

Polarization effects in infrared–infrared double resonance in methyl fluoride

A series of infrared–infrared double-resonance experiments are described in which a low-pressure gas sample interacts with pump and probe beams that have a variety of different polarizations. It is shown that orientation or alignment of the sample, previously demonstrated for electronic spectra with visible lasers, can be performed by irradiating a sample with a polarized infrared laser that is coincident with a vibration–rotation transition. By switching the polarization of the pump beam between horizontal and vertical polarization, linear dichroism is observed. By switching the polarization of the pump beam between right and left circular polarization, either circular dichroism or circular birefringence may be seen with the appropriate experimental arrangement. Also, as shown previously for electronic transitions, a combination of dichroism and birefringence experiments can be used to determine whether pump and probe transitions in the infrared region are P, Q, or R branch transitions. It is found that induced molecular alignment or orientation can be observed in four-level double resonance, indicating that alignment or orientation survives one or more collisionally induced rotational transitions. All of the three-level double-resonance effects may be predicted by means of the Jones calculus by using a Jones matrix for the pumped sample considered as an optical device. Equations for the elements of the Jones matrix have been derived for a sample pumped by either plane-polarized or circularly polarized radiation of arbitrary intensity.

Polarisation-insensitive high-isolation nonreciprocal device for optical circulator application

A novel high-isolation structure for a polarisation-insensitive nonreciprocal device intended for optical circulator application is proposed. It consists of birefringent crystals and polarisation rotators. Experimental demonstration shows an isolation of over 42 dB and an insertion loss of under 1.5 dB. >

Polarization characteristics of double-clad elliptical fibers

A scalar variational analysis based on a Gaussian approximation of the fundamental mode of a double-clad elliptical fiber with a depressed inner cladding is studied. The polarization properties and graphic results are presented; they are given in terms of three parameters: the ratio of the major axis to the minor axis of the core, the ratio of the inner cladding major axis to the core major axis, and the difference between the core index and the inner cladding index. The variations of both the spot size and the field intensity with core ellipticity are examined. It is shown that high birefringence and dispersion-free orthogonal polarization modes can be obtained within the single-mode region and that the field intensity distribution may be more confined to the fiber center than in a single-clad elliptical fiber.

Consistent expressions of refraction, polarization, light scattering and electric birefringence deduced from improved evaluations of local field effects and light scattered intensity - Applications to liquids

Classical orientation theories of rigid molecules in electro-optic fields are reexamined and significantly improved. Firstly a more consistent evaluation of local field effects is made within the practical spherical model by introducing approximations at the end of theoretical calculations only. This modification does not change classical formulae for refraction (Lorentz-Lorenz) and light scattering (depolarized Rayleigh intensity), but polarization and electric birefringence formulae are modified. Secondly a more correct derivation allows us to obtain a general expression of the light scattered intensity applicable both to dense fluids and to the perfect gas. Thirdly a more rigourous expression of the density fluctuation term is deduced without any approximation about the local field. The four electro-optic formulae are applied successfully to several liquids.

Propagation characteristics of dual-mode elliptical-core optical fibers

Propagation characteristics of dual-mode elliptical-core fibers are obtained by using a perturbation approach. It is found that for very high values of core aspect ratios (a/b > 2.3), the maximum possible value of the V parameter in such fibers is decided by the cutoff of the LP(21)(even) mode instead of the LP(11)(odd) mode. Further, as the core ellipticity increases, unlike the polarization birefringence, the birefringence between the LP(01) and the LP(21)(even) modes decreases and the V value, at which the LP(01) and LP(21)(even) modes have the same group velocities, moves toward the LP(21)(even) mode cutoff.

Polarization fluctuation characteristics of a highly birefringent fiber system under forced vibration

Polarization characteristics in environmental disturbance are evaluated, in terms of the signal-to-noise ratio (SNR), which is defined as the ratio of a mean to a standard deviation of time-varying signals. The SNR is computer-simulated, assuming a Gaussian probability distribution for the random variables, i.e. birefringent axis, linear retardance, and polarization mode-coupling. These parameters are assumed to fluctuate owing to the force vibration of a loudspeaker. A comparison of the numerical results with the experimental SNR provides a direct connection between fluctuations of the state of polarization (SOP) and SNR of received signals modulated by polarization noise in highly birefringent fiber systems. >

Optical, dielectric and DSC studies of “yellow-type” aluminate sodalite Sr8[Al12O24](CrO4)2

Abstract The ferroelectric orthorhombic phase and a new non-polar tetragonal phase of yellow single crystals of Sr8[Al12O24](CrO4)2 are studied by polarized light microscopy, differential scanning calorimetry (DSC), measurements of permittivity, spontaneous birefringence and spontaneous polarization.

Induced birefringence and dielectric polarization in fluids of non-polar ellipsoids

The local amplitude of an applied electric field polarizing a fluid comprising non-spherical molecules has components which depend on the average polarization of the sample and fluctuate with the molecular orientation. In isotropic fluids only the contraction of these fluctuations with the anisotropic part of the molecular polarizability gives a non-vanishing contribution to the dielectric polarization. In anisotropic fluids the angular average of these fluctuations of the electric field is non-vanishing and is of the same order of magnitude as the Lorentz field correction to the electric field. It contributes in all orders of the density to the dielectric virial expansion and to the molar coefficients of induced birefringence. It can serve as an explanation for the observation that the local field factor which best describes the density dependence of the Cotton-Mouton effect of CO 2 is 1 3 (ϵ + 2) and not [ 1 3 (ϵ + 2)] 2, as required by the classical Born-Langevin theory.

Malononitrile in Aromatic Solvents—Geometry of Solvation

Polarization and electric birefringence measurements are reported for malononitrile in dioxan , benzene and hexafluorobenzene solutions. These data, together with 1H n.m.r .shifts, are used to explore solute-solvent interactions. Changes in the proton shifts of CH2(CN)2 are studied with replacement of benzene solvent by fluorinated benzenes.

Photographic Images and Optical Effects Using Birefringent Materials

The author reveals a method of producing colorful abstract photographic prints using polarized light and simple materials such as cellophane. Until recently the use of birefringent materials and polarization had been limited to the production of light shows or light boxes with ever-changing patterns. This paper explains how permanent prints can be made using positive-to-positive photographic print papers and a modified enlarger. Methods for producing optical displays and special effects for television using birefringence are also discussed.

Fibre gyroscope with passive quadrature detection

A novel configuration for the optical fibre gyroscope is described which utilises highly birefringent fibre and polarisation mode selection to achieve a stable π/2 bias. By operating the system using a combination of both the unbiased and π/2 biased Sagnac outputs, the possibility of wide dynamic range operation is realised.

Low-loss single polarisation fibres with asymmetrical strain birefringence

Low-loss and highly birefringent single polarisation fibres have been fabricated. The minimum transmission loss and the modal birefringence of the fibre with refractive-index difference Δ=0.61% was 0.62 dB/km at λ=1.52 μm and 8.5×10−5 at λ=1.15 μm, respectively. The state of linear polarisation was stable against the handling conditions such as bending, twists, concentrated force, and temperature variations.