Showing papers on "Optical polarization published in 1986"

Antiresonant reflecting optical waveguides in SiO2‐Si multilayer structures

Abstract: A new type of optical waveguide utilizing an antiresonant reflector is described. Implementation in the SiO2‐Si system gave losses as low as 0.4 dB/cm for the TE mode. The TM mode loss is >60 dB/cm, making the device an excellent planar technology integrated optic polarizer.

Polarization-maintaining fibers and their applications

Abstract: Polarization-maintaining fibers and their applications are reviewed. The classification of high-birefringent fibers and low-birefringent fibers and their fabrication methods and characteristics are discussed in Section II. Analytical methods and numerical methods for fiber design on the birefringence are presented in Section III. Degradation factors of polarization maintenance expressed as crosstalk or mode-coupling parameters caused by internal origins such as structural imperfections, wavelength, and nonlinear effects, and by external origins such as temperature fluctuations, mechanical perturbations, and electromagnetic effects, are discussed in Section IV. Characterization methods on beat length, mode coupling, stress distribution, and mechanical strength are presented in Section V. Applications to the fiber devices and nonlinear effects, and splicing methods for the polarization-maintaining fibers are described in Sections VI and VII.

Depolarization and polarization indices of an optical system

Abstract: The depolarization index and the direct and reciprocal polarization indices may be derived from the Mueller matrix of any optical system. These indices give direct information about the depolarizing and polarizing power of the optical system.

Nonlinear-optical interactions in fluorescein-doped boric acid glass.

Abstract: Fluorescein-doped boric acid glass is a material characterized by an extremely low saturation intensity of \ensuremath{\sim}15 mW${\mathrm{?}}^{\mathrm{\ensuremath{-}}2}$ and a nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}$ as large as \ensuremath{\sim}1 esu. The saturated absorption of this material is shown both theoretically and experimentally to depend on the state of polarization of the saturating beam, even though the unsaturated absorption is polarization insensitive. Phase-conjugate reflectivities as large as 0.6% have been obtained through use of degenerate four-wave mixing in this material. These measured reflectivities are in good agreement with the predictions of a theory that includes the effects of excited-state absorption and grating washout. In addition, two-beam coupling due to the nonlinearity of saturable absorption has been demonstrated in this material. The magnitude of the coupling is maximized by inducing a frequency shift between the two beams of \ensuremath{\sim}0.1 Hz.

Experimental observation of polarization instability in a birefringent optical fiber

Abstract: We present the first experimental demonstration of spatial instability in the nonlinear evolution of the state of polarization of an intense light beam in a birefringent Kerr‐like medium. As the peak power crosses the threshold for the instability, we observed strong intensity‐dependent power transfer between the two counter‐rotating circularly polarized waves propagating along a birefringent optical fiber. The experimental results agree well with the theory.

Eigenstate of polarization in a fiber ring resonator and its effect in an optical passive ring-resonator gyro

Abstract: Resonance characteristics of an optical fiber ring resonator are derived taking the effect of birefringence into account. We introduce the concept of the eigenstate of polarization to discuss the resonance characteristics resulting from the polarization fluctuation. Using this concept, the polarization problem in an optical passive ring-resonator gyro (OPRG) is discussed to reveal that this causes gyro drift. A way to reduce the drift is to use not polarizers but two polarization controllers. The precision required for polarization control is estimated; it is found difficult to do in practice. We discuss another configuration to solve the polarization problem in an OPRG without polarization controllers.

Multipolarization Radar Images for Geologic Mapping and Vegetation Discrimination

Abstract: The NASA/JPL airborne synthetic aperture radar system produces radar image data simultaneously in four linear polarizations (HH, VV, VH, HV) at 24.6-cm wavelength (L-band), with 10-m resolution, across a swath width of approximately 10 km. The signal data are recorded optically and digitally and annotated in each of the channels to facilitate a completely automated digital correlation. Both standard amplitude, and also phase difference images are produced in the correlation process. Individual polarization and range-dependent gain functions improve the effective dynamic range, but as yet do not permit absolute quantitative measurements of the scattering coefficients. However, comparison of the relative intensities of the different polarizations in individual black-and-white and color composite images provides discriminatory mapping information. In the Death Valley, California, area, rough surfaces of young alluvial deposits produce strong responses at all polarizations. Smoother surfaces of older alluvial deposits show significantly lower responses. Evaporite deposits of different types and moisture contents have distinct polarization signatures. In the Wind River Basin, Wyoming, sedimentary rock units show polarization responses that relate to differences in weathering. Local intensity variations in like-polarization images result from topographic effects; strong cross-polarization responses denote the effects of vegetation cover and, in some cases, possible scattering from the subsurface. In the Savannah River Plant, South Carolina, forest cover characteristics are discriminated by polarization responses that reflect the density and structure of the canopy, and the presence or absence of standing water beneath the canopy.

Path dependence of the geometric rotation of polarization in optical fibers

Abstract: The geometric rotation of the polarization angle in a ideal cylindrical optical fiber without birefringence is obtained for arbitrary fiber paths in terms of the image of the path in the tangent vector space. The result extends a recent result of Chiao and Wu [Phys. Rev. Lett. 57, 933 (1986)] restricted to paths with parallel ends, which was derived from Berry's phase in the adiabatic limit of quantum mechanics [Proc. R. Soc. London Ser. A 392,45 (1984)]. The treatment given here is purely classical and uses differential geometry to extend earlier work by Ross [Opt. Quantum Electron. 16, 455 (1984)] on the uniform helix.

New all-optical devices based on third-order nonlinearity of birefringent fibers.

Abstract: Exact solutions for the evolution of the state of polarization along a nonlinear single-mode birefringent fiber are given by means of the Poincare sphere representation. This approach clearly shows the possibility of realizing a new class of devices, namely, a linear coherent amplifier–mixer and an optically activated polarization switch or a phase-sensitive optical discriminator with high fanout.

Photoinduced anisotropy in rigid dye solutions for transient polarization holography

Abstract: The characteristics of rigid solutions of organic dyes suitable for holographic recording-fluorescein/orthoboric acid, methyl red/polymethylmetacrylate, and methyl orange/polyvinylalcohol-are investigated. All of the three systems allow real-time recording and do not exhibit fatigue up to more than 104cycles of recording erasure. The system fluorescein/orthoboric acid possesses a faster response time than the other two systems-around 0.1 s. The phase character of the recording in the system methyl orange/polyvinylalcohol explains the high diffraction efficiency-up to 35 percent-in polarization holographic recording. New experimental results on the kinetics of the photoinduced anisotropy are presented and the mechanisms which could possibly speed up the processes, repeated periodically, are discussed.

Drift of an optical fiber gyroscope caused by the Faraday effect: influence of the earth's magnetic field

Abstract: The drift of an optical fiber gyroscope caused by the earth's magnetic field through the Faraday effect is studied theoretically in a simple model and also in a practical model. The mechanism of its reduction using polarization-maintaining optical fiber is clarified; it depends on the twist and the birefringence of the fiber. The presence of the twist component whose period is just equal to one turn of the sensing fiber loop causes the drift; ways of suppressing it are described. Influence of the practical parameters, such as imperfection of the polarizer, is also discussed.

Polarization and optical logic

Abstract: The design of an optical logic parallel processor is described. The central component is a Fabry-Perot cavity, filled with a nonlinear layer and a linear anisotropic layer, such as a sheet of mica. The two logic states are represented by two orthogonal states of the polarization of the light beam. Polarization logic, compared with on/off logic (bright or dark), requires less power, generates less heat, and is better suited for cascading.

On some properties of axicons

Abstract: The radial and axial pump power distribution in the line focus of a cone (as simplest example of an axicon) is discussed. It is also shown that four conical surfaces covered with antireflection coatings can make an efficient polarizer for radial and tangential polarization of a light beam. Glass cones can be used as efficient pump optics for laser-pumped lasers. The advantages of the novel pumping scheme are discussed in detail for the cases of dye-laser and x-ray laser pumping.

New implementation of symbolic substitution logic.

Abstract: Symbolic substitution is a spatial logic for digital optical computers that utilizes the specific advantages of optical signal processing. Previous implementations used the optical intensity for coding the binary values. In this implementation we are using polarization for coding, and we show how a complete recognition–substitution processor can be implemented. The advantages of this type of coding are: better utilization of the device area, an equal distribution of intensity, and symmetry between the two logic states.

Polarisation modulation-the measurement of linear and circular dichroism

Abstract: Dichroism is usually measured using two separate polarisation spectra. However, when the difference in the transmission of oppositely polarised light is very small, the superior method of modulating the polarisation of a single light beam should be used. The techniques involved in this method are reviewed.

Depolarization and cross polarization in ellipsometry of rough surfaces.

Abstract: In ellipsometry of rough surfaces, the commonly used parameters, psi and delta, are insufficient to characterize completely the changes in polarization state which occur when light is reflected from a rough surface. When an experimentally determined Mueller matrix is available, parameters indicative of depolarization, cross polarization, and change in ellipticity can be found. When the Mueller matrix is regarded as an operator mapping input polarization states depicted on a Poincare sphere to output states in a similar coordinate system, these new parameters can be illustrated in terms of their effects on the Poincare sphere. The depolarization and cross polarization parameters correlate with specimen roughness and reflectance.

Planetary surface texture and albedo from parameter plots of optical polarization data

Abstract: Mesures obtenues avec le polarimetre de l'observatoire de Meudon, appliquees sur des surfaces incluant des echantillons de roches et de poudres, des meteorites, des echantillons lunaires et des corps planetaires sans atmosphere

Comparison of four-wave mixing techniques for studying orientational relaxation

Abstract: Three four-wave mixing techniques for measuring orientational relaxation of molecules in solution using time-separated pulses are compared both theoretically and experimentally. This comparison is shown to be greatly facilitated by modifying the conventional third-order response functions to incorporate a portion due to the slowly varying reorientation of the transition dipoles. Ordinary Bragg diffraction of a probe field, in which a transient grating formed by excitation pulses of the same polarization is probed with parallel and perpendicular polarizations, has the advantage of yielding both the time dependence and the magnitude of the induced anisotropy. However, the accompanying acoustic grating interferes with the polarization-sensitive excited state concentration grating unless the probe wavelength falls within a very strong absorption band. The acoustic grating can be eliminated by using perpendicularly polarized pumping pulses (the "crossed grating" configuration). Polarization spectroscopy in which the generated field is collinear with the probe gives the same anisotropy decay kinetics as the crossed grating, but is more sensitive to interference from background birefringence. These three methods, together with time-resolved fluorescence polarization, have been used to examine rotational dynamics in the ground and excited states of rhodamine 6G, 9-aminoacridine, and benzophenone.

Moment analysis in depolarized light scattering: Determination of a single‐parameter empirical pair polarizability anisotropy for Ne, Ar, Kr, Xe, and CH4

Abstract: A method, based on classical physics, to utilize the first four even moments of the depolarized collision induced light scattering spectrum to derive an empirical model for the pair polarizability anisotropy of interacting molecules, with only one adjustable parameter, is described and applied to the spectra of Ne, Ar, Kr, Xe, and CH4. Good agreement with ab initio results in the literature is obtained and profiles calculated with these models are in excellent agreement with experiment.

Multifrequency Passive Microwave Observations of First-Year Sea Ice Grown in a Tank

Abstract: Microwave brightness temperatures of new, young, and optically opaque sea ice grown in a large tank were obtained in the course of a joint microwave experiment at CRREL in Hanover, New Hampshire, during the winters of 1983-1984 and 1984-1985. Dual-polarized observations were taken at frequencies of 10, 18, 37, and 90 GHz over a range of incidence angles, and the concurrent temperature and ice thickness were obtained. Bulk salinities as well as radar and dielectric properties were also measured concurrently by other investigators. Emissivity and degree of polarization were observed in detail during the early stages of ice growth and variations were found indicating that the ice became optically opaque at 10 GHz for ice thickness between 30 and 50 mm. The addition of a snow cover reduced the brightness temperature at the higher frequencies with little effect at 10 GHz. Artificial roughening of the surface reduced the degree of polarization considerably but changed the emissivity at vertical polarization only slightly. Cluster plots of the data shown six distinguishable surface types: optically opaque bare ice, thin ice (less than 15 mm), roughened ice, ridged ice, rotting wet ice, and open water.

Wavelength-independent, optical-damage-immune LiNbO3 TE-TM mode converter.

Abstract: A novel low-loss electro-optic Ti–LiNbO3 TE–TM mode converter is demonstrated. The polarization conversion is not wavelength selective. Extremely high conversion efficiency with an extinction ratio of more than 33 dB has been achieved with 7-V drive. The device is made immune from the optical damage and Li2O outdiffusion problems typically associated with LiNbO3 devices by the use of a z-propagation waveguide.

Optical computing using hybrid encoded shadow casting

Abstract: The parallel processing property of optics has been recog­ nized as the main driving force behind digital optical computing. A parallel pattern logic operation, first proposed by Tanida and Ichioka, overlaps spatially coded 2-D bina­ ry pixel patterns situated in an optical input plane. These patterns, when illuminated by divergent light beams ema­ nating from a group of LEDs, form different interlaced pro­ jections (shadows) representing different parallel logic oper­ ations in the optical output plane. Since the pattern overlap corresponds to a spatial domain filtering process, it is also known as optical shadow casting (OSC). Using OSC, a large number of 2-D binary or multiple-valued logic inputs can be parallel processed. Another pattern logic method, proposed by Bartelt et al., uses theta modulation to encode the signal grey-level values into different grating orienta­ tions. The combination of these grey-level-dependent grat­ ings form the logic inputs that are to be manipulated by a coherent optical processor. Using spatial-frequency domain filtering, different optical logic functions can be generated. Recently, Yatagai described another pattern logic method in which the spatially encoded patterns are overlapped with an operational mask. Instead of using the OSC LED pat­ terns, this method switches an operational mask for the different logic operations. However, in all these pattern logic methods, either the spatial filtering or pixel casting process is performed by either a transparent or opaque screen. In this communication, the use of a polarization encoding and filtering method to perform lensless OSC logic operations is proposed. Both linear orthogonally polarized and hybrid form polarizations with transparent/opaque mask input, logic signals are used. Using this polarization or hybrid encoded OSC (POSC), doubleor triple-instruction logic operations can be performed. This technique can be extended to generate multivariate binary as well as twovariable multiple-valued logic functions and can also be used in conjunction with the Yatagai's pattern logic method. Pertinent examples such as the design of a binary fulland a ternary half-adder are presented.

Simultaneous optical and infrared polarization measurements of blazars

Abstract: Resultats de mesure de la polarisation et du flux d'un echantillon de 28 blazars (21 objets BL Lac et Y quaasars variables) dans le domaine optique et IR proche. Des modeles comportant deux sources synchrotrons, d'indices spectraux differents, peuvent rendre compte de la variation avec la longueur d'onde tant du flux que de la polarisation

Fiber-optic frequency shifter using a surface acoustic wave incident at an oblique angle

Abstract: A fiber-optic single-sideband frequency shifter has been demonstrated that uses a surface acoustic wave incident upon an optical fiber at an angle to produce phase-matched polarization coupling. Coupling efficiencies as high as 95% at 4.4 MHz have been obtained using 25 W of input power (electrical). A tuning range of 290 kHz was achieved. Sideband suppressions of 40 dB and carrier suppressions as high as 25 dB have been observed.

Low crosstalk 4 × 4 TiLiNbO 3 optical switch with permanently attached polarization maintaining fiber array

Abstract: Several low crosstalk 4 × 4 crossbar optical switch arrays have been fabricated for use at \lambda = 1.3 \mu m. Each array consists of 16 independently functioning directional coupler switches. We describe the typical device performance characteristics. The average insertion loss is 5.2 dB. Crosstalk levels routinely measured < -35 dB. The voltage required to operate the device is ≈ 13 V. The inputs to one of the device arrays were permanently attached to four laser transmitters using lensed polarization maintaining fiber at the laser end and an array of polarization maintaining fibers at the device end.

Nonlinear polarization evolution and instability in a twisted birefringent fiber.

Abstract: We present an exact solution for the polarization evolution in a single-mode optical fiber when the self-induced, the intrinsic, and the twist-induced birefringences are taken into account and the stability characteristics of the nonlinear eigenpolarizations are studied. The relevance of the theory for the operation of nonlinear-optical signal-processing devices is discussed.

H 0323 + 022 - A new BL Lacertae object with extremely rapid variability

Abstract: Results of a multiband, multiepoch series of observations are reported, demonstrating beyond reasonable doubt that H 0323 + 022 is a remarkably variable BL Lac object. The optical nebulosity around the stellar object is confirmed, the stellar optical radiation is polarized, the radio characteristics and the overall electromagnetic spectrum resemble those of other BL Lac objects. Variability is seen in all bands, including radio and broad-band optical variations in days, optical polarization changes on time scales of tens of minutes, and X-ray changes on time scales of about 30 s. H 0323 + 022 is an active galactic nucleus with much of the observed emission emerging from a region less than about 10 to the 12th to 10 to the 14th cm in size.