Science.gov

Sample records for continuous birefringence compensation

  1. Birefringence compensated arrayed waveguide grating

    NASA Astrophysics Data System (ADS)

    Zou, Jun; Xia, Xiang; Lang, Tingting; He, Jian-Jun

    2014-10-01

    In this paper we review our work on birefringence compensated arrayed waveguide grating. We elaborate on a birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) and discuss several demonstrations both in low-index-contrast and high-index-contrast material systems. A 16-channel AWG with 100GHz channel spacing for DWDM application is designed and fabricated in silica-based low-index-contrast waveguide. The experimental results confirm that the polarization-dependent wavelength shift (PDλ) can be tuned by varying the incident/diffraction angle at the star couplers and a birefringence-free property can be achieved without additional fabrication process as compared to conventional AWG. A further validation of this technique is demonstrated in high-index-contrast silicon-on-insulator waveguide, in combination with different diffraction orders for TE and TM polarizations. A birefringence compensated silicon nanowire AWG for CWDM optical interconnects is designed and fabricated. The theoretical and experimental results show that the PDλ can be reduced from 380-420nm to 0.5-3.5 nm, below 25% of the 3 dB bandwidth of the channel response in the wavelength range of 1500 to 1600nm.

  2. New compensation method for bulk optical sensors with multiple birefringences.

    PubMed

    Lee, K S

    1989-06-01

    The dielectric tensor of an anisotropic crystal with multiple perturbations is presented to include the effects of multiple perturbations. To study electromagnetic wave propagation in anisotropic crystals subject to various influences the perturbed dielectric tensor is substituted into Maxwell's equation. Then, a 2 x 2 transmission matrix formalism, based on a normal-mode approach, is extended to anisotropic crystals possessing multiple birefringences to develop compensation schemes for ac optical sensors employing the crystal. It is shown that a new compensation method utilizing two analyzers can eliminate the effects of both unwanted linear birefringences and unwanted circular birefringences on the stability of the ac bulk polarimetric optical sensor. The conditions (here referred to as the quenching condition) in which the compensation method becomes important are also derived for both the voltage (or electric field) and current (or magnetic field) sensors.

  3. Birefringence compensated AWG demultiplexer with angled star couplers.

    PubMed

    Lang, Tingting; He, Jian-Jun; Kuang, Jing-Guo; He, Sailing

    2007-11-12

    A new approach to birefringence compensation in arrayed waveguide gratings (AWG) is proposed. The star couplers are designed according to Rowland circle construction with an oblique incident/diffraction angle, similar to the case of an echelle grating. Such an AWG design is more general and flexible, and the conventional AWG becomes its special case when the grating angle is zero. By appropriately designing the star coupler shape, the birefringence of the arrayed waveguides can be compensated by that of the slab waveguides. The details of the design method and simulation results are presented.

  4. Optical stress sensor based on electro-optic compensation for photoelastic birefringence in a single crystal

    SciTech Connect

    Li Changsheng

    2011-09-20

    An optical stress sensor is proposed by using a single crystal with both electro-optic and photoelastic effects. Different from previous crystal-based stress sensors, the proposed sensor is based on electro-optic compensation for stress-induced birefringence and does not need an additional quarter-wave plate or modulator, because the stress-sensing element is simultaneously used as an electro-optic compensator. Candidate sensing materials include electro-optic crystals of the 3 m symmetry group and all glass with large Kerr coefficients. A primary experiment has demonstrated that the stress-induced birefringence in lithium niobate crystal can be compensated by its electro-optic birefringence. The proposed stress sensor is compact and low cost, and it is possible to achieve closed-loop stress measurement.

  5. A broadband and compact femtosecond delay compensator with birefringent crystals

    NASA Astrophysics Data System (ADS)

    Cao, Yue; Liu, Xinyi; Liu, Wei-Tao

    2017-03-01

    The accurate control of time delay is key to many applications of ultrafast femtosecond lasers, while it often requires high precision optomechanics and specialized optics that may limit the tunability. Here we report a compact, broadband, and low-cost design for the accurate delay control using birefringent crystals. As a demonstration, we used it to synchronize input beams for a difference frequency generation (DFG) stage pumped by a commercial 60 fs optical parametric amplifier (OPA). The DFG power can be boosted up to ~160% in a wide range of 2.8–14 µm, without causing appreciable narrowing of the pulse bandwidth. Our design can be readily incorporated into existing ultrafast laser systems to improve the performance, or for accurate delay control between ultrafast laser pulses.

  6. Inherent temperature compensation of fiber-optic current sensors employing spun highly birefringent fiber.

    PubMed

    Müller, G M; Gu, X; Yang, L; Frank, A; Bohnert, K

    2016-05-16

    We investigate the various contributions to the temperature dependence of an interferometric fiber-optic current sensor employing spun highly-birefringent sensing fiber, in particular, the contributions from the fiber retarder at the fiber coil entrance, the spun fiber's birefringence, and the Faraday effect. We theoretically and experimentally demonstrate that an appropriately designed retarder inherently compensates the temperature dependence of the fiber birefringence and the Faraday effect. We demonstrate insensitivity to temperature to within ± 0.2% between -40 and + 85 °C. Furthermore, we analyze the influence of the retarder parameters on the linearity of the recovered magneto-optic phase shift vs. current and determine a set of parameters that results in a perfectly linear relationship.

  7. Nonplanar fiber-optic sensing head for the compensation of bending-induced birefringence in Faraday current sensors.

    PubMed

    Perciante, César D; Aparicio, Sofía; Illa, Ricardo; Ferrari, José A

    2015-06-20

    We demonstrate the compensation of bending-induced linear birefringence in single-mode fibers coiled in a nonplanar path by alternating orthogonal bending planes. This effect can be applied for the construction of birefringence-free fiber coils in Faraday sensor heads (e.g., in current sensors) to improve their sensitivity. Validation experiments are presented.

  8. Dispersion, birefringence, and amplification characteristics of newly designed dispersion compensating hole-assisted fibers.

    PubMed

    Saitoh, Kunimasa; Varshney, Shailendra K; Koshiba, Masanori

    2007-12-24

    We propose a new design of hole-assisted fiber (HAF) that can compensate for the accumulated dispersion in single-mode fiber link along with dispersion slope, thus providing broadband dispersion compensation over C-band as well as can amplify the signal channels by utilizing the stimulated Raman scattering phenomena. The proposed dispersion-compensating HAF (DCHAF) exhibits the lowest dispersion coefficient of -550 ps/nm/km at 1550 nm with an effective mode area of 15.6 microm(2). A 2.52 km long module of DCHAF amplifies incoming signals by rendering a gain of 4.2 dB with +/-0.8 dB gain flatness over whole C-band. To obtain accurate modal properties of DCHAF, a full-vector finite element method (FEM) solver is employed. The macro-bend loss characteristics of the proposed DCHAF are evaluated using FEM solver in cylindrical coordinate systems of a curved DCHAF, and low bending losses (<10(-2) dB/m for 1 cm bending radius) are obtained for improved DCHAF design while keeping intact its dispersion compensation and Raman amplification properties. We have further investigated the birefringence characteristics that can give significant information on the polarization mode dispersion of DCHAF by assuming a certain deformation (eccentricity e = 7%) either in air-holes or in the doped core or in both at a same time. It is noticed that the distortion in air-holes induces a birefringence of 10(-5), which is larger by a factor of 10 than the birefringence caused due to the core ellipticity. A PMD of 11.3 ps/ radicalkm is obtained at 1550 nm for distorted air-holes DCHAF structure.

  9. A device for continuous monitoring of true central fixation based on foveal birefringence.

    PubMed

    Gramatikov, Boris; Irsch, Kristina; Müllenbroich, Marie; Frindt, Nicole; Qu, Yinhong; Gutmark, Ron; Wu, Yi-Kai; Guyton, David

    2013-09-01

    A device for continuous monitoring of central fixation utilizes birefringence, the property of the Henle fibers surrounding the human fovea, to change the polarization state of light. A circular scan of retinal birefringence, where the scanning circle encompasses the fovea, allows identification of true central fixation-an assessment much needed in various applications in ophthalmology, psychology, and psychiatry. The device allows continuous monitoring for central fixation over an extended period of time in the presence of fixation targets and distracting stimuli, which may be helpful in detecting attention deficit hyperactivity disorder, autism spectrum disorders, and other disorders characterized by changes in the subject's ability to maintain fixation. A proof-of-concept has been obtained in a small study of ADHD patients and normal control subjects.

  10. Quantitative analysis with advanced compensated polarized light microscopy on wavelength dependence of linear birefringence of single crystals causing arthritis

    NASA Astrophysics Data System (ADS)

    Takanabe, Akifumi; Tanaka, Masahito; Taniguchi, Atsuo; Yamanaka, Hisashi; Asahi, Toru

    2014-07-01

    To improve our ability to identify single crystals causing arthritis, we have developed a practical measurement system of polarized light microscopy called advanced compensated polarized light microscopy (A-CPLM). The A-CPLM system is constructed by employing a conventional phase retardation plate, an optical fibre and a charge-coupled device spectrometer in a polarized light microscope. We applied the A-CPLM system to measure linear birefringence (LB) in the visible region, which is an optical anisotropic property, for tiny single crystals causing arthritis, i.e. monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate (CPPD). The A-CPLM system performance was evaluated by comparing the obtained experimental data using the A-CPLM system with (i) literature data for a standard sample, MgF2, and (ii) experimental data obtained using an established optical method, high-accuracy universal polarimeter, for the MSUM. The A-CPLM system was found to be applicable for measuring the LB spectra of the single crystals of MSUM and CPPD, which cause arthritis, in the visible regions. We quantitatively reveal the large difference in LB between MSUM and CPPD crystals. These results demonstrate the usefulness of the A-CPLM system for distinguishing the crystals causing arthritis.

  11. Fully vectorial laser resonator modeling of continuous-wave solid-state lasers including rate equations, thermal lensing and stress-induced birefringence.

    PubMed

    Asoubar, Daniel; Wyrowski, Frank

    2015-07-27

    The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator.

  12. Birefringent-multicrystal, single-pass, continuous-wave second-harmonic-generation in deep-ultraviolet

    NASA Astrophysics Data System (ADS)

    Devi, Kavita; Parsa, S.; Ebrahim-Zadeh, M.

    2016-04-01

    We report implementation of compact cascaded multicrystal scheme for single-pass second-harmonic-generation (SHG), using birefringent crystal, for continuous-wave (cw) deep ultraviolet (UV) generation. The system comprises of 4 cascaded stages, is based on critical phase-matched interaction in β-BaB2O4 (BBO), and pumped by a cw singlefrequency green source at 532 nm. A deep-UV cw output power of 37.7 mW at 266 nm has been obtained with a high passive power stability of 0.12 % rms over more than 4 hours in Gaussian spatial beam quality with a circularity of >70%.

  13. Finite-state compensators for continuous processes

    NASA Technical Reports Server (NTRS)

    Johnson, T. L.

    1978-01-01

    Mathematical representation of feedback systems composed of both continuous and finite-state processes is discussed. Such a representation provides a new viewpoint for the design of computer control systems for industrial processes, and clarifies areas in which further research is required. Some motivating examples are provided.

  14. Cross-splicing method for compensating fiber birefringence in polarization-maintaining fiber ring laser mode locked by nonlinear polarization evolution.

    PubMed

    Wang, Yunzheng; Zhang, Liqiang; Zhuo, Zhuang; Guo, Songzhen

    2016-07-20

    We propose a cross-splicing method, for the first time to our knowledge, to compensate the effect of fiber birefringence in a polarization-maintaining fiber ring laser mode locked by nonlinear polarization evolution. This method has been investigated numerically and experimentally. The results indicate that stable mode-locking pulses can be obtained in the cavity with this method; otherwise, no mode-locking states are achieved. The design processes of the laser cavity are presented. Pulses with single pulse energy of 2.1 nJ are generated at pump power of 460 mW. The spectral bandwidth and pulse duration are 17.5 nm and 11.7 ps, respectively. The tunability of the laser is also studied. The central wavelength can be tuned from 1023.2 to 1045.9 nm.

  15. Birefringence of solid-state laser media: broadband tuning discontinuities and application to laser line narrowing

    SciTech Connect

    Krasinski, J.S.; Band, Y.B.; Chin, T.; Heller, D.F.; Morris, R.C.; Papanestor, P.

    1989-04-15

    Spectral consequences that result from using birefringent media with broadband gain inside of laser cavities containing polarizing elements are described. We show that the laser intensity is modulated as a function of the output frequency unless the cavity elements are carefully aligned so that their polarization axis coincides with a principal optical axis of the gain medium. Analysis of the tuning characteristics of a birefringent polarization-dependent gain medium is exploited to provide a simple method for line narrowing the laser output. By introduction of an intracavity birefringent compensator the narrow-band output can be continuously tuned. Experimental results for alexandrite lasers are presented.

  16. Negative birefringent polyimide films

    NASA Technical Reports Server (NTRS)

    Harris, Frank W. (Inventor); Cheng, Stephen Z. D. (Inventor)

    1994-01-01

    A negative birefringent film, useful in liquid crystal displays, and a method for controlling the negative birefringence of a polyimide film is disclosed which allows the matching of an application to a targeted amount of birefringence by controlling the degree of in-plane orientation of the polyimide by the selection of functional groups within both the diamine and dianhydride segments of the polyimide which affect the polyimide backbone chain rigidity, linearity, and symmetry. The higher the rigidity, linearity and symmetry of the polyimide backbone, the larger the value of the negative birefringence of the polyimide film.

  17. 75 FR 60141 - Division of Longshore and Harbor Workers' Compensation Continuing Collection; Comment request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-29

    ... Death Benefit for Student (LS-266). A copy of the proposed information collection request can be...' Compensation Act. This Act was amended on October 27, 1972, to provide for continuation of death benefits for a child or certain other surviving dependents after the age of 18 years (to age 23) if the...

  18. Controlling birefringence in dielectrics

    NASA Astrophysics Data System (ADS)

    Danner, Aaron J.; Tyc, Tomáš; Leonhardt, Ulf

    2011-06-01

    Birefringence, from the very essence of the word itself, refers to the splitting of light rays into two parts. In natural birefringent materials, this splitting is a beautiful phenomenon, resulting in the perception of a double image. In optical metamaterials, birefringence is often an unwanted side effect of forcing a device designed through transformation optics to operate in dielectrics. One polarization is usually implemented in dielectrics, and the other is sacrificed. Here we show, with techniques beyond transformation optics, that this need not be the case, that both polarizations can be controlled to perform useful tasks in dielectrics, and that rays, at all incident angles, can even follow different trajectories through a device and emerge together as if the birefringence did not exist at all. A number of examples are shown, including a combination Maxwell fisheye/Luneburg lens that performs a useful task and is achievable with current fabrication materials.

  19. 20 CFR 10.500 - What are the basic rules governing continuing receipt of compensation benefits and return to work?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... receipt of compensation benefits and return to work? 10.500 Section 10.500 Employees' Benefits OFFICE OF... to return each disabled employee to suitable work as soon as he or she is medically able. In... § 10.500 What are the basic rules governing continuing receipt of compensation benefits and return...

  20. Mueller matrix microscope with a dual continuous rotating compensator setup and digital demodulation.

    PubMed

    Arteaga, Oriol; Baldrís, Marta; Antó, Joan; Canillas, Adolf; Pascual, Esther; Bertran, Enric

    2014-04-01

    In this paper we describe a new Mueller matrix (MM) microscope that generalizes and makes quantitative the polarized light microscopy technique. In this instrument all the elements of the MU are simultaneously determined from the analysis in the frequency domain of the time-dependent intensity of the light beam at every pixel of the camera. The variations in intensity are created by the two compensators continuously rotating at different angular frequencies. A typical measurement is completed in a little over one minute and it can be applied to any visible wavelength. Some examples are presented to demonstrate the capabilities of the instrument.

  1. New color filter with negative birefringence

    NASA Astrophysics Data System (ADS)

    Shao, Xibin; Yuan, Jianfeng; Wu, Yuan; Ma, Zhenjun; Li, Baozhong; He, Tianbei; Huang, Xinmin

    1998-02-01

    We have presented a special color film with negative optical-birefringence. It can work as color filter and viewing angle extension film of Normally White Twist Nematic Liquid Crystal Displays (NW TN-LCDs). To fabricate such film we synthesized oil-soluble high-performance polyimide (PI) which can be dissolved in the usual organic solvent and shows negative birefringence after lamination. Mixing PI with certain pigment of green, blue and red color in the solvent with suitable proportion individually and laminating on the glass substrate, we obtained color films of good transmission spectrum and suitable chromatic coordinates. The experimental results show that the color filter can work as compensation films of NW TN-LCDs.

  2. Optical birefringence of aorta tissues

    NASA Astrophysics Data System (ADS)

    Tang, G. C.; Wang, W. B.; Pu, Y.; Alfano, R. R.

    2010-02-01

    The optical birefringence of porcine aortic tissues including heated and non-heated tissues was studied using polarization technique. The measurements show that a whole piece of aortic tissue has birefringence properties like a uniaxial crystal. The experiment results indicate that the birefringence status of tissue have a potential application for monitoring changes of tissue structure due to burning, plastic surgery, laser tissue welding and wound healing.

  3. Application of active electrode compensation to perform continuous voltage-clamp recordings with sharp microelectrodes

    NASA Astrophysics Data System (ADS)

    Gómez-González, J. F.; Destexhe, A.; Bal, T.

    2014-10-01

    Objective. Electrophysiological recordings of single neurons in brain tissues are very common in neuroscience. Glass microelectrodes filled with an electrolyte are used to impale the cell membrane in order to record the membrane potential or to inject current. Their high resistance induces a high voltage drop when passing current and it is essential to correct the voltage measurements. In particular, for voltage clamping, the traditional alternatives are two-electrode voltage-clamp technique or discontinuous single electrode voltage-clamp (dSEVC). Nevertheless, it is generally difficult to impale two electrodes in a same neuron and the switching frequency is limited to low frequencies in the case of dSEVC. We present a novel fully computer-implemented alternative to perform continuous voltage-clamp recordings with a single sharp-electrode. Approach. To reach such voltage-clamp recordings, we combine an active electrode compensation algorithm (AEC) with a digital controller (AECVC). Main results. We applied two types of control-systems: a linear controller (proportional plus integrative controller) and a model-based controller (optimal control). We compared the performance of the two methods to dSEVC using a dynamic model cell and experiments in brain slices. Significance. The AECVC method provides an entirely digital method to perform continuous recording and smooth switching between voltage-clamp, current clamp or dynamic-clamp configurations without introducing artifacts.

  4. Birefringent coherent diffraction imaging

    NASA Astrophysics Data System (ADS)

    Karpov, Dmitry; dos Santos Rolo, Tomy; Rich, Hannah; Kryuchkov, Yuriy; Kiefer, Boris; Fohtung, E.

    2016-10-01

    Directional dependence of the index of refraction contains a wealth of information about anisotropic optical properties in semiconducting and insulating materials. Here we present a novel high-resolution lens-less technique that uses birefringence as a contrast mechanism to map the index of refraction and dielectric permittivity in optically anisotropic materials. We applied this approach successfully to a liquid crystal polymer film using polarized light from helium neon laser. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of emergent brilliant X-ray sources. Applications of this novel imaging technique are in disruptive technologies, including novel electronic devices, in which both charge and spin carry information as in multiferroic materials and photonic materials such as light modulators and optical storage.

  5. Optical 90-deg hybrid of birefringent crystals for freely propagating laser beams

    NASA Astrophysics Data System (ADS)

    Wan, Lingyu; Zhi, Yanan; Zhou, Yu; Liu, Liren

    2010-12-01

    An optical 90-deg hybrid of birefringent crystals for freely propagating laser beams is presented. It consists principally of a quarter-wave plate, two pairs of birefringent crystal plates, and a polarization analyzer. The splitting and recombination of the signal and local-oscillator beams are achieved through the birefringence of the crystals, and a 90-deg phase shift is introduced between orthogonally polarized beam components by use of a quarter-wave plate. The optical hybrid has a self-compensating light path, and its correct function is demonstrated in a self-heterodyne measurement setup.

  6. Temperature-independent zero-birefringence polymer for liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Shikanai, M. D.; Tagaya, A.; Koike, Y.

    2016-03-01

    A polymer film that shows almost no orientational birefringence even when the polymer main chain is in an oriented state and almost no temperature dependence of orientational birefringence in the temperature range from around -40 to 85 °C was prepared. This temperature range is important because it is where in-car liquid crystal displays (LCDs) are generally used; therefore, it is desirable to have constant orientational birefringence over this range. We suggest a method to compensate for the intrinsic birefringence and temperature coefficient of intrinsic birefringence of individual polymers by copolymerizing monomers of homopolymers that display opposite signs of the two parameters described above. Analysis of four types of polymers, methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate, benzyl methacrylate (BzMA), and phenyl methacrylate (PhMA), reveal that they possess both positive and negative signs of their temperature coefficient of intrinsic birefringence. Using this approach, we prepare P(MMA/PhMA/BzMA) (39:23:38 wt. %), which exhibits almost no intrinsic birefringence and almost no temperature dependence of intrinsic birefringence. The retardation of this polymer film when drawn uniaxially scarcely changed (between 0.3 and 0.8 nm) between 12 and 70 °C, which is small enough not to cause image degradation in LCDs.

  7. Birefringent corrugated waveguide

    DOEpatents

    Moeller, Charles P.

    1990-01-01

    A corrugated waveguide having a circular bore and noncircularly symmetric corrugations, and preferably elliptical corrugations, provides birefringence for rotation of polarization in the HE.sub.11 mode. The corrugated waveguide may be fabricated by cutting circular grooves on a lathe in a cylindrical tube or rod of aluminum of a diameter suitable for the bore of the waveguide, and then cutting an approximation to ellipses for the corrugations using a cutting radius R.sub.0 from the bore axis that is greater than the bore radius, and then making two circular cuts using a radius R.sub.1 less than R.sub.0 at centers +b and -b from the axis of the waveguide bore. Alternatively, stock for the mandrel may be formed with an elliptical transverse cross section, and then only the circular grooves need be cut on a lathe, leaving elliptical corrugations between the grooves. In either case, the mandrel is first electroplated and then dissolved leaving a corrugated waveguide with noncircularly symmetric corrugations. A transition waveguide is used that gradually varies from circular to elliptical corrugations to couple a circularly corrugated waveguide to an elliptically corrugated waveguide.

  8. Diastolic function and functional capacity after a single session of continuous positive airway pressure in patients with compensated heart failure

    PubMed Central

    Bussoni, Marjory Fernanda; Guirado, Gabriel Negretti; Matsubara, Luiz Shiguero; Roscani, Meliza Goi; Polegato, Bertha Furlan; Minamoto, Suzana Tanni; Bazan, Silméia Garcia Zanati; Matsubara, Beatriz Bojikian

    2014-01-01

    OBJECTIVE: The effects of acute continuous positive airway pressure therapy on left ventricular diastolic function and functional capacity in patients with compensated systolic heart failure remain unclear. METHODS: This randomized, double-blind, placebo-controlled clinical trial included 43 patients with heart failure and a left ventricular ejection fraction <0.50 who were in functional classes I-III according to the New York Heart Association criteria. Twenty-three patients were assigned to continuous positive airway pressure therapy (10 cmH2O), while 20 patients received placebo with null pressure for 30 minutes. All patients underwent a 6-minute walk test (6MWT) and Doppler echocardiography before and immediately after intervention. Clinicaltrials.gov: NCT01088854. RESULTS: The groups had similar clinical and echocardiographic baseline variables. Variation in the diastolic function index (e′) after intervention was associated with differences in the distance walked in both groups. However, in the continuous positive airway pressure group, this difference was greater (continuous positive airway pressure group: Δ6MWT = 9.44+16.05×Δe′, p = 0.002; sham group: Δ6MWT = 7.49+5.38×Δe′; p = 0.015). There was a statistically significant interaction between e′ index variation and continuous positive airway pressure for the improvement of functional capacity (p = 0.020). CONCLUSIONS: Continuous positive airway pressure does not acurately change the echocardiographic indexes of left ventricle systolic or diastolic function in patients with compensated systolic heart failure. However, 30-minute continuous positive airway pressure therapy appears to have an effect on left ventricular diastolic function by increasing functional capacity. PMID:24838902

  9. Note: In situ measurement of vacuum window birefringence by atomic spectroscopy.

    PubMed

    Steffen, Andreas; Alt, Wolfgang; Genske, Maximilian; Meschede, Dieter; Robens, Carsten; Alberti, Andrea

    2013-12-01

    We present an in situ method to measure the birefringence of a single vacuum window by means of microwave spectroscopy on an ensemble of cold atoms. Stress-induced birefringence can cause an ellipticity in the polarization of an initially linearly polarized laser beam. The amount of ellipticity can be reconstructed by measuring the differential vector light shift of an atomic hyperfine transition. Measuring the ellipticity as a function of the linear polarization angle allows us to infer the amount of birefringence Δn at the level of 10(-8) and identify the orientation of the optical axes. The key benefit of this method is the ability to separately characterize each vacuum window, allowing the birefringence to be precisely compensated in existing vacuum apparatuses.

  10. Note: In situ measurement of vacuum window birefringence by atomic spectroscopy

    SciTech Connect

    Steffen, Andreas; Alt, Wolfgang; Genske, Maximilian; Meschede, Dieter; Robens, Carsten; Alberti, Andrea

    2013-12-15

    We present an in situ method to measure the birefringence of a single vacuum window by means of microwave spectroscopy on an ensemble of cold atoms. Stress-induced birefringence can cause an ellipticity in the polarization of an initially linearly polarized laser beam. The amount of ellipticity can be reconstructed by measuring the differential vector light shift of an atomic hyperfine transition. Measuring the ellipticity as a function of the linear polarization angle allows us to infer the amount of birefringence Δn at the level of 10{sup −8} and identify the orientation of the optical axes. The key benefit of this method is the ability to separately characterize each vacuum window, allowing the birefringence to be precisely compensated in existing vacuum apparatuses.

  11. Compensation Chemistry

    ERIC Educational Resources Information Center

    Roady, Celia

    2008-01-01

    Congress, the news media, and the Internal Revenue Service (IRS) continue to cast a wary eye on the compensation of nonprofit leaders. Hence, any college or university board that falls short of IRS expectations in its procedures for setting the president's compensation is putting the president, other senior officials, and board members at…

  12. Pre-compensation for continuous-path running trajectory error in high-speed machining of parts with varied curvature features

    NASA Astrophysics Data System (ADS)

    Jia, Zhenyuan; Song, Dening; Ma, Jianwei; Gao, Yuanyuan

    2017-01-01

    Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.

  13. Continuous composite finite-time convergent guidance laws with autopilot dynamics compensation.

    PubMed

    He, Shaoming; Lin, Defu

    2015-09-01

    This paper has proposed two continuous composite finite-time convergent guidance laws to intercept maneuvering targets in the presence of autopilot lag: one is for hit-to-kill and the other is for zeroing the line-of-sight (LOS) angular rate. More specifically, the nonlinear disturbance observer (NDOB) is used to estimate the lumped uncertainty online while the finite-time control technique is used to fulfill the design goal in finite time. The key feature in derivation of the proposed guidance law is that two integral-type Lyapunov functions are used to avoid analytic differentiation of virtual control law encountered with traditional backstepping. The finite-time stability of the closed-loop nonlinear observer-controller system is established using finite-time bounded (FTB) function and Lyapunov function methods. Numerical simulations with some comparisons are carried out to demonstrate the superiority of the proposed method.

  14. A broadband Soleil-Babinet compensator for ultrashort light pulses

    NASA Astrophysics Data System (ADS)

    Xu, Shixiang; Ma, Yingkun; Cai, Yi; Lu, Xiaowei; Zeng, Xuanke; Chen, Hongyi; Li, Jingzhen

    2013-12-01

    This letter reports a novel design for a broadband Soleil-Babinet compensator including two pairs of optical wedges plus one plate. According to our birefringent dispersion compensation model, we can eliminate the first-order birefringent phase retardation (BPR) dispersion by using three different birefringent crystals. Our results show a Soleil-Babinet compensator based on a MgF2/ADP/KDP combination can work from 0° to 360° phase compensation with the maximal residual BPR less than 6° within the spectral region from 0.65 to 0.95 μm. The residual BPR of the compensator increases monotonically with the spectral deviation from the designed central wavelength, so our compensator is very suitable to be used for broadband laser pulses with most of their energies around the central wavelengths.

  15. Phase and birefringence aberration correction

    DOEpatents

    Bowers, Mark; Hankla, Allen

    1996-01-01

    A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90.degree. such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system.

  16. Phase and birefringence aberration correction

    DOEpatents

    Bowers, M.; Hankla, A.

    1996-07-09

    A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90{degree} such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system. 5 figs.

  17. Birefringence changes associated with isometric contraction and rapid shortening steps in frog skeletal muscle fibres.

    PubMed Central

    Irving, M

    1993-01-01

    1. Muscle birefringence, the difference between the refractive indices of light polarized parallel and perpendicular to the muscle fibre axis, was measured at 3 degrees C in intact single fibres isolated from frog muscle. Resting birefringence was 2.20 +/- 0.02 x 10(-3) (mean +/- S.E.M., n = 44) at sarcomere length 2.4-2.7 microns and 2.35 +/- 0.03 x 10(-3) (n = 19) at 3.5-3.8 microns. 2. Birefringence decreased during isometric twitch or tetanic contractions. The peak change in a twitch at sarcomere length 2.6 microns, determined by two independent methods, was 0.150 +/- 0.017 x 10(-3) (mean +/- S.E.M., n = 6). The corresponding value after 0.4 s of tetanic stimulation was 0.167 +/- 0.012 x 10(-3) (n = 6). 3. The birefringence change had a shorter latency than tension and reached its half-maximum value earlier than tension. The difference in time to half-maximum in tetani was 11.5 +/- 1.3 ms (mean +/- S.E.M., n = 6) at 3 degrees C. After stimulation birefringence recovered to its pre-stimulus baseline more slowly than tension. 4. The birefringence decrease after 0.4 s of tetanic stimulation was linearly related to the expected degree of overlap between actin and myosin filaments in the sarcomere length range 2.6-3.6 microns. The amplitude of the birefringence decrease at full filament overlap (sarcomere length 2.2 microns) was estimated to be 0.235 +/- 0.015 x 10(-3). 5. Birefringence changes associated with shortening steps of 0.9% fibre length at sarcomere length 2.6 microns exhibited four phases corresponding to those of the tension transient. There was no consistent birefringence change during the length step itself. During the rapid tension recovery birefringence increased by 0.014 +/- 0.001 x 10(-3) (n = 3), measured from the end of the length step to 2 ms later. Birefringence continued to increase as tension recovery slowed, reaching a peak about 10 ms after the step, then recovered with a rate similar to that of the final tension recovery. 6. These

  18. Birefringence in time-dependent moving media

    NASA Astrophysics Data System (ADS)

    Lin, Shirong; Zhang, Ruoyang; Zhai, Yanwang; Wei, Jianye; Zhao, Qing

    2016-08-01

    Electromagnetic wave propagation in one- and two-dimensional time-dependent moving media is investigated in this paper. We identify another origin of linear birefringence caused by the component of the flow perpendicular to the wave vector. Previously, birefringence is induced by applying external electric and magnetic fields to non-crystalline material. Here it is shown that the time-varying velocity field also contributes to such a phenomenon. Our results indicate that the parallel component, time-dependent or not, will not yield birefringence. Furthermore, the time-dependent flow also results in a frequency shift. One-dimensional simulation is conducted to demonstrate these effects.

  19. Spectral contents readout of birefringent sensor

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.

    1989-01-01

    The technical objective of this research program was to develop a birefringent sensor, capable of measuring strain/stress up to 2000 F and a readout system based on Spectral Contents analysis. As a result of the research work, a data acquisition system was developed, capable of measuring strain birefringence in a sensor at 2000 F, with multi-point static and dynamic capabilities. The system uses a dedicated spectral analyzer for evaluation of stress-birefringence and a PC-based readout. Several sensor methods were evaluated. Fused silica was found most satisfactory. In the final evaluation, measurements were performed up to 2000 F and the system performance exceeded expectations.

  20. Crystal chemistry of birefringent hydrogrossular

    NASA Astrophysics Data System (ADS)

    Antao, Sytle M.

    2015-06-01

    Crystal structure refinements of two fine-grained, massive, birefringent hydrogarnet samples from South Africa [1. green "jade" and 2. pink "jade"] were carried out with the Rietveld method, cubic space group and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Electron-microprobe analysis (EMPA) gave bulk compositions as follows: (1) (Ca2.997Mg0.003)Σ3{Al1.794Fe{0.196/3+}Cr{0.004/3+}Mn{0.003/3+}Ti{0.002/4+}}Σ2[(SiO4)2.851(O4H4)0.151]Σ3 and (2) (Ca2.993Mg0.007)Σ3{Al1.977Fe{0.020/3+}Mn{0.003/3+}Cr{0.001/3+}}Σ2[(SiO4)2.272(O4H4)0.730]Σ3. Their crystal structure was modeled well as indicated by the Rietveld refinement statistical indicators where the reduced χ2 and overall R ( F 2) values are 1.133 and 0.0467, respectively, for sample 1 and 1.308 and 0.0342 for sample 2. Two cubic phases are contained in each sample. For phase 1a in sample 1, the weight fraction (%), unit-cell parameter (Å), and O-H bond distance (Å) are as follows: 74.4(1), a = 11.88874(4), and O-H = 0.98(9); the corresponding data for phase 1b are 25.6(1), a = 11.9280(5), and O-H = 0.91(9). For phase 2a in sample 2, the corresponding data are 52.0(1), a = 12.0591(1), and O-H = 0.90(6); the corresponding data for phase 2b are 48.0(1), a = 11.9340(2), and O-H = 0.90(7). The anisotropic displacement ellipsoids for the O atoms show no unusual features and are not elongated along the "Si-O" bond direction, which is written as Z-O, because of the general formula, X3Y2Z3O12, for garnet. Phase 1a is near end-member grossular, ideally Ca3Al2Si3O12. The deficiencies of the site occupancy factors ( sofs) for the Si (=Z) site indicate that there are significant [O4H4]4- replacing [SiO4]4-. The Z-O distance is large in phase 1b, phases 2a, and 2b compared to a typical Z-O distance in anhydrous grossular or phase 1a. The H atoms occur in different environments around the vacant Z site in the two samples, and they may also bond to the O atoms surrounding the X and Y sites

  1. Giant birefringence and tunable differential group delay in Bragg reflector based on tapered three-dimensional hollow waveguide

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Sakagichi, Takahiro; Koyama, Fumio

    2009-02-01

    A tunable Bragg reflector based on a tapered three-dimensional (3D) hollow waveguide (HWG) with variable taper angle has been proposed and demonstrated. A large grating coupling coefficient for a large reflection band and a giant birefringence of 0.01 have been achieved by optimizing the structure of the 3D HWG. The large birefringence causes a delay difference between the orthogonal polarizations and the variable taper angle provides tuning in the delay difference. A 13 ps tuning in differential group delay has been reported with a 3 mm long compact device, which can be used for adjustable compensation of polarization mode dispersion in optical fiber links.

  2. Design of a pentagonal photonic crystal fiber with high birefringence and large flattened negative dispersion.

    PubMed

    Li, Xuyou; Liu, Pan; Xu, Zhenlong; Zhang, Zhiyong

    2015-08-20

    Novel pentagonal photonic crystal fiber with high birefringence, large flattened negative dispersion, and high nonlinearity is proposed. The dispersion and birefringence properties of this structure are simulated and analyzed numerically based on the full vector finite element method (FEM). Numerical results indicate that the fiber obtains a large average dispersion of -611.9  ps/nm/km over 1,460-1,625 nm and -474  ps/nm/km over 1425-1675 nm wavelength bands for two kinds of optimized designs, respectively. In addition, the proposed PCF shows a high birefringence of 1.67×10-2 and 1.75×10-2 at the operating wavelength of 1550 nm. Moreover, the influence of the possible variation in the parameters during the fabrication process on the dispersion and birefringence properties is studied. The proposed PCF would have important applications in polarization maintaining transmission systems, residual dispersion compensation, supercontinuum generation, and the design of widely tunable wavelength converters based on four-wave mixing.

  3. Form birefringent microstructures: modeling and design

    NASA Astrophysics Data System (ADS)

    Richter, I.; Sun, Pang Chen; Xu, Fang; Fainman, Yeshaiahu

    1995-04-01

    Diffraction characteristics of high-spatial-frequency gratings (HSF) are evaluated for application to polarization-selective computer generated holograms using two different approaches, second order effective-medium theory (EMT) and rigorous coupled-wave analysis (RCWA). The reflectivities and the phase differences for TE and TM polarized waves are investigated in terms of various input parameters, and results obtained with second order EMT and RCWA are compared. It is shown that while the reflection characteristics can be accurately modeled using the second order EMT, the phase difference created by form birefringence for TE and TM polarized waves requires the use of a more rigorous, RCWA approach. Design of HSF gratings in terms of their form birefringence and reflectivity properties is discussed in conjunction with polarization-selective computer generated holograms. A specific design optimization example furnishes a grating profile that provides a trade-off between largest form birefringence and lowest reflectivities.

  4. Design considerations of form birefringent microstructures

    NASA Astrophysics Data System (ADS)

    Richter, Ivan; Sun, Pang-Chen; Xu, Fang; Fainman, Yeshayahu

    1995-05-01

    Diffraction characteristics of high-spatial-frequency (HSF) gratings are evaluated for application to polarization-selective computer-generated second-order effective-medium theory (EMT) and rigorous coupled-wave analysis (RCWA). The reflectivities and the phase differences for TE-and TM-polarized waves are investigated in terms of various input parameters, and results obtained with second-order EMT and RCWA are compared. It is shown that although the reflection characteristics can be accurately modeled with the second-order EMT, the phase difference created by form birefringence for TE-and TM-polarized waves requires the use of a more rigorous, RCWA approach. The design of HSF gratings in terms of their form birefringence and reflectivity properties is discussed in conjunction with polarization-selective computer-generated holo-grams. A specific design optimization example furnishes a grating profile that provides a trade-off between the largest form birefringence and the lowest reflectivities.

  5. Electro-optical tunable birefringent filter

    SciTech Connect

    Levinton, Fred M

    2012-01-31

    An electrically tunable Lyot type filter is a Lyot that include one or more filter elements. Each filter element may have a planar, solid crystal comprised of a material that exhibits birefringence and is electro-optically active. Transparent electrodes may be coated on each face of the crystal. An input linear light polarizer may be located on one side of the crystal and oriented at 45 degrees to the optical axis of the birefringent crystal. An output linear light polarizer may be located on the other side of the crystal and oriented at -45 degrees with respect to the optical axis of the birefringent crystal. When an electric voltage is applied between the electrodes, the retardation of the crystal changes and so does the spectral transmission of the optical filter.

  6. Research on spectroscopic imaging. Volume 1: Technical discussion. [birefringent filters

    NASA Technical Reports Server (NTRS)

    Title, A.; Rosenberg, W.

    1979-01-01

    The principals of operation and the capabilities of birefringent filters systems are examined. Topics covered include: Lyot, Solc, and partial polarizer filters; transmission profile management; tuning birefringent filters; field of view; bandpass control; engineering considerations; and recommendations. Improvements for field of view effects, and the development of birefringent filters for spaceflight are discussed in appendices.

  7. Theoretical and experimental study of laser radiation propagating in a medium with thermally induced birefringence and cubic nonlinearity.

    PubMed

    Kuzmina, M S; Martyanov, M A; Poteomkin, A K; Khazanov, E A; Shaykin, A A

    2011-10-24

    We consider a problem of laser radiation propagating in a medium with birefringence of two types: linear birefringence independent of intensity and polarization, and intensity and polarization dependent circular birefringence caused by cubic nonlinearity. It is shown theoretically and experimentally that the efficiency of the broadly employed method of linear depolarization compensation by means of a 90° polarization rotator decreases with increasing В-integral (nonlinear phase incursion induced by cubic nonlinearity). The accuracy of polarization transformation by means of a half-wave and a quarter-wave plate also decreases if В > 1. By the example of a λ/4 plate it is shown that this parasitic effect may be suppressed considerably by choosing an optimal angle of inclination of the optical axis of the plate.

  8. Modeling and minimizing interference from corneal birefringence in retinal birefringence scanning for foveal fixation detection.

    PubMed

    Irsch, Kristina; Gramatikov, Boris; Wu, Yi-Kai; Guyton, David

    2011-07-01

    Utilizing the measured corneal birefringence from a data set of 150 eyes of 75 human subjects, an algorithm and related computer program, based on Müller-Stokes matrix calculus, were developed in MATLAB for assessing the influence of corneal birefringence on retinal birefringence scanning (RBS) and for converging upon an optical/mechanical design using wave plates ("wave-plate-enhanced RBS") that allows foveal fixation detection essentially independently of corneal birefringence. The RBS computer model, and in particular the optimization algorithm, were verified with experimental human data using an available monocular RBS-based eye fixation monitor. Fixation detection using wave-plate-enhanced RBS is adaptable to less cooperative subjects, including young children at risk for developing amblyopia.

  9. Modeling and minimizing interference from corneal birefringence in retinal birefringence scanning for foveal fixation detection

    PubMed Central

    Irsch, Kristina; Gramatikov, Boris; Wu, Yi-Kai; Guyton, David

    2011-01-01

    Utilizing the measured corneal birefringence from a data set of 150 eyes of 75 human subjects, an algorithm and related computer program, based on Müller-Stokes matrix calculus, were developed in MATLAB for assessing the influence of corneal birefringence on retinal birefringence scanning (RBS) and for converging upon an optical/mechanical design using wave plates (“wave-plate-enhanced RBS”) that allows foveal fixation detection essentially independently of corneal birefringence. The RBS computer model, and in particular the optimization algorithm, were verified with experimental human data using an available monocular RBS-based eye fixation monitor. Fixation detection using wave-plate-enhanced RBS is adaptable to less cooperative subjects, including young children at risk for developing amblyopia. PMID:21750772

  10. Polarized light in birefringent samples (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chue-Sang, Joseph; Bai, Yuqiang; Ramella-Roman, Jessica

    2016-02-01

    Full-field polarized light imaging provides the capability of investigating the alignment and density of birefringent tissue such as collagen abundantly found in scars, the cervix, and other sites of connective tissue. These can be indicators of disease and conditions affecting a patient. Two-dimensional polarized light Monte Carlo simulations which allow the input of an optical axis of a birefringent sample relative to a detector have been created and validated using optically anisotropic samples such as tendon yet, unlike tendon, most collagen-based tissues is significantly less directional and anisotropic. Most important is the incorporation of three-dimensional structures for polarized light to interact with in order to simulate more realistic biological environments. Here we describe the development of a new polarization sensitive Monte Carlo capable to handle birefringent materials with any spatial distribution. The new computational platform is based on tissue digitization and classification including tissue birefringence and principle axis of polarization. Validation of the system was conducted both numerically and experimentally.

  11. Flow-induced birefringence measurement system using dual-crystal transverse electro-optic modulator for microgravity fluid physics applications

    NASA Technical Reports Server (NTRS)

    Mackey, Jeffrey R.

    1999-01-01

    We have developed a new instrument that can measure fast transient birefringence and polymer chain orientation angle in complex fluids. The instrument uses a dual-crystal transverse electro-optic modulator with the second crystal's modulation voltage applied 180 deg out of phase from that of the first crystal. In this manner, the second crystal compensates for the intrinsic static birefringence of the first crystal, and it doubles the modulation depth. By incorporating a transverse electro-optic modulator with two lithium-niobate (LiNbO3) crystals oriented orthogonal to each other with a custom-designed optical system, we have produced a very small robust instrument capable of fast transient retardation measurements. By measuring the sample thickness or optical path length through the sample, we can calculate the transient birefringence. This system can also measure dichroism. We have compared the calibration results and retardation and orientation angle measurements of this instrument with those of a photoelastic modulator (PEM) based system using a quarter wave plate and a high-precision 1/16-wave plate to simulate a birefringent sample. Transient birefringence measurements on the order of 10(exp -9) can be measured using either modulator.

  12. Fringes of equal tangential inclination by curvature-induced birefringence

    NASA Astrophysics Data System (ADS)

    Medhat, M.; Hendawy, N. I.; Zaki, A. A.

    2003-02-01

    A new kind of interference fringes, fringes of equal tangential inclination by curvature-induced birefringence, is presented. These are two-beam interference fringes produced by bending a thin sheet of birefringent material into a part of an exact cylinder such that the curvature is constant. Due to this curvature there is a uniform birefringence being induced. The change in birefringence induced by applying different radii of curvatures to a Fortepan sheet is measured. The stored (fixed) or natural birefringence of this sheet is deduced.

  13. Micromanipulation studies of chromosome movement. II. Birefringent chromosomal fibers and the mechanical attachment of chromosomes to the spindle

    PubMed Central

    1979-01-01

    The degree of mechanical coupling of chromosomes to the spindles of Nephrotoma and Trimeratropis primary spermatocytes varies with the stage of meiosis and the birefringent retardation of the chromosomal fibers. In early prometaphase, before birefringent chromosomal fibers have formed, a bivalent can be displaced toward a spindle pole by a single, continuous pull with a microneedle. Resistance to poleward displacement increases with increased development of the chromosomal fibers, reaching a maximum at metaphase. At this stage kinetochores cannot be displaced greater than 1 micrometer toward either spindle pole, even by a force which is sufficient to displace the entire spindle within the cell. The abolition of birefringence with either colcemid or vinblastine results in the loss of chromosome-spindle attachment. In the absence of birefringent fibers a chromosome can be displaced anywhere within the cell. The photochemical inactivation of colcemid by irradiation with 366-nm light results in the reformation of birefringent chromosomal fibers and the concomitant re-establishment of chromosome attachment to the spindle. These results support the hypothesis that the birefringent chromosomal fibers anchor the chromosomes to the spindle and transmit the force for anaphase chromosome movement. PMID:479316

  14. A birefringence study of changes in myosin orientation during relaxation of skinned muscle fibers induced by photolytic ATP release.

    PubMed Central

    Peckham, M; Ferenczi, M A; Irving, M

    1994-01-01

    The birefringence of isolated skinned fibers from rabbit psoas muscle was measured continuously during relaxation from rigor produced by photolysis of caged ATP at sarcomere length 2.8-2.9 microns, ionic strength 0.1 M, 15 degrees C. Birefringence, the difference in refractive index between light components polarized parallel and perpendicular to the fiber axis, depends on the average degree of alignment of the myosin head domain with the fiber axis. After ATP release birefringence increased by 5.8 +/- 0.7% (mean +/- SE, n = 6) with two temporal components. A small fast component had an amplitude of 0.9 +/- 0.2% and rate constant of 63 s-1. By the completion of this component, the instantaneous stiffness had decreased to about half the rigor value, and the force response to a step stretch showed a rapid (approximately 1000 s-1) recovery phase. Subsequently a large slow birefringence component with rate constant 5.1 s-1 accompanied isometric force relaxation. Inorganic phosphate (10 mM) did not affect the fast birefringence component but accelerated the slow component and force relaxation. The fast birefringence component was probably caused by formation of myosin.ATP or myosin.ADP.Pi states that are weakly bound to actin. The average myosin head orientation at the end of this component is slightly more parallel to the fiber axis than in rigor. PMID:7811926

  15. Anisotropic Transverse Stress in Calcite and Sapphire Measured Using Birefringence

    NASA Astrophysics Data System (ADS)

    Tear, Gareth R.; Chapman, David J.; Eakins, Daniel E.; Proud, William G.

    2015-06-01

    Many significant geological minerals have anisotropic crystal structures leading to material properties that are anisotropic, including compressive elastic behaviour. A non-invasive approach to investigate the directional dependence of transverse stress in these materials during shock compression would supplement current understanding. As many geological minerals are transparent and hence optically anisotropic, measuring the change in birefringence induced by transverse stress in the material offers the possibility of a fast, non-invasive approach to probe transverse behaviour. Shock compression experiments have been performed on a-cut calcite and a-cut sapphire for strain rates of order 105 s-1 and up to longitudinal stresses of 2 GPa for calcite and 12 GPa for sapphire. We present measured changes in birefringence for these materials under shock compression, comparing with current and past literature as well as an in house optical model. The authors would like to thank Mr Steve Johnson and Mr David Pittman for technical support. The Institute of Shock Physics acknowledges the continued support of AWE and Imperial College London.

  16. Birefringence insensitive optical coherence domain reflectometry system

    DOEpatents

    Everett, Matthew J.; Davis, Joseph G.

    2002-01-01

    A birefringence insensitive fiber optic optical coherence domain reflectometry (OCDR) system is provided containing non-polarization maintaining (non-PM) fiber in the sample arm and the reference arm without suffering from signal degradation caused by birefringence. The use of non-PM fiber significantly reduces the cost of the OCDR system and provides a disposable or multiplexed section of the sample arm. The dispersion in the reference arm and sample arm of the OCDR system are matched to achieve high resolution imaging. This system is useful in medical applications or for non-medical in situ probes. The disposable section of non-PM fiber in the sample arm can be conveniently replaced when contaminated by a sample or a patient.

  17. Photo Replication of Birefringent Phase Structures

    NASA Astrophysics Data System (ADS)

    Verstegen, Emile J. K.; Hendriks, Benno H. W.; van As, Marco A. J.; Tukker, Teus W.

    2004-07-01

    Dual layer blu-ray disc (BD) and dual layer small form factor optical drive (SFFO) as well as BD / digital versatile disc (DVD) / compact disc (CD) compatible systems, require phase structures to cope with the different amount of spherical aberration for the various different operating modes. Birefringent phase structures open up to the possibility to cope with these different amounts of aberration in the various readout modes, but so far no manufacturing methods are known which lead to low cost and stable structures. A novel replication method, based on the photo-polymerization of a liquid crystalline monomer is presented to make birefringent phase structures. Apart from enabling mass production, the process allows a phase structure to be directly produced on top of an ordinary objective lens, allowing weight and size reduction of the compatible optical pick up.

  18. Spectral-Content Readout Of Birefringent Sensor

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.

    1993-01-01

    Stresses and strains measured optically at temperatures up to 2,000 degrees F. Spectrum of light processed through polarizer, sensor, analyzer, and associated optical components measured and processed to extract amount of retardation and, equivalently, stress-induced birefringence in sensor. Method offers same advantages as electrical strain sensors, including acquisition of data from multiple locations and under dynamic conditions. Additional advantage: immunity of fiber-optic transmission to interference by electromagnetic interference at radio and lower frequencies.

  19. Reconsidering the origins of Forsbergh birefringence patterns

    NASA Astrophysics Data System (ADS)

    Schilling, A.; Kumar, A.; McQuaid, R. G. P.; Glazer, A. M.; Thomas, P. A.; Gregg, J. M.

    2016-07-01

    In 1949, Forsbergh, Jr. reported spontaneous spatial ordering in the birefringence patterns seen in flux-grown BaTi O3 crystals under the transmission polarized light microscope [Phys. Rev. 76, 1187 (1949), 10.1103/PhysRev.76.1187]. Stunningly regular square-net arrays were often only found within a finite temperature window and could be induced on both heating and cooling, suggesting genuine thermodynamic stability. At the time, Forsbergh rationalized the patterns to have resulted from the impingement of ferroelastic domains, creating a complex tessellation of variously shaped domain packets. However, no direct evidence for the intricate microstructural arrangement proposed by Forsbergh has subsequently been found. Moreover, there are no robust thermodynamic arguments to explain the finite region of thermal stability, its occurrence just below the Curie temperature, and the apparent increase in entropy associated with the loss of the Forsbergh pattern on cooling. Despite decades of research on ferroelectrics, this ordering phenomenon and its thermodynamic origin have hence remained a mystery. In this paper, we reexamine the microstructure of flux-grown BaTi O3 crystals, which show Forsbergh birefringence patterns. Given an absence of any obvious arrays of domain polyhedra or even regular shapes of domain packets, we suggest an alternative origin for the Forsbergh pattern in which sheets of orthogonally oriented ferroelastic stripe domains simply overlay one another. We show explicitly that the Forsbergh birefringence pattern occurs if the periodicity of the stripe domains is above a critical value. Moreover, by considering well-established semiempirical models, we show that the significant domain coarsening needed to generate the Forsbergh birefringence is fully expected in a finite window below the Curie temperature. We hence present a much more straightforward rationalization of the Forsbergh pattern than that originally proposed in which exotic thermodynamic

  20. Transient birefringence effects in electromagnetically induced transparency

    SciTech Connect

    Parshkov, O M

    2015-11-30

    We report the results of numerical modelling of transient birefringence that arises as a result of electromagnetically induced transparency on degenerate quantum transitions between the states with J = 0, 1 and 2 in the presence of the Doppler broadening of spectral lines. It is shown that in the case of a linearly polarised control field, the effect of transient birefringence leads to a decay of the input circularly polarised probe pulse into separate linearly polarised pulses inside a medium. In the case of a circularly polarised control field, the effect of transient birefringence manifests itself in a decay of the input linearly polarised probe pulse into separate circularly polarised pulses. It is shown that the distance that a probe pulse has to pass in a medium before decaying into subpulses is considerably greater in the first case than in the second. The influence of the input probe pulse power and duration on the process of spatial separation into individual pulses inside a medium is studied. A qualitative analysis of the obtained results is presented. (nonlinear optical phenomena)

  1. Propagation of laser radiation in a medium with thermally induced birefringence and cubic nonlinearity.

    PubMed

    Kochetkova, M S; Martyanov, M A; Poteomkin, A K; Khazanov, E A

    2010-06-07

    A system of differential equations describing, neglecting diffraction, the propagation of laser radiation in a medium with birefringence and cubic nonlinearity is derived. It is shown that the efficiency of depolarization compensation by means of a 90 degrees polarization rotator or a Faraday mirror decreases with increasing B-integral (nonlinear phase incursion). Comparison of the effectiveness of the considered method in the case of incident linear and circular polarization showed that for the circular polarization the optimal angle of polarization rotator is different from 90 degrees and the degree of polarization is less than for the linear one.

  2. Detecting strain in birefringent materials using spectral polarimetry

    NASA Technical Reports Server (NTRS)

    Ragucci, Anthony J. (Inventor); Cisar, Alan J. (Inventor); Huebschman, Michael L. (Inventor); Garner, Harold R. (Inventor)

    2010-01-01

    A method, computer program product and system for analyzing multispectral images from a plurality of regions of birefringent material, such as a polymer film, using polarized light and a corresponding polar analyzer to identify differential strain in the birefringent material. For example, the birefringement material may be low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene chloride, polyester, nylon, or cellophane film. Optionally, the method includes generating a real-time quantitative strain map.

  3. Two-dimensional electronic spectroscopy with birefringent wedges

    SciTech Connect

    Réhault, Julien; Maiuri, Margherita; Oriana, Aurelio; Cerullo, Giulio

    2014-12-15

    We present a simple experimental setup for performing two-dimensional (2D) electronic spectroscopy in the partially collinear pump-probe geometry. The setup uses a sequence of birefringent wedges to create and delay a pair of phase-locked, collinear pump pulses, with extremely high phase stability and reproducibility. Continuous delay scanning is possible without any active stabilization or position tracking, and allows to record rapidly and easily 2D spectra. The setup works over a broad spectral range from the ultraviolet to the near-IR, it is compatible with few-optical-cycle pulses and can be easily reconfigured to two-colour operation. A simple method for scattering suppression is also introduced. As a proof of principle, we present degenerate and two-color 2D spectra of the light-harvesting complex 1 of purple bacteria.

  4. Transfer matrix for treating stratified media including birefringent crystals.

    PubMed

    Essinger-Hileman, Thomas

    2013-01-10

    Birefringent crystals are extensively used to manipulate polarized light. The generalized transfer matrix developed allows efficient calculation of the full polarization state of light transmitted through and reflected by a stack of arbitrarily many discrete layers of isotropic and birefringent materials at any frequency and angle of incidence. The matrix of a uniaxial birefringent crystal with arbitrary rotation is calculated, along with its reduction to the matrix of an isotropic medium. This method is of great practical importance where tight control of systematic effects is needed in optical systems employing birefringent crystals, one example being wave plates used by cosmic microwave background polarimetry with wide field-of-view telescopes.

  5. Distributed measurement of birefringence dispersion in polarization-maintaining fibers.

    PubMed

    Tang, Feng; Wang, Xiang-Zhao; Zhang, Yimo; Jing, Wencai

    2006-12-01

    A new method to measure the birefringence dispersion in high-birefringence polarization-maintaining fibers is presented using white-light interferometry. By analyzing broadening of low-coherence interferograms obtained in a scanning Michelson interferometer, the birefringence dispersion and its variation along different fiber sections are acquired with high sensitivity and accuracy. Birefringence dispersions of two PANDA fibers at their operation wavelength are measured to be 0.011 ps/(km nm) and 0.018 ps/(km nm), respectively. Distributed measurement capability of the method is also verified experimentally.

  6. Preferential alignment of birefringent tissue measured with polarization sensitive techniques

    NASA Astrophysics Data System (ADS)

    Ramella-Roman, J. C.; Ruiz, T.; Ghassemi, P.; Travis, T. E.; Shupp, J. W.; Chue-Sang, J.; Bai, Y.

    2015-02-01

    Assessing collagen alignment is of interest when evaluating a therapeutic strategy and evaluating its outcome in scar management. In this work we introduce a theoretical and experimental methodology for the quantification of collagen and birefringent media alignment based on polarized light transport. The technique relies on the fact that these materials exhibit directional anisotropy. A polarized Monte Carlo model and a spectro-polarimetric imaging system were devised to predict and measure the impact of birefringence on an impinging polarized light beam. Experiments conducted on birefringent phantoms, and biological samples consisting of highly packed parallel birefringent fibers, showed a good agreement with the analytical results.

  7. 10-Gb/s PMD compensation using ferroelectric liquid crystals and several PMD penalty signals

    NASA Astrophysics Data System (ADS)

    Hinz, S.; Sandel, D.; Yoshida-Dierolf, M.; Mirvoda, V.; Noe, Reinhold; Weyrauch, Thomas; Beresnev, L.; Haase, Wolfgang

    1999-04-01

    Polarization mode dispersion (PMD) hampers development of greater than or equal to 10 Gb/s trunk lines but can be compensated by endless polarization controllers and birefringent fiber. We demonstrate automatic 10 Gb/s PMD compensation using three deformed-helix ferroelectric liquid crystal cells.

  8. Method and apparatus for measuring birefringent particles

    DOEpatents

    Bishop, James K.; Guay, Christopher K.

    2006-04-18

    A method and apparatus for measuring birefringent particles is provided comprising a source lamp, a grating, a first polarizer having a first transmission axis, a sample cell and a second polarizer having a second polarization axis. The second polarizer has a second polarization axis that is set to be perpendicular to the first polarization axis, and thereby blocks linearly polarized light with the orientation of the beam of light passing through the first polarizer. The beam of light passing through the second polarizer is measured using a detector.

  9. Experiment to measure vacuum birefringence: Conceptual design

    NASA Astrophysics Data System (ADS)

    Mueller, Guido; Tanner, David; Doebrich, Babette; Poeld, Jan; Lindner, Axel; Willke, Benno

    2016-03-01

    Vacuum birefringence is another lingering challenge which will soon become accessible to experimental verification. The effect was first calculated by Euler and Heisenberg in 1936 and is these days described as a one-loop correction to the differential index of refraction between light which is polarized parallel and perpendicular to an external magnetic field. Our plan is to realize (and slightly modify) an idea which was originally published by Hall, Ye, and Ma using advanced LIGO and LISA technology and the infrastructure of the ALPS light-shining-through-walls experiment following the ALPS IIc science run. This work is supported by the Deutsche Forschungsgemeinschaft and the Heising-Simons Foundation.

  10. Study on retardance due to well-ordered birefringent cylinders in anisotropic scattering media.

    PubMed

    Guo, Yihong; Liu, Celong; Zeng, Nan; He, Honghui; Du, E; He, Yonghong; Ma, Hui

    2014-06-01

    We report an anisotropic tissue model containing well-ordered birefringent cylinders. Using simulations and experiments, we examined the different polarization features for nonbirefringent and birefringent cylinders and analyzed the influence of the birefringent cylinders on the retardance obtained from Mueller matrix polar decomposition. For the well-ordered birefringent cylinders, retardance increases linearly with the intrinsic birefringence and the scattering coefficient. Furthermore, the cylinders with a larger diameter generate more retardance. Compared with the cylinder-birefringence model, in which birefringent medium exists between the scatterers, the intrinsic birefringence on the cylinders usually contributes much less to the total retardance.

  11. Dual function microscope for quantitative DIC and birefringence imaging

    NASA Astrophysics Data System (ADS)

    Li, Chengshuai; Zhu, Yizheng

    2016-03-01

    A spectral multiplexing interferometry (SXI) method is presented for integrated birefringence and phase gradient measurement on label-free biological specimens. With SXI, the retardation and orientation of sample birefringence are simultaneously encoded onto two separate spectral carrier waves, generated by a crystal retarder oriented at a specific angle. Thus sufficient information for birefringence determination can be obtained from a single interference spectrum, eliminating the need for multiple acquisitions with mechanical rotation or electrical modulation. In addition, with the insertion of a Nomarski prism, the setup can then acquire quantitative differential interference contrast images. Red blood cells infected by malaria parasites are imaged for birefringence retardation as well as phase gradient. The results demonstrate that the SXI approach can achieve both quantitative phase imaging and birefringence imaging with a single, high-sensitivity system.

  12. Liquid microlenses and waveguides from bulk nematic birefringent profiles.

    PubMed

    Čančula, Miha; Ravnik, Miha; Muševič, Igor; Žumer, Slobodan

    2016-09-19

    We demonstrate polarization-selective microlensing and waveguiding of laser beams by birefringent profiles in bulk nematic fluids using numerical modelling. Specifically, we show that radial escaped nematic director profiles with negative birefringence focus and guide light with radial polarization, whereas the opposite - azimuthal - polarization passes through unaffected. A converging lens is realized in a nematic with negative birefringence, and a diverging lens in a positive birefringence material. Tuning of such single-liquid lenses by an external low-frequency electric field and by adjusting the profile and intensity of the beam itself is demonstrated, combining external control with intrinsic self-adaptive focusing. Escaped radial profiles of birefringence are shown to act as single-liquid waveguides with a single distinct eigenmode and low attenuation. Finally, this work is an approach towards creating liquid photonic elements for all-soft matter photonics.

  13. Magnetic birefringence of natural and synthetic ferritin

    NASA Astrophysics Data System (ADS)

    Koralewski, M.; Pochylski, M.; Mitróová, Z.; Timko, M.; Kopčanský, P.; Melníková, L.

    2011-10-01

    Magnetically induced optical birefringence (Δn) was measured for magnetoferritin (MFer), horse spleen ferritin (HSF) and nanoscale magnetite aqueous suspensions. The anisotropy of optical polarizability was calculated. The average magnetic dipole moment calculated assuming the Langevin model was about 20,000 and 8500 μB per particle, for magnetite nanoparticle and magnetoferritin, respectively. Poor fitting results and the unphysical value of average magnetic moment per Fe ion for MFer excluded the use of the simple Langevin model for description of Δn for this compound. It was deduced that for MFer the estimated average magnetic moment should be about 1125 μB per molecule. A magnetic contribution from the protein shell was found to be negligible. Results from the low-field region permit the calculation of the Cotton-Mouton (C-M) constants and their comparison for the substances studied. It was shown that magnetic birefringence and C-M constant can be powerful parameters in identification of the magnetic core structure of ferritins, especially useful in biomedicine.

  14. Stokes parameters modulator for birefringent filters

    NASA Technical Reports Server (NTRS)

    Dollfus, A.

    1985-01-01

    The Solar Birefringent Filter (Filter Polarisiant Solaire Selectif FPSS) of Meudon Observatory is presently located at the focus of a solar refractor with a 28 cm lens directly pointed at the Sun. It produces a diffraction limited image without instrumental polarization and with a spectral resolution of 46,000 in a field of 6 arc min. diameter. The instrument is calibrated for absolute Doppler velocity measurements and is presently used for quantitative imagery of the radial velocity motions in the photosphere. The short period oscillations are recorded. Work of adapting the instrument for the imagery of the solar surface in the Stokes parameters is discussed. The first polarizer of the birefringent filter, with a reference position angle 0 deg, is associated with a fixed quarter wave plate at +45 deg. A rotating quarter wave plate is set at 0 deg and can be turned by incremented steps of exactly +45 deg. Another quarter wave plate also initially set at 0 deg is simultaneously incremented by -45 deg but only on each even step of the first plate. A complete cycle of increments produces images for each of the 6 parameters I + or - Q, I + or - U and I + or - V. These images are then subtracted by pairs to produce a full image in the three Stokes parameters Q, U and V. With proper retardation tolerance and positioning accuracy of the quarter wave plates, the cross talk between the Stokes parameters was calculated and checked to be minimal.

  15. Michelson-Morley with a Birefringent Cavity

    NASA Astrophysics Data System (ADS)

    Monsalve, Francisco J.; Hohensee, Michael; Müller, Holger

    2012-06-01

    We report on the progress of a birefringent cavity test of the isotropy of the speed of light. Previous experimental tests have constrained anisotropies in the speed of light at the level of parts in 10^17 [1-2]. These experiments search for frame-dependent variations in the resonant frequencies of two orthogonally mounted optical cavities. Uncorrelated fluctuations in the cavity lengths are a significant challenge for such experiments. Our experiment uses a single dielectric-filled cavity, and measures the difference in the resonant frequency of two orthogonally polarized modes. Anisotropies in the speed of light will manifest as a frame-dependent strain on the dielectric [3-4], giving rise to a frame-dependent variation in the cavity birefringence. By making the length of each cavity mode identical, we expect that our experiment will be less sensitive to thermal cavity fluctuations. [4pt] [1] S. Herrmann, A. Senger, K. M"ohle, M. Nagel, E.V. Kovalchuk and A. Peters, PRD 80, 105011 (2009).[2] Ch. Eisel, A. Yu. Nevsky, and S. Schiller, PRL 103, 090401 (2009).[3] H. M"uller, PRD 71, 045004 (2005).[4] V.A. Kosteleck'y and M. Mewes, PRD 80, 015020 (2009).

  16. The Exicor DUV birefringence measurement system and its application to measuring lithography-grade CaF2 lens blanks

    NASA Astrophysics Data System (ADS)

    Wang, Baoliang; Griffiths, C. O.; Rockwell, Rick R.; List, Jennifer; Mark, Doug

    2003-11-01

    Optical lithography continues its transition to shorter wavelengths to support the semiconductor industry"s production of faster microchips to meet evolving market demands. The next step for optical lithography is likely to use the F2 excimer laser at 157.63 nm (157 nm,according to the industry" s naming convention).At 157 nm, among the limited number of fluoride crystals with acceptable optical properties calcium fluoride is the only practical lens material for step and scan systems due to its readiness for mass production. Since the discovery of intrinsic birefringence in CaF2 at deep ultraviolet (DUV)wavelengths,the optical lithography industry has developed a critical interest in measuring birefringence at 157 nm. In response to this need, we have developed a DUV birefringence measurement system. In this article,we describe the working principle, system construction, technical performance and selected applications for measuring lithography grade calcium fluoride lens blanks at DUV wavelengths.

  17. Emergency Unemployment Compensation Continuation Act

    THOMAS, 111th Congress

    Rep. McDermott, Jim [D-WA-7

    2010-11-17

    11/18/2010 On motion to suspend the rules and pass the bill, as amended Failed by the Yeas and Nays: (2/3 required): 258 - 154 (Roll no. 579). (All Actions) Tracker: This bill has the status Failed HouseHere are the steps for Status of Legislation:

  18. Flow Birefringence in Polymer Melt Rheology.

    NASA Astrophysics Data System (ADS)

    Subramanian, Ramesh Mani

    Optical techniques that are sensitive to structural changes induced by a flow field applied to polymers during processing have been used to study the fundamental relationships between applied deformation, mechanical stresses, and flow -induced molecular orientation. But most of the work done so far has used opto-mechanical techniques (i.e. mechanical measurement of stress and deformation, and optical measurement of flow-induced molecular orientation). This thesis reports the development and application of non-intrusive, opto-electronic techniques for rheo-optical studies on a 300 Pa.s polydimethylsiloxane (PDMS) melt flowing through a 5.00 cm wide converging wedge cell at room temperature. The two techniques used as tools of rheological characterization in the present study are laser doppler anemometry (LDA) to compute strain rate from local velocity measurements, and flow birefringence (double refraction) for measurement of the anisotropic refractive index tensor which, for flexible polymer solutions and melts, provides information the state of stress in the material via the stress-optical law. Birefringence measurements in extensional flow up to a pressure drop of 689 kPa across the converging wedge cell indicated that stress tensor and polarizability or anisotropic refractive index tensor were linearly related for the polymer over a range of strain rate that extended well into the non-Newtonian region. Along the cell centerline, the extensional flow behaviour of the polymer was studied via birefringence measurements in the linear stress-optical region, and it was found to be extension-thinning in nature. Assuming no boundary layer error, the optical techniques used in the present study provide a valuable test for constitutive relations between stress and deformation in the polymer by comparing predicted orientation angles with experimental measurements in combined shear and extension flows. The two constitutive equations tested were the Power-law model and the

  19. Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

    PubMed Central

    Pirnstill, Casey W.; Coté, Gerard L.

    2013-01-01

    Abstract. Noninvasive glucose monitoring is being investigated as a tool for effectively managing diabetes mellitus. Optical polarimetry has emerged as one such method, which can potentially be used to ascertain blood glucose levels by measuring the aqueous humor glucose levels in the anterior chamber of the eye. The key limitation for realizing this technique is the presence of sample noise due to corneal birefringence, which in the presence of motion artifact can confound the glucose signature in the aqueous humor of the eye. We present the development and characterization of a real-time, closed-loop, dual-wavelength polarimetric system for glucose monitoring using both a custom-built plastic eye phantom (in vitro) and isolated rabbit corneas (ex vivo) mounted in an artificial anterior chamber. The results show that the system can account for these noise sources and can monitor physiologic glucose levels accurately for a limited range of motion-induced birefringence. Using the dual-wavelength system in vitro and ex vivo, standard errors were 14.5  mg/dL and 22.4  mg/dL, respectively, in the presence of birefringence with motion. The results indicate that although dual-wavelength polarimetry has a limited range of compensation for motion-induced birefringence, when aligned correctly, it can minimize the effect of time-varying corneal birefringence for a range of motion larger than what has been reported in vivo. PMID:23299516

  20. Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Pirnstill, Casey W.; Coté, Gerard L.

    2013-01-01

    Noninvasive glucose monitoring is being investigated as a tool for effectively managing diabetes mellitus. Optical polarimetry has emerged as one such method, which can potentially be used to ascertain blood glucose levels by measuring the aqueous humor glucose levels in the anterior chamber of the eye. The key limitation for realizing this technique is the presence of sample noise due to corneal birefringence, which in the presence of motion artifact can confound the glucose signature in the aqueous humor of the eye. We present the development and characterization of a real-time, closed-loop, dual-wavelength polarimetric system for glucose monitoring using both a custom-built plastic eye phantom (in vitro) and isolated rabbit corneas (ex vivo) mounted in an artificial anterior chamber. The results show that the system can account for these noise sources and can monitor physiologic glucose levels accurately for a limited range of motion-induced birefringence. Using the dual-wavelength system in vitro and ex vivo, standard errors were 14.5 mg/dL and 22.4 mg/dL, respectively, in the presence of birefringence with motion. The results indicate that although dual-wavelength polarimetry has a limited range of compensation for motion-induced birefringence, when aligned correctly, it can minimize the effect of time-varying corneal birefringence for a range of motion larger than what has been reported in vivo.

  1. Current sensing using circularly birefringent twisted solid-core photonic crystal fiber.

    PubMed

    Beravat, R; Wong, G K L; Xi, X M; Frosz, M H; St J Russell, P

    2016-04-01

    Continuously twisted solid-core photonic crystal fiber (PCF) exhibits pure circular birefringence (optical activity), making it ideal for current sensors based on the Faraday effect. By numerical analysis, we identify the PCF geometry for which the circular birefringence (which scales linearly with twist rate) is a maximum. For silica-air PCF, this occurs at a shape parameter (diameter-to-spacing ratio of the hollow channels) of 0.37 and a scale parameter (spacing-to-wavelength) of 1.51. This result is confirmed experimentally by testing a range of different structures. To demonstrate the effectiveness of twisted PCF as a current sensor, a length of fiber is placed on the axis of a 7.6 cm long solenoid, and the Faraday rotation is measured at different values of dc current. The system is then used to chart the wavelength dependence of the Verdet constant.

  2. Detection of birefringent microcrystals in bile

    SciTech Connect

    Darrow, Chris; Mirhej, Andrew; Seger, Tino

    2003-09-30

    A transparent flow channel fluidly communicates a fluid source and a collection reservoir. A light beam passes through a first polarizer having a first plane of polarization. The flow channel is orthogonal to the light beam. The light beam passes through a fluid sample as it flows through the flow channel. The light beam is then filtered through a second polarizer having a second plane of polarization rotated 90.degree. from the first plane of polarization. The birefringence of certain crystalline materials present in the fluid sample rotates the plane of polarization of the light beam. The presence of these microcrystals thus causes a component of the beam to pass through the second polarizer and impinge an electronic photo-detector located in the path of the beam. The photo-detector signals the presence of the microcrystals by generating voltage pulses. A display device visually presents the quantitative results of the assay.

  3. Development of birefringent filters for spaceflight

    NASA Technical Reports Server (NTRS)

    Title, A. M.; Pope, T. P.; Ramsey, H. E.; Schoolman, S. A.

    1976-01-01

    The critical problem for flight of a birefringent filter is the shock mounting of the calcite. The design presented here bonds the calcite block with silicon rubbers to the calcite holder. The calcite together with its all necessary polarizers and rotating achromatic plates are mounted together in units called a filter module. By using a set of modules containing calcite crystals of differing lengths, a filter can be produced. A description of the modules is given. Also described is a container for the filter modules, which can be used both to hermetically seal the system or contain an index matching oil. The response of a filter element while being controlled by the Lockheed Temperature Control is described and the determination of the wavelength sensitivity to temperature of calcite is explained. Operation of the filter using a software control algorithm instead of a hardware temperature controller is shown. Some radiation considerations of filter systems are given.

  4. Structural origin of magnetic birefringence in rutile-type antiferromagnets

    NASA Astrophysics Data System (ADS)

    Jauch, W.

    1991-10-01

    The microscopic origin of magnetic birefringence in the rutile-type antiferromagnets XF2 (X=Mn, Fe, Co, or Ni) is analyzed on the basis of the theory of structural birefringence developed by Ewald and Born. The general principles of the Ewald-Born theory are reviewed. The magnetic birefringence can be explained by a small exchange-induced internal displacement of the fluorine atoms. Predictions from theory are compared with accurate crystal-structure analyses based on γ-ray-diffraction data. The agreement found between theory and experiment is excellent.

  5. Photonic quasi-crystal fiber with high birefringence

    NASA Astrophysics Data System (ADS)

    Liu, Hongfei; Xiao, Wei; Cai, Weicheng; Liu, Exian; Feng, Bo; Wang, Ziming; Liang, Taiyuan; Wang, Shuo; Liu, Jianjun

    2016-03-01

    A high-birefringence photonic quasi-crystal fiber (HB-PQF) based on SiO2 is proposed. The relationships between birefringence and structure parameters and between beat length and structure parameters are researched by finite difference beam propagation method. With the optimization of fiber structure parameters, the birefringence is 1.4207×10-2, which is two orders of magnitude higher than the normally used fiber when the wavelength is 1.55 μm. The radius of the fiber is 6.5 μm. The HB-PQF in a communication sensor will have important application prospects.

  6. Note: Ultra-low birefringence dodecagonal vacuum glass cell

    SciTech Connect

    Brakhane, Stefan Alt, Wolfgang; Meschede, Dieter; Robens, Carsten; Moon, Geol; Alberti, Andrea

    2015-12-15

    We report on an ultra-low birefringence dodecagonal glass cell for ultra-high vacuum applications. The epoxy-bonded trapezoidal windows of the cell are made of SF57 glass, which exhibits a very low stress-induced birefringence. We characterize the birefringence Δn of each window with the cell under vacuum conditions, obtaining values around 10{sup −8}. After baking the cell at 150 °C, we reach a pressure below 10{sup −10} mbar. In addition, each window is antireflection coated on both sides, which is highly desirable for quantum optics experiments and precision measurements.

  7. Infrared birefringence spectra for cadmium sulfide and cadmium selenide.

    PubMed

    Chenault, D B; Chipman, R A

    1993-08-01

    Measurements of the birefringence spectra for cadmium sulfide and cadmium selenide from 2.5 to 16.5µm obtained with a rotating sample spectropolarimeter are presented. Because of the similarity in the birefringence spectra for cadmium sulfide and cadmium selenide, a highly achromatic IR retarder can be constructed from a combination of these materials. The ordinary and extraordinary refractive indices for cadmium sulfide are estimated in the region from 10.6 to 15 µm and for cadmium selenide from 10.6 to 16.5 µm by combining these birefringence data with an extrapolation of previous dispersion relations.

  8. Intracavity diamond heatspreaders in lasers: the effects of birefringence

    NASA Astrophysics Data System (ADS)

    van Loon, Francesco; Kemp, Alan J.; Maclean, Alexander J.; Calvez, Stephane; Hopkins, John-Mark; Hastie, Jennifer E.; Dawson, Martin D.; Burns, David

    2006-10-01

    The birefringence of a number of commercially-available diamond platelets is assessed in the context of their use for intracavity thermal management in lasers. Although diamond is normally thought of as isotropic, significant birefringence is found to be present in some samples, with considerable variation from batch to batch, and in some cases across an individual sample. Nonetheless, low-loss operation is achieved in a laser cavity containing a Brewster element, either by rotating the sample or by using a diamond platelet with low birefringence.

  9. Angular tuning of the magnetic birefringence in rippled cobalt films

    NASA Astrophysics Data System (ADS)

    Arranz, Miguel A.; Colino, José M.

    2015-06-01

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  10. Angular tuning of the magnetic birefringence in rippled cobalt films

    SciTech Connect

    Arranz, Miguel A.; Colino, José M.

    2015-06-22

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  11. On the existence of Jones birefringence and Jones dichroism.

    PubMed

    Arteaga, Oriol

    2010-05-01

    We claim that the so-called Jones birefringence and Jones dichroism effects, understood as new optical phenomena of difficult experimental observation, cannot be deduced from Jones publications and were proposed due to a misinterpretation of his original work.

  12. Systematic design of highly birefringent photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Hsu, Jui-Ming

    2017-03-01

    This article systematically designs and theoretically investigates a highly birefringent photonic crystal fiber (HB-PCF) for reducing the effect of polarization mode dispersion in high-speed optical communication system. To achieve a high modal birefringence in the proposed HB-PCF, four types of HB-PCF were designed by adding some birefringence-enhancing factors step by step in sequence. Ultimately, as per the simulation results, in the condition of single-mode operation, the numeric values of modal birefringence and confinement loss of the proposed HB-PCF is about 21.85 × 10- 3 and 0.47 dB/km at the habitual wavelength λ = 1.55 µm of optical-fiber communications.

  13. Vacuum birefringence in high-energy laser-electron collisions

    NASA Astrophysics Data System (ADS)

    King, B.; Elkina, N.

    2016-12-01

    Real photon-photon scattering is a long-predicted phenomenon that is being searched for in experiment in the form of a birefringent vacuum at optical and x-ray frequencies. We present results of calculations and numerical simulations for a scenario to measure this effect using multi-MeV photons generated in the collision of electrons with a laser pulse. We find that the birefringence of the vacuum should be measurable using experimental parameters attainable in the near future.

  14. Singular optical manipulation of birefringent elastic media using nonsingular beams.

    PubMed

    Brasselet, Etienne

    2009-10-15

    It is shown that nonsingular light beams can generate singular birefringent patterns in homogeneous birefringent elastic media. These orientational defects of the optical-axis spatial distribution originate from an optical torque driven by a nonzero longitudinal field component. Singular radial and spin-dependent azimuthal light-induced elastic distortion patterns are described and experimentally observed in a uniform liquid-crystal film in the course of a focused circularly polarized Gaussian beam.

  15. Infrared hyperspectral imaging polarimeter using birefringent prisms.

    PubMed

    Craven-Jones, Julia; Kudenov, Michael W; Stapelbroek, Maryn G; Dereniak, Eustace L

    2011-03-10

    A compact short-wavelength and middle-wavelength infrared hyperspectral imaging polarimeter (IHIP) is introduced. The sensor includes a pair of sapphire Wollaston prisms and several high-order retarders to form an imaging Fourier transform spectropolarimeter. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration versus an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image. The IHIP operates over a ±5° field of view and implements a dual-scan false signature reduction technique to suppress polarimetric aliasing artifacts. In this paper, the optical layout and operation of the IHIP sensor are presented in addition to the radiometric, spectral, and polarimetric calibration techniques used with the system. Spectral and spectropolarimetric results from the laboratory and outdoor tests with the instrument are also presented.

  16. The influence of the fiber drawing process on intrinsic stress and the resulting birefringence optimization of PM fibers

    NASA Astrophysics Data System (ADS)

    Just, Florian; Spittel, Ron; Bierlich, Jörg; Grimm, Stephan; Jäger, Matthias; Bartelt, Hartmut

    2015-04-01

    The propagation properties of optical fibers can be significantly influenced by intrinsic stress. These effects are often undesired but in some cases essential for certain applications, e.g. in polarization maintaining (PM) fibers. In this paper, we present systematic studies on the influence of the fiber drawing process on the generated stress and demonstrate an approach to significantly increase the stress induced birefringence of PM-fibers. It is shown that the thermal stress caused by the material composition is superimposed with the mechanical stress caused by the fiber fabrication process. This intrinsic stress has a strong effect on the optical and mechanical properties of the glass and thus influences the fiber stability and modal behavior. By applying a thermal annealing step, the mechanical stress due to the fiber drawing process can be canceled. It is shown that this annealing step compensates the stress reducing influence of the drawing process on the birefringence of PM-fibers with panda structure. The comparison of the intrinsic stress states after fabrication with the state after the additional high temperature annealing step clearly shows that it is possible to improve the overall birefringence of panda fibers using appropriate preparation steps.

  17. Teacher Compensation.

    ERIC Educational Resources Information Center

    Minnesota State Office of the Legislative Auditor, St. Paul. Program Evaluation Div.

    Minnesota state policy makers are concerned about teacher compensation because it constitutes a major category of state and local spending and can affect education results. This report examines compensation issues by describing the pay structure of Minnesota's K-12 public school teachers, making pay comparisons with other professionals, and…

  18. Improved eye-fixation detection using polarization-modulated retinal birefringence scanning, immune to corneal birefringence.

    PubMed

    Irsch, Kristina; Gramatikov, Boris I; Wu, Yi-Kai; Guyton, David L

    2014-04-07

    We present an improved method for remote eye-fixation detection, using a polarization-modulated approach to retinal birefringence scanning (RBS), without the need for individual calibration or separate background measurements and essentially independent of corneal birefringence. Polarization-modulated RBS detects polarization changes generated in modulated polarized light passing through a unique pattern of nerve fibers identifying and defining the retinal region where fixation occurs (the fovea). A proof-of-concept demonstration in human eyes suggests that polarization-modulated RBS has the potential to reliably detect true foveal fixation on a specified point with an accuracy of at least ± 0.75°, and that it can be applied to the general population, including individuals with sub-optimal eyes and young children, where early diagnosis of visual problems can be critical. As could be employed in an eye-controlled display or in other devices, polarization-modulated RBS also enables and paves the way for new and reliable eye-fixation-evoked human-machine interfaces.

  19. Techniques for Fast and Sensitive Measurements of Two-Dimensional Birefringence Distributions

    NASA Astrophysics Data System (ADS)

    Shribak, Michael; Oldenbourg, Rudolf

    2003-06-01

    We propose image processing algorithms for measuring two-dimensional distributions of linear birefringence using a pair of variable retarders. Several algorithms that use between two and five recorded frames allow us to optimize measurements for speed, sensitivity, and accuracy. We show images of asters, which consist of radial arrays of microtubule polymers recorded with a polarized light microscope equipped with a universal compensator. Our experimental results confirm our theoretical expectations. The lowest noise level of 0.036 nm was obtained when we used the five-frame technique and four-frame algorithm without extinction setting. The two-frame technique allows us to increase the speed of measurement with acceptable image quality.

  20. Neural network calibration of a snapshot birefringent Fourier transform spectrometer with periodic phase errors.

    PubMed

    Luo, David; Kudenov, Michael W

    2016-05-16

    Systematic phase errors in Fourier transform spectroscopy can severely degrade the calculated spectra. Compensation of these errors is typically accomplished using post-processing techniques, such as Fourier deconvolution, linear unmixing, or iterative solvers. This results in increased computational complexity when reconstructing and calibrating many parallel interference patterns. In this paper, we describe a new method of calibrating a Fourier transform spectrometer based on the use of artificial neural networks (ANNs). In this way, it is demonstrated that a simpler and more straightforward reconstruction process can be achieved at the cost of additional calibration equipment. To this end, we provide a theoretical model for general systematic phase errors in a polarization birefringent interferometer. This is followed by a discussion of our experimental setup and a demonstration of our technique, as applied to data with and without phase error. The technique's utility is then supported by comparison to alternative reconstruction techniques using fast Fourier transforms (FFTs) and linear unmixing.

  1. Very high polarimetric sensitivity to strain of second order mode of highly birefringent microstructured fibre

    NASA Astrophysics Data System (ADS)

    Nasilowski, Tomasz; Skorupski, Krzysztof; Makara, Mariusz; Statkiewicz-Barabach, Gabriela; Mergo, Pawel; Marc, Pawel; Jaroszewicz, Leszek

    2011-05-01

    Microstructured fibres (MSF) or photonic crystal fibres (PCF) possess a number of unique properties enabling a wide range of novel applications either in the telecommunication or in the sensing domain. In this paper we show that highly birefringent (HB) MSF with a dedicated design that allows inscribing fibre Bragg gratings in the MSF core can serve as pressure or stress transducers with extremely large sensitivity of second order mode, while exhibiting a low sensitivity to temperature drifts. Therefore, Bragg gratings inscribed in such MSF may offer a viable alternative to traditional optical fibre sensors of much lower stress sensitivity that require temperature compensation mechanisms and that are not intrinsically capable of distinguishing stress and temperature.

  2. Polarization Compensation of Fresnel Aberrations in Telescopes

    NASA Technical Reports Server (NTRS)

    Clark, Natalie; Breckenridge, James B.

    2011-01-01

    Large aperture space telescopes are built with low F# s to accommodate the mechanical constraints of launch vehicles and to reduce resonance frequencies of the on-orbit system. Inherent with these low F# s is Fresnel polarization which affects image quality. We present the design and modeling of a nano-structure consisting of birefringent layers to control polarization and increase contrast. Analysis shows a device that functions across a 400nm bandwidth tunable from 300nm to 1200nm. This Fresnel compensator device has a cross leakage of less than 0.001 retardance.

  3. Birefringence and Enhanced Stability in Stable Organic Glasses

    NASA Astrophysics Data System (ADS)

    Liu, Tianyi; Exarhos, Annemarie; Cheng, Kevin; Jia, Tiezheng; Walsh, Patrick; Kikkawa, Jay; Fakhraai, Zahra

    Stable glasses can be prepared by physical vapor depositing organic molecules onto a cold substrate at slow rates. These glasses have many exceptional properties such as high thermal stability, high density, and birefringence. Regardless of the molecular shape or intermolecular interactions, birefringence has been observed in various stable glasses produced at low temperatures (below 80% of the molecule's glass transition temperature, Tg) . Here we prepare stable glasses of an organic molecule, 9-(3,5-di(naphthalen-1-yl)phenyl)anthracene, that possesses a nearly isotropic shape and intrinsic fluorescence. Ellipsometry is used to show that all stable glasses prepared in the temperature range from 73% Tg to 97% Tgshow positive birefringence. Angle- and polarization- dependent photoluminescence measurements show isotropic molecular orientation in these optically birefringent glasses. Furthermore, the values of birefringence are strongly correlated with the enhanced density, implying a general origin of the observed anisotropy in stable glasses. This correlation can elucidate the role of packing in the formation of such high-density glasses. The authors would like to acknowledge Ethan Alguire and Joe Subotnik for simulation. Z.F. acknowledges funding from NSF CAREER (DMR-1350044). P.J.W. acknowledges funding from NSF (CHE-1152488). J.M.K acknowledges funding from NSF (DMR-1206270).

  4. Measurements of flow-induced birefringence in microfluidics

    PubMed Central

    Sun, Chen-li; Huang, Hung-Yen

    2016-01-01

    In this study, we demonstrate the use of a microscopic circular polariscope to measure the flow-induced birefringence in a microfluidic device that represents the kinematics of fluid motion optically. Unlike the commercial birefringence microscope employed in the previous studies, our approach is able to provide direct measurement of retardance, which quantifies the difference in refractive index of the fluid experienced by the ordinary and extraordinary rays, from one single image frame. This capability facilitates unsteady full-field quantitation of flow-induced birefringence in microfluidics that has never been achieved before. At low flow rates, we find that the value of the retardance is independent of the microfluidic design and proportional to the nominal strain rates. This linearity bridges the measurement of birefringence and the deformation rate in the microflow environment, which yields the stress information of the fluid flow. In addition, the μPIV results confirm that both extensional and shear strain rates contribute to the flow-induced birefringence so that the retardance distribution can be used to represent the field of the principal strain rate in a microfluidic device. The outcome of this study proves that our approach provides a non-invasive method that enables an intuitive full-field representation of stress in the instantaneous flow field in a microfluidic device. PMID:26858809

  5. Characterization of distributed modal birefringence in a few-mode fiber based on Brillouin dynamic grating.

    PubMed

    Li, An; Hu, Qian; Chen, Xi; Kim, Byoung Yoon; Shieh, William

    2014-06-01

    We propose and demonstrate generation of Brillouin dynamic grating (BDG) in a few-mode fiber (FMF) with a Gaussian pulse pump and a counterpropagating continuous wave pump in LP01 mode. Brillouin optical time-domain analysis (BOTDA) is achieved by launching a third Gaussian pulse probe in LP11 mode. With coherent detection and time-domain analysis on the backreflected probe signal, the modal birefringence of the FMF is characterized via the distributed BDG with high spatial resolution and high accuracy.

  6. Utility of birefringence changes due to collagen thermal denaturation rate process analysis: vessel wall temperature estimation for new short term heating balloon angioplasty

    NASA Astrophysics Data System (ADS)

    Kaneko, Kenji; Shimazaki, Natsumi; Gotoh, Maya; Nakatani, Eriko; Arai, Tsunenori

    2007-02-01

    Our photo thermal reaction heating architecture balloon realizes less than 10 s short term heating that can soften vessel wall collagen without damaging surrounding tissue thermally. New thermal balloon angioplasty, photo-thermo dynamic balloon angioplasty (PTDBA) has experimentally shown sufficient opening with 2 atm low pressure dilation and prevention of chronic phase restenosis and acute phase thrombus in vivo. Even though PTDBA has high therapeutic potential, the most efficient heating condition is still under study, because relationship of treatment and thermal dose to vessel wall is not clarified yet. To study and set the most efficient heating condition, we have been working on establishment of temperature history estimation method from our previous experimental results. Heating target of PTDBA, collagen, thermally denatures following rate process. Denaturation is able to be quantified with measured collagen birefringence value. To express the denaturation with equation of rate process, the following ex vivo experiments were performed. Porcine extracted carotid artery was soaked in two different temperature saline baths to enforce constant temperature heating. Higher temperature bath was set to 40 to 80 degree Celsius and soaking duration was 5 to 40 s. Samples were observed by a polarizing microscope and a scanning electron microscope. The birefringence was measured by polarizing microscopic system using Brace-Koehler compensator 1/30 wavelength. The measured birefringence showed temperature dependency and quite fit with the rate process equation. We think vessel wall temperature is able to be estimated using the birefringence changes due to thermal denaturation.

  7. THE BIREFRINGENCE OF THE HUMAN RED CELL GHOSTS

    PubMed Central

    Ponder, Eric; Barreto, Delia

    1956-01-01

    The type of birefringence described by Mitchison, which extends some 0.5 µ in from the surface of the human red cell ghost in glycerol and which shows a maximum retardation of about 7 A, is only found in ghosts which are sufficiently well hemoglobinised to be seen with the ordinary microscope. Ghosts from which all hemoglobin has been lost are not visible with the ordinary microscope and are not birefringent, although they are clearly visible with phase contrast. About 90 per cent of the ghosts in glycerol preparations are of the latter type, the exact percentage being a function of time. Mitchison's measurements of birefringence, although reproducible, accordingly apply only to ghosts in which some hemoglobin still remains complexed with the lipoprotein layers of the red cell ultrastructure, and do not enable one to draw conclusions as to the thickness and orientation of the lipoprotein surface layers. PMID:13286451

  8. Gauge-origin independent calculations of Jones birefringence

    NASA Astrophysics Data System (ADS)

    Shcherbin, Dmitry; Thorvaldsen, Andreas J.; Jonsson, Dan; Ruud, Kenneth

    2011-10-01

    We present the first gauge-origin independent formulation of Jones birefringence at the Hartree-Fock level of theory. Gauge-origin independence is achieved through the use of London atomic orbitals. The implementation is based on a recently proposed atomic orbital-based response theory formulation that allows for the use of both time- and perturbation-dependent basis sets [Thorvaldsen, Ruud, Kristensen, Jørgensen, and Coriani, J. Chem. Phys. 129, 214108 (2008)]. We present the detailed expressions for the response functions entering the Jones birefringence when London atomic orbitals are used. The implementation is tested on a set of polar and dipolar molecules at the Hartree-Fock level of theory. It is demonstrated that London orbitals lead to much improved basis-set convergence, and that the use of small, conventional basis sets may lead to the wrong sign for the calculated birefringence. For large basis sets, London orbitals and conventional basis sets converge to the same results.

  9. Laser induced optically and thermally reversible birefringence in azopolymers

    NASA Astrophysics Data System (ADS)

    Nazarova, D.; Nedelchev, L.; Ivanov, D.; Blagoeva, B.; Berberova, N.; Stoykova, E.; Mateev, G.; Kostadinova, D.

    2016-01-01

    Azopolymers are well known organic materials for polarization holographic recording due to the induced anisotropy under illumination with polarized light. They possess all the desirable characteristics of the known polarization-sensitive materials, as high sensitivity and reversibility, but excel them substantially in the magnitude of the photoinduced birefringence. This makes possible to record reversible polarization gratings with high diffraction efficiency. In this paper results of experimental investigations on the reversibility properties of birefringence photoinduced in azopolymers are reported, depending on the conditions of subsequent optical and thermal treatment. Thin films of different polymers were prepared in order to examine the kinetics of multiple recording and erasure of birefringence in different types of azopolymers. The reversibility of the polarization recording has been studied using two different method of erasure - by increased temperature and on illumination with circularly polarized light.

  10. A melting point for the birefringent component of muscle.

    PubMed

    Aronson, J F

    1966-09-01

    The A filament of the striated muscle sarcomere is an ordered aggregate of one or a few species of proteins. Ordering of these filaments into a parallel array is the basis of birefringence in the A region, and loss of birefringence is therefore a measure of decreased order. Heating caused a large decrease in the birefringence of glycerinated rabbit psoas muscle fibers over a narrow temperature range ( approximately 3 degrees C) and a large decrease in both the birefringence and optical density of the A region of Drosophila melanogaster fibrils. These changes were interpreted as a loss of A filament structure and were used to define a transition temperature (T(tr)) as a measure of the stability of the A region. Since the transition temperature was sensitive to pH, ionic strength, and urea, solvent conditions which often affect protein structure, it is an experimentally useful indicator for factors affecting the structure of the A filament. Fibers from glycerinated frog muscle were less stable over a wide pH range than fibers from glycerinated rabbit muscle, a fact which demonstrates a species difference in structure. Glycerinated rabbit fibrils heated to 70 degrees C shortened to about 40% of their initial length. The extent of shortening was not correlated with the loss of birefringence, and phase-contrast microscopy showed that this shortening occurred in the I region as well as in the A region. This response may be useful for studying the I filament and actin in much the same way that the decrease in birefringence was used for studying the A filament and myosin. The observations presented show that some properties of muscle proteins can be studied essentially in situ without the necessity of first dispersing the structure in solutions of high or low ionic strength.

  11. Electric birefringence anomaly of solutions of ionically charged anisometric particles.

    PubMed

    Hoffmann, H; Gräbner, Dieter

    2015-02-01

    The term "electric birefringence anomaly" is known as the electric birefringence (EB) signal that occurs in solutions of ionically charged anisometric particles in a narrow concentration region. The signal is of opposite sign to the normal birefringence that occurs below and above this narrow concentration region. The normal electric birefringence signals in the dilute and more concentrated regions are due to the orientation of the particles in the direction of the applied electric field. The origin for the anomalous signal was not completely understood until now. The article summarises previous results in which the anomalous results had been observed but not well understood. It shows that the birefringence anomaly occurs in systems as diverse as micellar solutions, polyelectrolytes, solutions of clays, viruses and fibres. In all these systems the anomaly signals are present at the concentration when the length of the colloidal particles including the thickness of the electric double layer are about the same as the mean distance between the colloidal particles. Under these conditions the electric double layers of the particles overlap along the main axis of the particles but not in the direction across the particles. As a consequence of this situation a dipole is built up across the particles by the migration of the counter-ions of the particles in the electric field and this dipole leads to an orientation of the particles perpendicular to the electric field. The anomalous signal can usually be observed simultaneously with the normal signal. The amplitude of the anomalous signal can be larger than the amplitude of the normal signal. As a consequence the total birefringence changes its sign in the anomalous concentration region. The anomaly signal of the clays can also be explained by a fluctuating dipole around the particles, which is due to the fact that the centre of the ionic charges of the particles does not fall on the centre of the ionic charge of the counter

  12. Flow birefringence in lyotropic mixtures in the isotropic phase

    SciTech Connect

    Fernandes, P.R.G.; Figueiredo Neto, A.M. )

    1995-01-01

    The flow-induced birefringence ([delta][ital n]) in lyotropic mixtures in the isotropic phase (ISO) was measured by means of optical techniques. As a function of temperature, the ISO is surrounded by two lamellar (LAM) phases. The shear flow produced by a perturbation in ISO induces a birefringent phase, which relaxes back to ISO with a typical relaxation time [tau]. [tau] increases near the transition to the more ordered LAM phases, and the behavior of [tau] versus temperature indicates the existence of a virtual nematic phase in the isotropic domain.

  13. Mirror Birefringence in a Fabry-Perot Cavity and the Detection of Vacuum Birefringence in a Magnetic Field

    NASA Technical Reports Server (NTRS)

    Chui, T. C. P.; Shao, M.; Redding, D.; Gursel, Y.; Boden, A.

    1995-01-01

    We discuss the effect of mirror birefringence in two optical schemes designed to detect the quantum-electrodynamics (QED) predictions of vacuum birefringence under the influence of a strong magnetic field, B. Both schemes make use of a high finesse Fabry-Perot cavity (F-P) to increase the average path length of the light in the magnetic field. The first scheme, which we called the frequency scheme, is based on measurement of the beat frequency of two orthogonal polarized laser beams in the cavity. We show that mirror birefringence contributes to the detection uncertainties in first order, resulting in a high susceptibility to small thermal disturbances. We estimate that an unreasonably high thermal stability of 10-9 K is required to resolve the effect to 0.1%. In the second scheme, which we called the polarization rotation scheme, laser polarized at 45 relative to the B field is injected into the cavity.

  14. Dosage Compensation in Mammals

    PubMed Central

    Brockdorff, Neil; Turner, Bryan M.

    2015-01-01

    Many organisms show major chromosomal differences between sexes. In mammals, females have two copies of a large, gene-rich chromosome, the X, whereas males have one X and a small, gene-poor Y. The imbalance in expression of several hundred genes is lethal if not dealt with by dosage compensation. The male–female difference is addressed by silencing of genes on one female X early in development. However, both males and females now have only one active X chromosome. This is compensated by twofold up-regulation of genes on the active X. This complex system continues to provide important insights into mechanisms of epigenetic regulation. PMID:25731764

  15. Zero-birefringent polyimide for polymer optical waveguide

    NASA Astrophysics Data System (ADS)

    Baek, Sung-Ho; Kang, Jae-Wook; Li, Xiangdan; Lee, Myong-Hoon; Kim, Jang-Joo

    2003-07-01

    A novel zero birefringent and photosensitive polyimide was synthesized. The polymer is soluble in solvents and contains a chalcone group for photo-crosslinking by UV exposure. The glass transition and decomposition temperature of the polymer were 254°C and 430°C before cross-linking. Evolution of the absorption spectra upon UV exposure indicated that the cross-linking reaction is related to the cycloaddition of the double bonds in the chalcone group to form cyclobutane. The photo-crosslinking reaction not only increased the thermal stability, but also induced a refractive index change of the films. The refractive index of the film was reduced upon UV exposure from 1.5862 to 1.5697 for TE mode and from 1.5807 to 1.5697 for TM mode, respectively, resulting in zero birefringence after curing. Loss of p-conjugation in the chalcone group by the crosslinking reaction is supposed to induce the reduction of the refractive indices and orbital change from sp2 to sp3 makes the polymer chain be kinked, resulting in decrease of birefringence. The polymer film showed optical loss of 0.41 dB/cm at 1.3 mm and 0.54 dB/cm at 1.55 mm. Zero birefringence and low optical loss combined with photo-processibility of the material are making it an excellent candidate for the high performance waveguide materials.

  16. Dispersion characterization of group birefringence in polarization-maintaining fiber using a Kerr phase-interrogator

    NASA Astrophysics Data System (ADS)

    Lu, Yang; Baker, Chams; Bao, Xiaoyi

    2015-07-01

    We present a new approach to characterize dispersion of group birefringence in a long polarization-maintaining fiber (PMF). Two sinusoidal optical signals are respectively launched into fast and slow axes of a PMF under test. Wavelength dependent group-delay difference between two sinusoidal optical signals induced by group birefringence in the PMF is measured using a Kerr phase-interrogator, and dispersion of group birefringence is characterized from the group-delay difference. Measurements of wavelength dependent group birefringence and group birefringence dispersion for a 459.4-m Panda PMF are experimentally demonstrated.

  17. Most calcium pyrophosphate crystals appear as non-birefringent

    PubMed Central

    Ivorra, J.; Rosas, J.; Pascual, E.

    1999-01-01

    OBJECTIVE—To determine the proportion of calcium pyrophosphate dihydrate (CPPD) crystals that appear as non-birefringent when observed under the polarised light microscope.
METHODS—Two observers examined independently 10 synovial fluid samples obtained during an episode of arthritis attributable to CPPD crystals. Ten synovial fluid samples from patients with acute gout were used as a reference. The examination was performed after placing a fluid sample in a Niebauer haemocytometric chamber; a crystal count was done first under ordinary light, then in the area corresponding to a 0.1 ml, under polarised light
RESULTS—The percentages of birefringence appreciated for CPPD were 18% (confidence intervals (CI) 12, 24) for observer 1, and 17% (CI 10, 24) for observer 2 (difference NS). The percentages of birefringence for monosodium urate were 127% (CI 103, 151) for observer 1 and 107% (CI 100, 114) for observer 2 (difference NS). Percentages above 100% indicate that crystals missed under ordinary light became apparent under polarised light.
CONCLUSION—Only about one fifth of all CPPD crystals identified by bright field microscopy show birefringence when the same synovial fluid sample is observed under polarised light. If a search for CPPD crystals is conducted under polarised light, the majority of the crystals will be missed. Ordinary light allows a better rate of CPPD crystal detection but observation under polarised light of crystals showing birefringence is required for definitive CPPD crystal identification.

 PMID:10460193

  18. 7 CFR 1280.208 - Compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Compensation. 1280.208 Section 1280.208 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... Board § 1280.208 Compensation. Board members shall serve without compensation, but shall be...

  19. 7 CFR 1280.208 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Compensation. 1280.208 Section 1280.208 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... Board § 1280.208 Compensation. Board members shall serve without compensation, but shall be...

  20. 7 CFR 1280.208 - Compensation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Compensation. 1280.208 Section 1280.208 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... Board § 1280.208 Compensation. Board members shall serve without compensation, but shall be...

  1. 7 CFR 1280.208 - Compensation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Compensation. 1280.208 Section 1280.208 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... Board § 1280.208 Compensation. Board members shall serve without compensation, but shall be...

  2. Open source software for electric field Monte Carlo simulation of coherent backscattering in biological media containing birefringence.

    PubMed

    Radosevich, Andrew J; Rogers, Jeremy D; Capoğlu, Ilker R; Mutyal, Nikhil N; Pradhan, Prabhakar; Backman, Vadim

    2012-11-01

    ABSTRACT. We present an open source electric field tracking Monte Carlo program to model backscattering in biological media containing birefringence, with computation of the coherent backscattering phenomenon as an example. These simulations enable the modeling of tissue scattering as a statistically homogeneous continuous random media under the Whittle-Matérn model, which includes the Henyey-Greenstein phase function as a special case, or as a composition of discrete spherical scatterers under Mie theory. The calculation of the amplitude scattering matrix for the above two cases as well as the implementation of birefringence using the Jones N-matrix formalism is presented. For ease of operator use and data processing, our simulation incorporates a graphical user interface written in MATLAB to interact with the underlying C code. Additionally, an increase in computational speed is achieved through implementation of message passing interface and the semi-analytical approach. Finally, we provide demonstrations of the results of our simulation for purely scattering media and scattering media containing linear birefringence.

  3. Compensation for Phase Anisotropy of a Metal Reflector

    NASA Technical Reports Server (NTRS)

    Hong, John

    2007-01-01

    A method of compensation for the polarization- dependent phase anisotropy of a metal reflector has been proposed. The essence of the method is to coat the reflector with multiple thin alternating layers of two dielectrics that have different indices of refraction, so as to introduce an opposing polarization-dependent phase anisotropy. The anisotropy in question is a phenomenon that occurs in reflection of light at other than normal incidence: For a given plane wave having components polarized parallel (p) and perpendicular (s) to the plane of incidence, the phase of s-polarized reflected light differs from the phase p-polarized light by an amount that depends on the angle of incidence and the complex index of refraction of the metal. The magnitude of the phase difference is zero at zero angle of incidence (normal incidence) and increases with the angle of incidence. This anisotropy is analogous to a phase anisotropy that occurs in propagation of light through a uniaxial dielectric crystal. In such a case, another uniaxial crystal that has the same orientation but opposite birefringence can be used to cancel the phase anisotropy. Although it would be difficult to prepare a birefringent material in a form suitable for application to the curved surface of a typical metal reflector in an optical instrument, it should be possible to effect the desired cancellation of phase anisotropy by exploiting the form birefringence of multiple thin dielectric layers. (The term "form birefringence" can be defined loosely as birefringence arising, in part, from a regular array of alternating subwavelength regions having different indices of refraction.)

  4. Motion compensation for detecting glucose through dual wavelength polarimetric system

    NASA Astrophysics Data System (ADS)

    Dixon, J. B.; Wan, Qiujie; Cote, Gerard L.

    2005-03-01

    The increasing prevalence of diabetes in the United States has led many to pursue methods for non-invasive glucose detection using various optical approaches such as NIR absorption spectroscopy, Raman spectroscopy, fluorescence spectroscopy, and polarization. Polarization approaches using the aqueous humor as the sensing site have been previously shown to achieve 5 mg/dl accuracy in vitro, however accuracy in vivo has yet to be obtained due to motion induced birefringence changes in the cornea. A dual-wavelength close-looped system was developed to compensate for motion artifact. This method has shown 15 mg/dl accuracy in the presence of birefringence changes in the optical path in vitro similar to those that occur in the cornea -- something previous systems were not capable of doing.

  5. Birefringence Measurements of Spherulites formed in β-Lactoglobulin

    NASA Astrophysics Data System (ADS)

    Hardin, Eric; Kirkwood, Brad; Loman, Jazmine; Herat, Athula; Mahmood, Rizwan; Domike, Kristin

    2009-03-01

    Many proteins have a propensity to aggregate into amyloid fibril containing spherulite-like structures. In some instances these spherulitic protein aggregates have been observed in people suffering from a number of neurodegenerative diseases, including Alzheimer's, Parkinson's, and Creutzfeldt-Jakob's. However, the exact role these aggregates play in the body, their internal structure, and the aggregation mechanism still remains a mystery. The model protein used in our study, β-lactoglobulin (BLG), produce spherulites under low pH and high temperature conditions. We report birefringence measurement on BLG using phase retardation method as a function of temperature. Birefringence (˜0.0022 ± 0.0002) data suggest very weak ordering within the spherulites. These spherulites seem to disappear when we added an extensively studied thermotropic liquid crystal [4'-pentyl-4-cyanobiphenyl (5CB)] in β-Lactoglobulin + water+ hydrochloric acid. Our preliminary data suggests that the strong interaction energy between the two systems may lead to the destruction of spherulites.

  6. Observation of Birefringence of an Electrospinning Jet in Flight

    NASA Astrophysics Data System (ADS)

    Liu, Kaiyi; Reneker, Darrell

    2013-03-01

    Solutions of polystyrene in N,N-dimethylformamide, polyacrylonitrile in N,N-dimethylformamide, and polyethylene oxide in water were electrospun. The charged liquid jets in flight were illuminated with polarized light converged on the jets by a Fresnel lens with a black background at the center, and were observed using a high speed camera, coaxial with the Fresnel lens, behind an analyzer which was crossed with a polarizer in front of the light source. The first several turns of coiled jet after the onset of electrical bending instability showed birefringence for all solutions, while no obvious birefringence was observed in the straight segments of the jets. This indicated that molecular chains in the coiled jet were aligned under elongation to a higher extent than those in the thicker straight jet.

  7. Artificial birefringent metallic planar structures for terahertz wave polarization manipulation.

    PubMed

    Wang, Lei; Jiang, Suhua; Hu, Haifeng; Song, Haomin; Zeng, Wei; Gan, Qiaoqiang

    2014-01-15

    We propose an artificial birefringent terahertz (THz) device constructed by subwavelength L-shaped hole arrays on a single metallic layer. This structure is able to work as a polarizer when the incident frequency is between the cut-off frequencies of two eigenmodes. When the incident wave is beyond cut-off frequencies of these two modes, it can be designed as an efficient half- or quarter-wave plate with extraordinary transmission properties. A big effective index difference from 0.254 to 0.768 is obtained using a subwavelength-thick planar structure, which can reduce the thickness of the device to one tenth of conventional quartz birefringent crystals for THz waves.

  8. Reducing Birefringence Uncertainty in the Design of ATST Polarization Components

    NASA Astrophysics Data System (ADS)

    Sueoka, S. R.

    2014-10-01

    Scientific requirements for the Advanced Technology Solar Telescope push the limits of polarimetric calibration and modulation components. The super achromatic retarder and poly chromatic modulator designs comprise of a stack of wave plates with fast axes at different orientations. In order to design these elements over a broad wavelength range it is imperative to know the fundamental properties of the materials. Crystalline quartz, sapphire, and MgF2 have been selected as candidate materials due to their hardness, transmission, and unique birefringence properties. Previously published dispersion models for these crystals do not agree in areas of the design wavelength range. We performed a series of measurements to determine the birefringence from 0.38 μm to 5.0 μm in order to improve our design capabilities.

  9. Hydrostatic pressure sensing with high birefringence photonic crystal fibers.

    PubMed

    Fávero, Fernando C; Quintero, Sully M M; Martelli, Cicero; Braga, Arthur M B; Silva, Vinícius V; Carvalho, Isabel C S; Llerena, Roberth W A; Valente, Luiz C G

    2010-01-01

    The effect of hydrostatic pressure on the waveguiding properties of high birefringence photonic crystal fibers (HiBi PCF) is evaluated both numerically and experimentally. A fiber design presenting form birefringence induced by two enlarged holes in the innermost ring defining the fiber core is investigated. Numerical results show that modal sensitivity to the applied pressure depends on the diameters of the holes, and can be tailored by independently varying the sizes of the large or small holes. Numerical and experimental results are compared showing excellent agreement. A hydrostatic pressure sensor is proposed and demonstrated using an in-fiber modal interferometer where the two orthogonally polarized modes of a HiBi PCF generate fringes over the optical spectrum of a broad band source. From the analysis of experimental results, it is concluded that, in principle, an operating limit of 92 MPa in pressure could be achieved with 0.0003% of full scale resolution.

  10. Reducing stress-induced birefringence in optical fiber ribbons

    NASA Astrophysics Data System (ADS)

    Várallyay, Z.; Arashitani, Y.; Varga, G.

    2011-01-01

    Coated and ribboned optical fibers are liable to external stress of the coating materials which may induce additional birefringence in the fiber glass. This residual stress in the coating may increase the polarization mode dispersion (PMD) of the fibers with a value well above allowed in modern, optical telecommunication systems. We report our numerical efforts on reducing the stress caused birefringence in fiber ribbons optimizing the geometry as well as the material parameters of the coating materials. We found that changing the cross-sectional geometry of the fiber ribbon such as edge shape or the ratio of primary and secondary coatings may lead to significant stress and constitutively PMD reduction in optical fibers. Changing the stiffness or the glass transition temperature (GTT) of the different components may also yield optimal conditions for stress reduction according to our finite element analyzes.

  11. Fourier polarimetry of the birefringence distribution of myocardium tissue

    NASA Astrophysics Data System (ADS)

    Ushenko, O. G.; Dubolazov, O. V.; Ushenko, V. O.; Gorsky, M. P.; Soltys, I. V.; Olar, O. V.

    2015-11-01

    The results of optical modeling of biological tissues polycrystalline multilayer networks have been presented. Algorithms of reconstruction of parameter distributions were determined that describe the linear and circular birefringence. For the separation of the manifestations of these mechanisms we propose a method of space-frequency filtering. Criteria for differentiation of causes of death due to coronary heart disease (CHD) and acute coronary insufficiency (ACI) were found.

  12. POLARBEAR constraints on cosmic birefringence and primordial magnetic fields

    NASA Astrophysics Data System (ADS)

    Ade, Peter A. R.; Arnold, Kam; Atlas, Matt; Baccigalupi, Carlo; Barron, Darcy; Boettger, David; Borrill, Julian; Chapman, Scott; Chinone, Yuji; Cukierman, Ari; Dobbs, Matt; Ducout, Anne; Dunner, Rolando; Elleflot, Tucker; Errard, Josquin; Fabbian, Giulio; Feeney, Stephen; Feng, Chang; Gilbert, Adam; Goeckner-Wald, Neil; Groh, John; Hall, Grantland; Halverson, Nils W.; Hasegawa, Masaya; Hattori, Kaori; Hazumi, Masashi; Hill, Charles; Holzapfel, William L.; Hori, Yasuto; Howe, Logan; Inoue, Yuki; Jaehnig, Gregory C.; Jaffe, Andrew H.; Jeong, Oliver; Katayama, Nobuhiko; Kaufman, Jonathan P.; Keating, Brian; Kermish, Zigmund; Keskitalo, Reijo; Kisner, Theodore; Kusaka, Akito; Le Jeune, Maude; Lee, Adrian T.; Leitch, Erik M.; Leon, David; Li, Yun; Linder, Eric; Lowry, Lindsay; Matsuda, Frederick; Matsumura, Tomotake; Miller, Nathan; Montgomery, Josh; Myers, Michael J.; Navaroli, Martin; Nishino, Haruki; Okamura, Takahiro; Paar, Hans; Peloton, Julien; Pogosian, Levon; Poletti, Davide; Puglisi, Giuseppe; Raum, Christopher; Rebeiz, Gabriel; Reichardt, Christian L.; Richards, Paul L.; Ross, Colin; Rotermund, Kaja M.; Schenck, David E.; Sherwin, Blake D.; Shimon, Meir; Shirley, Ian; Siritanasak, Praween; Smecher, Graeme; Stebor, Nathan; Steinbach, Bryan; Suzuki, Aritoki; Suzuki, Jun-ichi; Tajima, Osamu; Takakura, Satoru; Tikhomirov, Alexei; Tomaru, Takayuki; Whitehorn, Nathan; Wilson, Brandon; Yadav, Amit; Zahn, Alex; Zahn, Oliver; Polarbear Collaboration

    2015-12-01

    We constrain anisotropic cosmic birefringence using four-point correlations of even-parity E -mode and odd-parity B -mode polarization in the cosmic microwave background measurements made by the POLARization of the Background Radiation (POLARBEAR) experiment in its first season of observations. We find that the anisotropic cosmic birefringence signal from any parity-violating processes is consistent with zero. The Faraday rotation from anisotropic cosmic birefringence can be compared with the equivalent quantity generated by primordial magnetic fields if they existed. The POLARBEAR nondetection translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG) on the amplitude of an equivalent primordial magnetic field inclusive of systematic uncertainties. This four-point correlation constraint on Faraday rotation is about 15 times tighter than the upper limit of 1380 nG inferred from constraining the contribution of Faraday rotation to two-point correlations of B -modes measured by Planck in 2015. Metric perturbations sourced by primordial magnetic fields would also contribute to the B -mode power spectrum. Using the POLARBEAR measurements of the B -mode power spectrum (two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial magnetic fields assuming a flat prior on the field amplitude. This limit is comparable to what was found in the Planck 2015 two-point correlation analysis with both temperature and polarization. We perform a set of systematic error tests and find no evidence for contamination. This work marks the first time that anisotropic cosmic birefringence or primordial magnetic fields have been constrained from the ground at subdegree scales.

  13. Tuning micropillar cavity birefringence by laser induced surface defects

    SciTech Connect

    Bonato, Cristian; Ding Dapeng; Gudat, Jan; Exter, Martin P. van; Thon, Susanna; Kim, Hyochul; Petroff, Pierre M.; Bouwmeester, Dirk

    2009-12-21

    We demonstrate a technique to tune the optical properties of micropillar cavities by creating small defects on the sample surface near the cavity region with an intense focused laser beam. Such defects modify strain in the structure, changing the birefringence in a controllable way. We apply the technique to make the fundamental cavity mode polarization-degenerate and to fine tune the overall mode frequencies, as needed for applications in quantum information science.

  14. Photoinduced Birefringence in Azo-Dye Doped Polyurethane

    NASA Astrophysics Data System (ADS)

    Aleksejeva, J.; Gerbreders, A.; Reinfelde, M.; Teteris, J.

    2011-01-01

    In this report we describe a photoinduced birefringence in disperse red (DR1) azo-dye doped polyurethane films. DR1 dye molecules in these films are chemically bound with the polyurethane polymer's main chain. Under laser radiation the DR1 molecules experience the isomerization process; as a result, the dipole moment of such a molecule changes and they align in the presence of electric field. Photo-birefringence was induced by linearly polarized laser radiation (532 nm, 448 nm, 375 nm and 632.8 nm) in the films with various concentrations of DR1 dye. The photo-induced birefringence (PIBR) Δn was measured at 634 nm wavelength, and its dependences on the pumping beam wavelength and intensity were evaluated. The Δn relaxation was studied both in the dark and under light illumi-nation. In DR1-doped polyurethane films the holographic recording was performed using laser light radiation (532 nm). The profile of surface relief grating (SRG) was studied using AFM. The relationship between SRG formation and PIBR is discussed.

  15. Anomalous birefringence of swollen lamellar phases : blue smectics

    NASA Astrophysics Data System (ADS)

    Nallet, F.; Barois, Ph.

    1994-06-01

    The birefringence of a lyotropic lamellar phase is calculated as a function of dilution. It is found to vanish and change sign, provided the natural birefringence of surfactant bilayers is positive. Dispersion is calculated about the point of zero birefringence. These predictions are illustrated with experiments of spectrophotometry: the intensity of light transmitted between crossed polarizers through several lamellar samples vanishes as expected at some particular wavelength. The dependence of the transmitted light on wavelength and cell thickness is consistent with theory. La biréfringence d'une phase lamellaire lyotrope est calculée en fonction de la dilution. Nous montrons qu'elle peut s'annuler à condition que la biréfringence naturelle des bicouches de tensioactif soit positive. La dispersion au voisinage du point de biréfringence nulle est calculée. Ces résultats sont confirmés par des mesures de spectrophotométrie : la transmission des échantillons étudiés entre polariseurs croisés s'annule exactement pour une longueur d'onde particulière. La variation de l'intensité transmise en fonction de la longueur d'onde et de l'épaisseur des échantillons est conforme aux prévisions du modèle.

  16. Spinning wave plate design for retinal birefringence scanning

    NASA Astrophysics Data System (ADS)

    Irsch, K.; Gramatikov, B. I.; Wu, Y.-K.; Guyton, D. L.

    2009-02-01

    To enhance foveal fixation detection while bypassing the deleterious effects of corneal birefringence in retinal birefringence scanning (RBS), we developed a new RBS design introducing a double-pass spinning half wave plate (HWP) and a fixed double-pass retarder into the optical system. Utilizing the measured corneal birefringence from a data set of 300 human eyes, an algorithm and a related computer program, based on Mueller-Stokes matrix calculus, were developed in MATLAB for optimizing the properties of both wave plates. Foveal fixation detection was optimized with the HWP spun 9/16 as fast as the circular scan, with the fixed retarder having a retardance of 45° and fast axis at 90°. With this new RBS design, a significant statistical improvement of 7.3 times in signal strength, i.e. FFT power, was achieved for the available data set compared with the previous RBS design. The computer-model-optimized RBS design has the potential not only for eye alignment screening, but also for remote fixation sensing and eye tracking applications.

  17. Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

    PubMed Central

    Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

    2016-01-01

    Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings. PMID:27356625

  18. Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

    NASA Astrophysics Data System (ADS)

    Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

    2016-06-01

    Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings.

  19. Computational study to evaluate the birefringence of uniaxially oriented film of cellulose triacetate.

    PubMed

    Hayakawa, Daichi; Ueda, Kazuyoshi

    2015-01-30

    The intrinsic birefringence of a cellulose triacetate (CTA) film is evaluated using the polarizability of the monomer model of the CTA repeating unit, which is calculated using the density functional theory (DFT). Since the CTA monomer is known to have three rotational isomers, referred to as gg, gt, and tg, the intrinsic birefringence of these isomers is evaluated separately. The calculation indicates that the monomer CTA with gg and gt structures shows a negative intrinsic birefringence, whereas the monomer unit with a tg structure shows a positive intrinsic birefringence. By using these values, a model of the uniaxially elongated CTA film is constructed with a molecular dynamics simulation, and the orientation birefringence of the film model was evaluated. The result indicates that the film has negative orientation birefringence and that its value is in good agreement with experimental results.

  20. High birefringence, low loss terahertz photonic crystal fibres with zero dispersion at 0.3 THz

    NASA Astrophysics Data System (ADS)

    Yin, Guo-Bing; Li, Shu-Guang; Wang, Xiao-Yan; Liu, Shuo

    2011-09-01

    A terahertz photonic crystal fibre (THz-PCF) is designed for terahertz wave propagation. The dispersion property and model birefringence are studied by employing the finite element method. The simulation result reveals the changing patten of dispersion parameter versus the geometry. The influence of the large frequency band of terahertz on birefringence is also discussed. The design of low loss, high birefringence THz-PCFs with zero dispersion frequency at 0.3 THz is presented.

  1. Highly birefringent large mode area photonic crystal fiber-based sensor for interferometry applications

    NASA Astrophysics Data System (ADS)

    Ademgil, Huseyin

    2016-12-01

    In this work, highly birefringent large mode area (LMA) photonic crystal fiber (PCF) structure for interferometric sensor applications is proposed. The effective mode area, birefringence and the sensitivity coefficient of the proposed PCF structure by employing the full vectorial finite element method (FV-FEM) have been thoroughly investigated. The numerical results have shown that proposed structure simultaneously offers high birefringence of order 10-3, adequately LMA and high sensitivity for various liquid analytes by employing the elliptical liquid core holes.

  2. Telescope birefringence and phase errors in the Gravity instrument at the VLT interferometer

    NASA Astrophysics Data System (ADS)

    Lazareff, B.; Blind, N.; Jocou, L.; Eisenhauer, F.; Perraut, K.; Lacour, S.; Delplancke, F.; Schoeller, M.; Amorim, A.; Brandner, W.; Perrin, G.; Straubmeier, C.

    2014-07-01

    We use a numerical model of the birefringence in the VLT Interferometer (VLTI) and the Gravity instrument to study the astrometric phase errors that arise when two conditions are simultaneously present: differential birefringence between two VLTI arms, and different polarizations of the science and fringe tracker sources. We present measurements of the VLTI birefringence, that are used to validate our model. We show how a suitable alignment of the eigenvectors of the optical train eliminates the phase error.

  3. Measurement of the complex refractive-index spectrum for birefringent and absorptive liquids.

    PubMed

    Saito, M; Matsumoto, N; Nishimura, J

    1998-08-01

    The optical constants of birefringent and/or opaque liquids, e.g., liquid crystals and magnetic fluids, are difficult to measure at wavelengths at which a strong light source such as a laser or an arc lamp is not accessible. The refractive index n and the extinction coefficient kappa of these liquids can be simultaneously evaluated from the reflectance curves that are measured in the large incident angle range. A semicylindrical sample cell allows the spectral reflectance measurement with a weak light source even at large incident angles. By using this method, we evaluated the ordinary and the extraordinary indices of a nematic liquid crystal in the continuous wavelength range of 0.55-1.60 mum. The complex refractive indices of magnetic fluids were also evaluated, and the affect of the magnetic field was demonstrated.

  4. Birefringence properties of a polarization maintaining Panda fibre during Bragg grating regeneration

    NASA Astrophysics Data System (ADS)

    Polz, Leonhard; Jarsen, Andreas; Bartelt, Hartmut; Roths, Johannes

    2015-09-01

    Regeneration of fibre Bragg gratings under application of a high temperature annealing process in a high birefringent polarisation maintaining fibre of type Panda was investigated. During the annealing process, a distinct nonlinearity and hysteresis of the birefringence with temperature was observed. After the temperature process, the birefringence between slow and fast axis at room temperature was nearly doubled, which is in agreement with observations of other researchers. The hysteresis in birefringence might be explained by the crossing of the transition temperature of the stress applying parts and the relief of in-frozen mechanical and thermal stresses.

  5. Birefringence measurements in single crystal sapphire and calcite shocked along the a axis

    NASA Astrophysics Data System (ADS)

    Tear, Gareth R.; Chapman, David J.; Eakins, Daniel E.; Proud, William G.

    2017-01-01

    Calcite and sapphire were shock compressed along the <10 1 ¯0 > direction (a axis) in a plate impact configuration. Polarimetery and Photonic Doppler Velocimetery (PDV) were used to measure the change in birefringence with particle velocity in the shock direction. Results for sapphire agree well with linear photoelastic theory and current literature showing a linear relationship between birefringence and particle velocity up to 310 m s-1. A maximum change in birefringence of 5% was observed. Calcite however showed anomolous behaviour with no detectable change in birefringence (less than 0.1%) over the range of particle velocities studied (up to 75 m s-1).

  6. Nonlinear Cherenkov difference-frequency generation exploiting birefringence of KTP

    SciTech Connect

    Ni, R.; Du, L.; Wu, Y.; Hu, X. P. Zou, J.; Zhang, Y.; Zhu, S. N.; Sheng, Y.; Arie, A.

    2016-01-18

    In this letter, we demonstrate the realization of nonlinear Cherenkov difference-frequency generation (CDFG) exploiting the birefringence property of KTiOPO{sub 4} (KTP) crystal. The pump and signal waves were set to be along different polarizations, thus the phase-matching requirement of CDFG, which is, the refractive index of the pump wave should be smaller than that of the signal wave, was fulfilled. The radiation angles and the intensity dependence of the CDFG on the pump wave were measured, which agreed well with the theoretical ones.

  7. Highly sensitive recognition element based on birefringent porous silicon layers

    NASA Astrophysics Data System (ADS)

    Gross, E.; Kovalev, D.; Künzner, N.; Timoshenko, V. Yu.; Diener, J.; Koch, F.

    2001-10-01

    Anisotropically nanostructured silicon layers exhibit a strong in-plane birefringence. Their optical anisotropy parameters are found to be extremely sensitive to the presence of dielectric substances inside of the pores. Polarization-resolved transmittance measurements provide an extremely sensitive tool to analyze the adsorption of various atoms and molecules in negligible quantities. A variation of the transmitted linearly polarized light intensity up to two orders of magnitude combined with a fast optical response in the range of seconds make these layers a good candidate for sensor applications.

  8. Dichroic Bragg reflectors based on birefringent porous silicon

    SciTech Connect

    Diener, J.; Kunzner, N.; Kovalev, D.; Gross, E.; Timoshenko, V. Yu.; Polisski, G.; Koch, F.

    2001-06-11

    Multilayers of anisotropically nanostructured silicon (Si) have been fabricated and studied by polarization-resolved reflection measurements. Alternating layers having different refractive indices exhibit additionally a strong in-plane anisotropy of their refractive index (birefringence). Therefore, a stack of layers, acting as a distributed Bragg reflector, has two distinct reflection bands, depending on the polarization of the incident linearly polarized light. This effect is governed by a three-dimensional (in-plane and in-depth) variation of the refractive index. These structures can yield optical effects which are difficult to achieve with conventional Bragg reflectors. {copyright} 2001 American Institute of Physics.

  9. Comparison of two synthesis methods for birefringent metasurfaces

    NASA Astrophysics Data System (ADS)

    Achouri, Karim; Lavigne, Guillaume; Caloz, Christophe

    2016-12-01

    Birefringent metasurfaces are two-dimensional structures capable of independently controlling the amplitude, phase, and polarization of orthogonally polarized incident waves. In this work, we propose an in-depth discussion on the mathematical synthesis of such metasurfaces. We compare the two methods, one that is rigorous and based on the exact electromagnetic fields involved in the transformation and one that is based on approximate reflection and transmission coefficients. We next validate the synthesis technique in metasurfaces performing the operations of a half- and quarter-wave plates, polarization beam splitting, and orbital angular momentum multiplexing and present the corresponding microwave experimental demonstrations.

  10. X-ray natural birefringence in reflection from graphene

    NASA Astrophysics Data System (ADS)

    Jansing, C.; Mertins, H.-Ch.; Gilbert, M.; Wahab, H.; Timmers, H.; Choi, S.-H.; Gaupp, A.; Krivenkov, M.; Varykhalov, A.; Rader, O.; Legut, D.; Oppeneer, P. M.

    2016-07-01

    The existence of natural birefringence in x-ray reflection on graphene is demonstrated at energies spanning the carbon 1 s absorption edge. This new x-ray effect has been discovered with precision measurements of the polarization-plane rotation and the polarization-ellipticity changes that occur upon reflection of linearly polarized synchrotron radiation on monolayer graphene. Extraordinarily large polarization-plane rotations of up to 30∘, accompanied by a change from linearly to circularly polarized radiation have been measured for graphene on copper. Graphene on single crystalline cobalt, grown on tungsten, exhibits rotation values of up to 17∘. Both graphene systems show resonantly enhanced effects at the π* and σ* energies. The results are referenced against those obtained for polycrystalline carbon and highly oriented pyrolytic graphite (HOPG), respectively. As expected, polycrystalline carbon shows negligible rotation, whereas a huge maximum rotation of 140∘ has been observed for HOPG that may be considered a graphene multilayer system. HOPG is found to exhibit such large rotation values over a broad energy range, even well beyond the π* resonance energy due to the contributions of numerous graphene layers. To explain the origin of the observed natural birefringence of graphene, the Stokes parameters as well as the x-ray natural linear dichroism in reflection have been determined. It is shown that the birefringence directly results from the optical anisotropy related to the orthogonal alignment of π* and σ* bonds in the graphene layer. Our polarization analysis reveals a strong bonding of graphene on Co with a reduced σ* excitation energy and a strong tilt of 50 % of the pz orbitals towards diagonal orientation. In contrast, graphene on Cu is weakly bound with an orthogonal orientation of the pz orbitals. Exhibiting such a large natural birefringence that can be controlled through substrate choice, and because of excellent heat conductivity

  11. Automated Detection of Ocular Alignment with Binocular Retinal Birefringence Scanning

    NASA Astrophysics Data System (ADS)

    Hunter, David G.; Shah, Ankoor S.; Sau, Soma; Nassif, Deborah; Guyton, David L.

    2003-06-01

    We previously developed a retinal birefringence scanning (RBS) device to detect eye fixation. The purpose of this study was to determine whether a new binocular RBS (BRBS) instrument can detect simultaneous fixation of both eyes. Control (nonmyopic and myopic) and strabismic subjects were studied by use of BRBS at a fixation distance of 45 cm. Binocularity (the percentage of measurements with bilateral fixation) was determined from the BRBS output. All nonstrabismic subjects with good quality signals had binocularity >75%. Binocularity averaged 5% in four subjects with strabismus (range of 0 -20%). BRBS may potentially be used to screen individuals for abnormal eye alignment.

  12. Simultaneous dispersion compensation and polarization mode dispersion compensation using linearly chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Li, Zhiquan; Chen, Ying; Xu, Mingyan; Zhu, Qiguang

    2005-01-01

    A composite structure based on linearly chirped fiber Bragg grating which can compensate for dispersion and polarization mode dispersion simultaneously has been proposed and characterized. On one hand, a chirped fiber Bragg grating can be regarded as a filter that is composed of several uniform sub-gratings. Therefore, optical signals with different wavelengths can be reflected at different points of the grating, which will result in different time delays, by which the dispersion compensation can be implemented easily. On the other hand, a chirped fiber Bragg grating has the pressure-induced birefringence effect. In the experiment, a piezoelectric transducer is used to apply the pressure on the linearly chirped fiber Bragg grating. Then the change of reflection spectra can be obtained when the pressure is applied at different points of the grating. From the reflection spectra response, the transverse pressure is found to lead to the split of the spectra of the grating. Through the observation of the group delay characteristics, we find that the differential group delay moves towards a bigger value with the increased voltage, and the maximal range of differential group delay (DGD) is 50 ps. By consequence, first-order polarization mode dispersion (PMD) can be compensated for with linearly chirped fiber Bragg grating. Thus, when the data rate of the fiber communication system is above 10 Gb/s and below 40 Gb/s, the simultaneous compensation of DGD and PMD is necessary and can be achieved by the composite structure.

  13. Crystallization and birefringence studies on fast structural changes followed by non-contact spectral birefringence and Raman spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Serhatkulu, Toprak Fakr

    2000-11-01

    The structural characteristics of the manufactured polymers such as crystallinity and orientation are controlled by the thermal-deformation history imposed by the processing machinery. Therefore it is essential to monitor these structural characteristics and use the information advantageously to optimize the properties of interest by controlling the process conditions. The focus of this study is to develop robust automated techniques to monitor birefringence and crystallization in real-time. In many of the polymer processing operations involving film stretching where the polymer undergoes a series of thermal deformation treatments, the quantitative changes that take place during the course of these processing operations is poorly understood partly as a result of very rapid structural changes that occur when the polymer's initial condition is not isotropic melt of isotropic solid. There is a great need to quantify the kinetics of the structural changes from preoriented/partially-crystallized states. As part of this dissertation, the birefringence development of preoriented polyethylene terephthalate (PET) films is monitored on-line by the developed spectral birefringence technique with the intent of simulating the heat-setting stage of a tenter film stretching process. Theoretical improvements, software development and optimization, and the equipment design and construction are some of the major tasks accomplished in this dissertation. The automated spectral birefringence technique not only allows the measurement of retardations to very high values, but also enables one to detect the changes in the trend in birefringence (such as a decrease as a result of relaxation, or an increase as a result of crystallization) and to investigate changes that occur very rapidly in the order of a few hundred milliseconds. The effects of stretching conditions on the kinetics of the structural changes in PET films were also investigated using characterization techniques such as

  14. Detecting fixation on a target using time-frequency distributions of a retinal birefringence scanning signal

    PubMed Central

    2013-01-01

    Background The fovea, which is the most sensitive part of the retina, is known to have birefringent properties, i.e. it changes the polarization state of light upon reflection. Existing devices use this property to obtain information on the orientation of the fovea and the direction of gaze. Such devices employ specific frequency components that appear during moments of fixation on a target. To detect them, previous methods have used solely the power spectrum of the Fast Fourier Transform (FFT), which, unfortunately, is an integral method, and does not give information as to where exactly the events of interest occur. With very young patients who are not cooperative enough, this presents a problem, because central fixation may be present only during very short-lasting episodes, and can easily be missed by the FFT. Method This paper presents a method for detecting short-lasting moments of central fixation in existing devices for retinal birefringence scanning, with the goal of a reliable detection of eye alignment. Signal analysis is based on the Continuous Wavelet Transform (CWT), which reliably localizes such events in the time-frequency plane. Even though the characteristic frequencies are not always strongly expressed due to possible artifacts, simple topological analysis of the time-frequency distribution can detect fixation reliably. Results In all six subjects tested, the CWT allowed precise identification of both frequency components. Moreover, in four of these subjects, episodes of intermittent but definitely present central fixation were detectable, similar to those in Figure 4. A simple FFT is likely to treat them as borderline cases, or entirely miss them, depending on the thresholds used. Conclusion Joint time-frequency analysis is a powerful tool in the detection of eye alignment, even in a noisy environment. The method is applicable to similar situations, where short-lasting diagnostic events need to be detected in time series acquired by means of

  15. Process-induced birefringence variations in fiber optic embedded in composite materials

    NASA Astrophysics Data System (ADS)

    Turpin, M.; Chazelas, J.; Stoppiglia, H.

    The use of embedded fiber optic sensors for the impact detection on woven-composite panels has been developed using interfero-polarimetric measurements. Preliminary results on the study of the process-induced birefringence properties modifications of two different types of specific optical fibers: Hi-Bi 'Bow-Tie' fibers and Side-hole birefringent 'FASE' fibers are discussed.

  16. Birefringence-Directed Raman Selection Rules in 2D Black Phosphorus Crystals.

    PubMed

    Mao, Nannan; Wu, Juanxia; Han, Bowen; Lin, Jingjing; Tong, Lianming; Zhang, Jin

    2016-05-01

    The incident and scattered light engaged in the Raman scattering process of low symmetry crystals always suffer from the birefringence-induced depolarization. Therefore, for anisotropic crystals, the classical Raman selection rules should be corrected by taking the birefringence effect into consideration. The appearance of the 2D anisotropic materials provides an excellent platform to explore the birefringence-directed Raman selection rules, due to its controllable thickness at the nanoscale that greatly simplifies the situation comparing with bulk materials. Herein, a theoretical and experimental investigation on the birefringence-directed Raman selection rules in the anisotropic black phosphorus (BP) crystals is presented. The abnormal angle-dependent polarized Raman scattering of the Ag modes in thin BP crystal, which deviates from the normal Raman selection rules, is successfully interpreted by the theoretical model based on birefringence. It is further confirmed by the examination of different Raman modes using different laser lines and BP samples of different thicknesses.

  17. Integrated quantitative phase and birefringence microscopy for imaging malaria-infected red blood cells

    NASA Astrophysics Data System (ADS)

    Li, Chengshuai; Chen, Shichao; Klemba, Michael; Zhu, Yizheng

    2016-09-01

    A dual-modality birefringence/phase imaging system is presented. The system features a crystal retarder that provides polarization mixing and generates two interferometric carrier waves in a single signal spectrum. The retardation and orientation of sample birefringence can then be measured simultaneously based on spectral multiplexing interferometry. Further, with the addition of a Nomarski prism, the same setup can be used for quantitative differential interference contrast (DIC) imaging. Sample phase can then be obtained with two-dimensional integration. In addition, birefringence-induced phase error can be corrected using the birefringence data. This dual-modality approach is analyzed theoretically with Jones calculus and validated experimentally with malaria-infected red blood cells. The system generates not only corrected DIC and phase images, but a birefringence map that highlights the distribution of hemozoin crystals.

  18. On the birefringence of healthy and malaria-infected red blood cells

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, Aditya K.; Basu, Himanish; Dharmadhikari, Jayashree A.; Sharma, Shobhona; Mathur, Deepak

    2013-12-01

    The birefringence of a red blood cell (RBC) is quantitatively monitored as it becomes infected by a malarial parasite. Large changes occur in the cell's refractive index at different stages of malarial infection. The observed rotation of an optically trapped, malaria-infected RBC is not a simple function of shape distortion: the malarial parasite is found to itself exercise a profound influence on the rotational dynamics by inducing stage-specific birefringence. Our measurements shed new light on the competition between shape- and form-birefringence in RBCs. We demonstrate the possibility of using birefringence to establish very early stages of infected parasites and of assessing various factors that contribute to birefringence in normal and infected cells. Our results have implications for the development and use of noninvasive techniques of quantifying changes in cell properties induced by malaria disease pathology.

  19. Use of shape induced birefringence for rotation in optical tweezers

    NASA Astrophysics Data System (ADS)

    Asavei, Theodor; Nieminen, Timo A.; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina

    2010-08-01

    Since a light beam can carry angular momentum (AM) it is possible to use optical tweezers to exert torques to twist or rotate microscopic objects. The alignment torque exerted on an elongated particle in a polarized light field represents a possible torque mechanism. In this situation, although some exchange of orbital angular momentum occurs, scattering calculations show that spin dominates, and polarization measurements allow the torque to be measured with good accuracy. This phenomenon can be explained by considering shape birefringence with an induced polarizability tensor. Another example of a shape birefringent object is a microsphere with a cylindrical cavity. Its design is based on the fact that due to its symmetry a sphere does not rotate in an optical trap, but one could break the symmetry by designing an object with a spherical outer shape with a non spherical cavity inside. The production of such a structure can be achieved using a two photon photo-polymerization technique. We show that using this technique, hollow spheres with varying sizes of the cavity can be successfully constructed. We have been able to demonstrate rotation of these spheres with cylindrical cavities when they are trapped in a laser beam carrying spin angular momentum. The torque efficiency achievable in this system can be quantified as a function of a cylinder diameter. Because they are biocompatible and easily functionalized, these structures could be very useful in work involving manipulation, control and probing of individual biological molecules and molecular motors.

  20. Development of orthotropic birefringent materials for photoelastic stress analysis

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.; Niiro, T.; Koller, G. M.

    1981-01-01

    Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis.

  1. Development and characterization of orthotropic-birefringent materials

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.; Koller, G. M.; Niiro, T.

    1984-01-01

    Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis. Previously announced in STAR as N81-26183

  2. 33 CFR 136.229 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.229 Section 136.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  3. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Other compensation. 136.113 Section 136.113 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  4. 33 CFR 136.211 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.211 Section 136.211 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  5. 33 CFR 136.235 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.235 Section 136.235 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  6. 33 CFR 136.205 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.205 Section 136.205 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  7. 33 CFR 136.223 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.223 Section 136.223 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  8. 33 CFR 136.217 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.217 Section 136.217 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  9. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Other compensation. 136.113 Section 136.113 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  10. 7 CFR 930.61 - Handler compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Handler compensation. 930.61 Section 930.61 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... Handling Regulations § 930.61 Handler compensation. Each handler handling cherries from a...

  11. 7 CFR 930.61 - Handler compensation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Handler compensation. 930.61 Section 930.61 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Handling Regulations § 930.61 Handler compensation. Each handler handling cherries from a...

  12. 7 CFR 930.61 - Handler compensation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Handler compensation. 930.61 Section 930.61 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... Handling Regulations § 930.61 Handler compensation. Each handler handling cherries from a...

  13. 7 CFR 930.61 - Handler compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Handler compensation. 930.61 Section 930.61 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Handling Regulations § 930.61 Handler compensation. Each handler handling cherries from a...

  14. 33 CFR 136.211 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.211 Section 136.211 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  15. 33 CFR 136.229 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.229 Section 136.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  16. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Other compensation. 136.113 Section 136.113 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  17. 33 CFR 136.211 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.211 Section 136.211 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  18. 33 CFR 136.241 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.241 Section 136.241 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  19. 33 CFR 136.229 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.229 Section 136.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  20. 33 CFR 136.211 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.211 Section 136.211 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  1. 33 CFR 136.223 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.223 Section 136.223 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  2. 33 CFR 136.205 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.205 Section 136.205 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  3. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Other compensation. 136.113 Section 136.113 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  4. 33 CFR 136.217 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.217 Section 136.217 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  5. 33 CFR 136.229 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.229 Section 136.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  6. 33 CFR 136.205 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.205 Section 136.205 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  7. 33 CFR 136.217 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.217 Section 136.217 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  8. 33 CFR 136.241 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.241 Section 136.241 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  9. 33 CFR 136.235 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.235 Section 136.235 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  10. 33 CFR 136.241 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.241 Section 136.241 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  11. 33 CFR 136.223 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.223 Section 136.223 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  12. 33 CFR 136.205 - Compensation allowable.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Compensation allowable. 136.205 Section 136.205 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  13. 33 CFR 136.241 - Compensation allowable.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Compensation allowable. 136.241 Section 136.241 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  14. 33 CFR 136.223 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.223 Section 136.223 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  15. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Other compensation. 136.113 Section 136.113 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  16. 33 CFR 136.217 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.217 Section 136.217 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  17. 33 CFR 136.235 - Compensation allowable.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Compensation allowable. 136.235 Section 136.235 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  18. 33 CFR 136.235 - Compensation allowable.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Compensation allowable. 136.235 Section 136.235 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND;...

  19. 47 CFR 32.24 - Compensated absences.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Compensated absences. 32.24 Section 32.24 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES General Instructions § 32.24 Compensated absences. (a)...

  20. 47 CFR 32.24 - Compensated absences.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Compensated absences. 32.24 Section 32.24 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES General Instructions § 32.24 Compensated absences. (a)...

  1. 47 CFR 32.24 - Compensated absences.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Compensated absences. 32.24 Section 32.24 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES General Instructions § 32.24 Compensated absences. (a)...

  2. 47 CFR 32.24 - Compensated absences.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Compensated absences. 32.24 Section 32.24 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES General Instructions § 32.24 Compensated absences. (a)...

  3. Reactive power compensating system

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1987-01-01

    The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

  4. Faculty Compensation Policies.

    ERIC Educational Resources Information Center

    Silander, Fred

    1983-01-01

    Faculty compensation policy is seen as one means by which an institution influences the faculty to work toward institutional goals. Among the broad criteria for compensation are worth, equity, need, and market measures. Benefits and issues in compensation including differentials in compensation, merit, part-time instruction, etc. are discussed.…

  5. A simple and low-cost technique to fabricate and experience interference birefringent filters

    NASA Astrophysics Data System (ADS)

    Velasquez, Pablo; Moreno, Ignacio S.; Sanchez-Lopez, M. d. M.; Puerto, D.

    2004-10-01

    In this work we propose and demonstrate a very simple method to produce interference birefringent filters. We use the birefringence properties of usual commercial scotch, which acts as a uniaxial material. By superimposing several scotch layers with parallel orientation, and placing them between two crossed polarizers oriented at 45 degrees, we can measure the birefringence of the material. We use a portable fiber spectrophotometer to characterize the layers birefringence in the visible range. We developed a software to calculate the transmission properties of different types of birefringent filters, including folded and fan Solc filters. In the simulations we include the information of the material birefringence that we obtain experimentally, thus leading to a precise description of the transmission properties in the entire visible range. A very simple system permits to align the scotch layers with the proper angles and create a birefringent filter. We have designed several filters with different spectral properties. The measurement of the transmission obtained with the portable spectrophotometer confirms experimentally the prediction given by the simulation software.

  6. Thermal characterization of Bragg gratings in polarization-maintaining optical fibres: analysis of birefringence and regeneration

    NASA Astrophysics Data System (ADS)

    Abe, I.; de Oliveira, V.; Fiorin, R.; Kalinowski, H. J.

    2017-04-01

    This paper presents an analysis of birefringence and regeneration of fibre Bragg gratings (FBGs) in two types of polarization-maintaining (PM) optical fibres, bow tie and internal elliptical cladding (IEC), with different diameters. The thermal regeneration of FBGs in PM fibres with different degrees of saturation (weakly, slightly, and strongly saturated) is presented and the influence of the gratings’ saturation degree on the birefringence of PM fibres is shown. The birefringence values obtained for IEC fibres with 80 µm of diameter were for a strongly saturated seed grating of 5.3  ×  10‑4 and 6.2  ×  10‑4 refractive index units after the regeneration. The evolution of the fibre birefringence as a function of the temperature is presented and the results show hysteresis and nonlinear dependence of the birefringence on temperature. The thermal stability of regenerated gratings in PM fibres is demonstrated, and a sensitivity coefficient value of 0.0035 dBm min‑1 at 900 °C was obtained. The results obtained show the feasibility of optimization of fibre birefringence; this could allow such fibers to be used as temperature sensors and even improve the birefringence after the grating regeneration.

  7. Including birefringence into time evolution of CMB: current and future constraints

    SciTech Connect

    Gubitosi, G.; Pagano, L.; Martinelli, M. E-mail: martinelli@thphys.uni-heidelberg.de

    2014-12-01

    We introduce birefringence effects within the propagation history of CMB, considering the two cases of a constant effect and of an effect that increases linearly in time, as the rotation of polarization induced by birefringence accumulates during photon propagation. Both cases result into a mixing of E and B modes before lensing effects take place, thus leading to the fact that lensing is acting on spectra that are already mixed because of birefringence. Moreover, if the polarization rotation angle increases during propagation, birefringence affects more the large scales that the small scales. We put constraints on the two cases using data from WMAP 9yr and BICEP 2013 and compare these results with the constraints obtained when the usual procedure of rotating the final power spectra is adopted, finding that this dataset combination is unable to distinguish between effects, but it nevertheless hints for a non vanishing value of the polarization rotation angle. We also forecast the sensitivity that will be obtained using data from Planck and PolarBear, highlighting how this combination is capable to rule out a vanishing birefringence angle, but still unable to distinguish the different scenarios. Nevertheless, we find that the combination of Planck and PolarBear is sensitive enough to highlight the existence of degeneracies between birefringence rotation and gravitational lensing of CMB photons, possibly leading to false detection of non standard lensing effects if birefringence is neglected.

  8. Determination of the magnetic field induced circular birefringence using the Mueller matrix of FBGs

    NASA Astrophysics Data System (ADS)

    Descamps, Frédéric; Bette, Sébastien; Kinet, Damien; Caucheteur, Christophe

    2016-04-01

    Different methods have already been developed to measure the magnetic field with fiber Bragg gratings (FBGs). They are based on the use of a magnetic fluid or magnetostrictive materials. In addition to these methods, a direct measurement of the magnetic field is also possible by determining the circular birefringence created by the magnetic field inside the fiber. In standard optical fiber, this circular birefringence is of the same order as the intrinsic fiber birefringence or even below. The polarization properties of FBGs are therefore used to perform such measurement since they allow to determine weak birefringence with higher accuracy than standard read-out techniques. However, the obtained accuracy is usually low due to the influence of the intrinsic fiber birefringence. To mitigate this issue, we study in this work the use of the diattenuation vector. This parameter is obtained from the Mueller matrix and we show that it evolves in response to a magnetic field. In practice, we analyze its response by both simulation and experiment. In our simulations, we solve numerically the coupled mode equations of the FBG. For the experiments, the Mueller matrix is measured by an optical vector analyzer for the gratings connected in transmission. We apply an increasing magnetic field on different Bragg gratings photo-written in SMF28 fibers. The rotation of the diattenuation vector is then used to retrieve the magnetic field induced circular birefringence. A linear increase of the reconstructed circular birefringence is reported for increasing magnetic field values in the range 0-1T.

  9. Compact optical isolator for fibers using birefringent wedges.

    PubMed

    Shirasaki, M; Asama, K

    1982-12-01

    A new type of optical isolator for fibers is proposed in this paper. A birefringent wedge used to separate and combine the polarized light is developed, giving the isolator low forward loss and high isolation. The antire-flection process at the fiber endface reduces the forward loss and reflected return. A forward loss of 0.8 dB, a backward loss of 35 dB, and a reflected return of -32 dB were obtained. These characteristics were measured from fiber to fiber using multimode fibers with 50-/microm core diam at a wavelength of 1.3 microm. Details of the design, fabrication, and characteristics of this isolator are presented.

  10. The Double Jones Birefringence in Magneto-electric Medium

    NASA Astrophysics Data System (ADS)

    Mahmood, Waqas; Zhao, Qing

    2015-09-01

    In this paper, the Maxwell’s equations for a tensorial magneto-electric (ME) medium are solved, which is an extension to the work on the uniaxial anisotropic nonmagnetic medium. The coefficients of the dielectric permittivity, magnetic permeability, and of the magneto-electric effect are considered as tensors. The polarization is shown lying in the plane of two perpendicular independent vectors, and the relationship for the transverse polarization is given. The propagation of an electromagnetic wave through a ME medium gives rise to double Jones birefringence. Besides, the condition for an independent phenomenon of D’yakonov surface wave in a magneto-isotropic but with magneto-electric medium is given, which is measurable experimentally when the incident angle is . Lastly, it is shown that the parameter for the magneto-electric effect plays a role in the damping of the wave.

  11. Improvement in birefringent filters. IV - The alternate partial polarizer filter

    NASA Technical Reports Server (NTRS)

    Title, A. M.

    1976-01-01

    The design and performance of a birefringent filter with alternate partial polarizers are analyzed. The properties of several filter configurations with imperfect intermediate polarizers are examined. It is shown that such filters have significant advantages in transmission and profile shape over both the standard Lyot and the contrast element Lyot filters. These theoretical advantages are demonstrated by the measured properties of an actual filter using the alternate partial polarizer (APP) design. This filter is a four-module eight-crystal APP device which has been built using Polaroid HN-38 for the perfect polarizers and two laminated sheets of HN-55 for the partial polarizers. The measured characteristics of the filter are found to be in good agreement with theory.

  12. The Double Jones Birefringence in Magneto-electric Medium

    PubMed Central

    Mahmood, Waqas; Zhao, Qing

    2015-01-01

    In this paper, the Maxwell’s equations for a tensorial magneto-electric (ME) medium are solved, which is an extension to the work on the uniaxial anisotropic nonmagnetic medium. The coefficients of the dielectric permittivity, magnetic permeability, and of the magneto-electric effect are considered as tensors. The polarization is shown lying in the plane of two perpendicular independent vectors, and the relationship for the transverse polarization is given. The propagation of an electromagnetic wave through a ME medium gives rise to double Jones birefringence. Besides, the condition for an independent phenomenon of D’yakonov surface wave in a magneto-isotropic but with magneto-electric medium is given, which is measurable experimentally when the incident angle is . Lastly, it is shown that the parameter for the magneto-electric effect plays a role in the damping of the wave. PMID:26354609

  13. Spectral manipulation and complementary spectra with birefringence polarization control

    NASA Astrophysics Data System (ADS)

    Ding, Pan-Feng; Han, Pin

    2017-03-01

    A polarization control method using crystal birefringence is suggested to manipulate polychromatic light. This scheme can be used with narrower bandwidth to produce various spectral effects, such as a notch filter, a flat top, and triangle-type, nipple-type, and central-frequency-dominant distributions. A modulated spectrum with greater bandwidth can be used as an optical frequency ruler, and phenomena called complementary spectra are also proposed, where the two spectral distributions, produced by rotating the polarizer, complement each other in the sense that the peaks and valleys in one spectrum are the reverse in the other. These results benefit the controlling of the spectral shape and the measurement of an unknown optical frequency.

  14. Directional eye fixation sensor using birefringence-based foveal detection

    NASA Astrophysics Data System (ADS)

    Gramatikov, Boris I.; Zalloum, Othman H. Y.; Wu, Yi Kai; Hunter, David G.; Guyton, David L.

    2007-04-01

    We recently developed and reported an eye fixation monitor that detects the fovea by its radial orientation of birefringent nerve fibers. The instrument used a four-quadrant photodetector and a normalized difference function to check for a best match between the detector quadrants and the arms of the bow-tie pattern of polarization states surrounding the fovea. This function had a maximum during central fixation but could not tell where the subject was looking relative to the center. We propose a linear transformation to obtain horizontal and vertical eye position coordinates from the four photodetector signals, followed by correction based on a priori calibration information. The method was verified on both a computer model and on human eyes. The major advantage of this new eye-tracking method is that it uses true information coming from the fovea, rather than reflections from other structures, to identify the direction of foveal gaze.

  15. Birefringence and DNA Condensation of Liquid Crystalline Chromosomes ▿

    PubMed Central

    Chow, Man H.; Yan, Kosmo T. H.; Bennett, Michael J.; Wong, Joseph T. Y.

    2010-01-01

    DNA can self-assemble in vitro into several liquid crystalline phases at high concentrations. The largest known genomes are encoded by the cholesteric liquid crystalline chromosomes (LCCs) of the dinoflagellates, a diverse group of protists related to the malarial parasites. Very little is known about how the liquid crystalline packaging strategy is employed to organize these genomes, the largest among living eukaryotes—up to 80 times the size of the human genome. Comparative measurements using a semiautomatic polarizing microscope demonstrated that there is a large variation in the birefringence, an optical property of anisotropic materials, of the chromosomes from different dinoflagellate species, despite their apparently similar ultrastructural patterns of bands and arches. There is a large variation in the chromosomal arrangements in the nuclei and individual karyotypes. Our data suggest that both macroscopic and ultrastructural arrangements affect the apparent birefringence of the liquid crystalline chromosomes. Positive correlations are demonstrated for the first time between the level of absolute retardance and both the DNA content and the observed helical pitch measured from transmission electron microscopy (TEM) photomicrographs. Experiments that induced disassembly of the chromosomes revealed multiple orders of organization in the dinoflagellate chromosomes. With the low protein-to-DNA ratio, we propose that a highly regulated use of entropy-driven force must be involved in the assembly of these LCCs. Knowledge of the mechanism of packaging and arranging these largest known DNAs into different shapes and different formats in the nuclei would be of great value in the use of DNA as nanostructural material. PMID:20400466

  16. Polarized X-ray Scattering and Birefringence in Magnetars

    NASA Astrophysics Data System (ADS)

    Barchas, Joseph; Baring, Matthew G.

    2017-01-01

    Interest in radiative processes in the super-strong magnetic regime germane to magnetars has grown over the last two decades. These processes have an inherently anisotropic and polarization-dependent character. Of particular interest is the resonant cyclotron scattering domain, where the Compton cross section is enhanced by orders of magnitude very near the cyclotron frequency -- for electrons in magnetar atmospheres, this is above 10 MeV in energy, and for protons this can be at 1-10 keV. The Compton process is dominant in the highly optically thick environs of magnetar atmospheres, and also in the magnetospheric locales for the production of the hard X-ray bursts. The detailed forms of X-ray spectra will depend intimately on the character of the Compton cross section and the emission zone geometry. The practical determination of the rate of Compton scattering depends on the polarization configuration of incoming photons. This in turn is sensitive to the details of radiation dispersion and transport in hot plasmaspheres near neutron stars. This birefringent dispersion present in strongly-magnetized plasmas can profoundly influence the determination of scattering probabilities. Such polarization transfer is usually addressed by simplifying to the transfer two normal mode intensities. The assumptions involved in this simplification such as orthonormality and "large Faraday depolarization" are valid for a wide range of parameter space, but are known to break down in important cases, such as near a cyclotron resonance. We explore the polarization transfer problem for Compton scattering including the regime where Faraday depolarization is not large. Accordingly, plasma birefringence and the generalized Faraday effect are considered explicitly as part of the transfer problem. Spectra generated from two Monte Carlo models of the transfer problem are presented, one treating isothermal atmospheres in the normal X-ray band, and the other addressing hard X-ray flares in

  17. Quantification of fatigue state in CFRP using ultrasonic birefringence

    NASA Astrophysics Data System (ADS)

    Fey, Peter; Kreutzbruck, Marc

    2016-02-01

    Fiber reinforced plastics are widely used in high performance application areas such as aerospace, automotive and wind energy. They are preferred over classic materials such as metals because of their superior weight to stiffness ratio. When subjected to cyclic or static loading, micro-cracks develop and hence their stiffness degrades. The rate of stiffness degradation depends on the angle between the fibers and the applied load. Because commonly used fiber reinforced composites consist of multiple layers with different fiber directions to cope with different loads applied to the material, the stiffness degradation has to be analyzed for each fiber direction. One method to analyze the stiffness degradation in fiber reinforced materials is ultrasonic birefringence. A birefringent effect as it is known for light in optics is also observed for ultrasonic shear waves in fiber reinforced composites because of their elastic anisotropy. The role of the polarization dependent refractive index is taken by the propagation velocity of shear waves. If polarized parallel to the fiber direction they have a higher velocity than polarized perpendicularly to the fiber direction. The velocity depends on shear stiffness of the material. A model to predict the behavior of shear waves in multi-ply layups has been presented previously by Rheinfurth, Fey, Allinger and Busse[1]. That model was used to manually match measured and simulated phase and amplitude curves for waves that traversed the material under different angles between polarization direction of the emitting transducer and fiber direction in the first ply. Here another mode of interpreting the simulated results is used: amplitude and phase for each transducer orientation angle are combined to a complex number. Displaying them in the complex plane for one half rotation of the transducer yields an ellipse. Semi axis lengths and orientation can be obtained by Fourier transform and are used to compare the simulation to measured

  18. Modulation instabilities in randomly birefringent two-mode optical fibers

    NASA Astrophysics Data System (ADS)

    Li, Jin-Hua; Ren, Hai-Dong; Pei, Shi-Xin; Cao, Zhao-Lou; Xian, Feng-Lin

    2016-12-01

    Modulation instabilities in the randomly birefringent two-mode optical fibers (RB-TMFs) are analyzed in detail by accounting the effects of the differential mode group delay (DMGD) and group velocity dispersion (GVD) ratio between the two modes, both of which are absent in the randomly birefringent single-mode optical fibers (RB-SMFs). New MI characteristics are found in both normal and anomalous dispersion regimes. For the normal dispersion, without DMGD, no MI exists. With DMGD, a completely new MI band is generated as long as the total power is smaller than a critical total power value, named by Pcr, which increases significantly with the increment of DMGD, and reduces dramatically as GVD ratio and power ratio between the two modes increases. For the anomalous dispersion, there is one MI band without DMGD. In the presence of DMGD, the MI gain is reduced generally. On the other hand, there also exists a critical total power (Pcr), which increases (decreases) distinctly with the increment of DMGD (GVD ratio of the two modes) but varies complicatedly with the power ratio between the two modes. Two MI bands are present for total power smaller than Pcr, and the dominant band can be switched between the low and high frequency bands by adjusting the power ratio between the two modes. The MI analysis in this paper is verified by numerical simulation. Project supported by the Natural Science Foundation of Jiangsu Provincial Universities (Grant No. 14KJB140009), the National Natural Science Foundation of China (Grant No. 11447113), and the Startup Foundation for Introducing Talent of NUIST (Grant No. 2241131301064).

  19. Highly Birefringent Microstructure Fiber with Zero Dispersion Wavelength at 0.64 Micrometer

    NASA Astrophysics Data System (ADS)

    Konar, Swapan; Ghorai, Swapan K.; Bhattacharya, Rakhi

    In this article, we have designed a microstructure fiber, which consists of elliptical air holes at the core region. We have investigated its optical properties using finite difference time domain method. The fundamental mode of the proposed microstructure fiber can induce very high birefringenceE It has been realized that the value of birefringence is mainly decided by the shape of the air holes present in the first and second rings. The zero dispersion wavelengths of both fast and slow axes have been shifted to 0E64 micrometer. The proposed birefringent microstructure fiber may be useful in optical communication and sensors.

  20. Numerical analysis of a side-hole birefringent photonic crystal fiber with high-pressure sensitivity

    NASA Astrophysics Data System (ADS)

    Li, Duanming; Zhang, Wei; Zhou, Guiyao

    2016-09-01

    A birefringent structured side-holes photonic crystal fiber (PCF) with high sensitivity is designed for pressure sensing. Simulation results show that the birefringence and relevant sensitivity are strongly influenced by the air-holes' sizes and the distance between the fiber core and side-hole. The modal birefringence and the polarimetric pressure sensitivity can be up to 3.943×10-3 and -3.67×10-5 MPa-1 at 1.55 μm, respectively. The proposed side-holes PCF possesses promising applications for pressure sensing.

  1. Determination of photoinduced and intrinsic birefringences in PMMA/DR13 guest-host film

    NASA Astrophysics Data System (ADS)

    Dall'Agnol, Fernando Fuzinatto; Shimizu, Flávio Makoto; Giacometti, José A.

    2014-07-01

    We report measurements and analysis of photoinduced birefringence (PIB) in polymeric stretched films, hence, with an intrinsic birefringence (IB) associated to the polymeric chain orientation. It was found that transmittance signal is dependent on the angle between the film stretching direction and the probe light polarization, increasing or decreasing relatively to IB signal. Theoretical analysis considered that light propagates through the film having a photoinduced and intrinsic birefringences with independent optical axes. The transmittance signal dependence on the film angle is correctly accounted and our approach could give a phenomenological elucidation to the effect known as the inverse relaxation effect.

  2. Dielectric relaxation and birefringence study of 7.O5O.7 dimeric liquid crystal compound

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Debanjan; Paul-Choudhury, Sandip; Alapati, Parameswara Rao; Bhattacharjee, Ayon

    2016-05-01

    Measurement of dielectric relaxation and birefringence phenomenon of dimeric liquid crystal compound with the dependence of temperature was reported in this paper. Homogeneous (HG) and homeotropic (HT) alignment of the cell are introduced to investigate the dielectric relaxation, activation energy and birefringence. Cole-Cole plots analyzed the dielectric relaxation of the dimeric compound. The observed Cole-Cole plots were semi-circular, and the relaxation mechanism obeys the non-Debye type of relaxation behaviour. Slater's perturbation equations have been used to analysis the activation energy of the compound. The birefringence of the compound has positively anisotropy and thin prism mechanism was used to study the anisotropy of the compound.

  3. Determination of the Dispersion of the Principal Refractive Indices for Birefringent Polypropylene Films

    NASA Astrophysics Data System (ADS)

    Bezruchenko, V. S.; Murauski, An. A.; Muravsky, Al. A.

    2014-07-01

    We present a novel method for determining the dispersion of the refractive indices of birefringent films, based on treatment of transmission spectra, in which we observe interference of light. The dispersion curves n x (λ) and n y (λ) were determined by treatment of transmission spectra obtained for normal incidence of radiation on a P2-25 birefringent fi lm, and n z (λ) was determined for oblique incidence of radiation. From the results of determination of the dispersions of the principal refractive indices of a birefringent P2-25 polypropylene film (Mogilevkhimvolokno OAO, Belarus), we established that the sample is a negative biaxial retarder with N z = 2.9.

  4. Compensation Review Analyst

    SciTech Connect

    2003-06-03

    COMPERA is a decision support system designed to facilitate the compensation review process. With parameters provided by the user(s), the system generates recommendations for base increases and nonbase compensation that strives to align total compensation with performance compensation targets. The user(s) prescribe(s) compensation targets according to performance (or value of contribution) designators. These targets are presented in look-up tables, which are then used by embedded formulas in the worksheet to determine the recommended compensation for each individual.

  5. 26 CFR 1.415(c)-2 - Compensation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 5 2011-04-01 2011-04-01 false Compensation. 1.415(c)-2 Section 1.415(c)-2...) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.415(c)-2 Compensation. (a) General definition. Except as otherwise provided in this section, compensation from the employer...

  6. 49 CFR 371.9 - Rebating and compensation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 5 2014-10-01 2014-10-01 false Rebating and compensation. 371.9 Section 371.9 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY... Requirements § 371.9 Rebating and compensation. (a) A broker shall not charge or receive compensation from...

  7. 49 CFR 371.9 - Rebating and compensation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 5 2012-10-01 2012-10-01 false Rebating and compensation. 371.9 Section 371.9 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY... Requirements § 371.9 Rebating and compensation. (a) A broker shall not charge or receive compensation from...

  8. 47 CFR 51.711 - Symmetrical reciprocal compensation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 3 2011-10-01 2011-10-01 false Symmetrical reciprocal compensation. 51.711... (CONTINUED) INTERCONNECTION Reciprocal Compensation for Transport and Termination of Telecommunications Traffic § 51.711 Symmetrical reciprocal compensation. (a) Rates for transport and termination...

  9. 26 CFR 1.415(c)-2 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 5 2013-04-01 2013-04-01 false Compensation. 1.415(c)-2 Section 1.415(c)-2...) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.415(c)-2 Compensation. (a) General definition. Except as otherwise provided in this section, compensation from the employer...

  10. 47 CFR 51.711 - Symmetrical reciprocal compensation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Symmetrical reciprocal compensation. 51.711... (CONTINUED) INTERCONNECTION Reciprocal Compensation for Transport and Termination of Telecommunications Traffic § 51.711 Symmetrical reciprocal compensation. (a) Rates for transport and termination...

  11. 26 CFR 1.415(c)-2 - Compensation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 5 2014-04-01 2014-04-01 false Compensation. 1.415(c)-2 Section 1.415(c)-2...) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.415(c)-2 Compensation. (a) General definition. Except as otherwise provided in this section, compensation from the employer...

  12. 26 CFR 1.415(c)-2 - Compensation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 5 2012-04-01 2011-04-01 true Compensation. 1.415(c)-2 Section 1.415(c)-2...) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.415(c)-2 Compensation. (a) General definition. Except as otherwise provided in this section, compensation from the employer...

  13. 26 CFR 1.85-1 - Unemployment compensation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Unemployment compensation. 1.85-1 Section 1.85-1...) INCOME TAXES (CONTINUED) Items Specifically Included in Gross Income § 1.85-1 Unemployment compensation... unemployment compensation (as defined in paragraph (b)(1) of this section) paid in taxable years...

  14. 26 CFR 1.85-1 - Unemployment compensation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Unemployment compensation. 1.85-1 Section 1.85-1...) INCOME TAXES (CONTINUED) Items Specifically Included in Gross Income § 1.85-1 Unemployment compensation... unemployment compensation (as defined in paragraph (b)(1) of this section) paid in taxable years...

  15. 26 CFR 1.85-1 - Unemployment compensation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Unemployment compensation. 1.85-1 Section 1.85-1...) INCOME TAXES (CONTINUED) Items Specifically Included in Gross Income § 1.85-1 Unemployment compensation... unemployment compensation (as defined in paragraph (b)(1) of this section) paid in taxable years...

  16. 26 CFR 1.85-1 - Unemployment compensation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Unemployment compensation. 1.85-1 Section 1.85-1...) INCOME TAXES (CONTINUED) Items Specifically Included in Gross Income § 1.85-1 Unemployment compensation... unemployment compensation (as defined in paragraph (b)(1) of this section) paid in taxable years...

  17. 26 CFR 1.85-1 - Unemployment compensation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Unemployment compensation. 1.85-1 Section 1.85-1...) INCOME TAXES (CONTINUED) Items Specifically Included in Gross Income § 1.85-1 Unemployment compensation... unemployment compensation (as defined in paragraph (b)(1) of this section) paid in taxable years...

  18. 28 CFR 104.41 - Amount of compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 104.41 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION FUND OF 2001 Amount of Compensation for Eligible Claimants. § 104.41 Amount of compensation. As... the terrorist-related aircraft crashes of September 11, 2001. In no event shall an award...

  19. 28 CFR 104.21 - Filing for compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 104.21 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION FUND OF 2001 Filing for Compensation; Application for Advance Benefits § 104.21 Filing for compensation... airplane crashes of September 11, 2001 (except for actions seeking collateral source benefits) within...

  20. 28 CFR 104.21 - Filing for compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 104.21 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION FUND OF 2001 Filing for Compensation; Application for Advance Benefits § 104.21 Filing for compensation... airplane crashes of September 11, 2001 (except for actions seeking collateral source benefits) within...

  1. 28 CFR 104.41 - Amount of compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 104.41 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION FUND OF 2001 Amount of Compensation for Eligible Claimants. § 104.41 Amount of compensation. As... the terrorist-related aircraft crashes of September 11, 2001. In no event shall an award...

  2. 21 CFR 868.2340 - Compensated thorpe tube flowmeter.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Compensated thorpe tube flowmeter. 868.2340... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for medical...

  3. 21 CFR 868.2340 - Compensated thorpe tube flowmeter.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Compensated thorpe tube flowmeter. 868.2340... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for medical...

  4. 21 CFR 868.2340 - Compensated thorpe tube flowmeter.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Compensated thorpe tube flowmeter. 868.2340... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for medical...

  5. 21 CFR 868.2340 - Compensated thorpe tube flowmeter.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Compensated thorpe tube flowmeter. 868.2340... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for medical...

  6. 21 CFR 868.2340 - Compensated thorpe tube flowmeter.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Compensated thorpe tube flowmeter. 868.2340... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Monitoring Devices § 868.2340 Compensated thorpe tube flowmeter. (a) Identification. A compensated thorpe tube flowmeter is a device intended for medical...

  7. Birefringence in the transparency region of GaAs/AlAs multiple quantum wells

    SciTech Connect

    Sirenko, A.A.; Etchegoin, P.; Fainstein, A.; Eberl, K.; Cardona, M.

    1999-09-01

    Birefringence measurements for in-plane propagation of light below the absorption edge in GaAs/AlAs multiple quantum wells (MQW{close_quote}s) are reported for different well/barrier widths. A remarkable drop in the low-frequency limit of the birefringence has been observed for MQW structures with small periods and ascribed to the presence of local fields. The temperature dependence of the birefringence is also studied and complementary results in InP quantum dot structures are also presented. The latter exhibit a strong resonant birefringence, which can be explained by the reduced dimensionality in the joint density of states for optical transitions in the dots. {copyright} {ital 1999} {ital The American Physical Society}

  8. Birefringence measurement of glass ion-exchanged waveguides: burying depth or cover layer influence

    NASA Astrophysics Data System (ADS)

    Jamon, D.; Garayt, J. P.; Jordan, E.; Parsy, F.; Ghibaudo, E.; Neveu, S.; Broquin, J.-E.; Royer, F.

    2016-02-01

    This paper deals with an experimental non-destructive technique for the measurement of polarization behavior of integrated optical waveguides. It is based on a high resolution polarimeter associated to an ellipsometric-type calibration which allows determining the full state of polarization of the output light. A magneto-optic perturbation is also added to generate TE/TM mode beating, whose spatial period is directly linked to the modal TE/TM birefringence. This equipment is first qualified by the measurement of modal birefringence in totally or partially buried ion exchanged waveguides. The results show that the value of the birefringence varies as a function of the diffusion aperture width or with the burying depth. By adding a magneto-optical cover layer, consisting in magnetic nanoparticles doped silica matrix obtained by a sol gel process 1, we evidence a huge increase of the beating magnitude and a decrease of the modal birefringence.

  9. Measurement of modal birefringence in optical waveguides based on the Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Zhong, Ze Bing; Fu, Zhi Cheng; Shi, Jian Dong; Tan, Qi Long; Huang, Wo Bin; Huang, Xu Guang

    2014-05-01

    A method for measuring the birefringence in planar waveguide circuits is theoretically proposed and validated. The method is based on the Mach-Zehnder interference and by measuring the spectral shift due to orthogonal polarization states. The birefringence of a silica waveguide is measured to be 2.33 × 10-4 at nearby 1550 nm. In addition, the birefringence variations with the wavelength and its dependence on the external stress are investigated with the proposed method experimentally. The results in measuring birefringence demonstrate a high accuracy with the order of 10-5, a wide dynamic range from 10-5 to 10-3, and a characteristic of multi-wavelength evaluation.

  10. Birefringence measurements in human skin using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Pierce, Mark C.; Strasswimmer, John; Park, B. H.; Cense, Barry; de Boer, Johannes F.

    2004-07-01

    Optical coherence tomography enables cross-sectional imaging of tissue structure to depths of around 1.5 mm, at high-resolution and in real-time. Incorporation of polarization-sensitivity enables the birefringent properties of tissues to be visualized and quantified. We present polarization-sensitive optical coherence tomography images and quantitative birefringence analysis of in vivo human skin. From measurements on a sample of 5 human volunteers, mean double-pass phase retardation rates of 0.340 +/- 0.143, 0.250 +/- 0.076 and 0.592 +/- 0.142°/μm were obtained for normal skin at the dorsal hand, temple and lower back regions respectively. Compared to these values measured in normal skin, a reduction in birefringence was observed and quantified in human skin following thermal injury. Conversely, increased birefringence was consistently measured at skin sites following wound healing and repair.

  11. Analysis of a highly birefringent asymmetric photonic crystal fibre based on a surface plasmon resonance sensor

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Wang, Famei; Zheng, Shijie; Sun, Tao; Lv, Jingwei; Liu, Qiang; Yang, Lin; Mu, Haiwei; Chu, Paul K.

    2016-07-01

    A highly birefringent photonic crystal fibre is proposed and characterized based on a surface plasmon resonance sensor. The birefringence of the sensor is numerically analyzed by the finite-element method. In the numerical simulation, the resonance wavelength can be directly positioned at this birefringence abrupt change point and the depth of the abrupt change of birefringence reflects the intensity of excited surface plasmon. Consequently, the novel approach can accurately locate the resonance peak of the system without analyzing the loss spectrum. Simulated average sensitivity is as high as 1131 nm/RIU, corresponding to a resolution of 1 × 10-4 RIU in this sensor. Therefore, results obtained via the approach not only show polarization independence and less noble metal consumption, but also reveal better performance in terms of accuracy and computation efficiency.

  12. Approach for fast numerical propagation of uniformly polarized random electromagnetic fields in dispersive linearly birefringent systems.

    PubMed

    Makowski, Piotr L; Domanski, Andrzej W

    2013-09-01

    An efficient simulation technique is proposed for computing propagation of uniformly polarized statistically stationary fields in linear nonimage-forming systems that includes dispersion of linear birefringence to all orders. The method is based on the discrete-time Fourier transformation of modified frequency profiles of the spectral Stokes parameters. It works under the condition that all (linearly) birefringent sections present in the system are described by the same phase birefringence dispersion curve, being a monotonic function of the optical frequency within the bandwidth of the light. We demonstrate the technique as a supplement for the Mueller-Stokes matrix formalism extended to any uniformly polarized polychromatic illumination. Accuracy of its numerical implementation has been verified by using parameters of a Lyot depolarizer made of a highly birefringent and dispersive monomode photonic crystal fiber.

  13. Electric Birefringence: A Simple Apparatus for Determining Physical Parameters of Macromolecules and Colloids.

    ERIC Educational Resources Information Center

    Trimm, Harold H.; And Others

    1984-01-01

    Describes a birefringence apparatus that can be assembled for less than $100 and can be used to measure both the dimensions and dipole moments of many macromolecules. Details are given of the construction and manipulation of the apparatus. (JN)

  14. Quantum-electrodynamical birefringence vanishing in a thermal relativistic pair plasma

    PubMed Central

    Huang, Y. S.

    2015-01-01

    Quantum electrodynamical (QED) birefringence in a thermal relativistic pair plasma with the presence of the strong crossed field: , is proposed and investigated. We clarify the coupling relationship and competition between the QED effect and the plasma collective effect and find the critical condition that makes the birefringence vanish. In a relative weak electromagnetic field, the birefringence is dominated by the coupling of the QED-effect, the collective effect and the drift effect. In a relative strong electromagnetic field, we obtain the formulations stating the competition between the QED effect and the collective effect and then the critical conditions so that they are canceled with each other and the birefringence vanishes. With our results, a new possible scheme is proposed to estimate the thickness of the magnetosphere in a millisecond pulsar and the plasma density of a pulsar, if the magnetic field is known beforehand. PMID:26522493

  15. Modeling Interferometric Structures with Birefringent Elements: A Linear Vector-Space Formalism

    DTIC Science & Technology

    2013-11-12

    Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 V APPLICATION ...24 Application to birefringent propagation and optical coupling . . . . . . . . . . . . . 26 Conclusion...in digital optical communications, which in- creasingly use phase modulation to avoid optical impairments[4, 5]. Evolving system metrics will

  16. Accurate and quantitative polarization-sensitive OCT by unbiased birefringence estimator with noise-stochastic correction

    NASA Astrophysics Data System (ADS)

    Kasaragod, Deepa; Sugiyama, Satoshi; Ikuno, Yasushi; Alonso-Caneiro, David; Yamanari, Masahiro; Fukuda, Shinichi; Oshika, Tetsuro; Hong, Young-Joo; Li, En; Makita, Shuichi; Miura, Masahiro; Yasuno, Yoshiaki

    2016-03-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that contrasts the polarization properties of tissues. It has been applied to ophthalmology, cardiology, etc. Proper quantitative imaging is required for a widespread clinical utility. However, the conventional method of averaging to improve the signal to noise ratio (SNR) and the contrast of the phase retardation (or birefringence) images introduce a noise bias offset from the true value. This bias reduces the effectiveness of birefringence contrast for a quantitative study. Although coherent averaging of Jones matrix tomography has been widely utilized and has improved the image quality, the fundamental limitation of nonlinear dependency of phase retardation and birefringence to the SNR was not overcome. So the birefringence obtained by PS-OCT was still not accurate for a quantitative imaging. The nonlinear effect of SNR to phase retardation and birefringence measurement was previously formulated in detail for a Jones matrix OCT (JM-OCT) [1]. Based on this, we had developed a maximum a-posteriori (MAP) estimator and quantitative birefringence imaging was demonstrated [2]. However, this first version of estimator had a theoretical shortcoming. It did not take into account the stochastic nature of SNR of OCT signal. In this paper, we present an improved version of the MAP estimator which takes into account the stochastic property of SNR. This estimator uses a probability distribution function (PDF) of true local retardation, which is proportional to birefringence, under a specific set of measurements of the birefringence and SNR. The PDF was pre-computed by a Monte-Carlo (MC) simulation based on the mathematical model of JM-OCT before the measurement. A comparison between this new MAP estimator, our previous MAP estimator [2], and the standard mean estimator is presented. The comparisons are performed both by numerical simulation and in vivo measurements of anterior and

  17. Light-induced rotations of chiral birefringent microparticles in optical tweezers

    PubMed Central

    Donato, M. G.; Mazzulla, A.; Pagliusi, P.; Magazzù, A.; Hernandez, R. J.; Provenzano, C.; Gucciardi, P. G.; Maragò, O. M.; Cipparrone, G.

    2016-01-01

    We study the rotational dynamics of solid chiral and birefringent microparticles induced by elliptically polarized laser light in optical tweezers. We find that both reflection of left circularly polarized light and residual linear retardance affect the particle dynamics. The degree of ellipticity of laser light needed to induce rotations is found. The experimental results are compared with analytical calculations of the transfer of angular moment from elliptically polarized light to chiral birefringent particles. PMID:27601200

  18. Risk and Combat Compensation

    DTIC Science & Technology

    2011-08-01

    Leader iii Executive Summary The Eleventh Quadrennial Review of Military Compensation (11th QRMC) was chartered to review four areas of the military...compensation is an important element in the remuneration of military personnel. The principal justification for combat compensation is to recognize...combat zone received at least $4,660 in federal tax savings and benefits. One unexpected aspect of CZTE-related compensation is that senior officers

  19. Birefringence of the central cornea in children assessed with scanning laser polarimetry

    NASA Astrophysics Data System (ADS)

    Irsch, Kristina; Shah, Ashesh A.

    2012-08-01

    Corneal birefringence is a well-known confounding factor with all polarization-sensitive technology used for retinal scanning and other intraocular assessment. It has been studied extensively in adults, but little is known regarding age-related differences. Specifically, no information is available concerning corneal birefringence in children. For applications that are geared towards children, such as retinal birefringence scanning for strabismus screening purposes, it is important to know the expected range of both corneal retardance and azimuth in pediatric populations. This study investigated central corneal birefringence in children (ages three and above), by means of scanning laser polarimetry (GDx-VCC™, Carl Zeiss Meditec, Inc.). Children's measures of corneal retardance and azimuth were compared with those obtained in adults. As with previous studies in adults, corneal birefringence was found to vary widely in children, with corneal retardance ranging from 10 to 77 nm, and azimuth (slow axis) ranging from -11° to 71° (measured nasally downward). No significant differences in central corneal birefringence were found between children and adults, nor were significant age-related differences found in general. In conclusion, establishing knowledge of the polarization properties of the central cornea in children allows better understanding, exploitation, or bypassing of these effects in new polarization-sensitive pediatric ophthalmic applications.

  20. Fluorescence spectroscopy and birefringence of molecular changes in maturing rat tail tendon.

    PubMed

    Korol, Renee M; Finlay, Helen M; Josseau, Melanie J; Lucas, Alexandra R; Canham, Peter B

    2007-01-01

    Tissue remodeling during maturation, wound healing, and response to vascular stress involves molecular changes of collagen and elastin in the extracellular matrix (ECM). Two optical techniques are effective for investigating these changes--laser-induced fluorescence (LIF) spectroscopy and polarizing microscopy. LIF spectroscopy integrates the signal from both elastin and collagen cross-linked structure, whereas birefringence is a measure of only collagen. Our purpose is (1) to evaluate the rat tail tendon (RTT) spectroscopy against data from purified extracted protein standards and (2) to correlate the two optical techniques in the study of RTT and skin. Spectra from tissue samples from 27 male rats and from extracted elastin and collagen were obtained using LIF spectroscopy (357 nm). Birefringence was measured on 5-mum histological sections of the same tissue. Morphometric analysis reveals that elastin represents approximately 10% of tendon volume and contributes to RTT fluorescence. RTT maximum fluorescence emission intensity (FEI(max)), which includes collagen and elastin, increases with animal weight (R(2)=0.64). Birefringence, when plotted against weight, increases to a plateau (nonlinear correlation: R(2)=0.90), tendon having greater birefringence than skin. LIF spectroscopy and collagen fiber birefringence are shown to provide complementary measurements of molecular structure (tendon birefringence versus FEI(max) at R(2)=0.60).

  1. Effect of laser pulse propagation on ultrafast magnetization dynamics in a birefringent medium

    NASA Astrophysics Data System (ADS)

    de Jong, J. A.; Kalashnikova, A. M.; Pisarev, R. V.; Balbashov, A. M.; Kimel, A. V.; Kirilyuk, A.; Rasing, Th

    2017-04-01

    Light propagation effects can strongly influence the excitation and the detection of laser-induced magnetization dynamics. We investigated experimentally and analytically the effects of crystallographic linear birefringence on the excitation and detection of ultrafast magnetization dynamics in the rare-earth orthoferrites (Sm0.5Pr0.5)FeO3 and (Sm0.55Tb0.45)FeO3, which possess weak and strong linear birefringence, respectively. Our finding is that the effect of linear birefringence on the result of a magneto-optical pump-probe experiment strongly depends on the mechanism of excitation. When magnetization dynamics, probed by means of the Faraday effect, is excited via a rapid, heat-induced phase transition, the measured rotation of the probe pulse polarization is strongly suppressed due to the birefringence. This contrasts with the situation for magnetization dynamics induced by the ultrafast inverse Faraday effect, where the corresponding probe polarization rotation values were larger in the orthoferrite with strong linear birefringence. We show that this striking difference results from an interplay between the polarization transformations experienced by pump and probe pulses in the birefringent medium.

  2. Quantification of birefringence readily measures the level of muscle damage in zebrafish

    SciTech Connect

    Berger, Joachim; Sztal, Tamar; Currie, Peter D.

    2012-07-13

    Highlights: Black-Right-Pointing-Pointer Report of an unbiased quantification of the birefringence of muscle of fish larvae. Black-Right-Pointing-Pointer Quantification method readily identifies level of overall muscle damage. Black-Right-Pointing-Pointer Compare zebrafish muscle mutants for level of phenotype severity. Black-Right-Pointing-Pointer Proposed tool to survey treatments that aim to ameliorate muscular dystrophy. -- Abstract: Muscular dystrophies are a group of genetic disorders that progressively weaken and degenerate muscle. Many zebrafish models for human muscular dystrophies have been generated and analysed, including dystrophin-deficient zebrafish mutants dmd that model Duchenne Muscular Dystrophy. Under polarised light the zebrafish muscle can be detected as a bright area in an otherwise dark background. This light effect, called birefringence, results from the diffraction of polarised light through the pseudo-crystalline array of the muscle sarcomeres. Muscle damage, as seen in zebrafish models for muscular dystrophies, can readily be detected by a reduction in the birefringence. Therefore, birefringence is a very sensitive indicator of overall muscle integrity within larval zebrafish. Unbiased documentation of the birefringence followed by densitometric measurement enables the quantification of the birefringence of zebrafish larvae. Thereby, the overall level of muscle integrity can be detected, allowing the identification and categorisation of zebrafish muscle mutants. In addition, we propose that the establish protocol can be used to analyse treatments aimed at ameliorating dystrophic zebrafish models.

  3. THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

    PubMed Central

    Nakajima, Hiromichi; Allen, Robert D.

    1965-01-01

    Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light. PMID:14287186

  4. Imaging of skin birefringence for human scar assessment using polarization-sensitive optical coherence tomography aided by vascular masking

    NASA Astrophysics Data System (ADS)

    Gong, Peijun; Chin, Lixin; Es'haghian, Shaghayegh; Liew, Yih Miin; Wood, Fiona M.; Sampson, David D.; McLaughlin, Robert A.

    2014-12-01

    We demonstrate the in vivo assessment of human scars by parametric imaging of birefringence using polarization-sensitive optical coherence tomography (PS-OCT). Such in vivo assessment is subject to artifacts in the detected birefringence caused by scattering from blood vessels. To reduce these artifacts, we preprocessed the PS-OCT data using a vascular masking technique. The birefringence of the remaining tissue regions was then automatically quantified. Results from the scars and contralateral or adjacent normal skin of 13 patients show a correspondence of birefringence with scar type: the ratio of birefringence of hypertrophic scars to corresponding normal skin is 2.2±0.2 (mean±standard deviation), while the ratio of birefringence of normotrophic scars to normal skin is 1.1±0.4. This method represents a new clinically applicable means for objective, quantitative human scar assessment.

  5. Extension of the hole-drilling method to birefringent composites

    NASA Technical Reports Server (NTRS)

    Prabhakaran, R.

    1982-01-01

    A complete stress analysis and reliable failure criteria are essential for important structural applications of composites in order to fully utilize their unique properties. The inhomogeneity, anisotropy and inelasticity of many composites make the use of experimental methods indispensable. Among the experimental techniques, transmission photoelasticity has been extended to birefringent composites in recent years. The extension is not straight-forward, in view of the complex nature of the photoelastic response of such model materials. This paper very briefly reviews the important developments in the subject and then describes the theoretical basis for a new method of determining the individual values of principal stresses in composite models. The method consists in drilling very small holes at points where the state of stress has to be determined. Experiments are then described which verify the theoretical predictions. The limitations of the method are pointed out and it is concluded that valuable information concerning the state of stress in a composite model can be obtained through the suggested method.

  6. Measurement of birefringence for optical recording disk substrates

    NASA Technical Reports Server (NTRS)

    Fu, Hong; Sugaya, S.; Erwin, J. K.; Goodman, T.; Yan, Z.; Tang, W. J.; Mansuripur, M.

    1993-01-01

    The birefringence of bare and coated substrates for magneto-optical recording is experimentally investigated using ellipsometry at the wavelengths of 632.8 nm and 780 nm. The rotation and ellipticity of the polarization state of the reflected or transmitted light is measured for different incident angles and different orientations of the incident linear polarization. The measured data is then fitted by a computer program which solves the Maxwell equations for the plane-wave propagation in a multilayer structure and minimizes the error between the measured and calculated data by adjusting the unknown parameters of the multilayer. This approach enables us to determine orientations of the three principal axes in the substrate and the corresponding refractive indices. A special feature of our ellipsometers is that a glass hemisphere is placed in contact with the substrate, which eliminates the refraction of the incident light and enables a maximum propagation angle of 70 degrees (with respect to the normal) in the substrate. This increases the sensitivity of the measurement. Certain anomalies were observed, which we believe are associated with the presence of grooves on these substrates.

  7. Magnetic birefringence study of isotropic suspensions of tobacco mosaic virus

    NASA Astrophysics Data System (ADS)

    Photinos, P.; Rosenblatt, C.; Schuster, T. M.; Saupe, A.

    1987-12-01

    The magnetic field induced birefringence in isotropic aqueous suspensions of tobacco mosaic virus (TMV) was measured as a function of temperature and concentration in high magnetic fields (100 kG). The temperature range was between 15 and 50 °C and the concentration range was between 4 and 20 mg/cm3. We find that the Cotton-Mouton constant (C) increases with decreasing temperature by 15%-20% over the entire range and extrapolates to infinity at a finite temperature of 110 to 150 K. At constant temperature, the measured ρ/C(ρ=number of TMV particles per cm3 of suspension) can be expanded in a power series of ρ, where the coefficients are expressed by the irreducible cluster integrals. At 20 °C the experimental values can be fitted to the linear form: ρ/λC=(2.09×1030-1.35×1015ρ)G2/cm3. For rigid cylindrical particles with l=3000 Å and d=180 Å, and using the rigid hard particle interaction model, we find for the first order coefficient 0.62×1015, i.e., a significant deviation for the rigid hard-rod model. This deviation is also indicated by the variation of C with temperature. We discuss the results on TMV and of similar measurements on phage fd in terms of the interparticle interaction and rigidity of the particles.

  8. Validating Laser-Induced Birefringence Theory with Plasma Interferometry

    SciTech Connect

    Chen, Cecilia

    2015-09-02

    Intense laser beams crossing paths in plasma is theorized to induce birefringence in the medium, resulting from density and refractive index modulations that affect the polarization of incoming light. The goal of the associated experiment, conducted on Janus at Lawrence Livermore’s Jupiter Laser Facility, was to create a tunable laser-plasma waveplate to verify the relationship between dephasing angle and beam intensity, plasma density, plasma temperature, and interaction length. Interferometry analysis of the plasma channel was performed to obtain a density map and to constrain temperature measured from Thomson scattering. Various analysis techniques, including Fast Fourier transform (FFT) and two variations of fringe-counting, were tried because interferograms captured in this experiment contained unusual features such as fringe discontinuity at channel edges, saddle points, and islands. The chosen method is flexible, semi-automated, and uses a fringe tracking algorithm on a reduced image of pre-traced synthetic fringes. Ultimately, a maximum dephasing angle of 49.6° was achieved using a 1200 μm interaction length, and the experimental results appear to agree with predictions.

  9. A simple and easily implemented design for an ultra-broadband variable phase compensator

    NASA Astrophysics Data System (ADS)

    Xu, Shixiang; Chen, Wenting; Cai, Yi; Lu, Xiaowei; Chen, Hongyi; Zheng, Guoliang; Li, Jingzhen

    2015-03-01

    We propose a novel design for a variable phase compensator (VPC) to improve bandwidth by minimizing the birefringent phase retardation (BPR) dispersion. Especially at the near-zero BPR point, the VPC has an extremely broad bandwidth. The VPC is based on only two kinds of birefringent crystals, and all its included components can be manufactured almost without need of dimension tolerance, which greatly simplifies its manufacture. According to our calculations, the VPC can keep its relative residual BPR within 2.4% with an ADP/KDP material combination, much smaller than that of the traditional quartz VPC for the tunable BPR from -180° to 180° in the spectral zone from 0.6 to 1.0 μm. This kind of VPC is suitable for accurately manipulating the polarization of broadband light pulses.

  10. Photonic variable delay devices based on optical birefringence

    NASA Technical Reports Server (NTRS)

    Yao, X. Steve (Inventor)

    2005-01-01

    Optical variable delay devices for providing variable true time delay to multiple optical beams simultaneously. A ladder-structured variable delay device comprises multiple basic building blocks stacked on top of each other resembling a ladder. Each basic building block has two polarization beamsplitters and a polarization rotator array arranged to form a trihedron; Controlling an array element of the polarization rotator array causes a beam passing through the array element either going up to a basic building block above it or reflect back towards a block below it. The beams going higher on the ladder experience longer optical path delay. An index-switched optical variable delay device comprises of many birefringent crystal segments connected with one another, with a polarization rotator array sandwiched between any two adjacent crystal segments. An array element in the polarization rotator array controls the polarization state of a beam passing through the element, causing the beam experience different refractive indices or path delays in the following crystal segment. By independently control each element in each polarization rotator array, variable optical path delays of each beam can be achieved. Finally, an index-switched variable delay device and a ladder-structured variable device are cascaded to form a new device which combines the advantages of the two individual devices. This programmable optic device has the properties of high packing density, low loss, easy fabrication, and virtually infinite bandwidth. The device is inherently two dimensional and has a packing density exceeding 25 lines/cm2. The delay resolution of the device is on the order of a femtosecond (one micron in space) and the total delay exceeds 10 nanosecond. In addition, the delay is reversible so that the same delay device can be used for both antenna transmitting and receiving.

  11. Toxic compensation bills

    SciTech Connect

    Anderson, R.C.

    1985-10-01

    Congress has demonstrated interest in toxic compensation legislation, but not enough agreement to make significant progress. Advocates of reform claim that the legal system is heavily weighed against victims who seek compensation through the courts. Proposed reforms include a compensation fund and a cause of action in federal court. Critics have questioned whether these changes in the law would represent an improvement. Existing income replacement, medical cost reimbursement, and survivor insurance programs largely cover the losses of individuals with chronic disease. Thus, the need for an additional compensation is not clear. Furthermore, experience with compensation funds such as the Black Lung Fund suggests that political rather than scientific criteria may be used to determine eligibility. Finally, under the proposed financing mechanisms the compensation funds that are being debated would not increase incentives for care in the handling of hazardous wastes or toxic substances.

  12. Toxic compensation bills.

    PubMed Central

    Anderson, R C

    1985-01-01

    Congress has demonstrated interest in toxic compensation legislation, but not enough agreement to make significant progress. Advocates of reform claim that the legal system is heavily weighed against victims who seek compensation through the courts. Proposed reforms include a compensation fund and a cause of action in federal court. Critics have questioned whether these changes in the law would represent an improvement. Existing income replacement, medical cost reimbursement, and survivor insurance programs largely cover the losses of individuals with chronic disease. Thus, the need for an additional compensation is not clear. Furthermore, experience with compensation funds such as the Black Lung Fund suggests that political rather than scientific criteria may be used to determine eligibility. Finally, under the proposed financing mechanisms the compensation funds that are being debated would not increase incentives for care in the handling of hazardous wastes or toxic substances. PMID:4085440

  13. At-sea Validation of a Birefringence Method for Determining PIC Concentrations in Seawater

    NASA Astrophysics Data System (ADS)

    Guay, C. K.; Bishop, J. K.

    2001-12-01

    We have previously described a spectrophotometer-based method for making optical measurements of particulate inorganic carbon (PIC) in seawater. This method, based on the extreme birefringence of calcium carbonate (CaCO3) relative to other major components of marine particulate matter, was developed in the laboratory using sample suspensions prepared from calcareous marine sediment material and varying amounts of non-birefringent diatomaceous earth. Here we report the first successful measurements of birefringence signals in natural seawater samples, which were obtained during a recent cruise to the North Pacific off the California coast. The spectrophotometer-based method was used onboard to measure PIC in samples collected from Niskin bottle casts in a variety of environments (nearshore to open ocean, eutrophic to oligotrophic). These samples contained a diverse mixture of particles, including calcareous, siliceous and organic material. Birefringence signals clearly above the detection level were observed in several samples, with the strongest signals occurring in productive surface waters off Point Concepcion. The spectrophotometer-based method was validated against PIC concentrations determined by chemical analysis of particulate matter collected by filtration of the Niskin bottle samples and from large-volume (1000's of L) in situ filtration performed immediately after the Niskin casts. In addition, these data were compared with in situ birefringence measurements made using a prototype profiling PIC sensor deployed on the rosette during the Niskin casts.

  14. Orientation birefringence of cross-linked rubber containing low-mass compound

    NASA Astrophysics Data System (ADS)

    Kiyama, Ayumi; Nobukawa, Shogo; Yamauchi, Masayuki

    2015-05-01

    Molecular orientation of low-mass compounds (LMCs) in a cross-linked rubber is studied in order to obtain the basic information on the dynamics of LMC molecules in a polymer beyond the glass transition temperature. A small amount of LMCs such as 4-cyano-4'-pentylbiphenyl (5CB), tricresylphosphate (TCP), and styrene-based tackifier (TF) is added into polybutadiene rubber (BR). After cross-linking reaction, the sheet samples are used to evaluate the orientation birefringence during stretching and stress relaxation. The rectangular films, cut out from the cross-linked sheets, are set in a uniaxial stretching machine equipped with an optical system to measure both birefringence and tensile stress simultaneously. It is confirmed that orientation birefringence is proportional to the stress for not only pure cross-linked BR, but also cross-linked BR containing an LMC in a wide range of strain. Even after stretching, the birefringence does not change as far as the sample is kept at a constant strain. The results suggest that the LMC molecules are forced to orient with polymer chains by the strong intermolecular orientation correlation. Because of the LMC orientation, the stress-optical coefficient CR is enhanced by the addition of 5CB and TCP, but depressed by TF. Therefore, the LMC doping can be used to control the birefringence of a retardation film.

  15. Exposure and compositional factors that influence polarization induced birefringence in silica glass

    NASA Astrophysics Data System (ADS)

    Allan, Douglas C.; Mlejnek, Michal; Neukirch, Ulrich; Smith, Charlene M.; Smith, Frances M.

    2007-03-01

    Silica glass exhibits a permanent anisotropic response, referred to as polarization induced birefringence (PIB), when exposed to short wavelength, polarized light. The magnitude of the PIB has been empirically correlated with the OH content of the glass. Our recent studies pertaining to PIB have focused on careful characterization of PIB, with particular emphasis on understanding all of the contributions to the measured birefringence signal and finally extracting only that signal associated with birefringence arising from exposure to a polarized light beam. We will demonstrate that a critical contributor to the total birefringence signal is birefringence that comes from exposure beam inhomogeneities. After subtracting beam profile effects we are able to show that PIB is proportional to the OH content of the glass. Polarized infrared (IR) measurements were performed on glasses that developed PIB as a consequence of exposure to polarized 157-nm light. These studies reveal that there is preferential bleaching of a specific hydroxyl (OH) species in the glass with OH aligned parallel to the incident polarization undergoing more bleaching than those perpendicular. Further, we observe a very strong correlation between the measured PIB of these samples and the anisotropic bleaching. From these studies we propose a mechanism that can explain the role of hydroxyl in PIB.

  16. Birefringence imaging of posterior eye by multi-functional Jones matrix optical coherence tomography

    PubMed Central

    Sugiyama, Satoshi; Hong, Young-Joo; Kasaragod, Deepa; Makita, Shuichi; Uematsu, Sato; Ikuno, Yasushi; Miura, Masahiro; Yasuno, Yoshiaki

    2015-01-01

    A clinical grade prototype of posterior multifunctional Jones matrix optical coherence tomography (JM-OCT) is presented. This JM-OCT visualized depth-localized birefringence in addition to conventional cumulative phase retardation imaging through local Jones matrix analysis. In addition, it simultaneously provides a sensitivity enhanced scattering OCT, a quantitative polarization uniformity contrast, and OCT-based angiography. The probe beam is at 1-μm wavelength band. The measurement speed and the depth-resolution were 100,000 A-lines/s, and 6.6 μm in tissue, respectively. Normal and pathologic eyes are examined and several clinical features are revealed, which includes high birefringence in the choroid and lamina cribrosa, and birefringent layered structure of the sclera. The theoretical details of the depth-localized birefringence imaging and conventional phase retardation imaging are formulated. This formulation indicates that the birefringence imaging correctly measures a depth-localized single-trip phase retardation of a tissue, while the conventional phase retardation can provide correct single-trip phase retardation only for some specific types of samples. PMID:26713208

  17. Rationalizing vaccine injury compensation.

    PubMed

    Mello, Michelle M

    2008-01-01

    Legislation recently adopted by the United States Congress provides producers of pandemic vaccines with near-total immunity from civil lawsuits without making individuals injured by those vaccines eligible for compensation through the Vaccine Injury Compensation Program. The unusual decision not to provide an alternative mechanism for compensation is indicative of a broader problem of inconsistency in the American approach to vaccine-injury compensation policy. Compensation policies have tended to reflect political pressures and economic considerations more than any cognizable set of principles. This article identifies a set of ethical principles bearing on the circumstances in which vaccine injuries should be compensated, both inside and outside public health emergencies. A series of possible bases for compensation rules, some grounded in utilitarianism and some nonconsequentialist, are discussed and evaluated. Principles of fairness and reasonableness are found to constitute the strongest bases. An ethically defensible compensation policy grounded in these principles would make a compensation fund available to all individuals with severe injuries and to individuals with less-severe injuries whenever the vaccination was required by law or professional duty.

  18. Highly birefringent polymer side-hole fiber for hydrostatic pressure sensing.

    PubMed

    Martynkien, Tadeusz; Wojcik, Grzegorz; Mergo, Pawel; Urbanczyk, Waclaw

    2015-07-01

    We report on the fabrication of a birefringent side-hole polymer optical fiber with an elliptical core made of polymethyl metacrylate-polystyrene (PMMA/PS) copolymer and pure PMMA cladding. The fiber core is located in a narrow PMMA bridge separating the holes. Two fibers with different bridge thickness were fabricated and characterized. We demonstrate, experimentally and numerically, that, by narrowing the bridge between the holes, one can increase simultaneously the fiber birefringence and the polarimetric sensitivity to hydrostatic pressure. In the fiber with the bridge as narrow as 5 μm, we achieved a record-high polarimetric sensitivity to hydrostatic pressure ranging between 175 and 140 rad/MPa/m in the spectral range of 600-830 nm. The phase modal birefringence in this fiber is also high and exceeds 3×10(-5) at 600 nm, which results in small polarization cross talk.

  19. A bifunctional amorphous polymer exhibiting equal linear and circular photoinduced birefringences.

    PubMed

    Royes, Jorge; Provenzano, Clementina; Pagliusi, Pasquale; Tejedor, Rosa M; Piñol, Milagros; Oriol, Luis

    2014-11-01

    The large and reversible photoinduced linear and circular birefringences in azo-compounds are at the basis of the interest in these materials, which are potentially useful for several applications. Since the onset of the linear and circular anisotropies relies on orientational processes, which typically occur on the molecular and supramolecular length scale, respectively, a circular birefringence at least one order of magnitude lower than the linear one is usually observed. Here, the synthesis and characterization of an amorphous polymer with a dimeric repeating unit containing a cyanoazobenzene and a cyanobiphenyl moiety are reported, in which identical optical linear and circular birefringences are induced for proper light dose and ellipticity. A pump-probe technique and an analytical method based on the Stokes-Mueller formalism are used to investigate the photoinduced effects and to evaluate the anisotropies. The peculiar photoresponse of the polymer makes it a good candidate for applications in smart functional devices.

  20. Temperature sensibility of the birefringence properties in side-hole photonic crystal fiber filled with Indium

    SciTech Connect

    Reyes-Vera, Erick Gómez-Cardona, Nelson D.; Chesini, Giancarlo; Cordeiro, Cristiano M. B.; Torres, Pedro

    2014-11-17

    We report on the temperature sensitivity of the birefringence properties of a special kind of photonic crystal fiber containing two side holes filled with Indium metal. The modulation of the fiber birefringence is accomplished through the stress field induced by the expansion of the metal. Although the fiber was made at low gas pressures during the indium infiltration process, the birefringence showed anomalous property at a relatively low temperature value, which is completely different from those reported in conventional-like fibers with two holes filled with metal. By modeling the anisotropic changes induced by the metal expansion to the refractive index within the fiber, we are able to reproduce the experimental results. Our results have practical relevance for the design of devices based on this technology.

  1. Form birefringence induced in multicomponent glass by femtosecond laser direct writing.

    PubMed

    Cao, Jing; Mazerolles, Léo; Lancry, Matthieu; Solas, Denis; Brisset, François; Poumellec, Bertrand

    2016-06-15

    We demonstrate a new kind of form birefringence in lithium niobium silicate glass induced by femtosecond laser direct writing. By combining electron backscatter diffraction and transmission electron microscopy, we reveal a self-assembled nanostructure consisting of periodic phase change: nonlinear optical nanocrystals embedded in a network of "walls" in a vitreous phase. These "walls" are aligned perpendicular to the laser polarization direction. This self-organized nanostructure may successfully explain the origin of the laser-induced birefringence in this multicomponent glass quite differently from pure silica. These findings highlight a spectacular modification of glass, and enable construction of a high contrast three-dimensional refractive index and birefringent structures at the micrometer scale in multicomponent glasses.

  2. Birefringence effects in multi-core fiber: coupled local-mode theory.

    PubMed

    Macho, Andrés; García-Meca, Carlos; Fraile-Peláez, F Javier; Morant, Maria; Llorente, Roberto

    2016-09-19

    In this paper, we evaluate experimentally and model theoretically the intra- and inter-core crosstalk between the polarized core modes in single-mode multi-core fiber media including temporal and longitudinal birefringent effects. Specifically, extensive experimental results on a four-core fiber indicate that the temporal fluctuation of fiber birefringence modifies the intra- and inter-core crosstalk behavior in both linear and nonlinear optical power regimes. To gain theoretical insight into the experimental results, we introduce an accurate multi-core fiber model based on local modes and perturbation theory, which is derived from the Maxwell equations including both longitudinal and temporal birefringent effects. Numerical calculations based on the developed theory are found to be in good agreement with the experimental data.

  3. Birefringence imaging in biological tissue using polarization sensitive optical coherent tomography

    DOEpatents

    De Boer, Johannes F.; Milner, Thomas E.; Nelson, J. Stuart

    2001-01-01

    Employing a low coherence Michelson interferometer, two dimensional images of optical birefringence in turbid samples as a function of depth are measured. Polarization sensitive detection of the signal formed by interference of backscattered light from the sample and a mirror or reference plane in the reference arm which defines a reference optical path length, give the optical phase delay between light propagating along the fast and slow axes of the birefringence sample. Images showing the change in birefringence in response to irradiation of the sample are produced as an example of the detection apparatus and methodology. The technique allow rapid, noncontact investigation of tissue or sample diagnostic imaging for various medical or materials procedures.

  4. Collinear mixing of orthogonally polarized waves via polarization hole burning in birefringent Er-doped fiber

    NASA Astrophysics Data System (ADS)

    Stepanov, S.; Hernández, E.; Plata, M.

    2005-01-01

    We report on experimental observation of transient mixing of two mutually coherent waves of orthogonal polarizations collinearly propagating through birefringent Er-doped fiber. The dynamic grating responsible for this two-wave mixing (TWM) process is formed via effect of polarization hole burning (PHB) and has spatial period equal to the beat length of the fiber birefringence. Experiments were performed at the laser wavelength 1549 nm in 2-m long Er-doped fiber with 2-cm birefringence beat length without optical pumping. We observed that the transient collinear TWM has amplitude and characteristic relaxation time close to those of transient PHB effect measured for linearly polarized light and similar to corresponding characteristics of transient TWM observed for counter-propagating orthogonally polarized waves in the same fiber.

  5. Novel technique for distributed fibre sensing based on coherent Rayleigh scattering measurements of birefringence

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Soto, Marcelo A.; Thévenaz, Luc

    2016-05-01

    A novel distributed fibre sensing technique is described and experimentally validated, based on birefringence measurements using coherent Rayleigh scattering. It natively provides distributed measurements of temperature and strain with more than an order of magnitude higher sensitivity than Brillouin sensing, and requiring access to a single fibre-end. Unlike the traditional Rayleigh-based coherent optical time-domain reflectometry, this new method provides absolute measurements of the measurand and may lead to a robust discrimination between temperature and strain in combination with another technique. Since birefringence is purposely induced in the fibre by design, large degrees of freedom are offered to optimize and scale the sensitivity to a given quantity. The technique has been validated in 2 radically different types of birefringent fibres - elliptical-core and Panda polarization-maintaining fibres - with a good repeatability.

  6. High average power pulsed phase conjugate laser with birefringence correction. Revision 1

    SciTech Connect

    Bowers, M.W.; Hankla, A.K.; Jacobson, G.F.

    1994-05-01

    Nd:YAG rod lasers have been plagued with the inability to go to high average powers because of thermally induced birefringence and focusing. Several methods have been employed to correct for the birefringence and the thermal aberrations of such systems, but place stringent constraints on the laser heads and/or the system alignment. They have developed a scalable Nd: YAG master oscillator/power amplifier (MOPA) laser system which employs a novel phase conjugation scheme to correct both for the material and thermal distortions as well as the thermal birefringence in double pass amplifier systems. This method reduces the double pass depolarization from 42% to less than 2% and is easy to align.

  7. En face parametric imaging of tissue birefringence using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chin, Lixin; Yang, Xiaojie; McLaughlin, Robert A.; Noble, Peter B.; Sampson, David D.

    2013-06-01

    A technique for generating en face parametric images of tissue birefringence from scans acquired using a fiber-based polarization-sensitive optical coherence tomography (PS-OCT) system utilizing only a single-incident polarization state is presented. The value of birefringence is calculated for each A-scan in the PS-OCT volume using a quadrature demodulation and phase unwrapping algorithm. The algorithm additionally uses weighted spatial averaging and weighted least squares regression to account for the variation in phase accuracies due to varying OCT signal-to-noise-ratio. The utility of this technique is demonstrated using a model of thermally induced damage in porcine tendon and validated against histology. The resulting en face images of tissue birefringence are more useful than conventional PS-OCT B-scans in assessing the severity of tissue damage and in localizing the spatial extent of damage.

  8. Fourier transform spectroscopy in the vibrational fingerprint region with a birefringent interferometer.

    PubMed

    Réhault, J; Borrego-Varillas, R; Oriana, A; Manzoni, C; Hauri, C P; Helbing, J; Cerullo, G

    2017-02-20

    We introduce a birefringent interferometer for Fourier transform (FT) spectroscopy in the mid-infrared, covering the vibrational fingerprint region (5-10 µm, 1000-2000 cm-1), which is crucial for molecular identification. Our interferometer employs the crystal calomel (Hg2Cl2), which combines high birefringence (ne-no≈0.55) with a broad transparency range (0.38-20 µm). We adopt a design based on birefringent wedges, which is simple and compact and guarantees excellent delay accuracy and long-term stability. We demonstrate FTIR spectroscopy, with a frequency resolution of 3 cm-1, as well as two-dimensional IR (2DIR) spectroscopy. Our setup can be extended to other spectroscopic modalities such as vibrational circular dichroism and step-scan FT spectroscopy.

  9. Design and analysis of surface plasmon resonance sensor based on high-birefringent microstructured optical fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Nancy Meng Ying; Juan Juan Hu, Dora; Shum, Perry Ping; Wu, Zhifang; Li, Kaiwei; Huang, Tianye; Wei, Lei

    2016-06-01

    Optical fiber based surface plasmon resonance (SPR) sensors are favored by their high sensitivity, compactness, remote and in situ sensing capabilities. Microstructured optical fibers (MOFs) possess microfluidic channels extended along the entire length right next to the fiber core, thereby enabling the infiltrated biochemical analyte to access the evanescent field of guided light. Since SPR can only be excited by the polarization vertical to metal surface, external perturbation could induce the polarization crosstalk in fiber core, thus leading to the instability of sensor output. Therefore for the first time we analyze how the large birefringence suppresses the impact of polarization crosstalk. We propose a high-birefringent MOF based SPR sensor with birefringence larger than 4 × 10-4 as well as easy infiltration of microfluidic analyte, while maintaining sensitivity as high as 3100 nm/RIU.

  10. Magnetic field fiber sensor based on the magneto-birefringence effect of magnetic fluid

    NASA Astrophysics Data System (ADS)

    Lei, Xueqin; Chen, Jiajia; Shi, Fuquan; Chen, Daru; Ren, Zhijun; Peng, Baojin

    2016-09-01

    In this study, the magneto-birefringence effect of magnetic fluid (MF) is adopted to form an innovative fiber optic magnetic field sensor. The sensitive section is fabricated via a D-shaped microstructure inscribed in a high-birefringence fiber Sagnac loop with a femtosecond laser. The D-shaped microstructure facilitates good combination of the optical-fiber Sagnac interferometer with the magneto-birefringence effect of MF without suffering from absorption loss and manual alignment. Experimental results show the good performance of the magnetic field fiver sensor, particularly its high stable extinction ratio. Preliminary results are provided, and the magnetic field sensitivity of 0.0823 nm/mT can be further improved by increasing the depth and length of the D-shaped microstructure.

  11. Note: mounting ultra-high vacuum windows with low stress-induced birefringence.

    PubMed

    Solmeyer, Neal; Zhu, Kunyan; Weiss, David S

    2011-06-01

    We have developed a way to mount ultra-high vacuum windows onto standard ConFlat(®) vacuum systems with very low stress-induced birefringence. Each window is sealed to a stainless steel flange with a compressed indium wire, and that flange is connected to a vacuum chamber with another indium seal. We find that deformation of a standard ConFlat flange during indium sealing dominates the stress on the window, so an extra-rigid flange is needed for minimal birefringence. With this mounting scheme, the typical residual birefringence is Δn = 2.3 × 10(-7) and is unchanged by a 120 °C bake.

  12. Probing vacuum birefringence using x-ray free electron and optical high-intensity lasers

    NASA Astrophysics Data System (ADS)

    Karbstein, Felix; Sundqvist, Chantal

    2016-07-01

    Vacuum birefringence is one of the most striking predictions of strong field quantum electrodynamics: Probe photons traversing a strong field region can indirectly sense the applied "pump" electromagnetic field via quantum fluctuations of virtual charged particles which couple to both pump and probe fields. This coupling is sensitive to the field alignment and can effectively result in two different indices of refraction for the probe photon polarization modes giving rise to a birefringence phenomenon. In this article, we perform a dedicated theoretical analysis of the proposed discovery experiment of vacuum birefringence at an x-ray free electron laser/optical high-intensity laser facility. Describing both pump and probe laser pulses realistically in terms of their macroscopic electromagnetic fields, we go beyond previous analyses by accounting for various effects not considered before in this context. Our study facilitates stringent quantitative predictions and optimizations of the signal in an actual experiment.

  13. Flow-induced birefringence: the hidden PSF killer in high performance injection-molded plastic optics

    NASA Astrophysics Data System (ADS)

    Chidley, Matthew D.; Tkaczyk, Tomasz; Kester, Robert; Descour, Michael R.

    2006-02-01

    A 7-mm OD, NA = 1 water immersion injection-molded plastic endoscope objective has been fabricated for a laser scanning fiber confocal reflectance microscope (FCRM) system specifically designed for in vivo detection of cervical and oral pre-cancers. Injection-molded optics was selected for the ability to incorporate aspheric surfaces into the optical design and its high volume capabilities. Our goal is high performance disposable endoscope probes. This objective has been built and tested as a stand-alone optical system, a Strehl ratio greater than 0.6 has been obtained. One of the limiting factors of optical performance is believed to be flow-induced birefringence. We have investigated different configurations for birefringence visualization and believe the circular polariscope is most useful for inspection of injection-molded plastic optics. In an effort to decrease birefringence effects, two experiments were conducted. They included: (1) annealing of the optics after fabrication and (2) modifying the injection molding prameters (packing pressures, injection rates, and hold time). While the second technique showed improvement, the annealing process could not improve quality without physically warping the lenses. Therefore, to effectively reduce flow-induced birefringence, molding conditions have to be carefully selected. These parameters are strongly connected to the physical part geometry. Both optical design and fabrication technology have to be considered together to deliver low birefringence while maintaining the required manufacturing tolerances. In this paper we present some of our current results that illustrate how flow-induced birefringence can degrade high performance injection-molded plastic optical systems.

  14. Reflectance Spectrum and Birefringence of the Retinal Nerve Fiber Layer With Hypertensive Damage of Axonal Cytoskeleton

    PubMed Central

    Huang, Xiang-Run; Knighton, Robert W.; Spector, Ye Z.; Qiao, Jianzhong; Kong, Wei; Zhao, Qi

    2017-01-01

    Purpose Glaucoma damages the retinal nerve fiber layer (RNFL). This study used precise multimodal image registration to investigate the changes of the RNFL reflectance spectrum and birefringence in nerve fiber bundles with different degrees of axonal damage. Methods The reflectance spectrum of individual nerve fiber bundles in normal rats and rats with experimental glaucoma was measured from 400 to 830 nm and their birefringence was measured at 500 nm. Optical measurements of the same bundles were made at different distances from the optic nerve head (ONH). After the optical measurements, the axonal cytoskeleton of the RNFL was evaluated by confocal microscopy to assess the severity of cytoskeletal change. Results For normal bundles, the shape of the RNFL reflectance spectrum and the value of RNFL birefringence did not change along bundles. In treated retinas, damage to the cytoskeleton varied within and across retinas. The damage in retinal sectors was subjectively graded from normal-looking to severe. Change of spectral shape occurred near the ONH in all sectors studied. This change became more prominent and occurred farther from the ONH with increased damage severity. In contrast, RNFL birefringence did not show change in normal-looking sectors, but decreased in sectors with mild and moderate damage. The birefringence of severely damaged sectors was either within or below the normal range. Conclusions Varying degrees of cytoskeletal damage affect the RNFL reflectance spectrum and birefringence differently, supporting differences in the ultrastructural basis for the two optical properties. Both properties, however, may provide a means to detect disease and to estimate ultrastructural damage of the RNFL in glaucoma. PMID:28395028

  15. Gmti Motion Compensation

    DOEpatents

    Doerry, Armin W.

    2004-07-20

    Movement of a GMTI radar during a coherent processing interval over which a set of radar pulses are processed may cause defocusing of a range-Doppler map in the video signal. This problem may be compensated by varying waveform or sampling parameters of each pulse to compensate for distortions caused by variations in viewing angles from the radar to the target.

  16. Birefringence of Polymer Solutions in Time-Dependent Flows.

    NASA Astrophysics Data System (ADS)

    Geffroy-Aguilar, Enrique

    1990-01-01

    This is a study of changes of conformation of macromolecules in polymeric solutions which are subjected to time-dependent extensional flows generated by a two -roll mill flow device. The flows produced by the two-roll mill are linear, and two-dimensional. It has a stagnation point at the center of the flow field where the magnitudes of the strain-rates are greater than the vorticity. This study of conformational changes is based on data around the vicinity of the stagnation point, I for steady state flows, and several transient flow histories such as start -up, cessation, and double-step flows. We also present an analytical solution for the creeping flow generated by an infinitely long two-roll mill embedded in an unbounded fluid. This solution is used as a benchmark to compare the behavior of the polymer solutions when subjected to flows with different values for the ratio of rate-of-strain to vorticity. The conformational changes are determined experimentally using the Two-color Flow-Birefringence which provides an instantaneous and point-wise measure of the anisotropy of the fluid, together with the relative orientation of the anisotropy with respect to the principal axes of the flow field. Based on relaxation of the fluid anisotropy the characteristic time-scales of the polymer have been evaluated as a function of the flow field properties and the degree of conformational change of the macromolecules. Data for two polymeric solutions is presented. The first polymer system is the so-called test-fluid M1. This polymeric solution is shown to degrade significantly, even for small values of the velocity gradient, as measured by the changes in the macroscopic relaxation time-scales. The second solution is a concentrated polystyrene solution that presents overshoots and undershoots of the polymer conformation dependent of the ratio of vorticity to rate-of-strain. When subjected to large deformations, this polystyrene solution shows not only the possibility of a

  17. Femtosecond laser fabrication of birefringent directional couplers as polarization beam splitters in fused silica.

    PubMed

    Fernandes, Luís A; Grenier, Jason R; Herman, Peter R; Aitchison, J Stewart; Marques, Paulo V S

    2011-06-20

    Integrated polarization beam splitters based on birefringent directional couplers are demonstrated. The devices are fabricated in bulk fused silica glass by femtosecond laser writing (300 fs, 150 nJ at 500 kHz, 522 nm). The birefringence was measured from the spectral splitting of the Bragg grating resonances associated with the vertically and horizontally polarized modes. Polarization splitting directional couplers were designed and demonstrated with 0.5 dB/cm propagation losses and -19 dB and -24 dB extinction ratios for the polarization splitting.

  18. Characterization on the effect of linear stress birefringence in a total reflection prism (TRP) ring resonator

    NASA Astrophysics Data System (ADS)

    Li, Dong; Bi, Chao; Jiang, Yajun; Zhao, Jianlin

    2016-10-01

    Based on the theory of Jones matrix and the condition of eigenmode self-consistency, we analyze the effect of linear stress birefringence of prismon the beam polarization (described with the ellipticity and loss of the eigenmodes) and null drift (described with the output frequency difference of the eigenmodes) in a TRP resonator. It is found that the linear stress birefringence of prisms can cause larger polarization ellipticity for both CW (clockwise) and CCW (counterclockwise) beams. The results may be useful for designing and optimizing the structure of super high precision TRP ring laser gyroscopes.

  19. Dispersion characterization of two orthogonal modes in a birefringence tellurite microstructured optical fiber.

    PubMed

    Deng, Dinghuan; Sega, Daisuke; Cheng, Tonglei; Gao, Weiqing; Xue, Xiaojie; Suzuki, Takenobu; Ohishi, Yasutake

    2014-10-06

    An elliptical core tellurite microstructured optical fiber with high birefringence was demonstrated and the chromatic dispersion of the two orthogonal modes in this fiber was experimentally characterized by a white light spectral interferometric technique over a wide spectral range. A series of spectral interferograms as a function of the optical path difference were recorded in the Mach-Zehnder interferometer. The birefringence dependence of the wavelength in the fiber was determined by interferograms. The measured and calculated dispersion matched well within the whole spectrum range under test.

  20. Birefringent photonic crystal fiber coils and their application to transverse displacement sensing.

    PubMed

    Fan, Chen-Feng; Chiang, Chih-Lun; Yu, Chin-Ping

    2011-10-10

    We have experimentally investigated the birefringent properties of photonic crystal fiber (PCF) coils in cooperation with a Sagnac loop interferometer. By reducing the bending radius of the PCF coils, very clear interference patterns can be observed for the bending-induced stress effect. Increasing the fiber turns can result in more obvious interference patterns with smaller fringe spacing but has no contribution to the increment of the birefringence value. The fabricated PCF coil is employed in the transverse displacement sensing. Very high sensing sensitivity of 90.4 nm/mm can be achieved due to the large displacement-induced bending radius variations.

  1. The effect of vacuum birefringence on the polarization of X-ray binaries and pulsars

    NASA Technical Reports Server (NTRS)

    Novick, R.; Weisskopf, M. C.; Angel, J. R. P.; Sutherland, P. G.

    1977-01-01

    In a strong magnetic field the vacuum becomes birefringent. This effect is especially important for pulsars at X-ray wavelengths. Any polarized X-ray emission from the surface of a magnetic neutron star becomes depolarized as it propagates through the magnetic field. The soft X-ray emission from AM Her, believed to be a magnetic white dwarf, may show about one radian of phase retardation. In this case, circular polarization of the X-ray flux would be a characteristic signature of vacuum birefringence.

  2. Investigation of Vortex Development during Polymer Melt Flows by Flow Birefringence

    NASA Astrophysics Data System (ADS)

    Musil, Jan; Zatloukal, Martin; Gough, Tim; Martyn, Mike

    2011-07-01

    The vortex development of low-density polyethylene Lupolen 1840H polymer melt under various processing conditions has been investigated by flow induced stress birefringence technique. It has been revealed that effect of mass flow rate and temperature on the vortex size has non-monotonic character, which is in good agreement with laser-Doppler velocimetry based measurements reported for the same polymer in the open literature. This suggests that the flow induced stress birefringence technique can be considered as the quick and reasonably precise tool for vortices shape/size visualization and quantification at the slit die entry region.

  3. STUDIES ON THE ANOMALOUS VISCOSITY AND FLOW-BIREFRINGENCE OF PROTEIN SOLUTIONS

    PubMed Central

    Lawrence, A. S. C.; Needham, Joseph; Shen, Shih-Chang

    1944-01-01

    1. A coaxial viscosimeter which permits the simultaneous determination of relative and anomalous viscosity and of flow-birefringence is described. Flow-anomaly and flow-birefringence are regarded as characteristic of elongated micelles and molecules. 2. Such methods have been applied to dilute solutions of proteins. The conditions under which the coaxial (Couette) viscosimeter measures the viscosity of the bulk phase and the surface film phase respectively have been investigated and are described. 3. The general behaviour of protein solutions subjected to shear is summarised. PMID:19873384

  4. Dark three-sister rogue waves in normally dispersive optical fibers with random birefringence.

    PubMed

    Chen, Shihua; Soto-Crespo, Jose M; Grelu, Philippe

    2014-11-03

    We investigate dark rogue wave dynamics in normally dispersive birefringent optical fibers, based on the exact rational solutions of the coupled nonlinear Schrödinger equations. Analytical solutions are derived up to the second order via a nonrecursive Darboux transformation method. Vector dark "three-sister" rogue waves as well as their existence conditions are demonstrated. The robustness against small perturbations is numerically confirmed in spite of the onset of modulational instability, offering the possibility to observe such extreme events in normal optical fibers with random birefringence, or in other Manakov-type vector nonlinear media.

  5. Method and apparatus for measuring micro structures, anisotropy and birefringence in polymers using laser scattered light

    DOEpatents

    Grek, Boris; Bartolick, Joseph; Kennedy, Alan D.

    2000-01-01

    A method and apparatus for measuring microstructures, anistropy and birefringence in polymers using laser scattered light includes a laser which provides a beam that can be conditioned and is directed at a fiber or film which causes the beam to scatter. Backscatter light is received and processed with detectors and beam splitters to obtain data. The data is directed to a computer where it is processed to obtain information about the fiber or film, such as the birefringence and diameter. This information provides a basis for modifications to the production process to enhance the process.

  6. Highly birefringent suspended-core photonic microcells for refractive-index sensing

    SciTech Connect

    Wang, Chao; Jin, Wa; Ma, Jun; Jin, Wei Yang, Fan; Ho, Hoi Lut; Liao, Changrui; Wang, Yiping

    2014-08-11

    An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10{sup −2}. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

  7. Intermittent redesign of continuous controllers

    NASA Astrophysics Data System (ADS)

    Gawthrop, Peter J.; Wang, Liuping

    2010-08-01

    The reverse-engineering idea developed by Maciejowski in the context of model-based predictive control is applied to the redesign of continuous-time compensators as intermittent controllers. Not only does this give a way of designing constrained input and state versions of continuous-time compensators but also provides a method for turning continuous-time compensators into event-driven versions. The procedure is illustrated by three examples: an event-driven PID controller relevant to the human balance control problem, a constrained version of the classical mechanical vibration absorber of den Hartog and an event driven and constrained vibration absorber.

  8. Reactive Power Compensator.

    DOEpatents

    El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

    1992-07-28

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

  9. Reactive power compensator

    DOEpatents

    El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony

    1992-01-01

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

  10. Precision Interferometric Measurements of Mirror Birefringence in High-Finesse Optical Resonators

    PubMed Central

    Fleisher, Adam J.; Long, David A.; Liu, Qingnan; Hodges, Joseph T.

    2016-01-01

    High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings. Strictly speaking, however, the optical coatings are often non-uniformly stressed during the deposition process and therefore do possess some small amount of birefringence. When physically mounted the cavity mirrors can be additionally stressed in such a way that large optical birefringence is induced. Here we report a direct measurement of optical birefringence in a two-mirror Fabry-Pérot cavity with R = 99.99 % by observing TEM00 mode beating during cavity decays. Experiments were performed at a wavelength of 4.53 μm, with precision limited by both quantum and technical noise sources. We report a splitting of δν = 618(1) Hz, significantly less than the intrinsic cavity linewidth of δcav ≈ 3 kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore Δn/n = 6.38(1) × 10−6. PMID:27088133

  11. Estimation of the Intrinsic Birefringence of the A, B and V Crystalline Forms of Amylose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical birefringence (Delta n) for A, B, Va, Vh amylose crystals were calculated by vector summation of bond polarizabilities. Orientation of the O-H bond vectors in these amylose crystals is not well understood so results are given for likely O-H conformers. For B amylose, Delta n ranges from 0....

  12. Dynamics of laser-induced radial birefringence in silver-doped glasses.

    PubMed

    Ahangary, Ali Akbar; Bouchard, Frédéric; Santamato, Enrico; Karimi, Ebrahim; Khalesifard, Hamid Reza

    2015-09-01

    Silver ion-exchanged glass exhibits nonlinear optical properties upon interacting with intense light beams. The thermal effect due to the nanoparticles' light-absorption induces radial stress, and consequently, a radial birefringence on the glass surface. The induced birefringence possesses a topological charge of 1 in the transverse plane of the glass, i.e., cylindrical symmetry. Therefore, when the glass is illuminated with a circularly polarized light beam, a portion of the incoming beam flips its polarization handedness, since the plate is birefringent, and gains an orbital angular momentum of ±2 in units of the Planck constant. This is referred to as optical spin-to-orbital angular momentum conversion, and can be understood by means of the Pancharatnam-Berry phase. Here, we design a pump-probe setup to study and observe the dynamics of optical angular momentum coupling in real time. We show that this effect can be permanent or reversible, depending on the power and interaction time of the pump beam. In particular, an intrinsic power-dependent birefringence hysteresis is observed on the sample after interaction with and the relaxation of the irradiated point.

  13. Artificial high birefringence in all-dielectric gradient grating for broadband terahertz waves

    PubMed Central

    Chen, Meng; Fan, Fei; Xu, Shi-Tong; Chang, Sheng-Jiang

    2016-01-01

    Subwavelength dielectric gratings are widely applied in the phase and polarization manipulation of light. However, the dispersion of the normal dielectric gratings is not flat while their birefringences are not enough in the THz regime. In this paper, we have fabricated two all-dielectric gratings with gradient grids in the THz regime, of which artificial birefringence is much larger than that of the equal-grid dielectric grating demonstrated by both experiments and simulations. The transmission and dispersion characteristics are also improved since the gradient grids break the periodicity of grating lattices as a chirp feature. From 0.6–1.4 THz, a broadband birefringence reaches 0.35 with a low dispersion and good linearity of phase shift, and the maximum phase shift is 1.4π. Furthermore, these gradient gratings are applied as half-wave plates and realize a linear polarization conversion with a conversion rate over 99%, also much higher than the equal-grid gratings. These gradient gratings show great advantages compared to the periodic gratings and provide a new way in the designing of artificial birefringence material. PMID:27934962

  14. First results from the new PVLAS apparatus: A new limit on vacuum magnetic birefringence

    NASA Astrophysics Data System (ADS)

    Della Valle, F.; Milotti, E.; Ejlli, A.; Messineo, G.; Piemontese, L.; Zavattini, G.; Gastaldi, U.; Pengo, R.; Ruoso, G.

    2014-11-01

    Several groups are carrying out experiments to observe and measure vacuum magnetic birefringence, predicted by quantum electrodynamics (QED). We have started running the new PVLAS apparatus installed in Ferrara, Italy, and have measured a noise floor value for the unitary field magnetic birefringence of vacuum Δ nu(vac )=(4 ±20 )×1 0-23 T-2 (the error represents a 1 σ deviation). This measurement is compatible with zero and hence represents a new limit on vacuum magnetic birefringence deriving from nonlinear electrodynamics. This result reduces to a factor of 50 the gap to be overcome to measure for the first time the value of Δ nu(vac ,QED ) predicted by QED: Δ nu(vac ,QED )=4 ×10-24 T-2 . These birefringence measurements also yield improved model-independent bounds on the coupling constant of axion-like particles to two photons, for masses greater than 1 meV, along with a factor-2 improvement of the fractional charge limit on millicharged particles (fermions and scalars), including neutrinos.

  15. The Interplay between Viscoelastic and Thermodynamic Properties Determines the Birefringence of F-Actin Gels

    PubMed Central

    Helfer, Emmanuèle; Panine, Pierre; Carlier, Marie-France; Davidson, Patrick

    2005-01-01

    F-actin gels of increasing concentrations (25–300 μM) display in vitro a progressive onset of birefringence due to orientational ordering of actin filaments. At F-actin concentrations <100 μM, this birefringence can be erased and restored at will by sonication and gentle flow, respectively. Hence, the orientational ordering does not result from a thermodynamic transition to a nematic phase but instead is due to mechanical stresses stored in the gels. In contrast, at F-actin concentrations ≥100 μM, gels display spontaneous birefringence recovery, at rest, which is the sign of true nematic ordering, in good agreement with statistical physics models of the isotropic/nematic transition. Well-aligned samples of F-actin gels could be produced and their small-angle x-ray scattering patterns are quite anisotropic. These patterns show no sign of filament positional short-range order and could be modeled by averaging the form factor with the Maier-Saupe nematic distribution function. The derived nematic order parameter S of the gels ranged from S = 0.7 at 300 μM to S = 0.4 at 25 μM. Both birefringence and small-angle x-ray scattering data indicate that, even in absence of cross-linking proteins, spontaneous cooperative alignment of actin filaments may arise in motile regions of living cells where F-actin concentrations can reach values of a few 100 μM. PMID:15863487

  16. High-birefringence photonic crystal fiber structures based on the binary morse-thue fractal sequence

    NASA Astrophysics Data System (ADS)

    Al-Muraeb, Ahmed; Abdel-Aty-Zohdy, Hoda

    2016-09-01

    A novel index-guiding Silica glass-core hexagonal High-Birefringence Photonic Crystal Fiber (HB-PCF) is proposed, with five rings of standard cladding air circular holes arranged in four formations inspired by the Binary Morse-Thue fractal Sequence (BMTS). The form birefringence, confinement loss, chromatic dispersion, effective mode area, and effective normalized frequency are evaluated for the four PCFs operating within (1.8 - 2 μm) eye-safe wavelength range. Modeling and analysis of the four PCF formations are performed deploying full-vector analysis in Finite Element Method (FEM) using COMSOL Multiphysics. Respecting fabrication and in light of commercial availability in designing the proposed PCF structures, a high birefringence of up to (6.549 × 10-3 at 2 μm) is achieved with dispersionfree single-mode operation. Confinement loss as low as (3.2 × 10-5 - 6.5 × 10-4 dB/m for 1.8 - 2 μm range) is achieved as well. Comparison against previously reported PCF structures reveals the desirably higher birefringence of our BMTS HB-PCF. The proposed PCFs are of vital use in various optical systems (e.g.: multi-wavelength fiber ring laser systems, and tunable lasers), catering for applications such as: optical sensing, LIDAR systems, material processing, optical signal processing, and optical communication.

  17. Advancement in polarimetric glucose sensing: simulation and measurement of birefringence properties of cornea

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Coté, Gerard L.

    2011-03-01

    Clinical guidelines dictate that frequent blood glucose monitoring in diabetic patients is critical towards proper management of the disease. Although, several different types of glucose monitors are now commercially available, most of these devices are invasive, thereby adversely affecting patient compliance. To this end, optical polarimetric glucose sensing through the eye has been proposed as a potential noninvasive means to aid in the control of diabetes. Arguably, the most critical and limiting factor towards successful application of such a technique is the time varying corneal birefringence due to eye motion artifact. We present a spatially variant uniaxial eye model to serve as a tool towards better understanding of the cornea's birefringence properties. The simulations show that index-unmatched coupling of light is spatially limited to a smaller range when compared to the index-matched situation. Polarimetric measurements on rabbits' eyes indicate relative agreement between the modeled and experimental values of corneal birefringence. In addition, the observed rotation in the plane of polarized light for multiple wavelengths demonstrates the potential for using a dual-wavelength polarimetric approach to overcome the noise due to timevarying corneal birefringence. These results will ultimately aid us in the development of an appropriate eye coupling mechanism for in vivo polarimetric glucose measurements.

  18. Federal Employees' Compensation Act.

    PubMed

    Ladou, Joseph

    2009-01-01

    The Federal Employees' Compensation Act (FECA) program provides wage loss compensation and payments for medical treatment to federal civilian employees. Administered by the Department of Labor (DOL), FECA covers over 2.7 million federal employees in more than 70 different agencies. FECA costs rose from $1.4 billion in 1990 to $2.6 in 2006, while the federal workforce remained essentially unchanged. While federal civilian employees represent only 2.1% of all workers eligible for workers' compensation benefits, federal programs account for 6% of the benefits paid. Disability benefits under FECA are far greater than those in the state workers' compensation programs. The benefit payments often exceed the former salary of the injured employee. The last congressional hearings on the FECA program were held over thirty years ago. It is unlikely that Congressional review will occur any time soon, as the entrenched bureaucracy that benefits from the FECA program defines and protects its future.

  19. Ultra-flattened negative dispersion for residual dispersion compensation using soft glass equiangular spiral photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Imran Hasan, Md.; Mahmud, R. R.; Morshed, Monir; Rabiul Hasan, Md.

    2016-09-01

    We present a numerical investigation of an equiangular spiral photonic crystal fibre (ES-PCF) in soft glass for negative flattened dispersion and ultra-high birefringence. An accurate numerical approach based on finite element method is used for the simulation of the proposed structure. It is demonstrated that it is possible to obtain average negative dispersion of -526.99 ps/nm/km over 1.05-1.70 μm wavelength range with dispersion variation of 3.7 ps/nm/km. The proposed ES-PCF also offers high birefringence of 0.0226 at the excitation wavelength of 1.55 μm. The results here show that the idea of using the proposed fibre can be potential means of effectively directing for residual dispersion compensation, fibre sensor design, long distance data transmission system and so forth.

  20. ACTS Rain Fade Compensation

    NASA Technical Reports Server (NTRS)

    Coney, Thom A.

    1996-01-01

    Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.

  1. Compensation law in composites

    NASA Astrophysics Data System (ADS)

    Dufresne, A.; Lavergne, C.; Lacabanne, C.

    1993-12-01

    The experimental resolution of the α retardation / relaxation mode of model composites epoxy resin- glass beads has been performed using Thermo Stimulated Creep (TSCr) and Thermo Stimulated Currents (TSC) spectroscopies. The distributed retardation / relaxation times τ are found to obey a compensation law, which is characteristic of cooperative movements liberated at the vicinity of T g. The T c and τ c compensation parameters reveal that the microstructure is strongly linked to the nature of the interface.

  2. Evaluating Military Compensation

    DTIC Science & Technology

    2007-06-01

    has also compared the out-of-pocket health costs of families who use its preferred-provider organization ( PPO ) or fee-for-service options with those...comparison controlled for demographic differ- ences between military and civilian families. EVALUATING MILITARY COMPENSATION 17using PPO plans. In 2005...governments would have to absorb the difference. A PP E N D IX A Total Compensation for the Median Enlisted MemberUsing a different approach from

  3. The measurement system of birefringence and Verdet constant of optical fiber

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun

    2013-12-01

    The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.

  4. Microtubular origin of mitotic spindle form birefringence. Demonstration of the applicability of Wiener's equation

    PubMed Central

    1975-01-01

    Meiosis I metaphase spindles were isolated from oocytes of the sea-star Pisaster ochraceus by a method that produced no detectable net loss in spindle birefringence. Some of the spindles were fixed immediately and embedded and sectioned for electron microscopy. Others were laminated between gelatine pellicles in a perfusion chamber, then fixed and sequentially and reversibly imbibed with a series of media of increasing refractive indices. Electron microscopy showed little else besides microtubules in the isolates, and no other component present could account for the observed form birefringence. An Ambronn plot of the birefringent retardation measured during imbibition was a good least squares fit to a computer generated theoretical curve based on the Bragg-Pippard rederivation of the Wiener curve for form birefringence. The data were best fit by the curve for rodlet index (n1) = 1.512, rodlet volume fraction (f) = 0.0206, and coefficient of intrinsic birefringence = 4.7 X 10(-5). The value obtained for n1 is unequivocal and is virtually as good as the refractometer determinations of imbibing medium index on which it is based. The optically interactive volume of the microtubule subunit, calculated from our electron microscope determination of spindle microtubule distribution (106/mum2), 13 protofilaments per microtubules, an 8 nm repeat distance and our best value for f, is compatible with known subunit dimensions as determined by other means. We also report curves fitted to the results of Ambronn imbibition of Bouin's-fixed Lytechinus spindles and to the Noll and Weber muscle imbibition data. PMID:1238403

  5. 45 CFR 2555.515 - Compensation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 4 2011-10-01 2011-10-01 false Compensation. 2555.515 Section 2555.515 Public Welfare Regulations Relating to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE... at a rate less than that paid to employees of the opposite sex for equal work on jobs the...

  6. 45 CFR 2555.515 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 4 2013-10-01 2013-10-01 false Compensation. 2555.515 Section 2555.515 Public Welfare Regulations Relating to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE... at a rate less than that paid to employees of the opposite sex for equal work on jobs the...

  7. 33 CFR 136.223 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.223 Section 136.223 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.223...

  8. 33 CFR 136.217 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.217 Section 136.217 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.217...

  9. 33 CFR 136.241 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.241 Section 136.241 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.241...

  10. 33 CFR 136.235 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.235 Section 136.235 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.235...

  11. 33 CFR 136.205 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.205 Section 136.205 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.205...

  12. 33 CFR 136.229 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.229 Section 136.229 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.229...

  13. 33 CFR 136.211 - Compensation allowable.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Compensation allowable. 136.211 Section 136.211 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... PROCEDURES; DESIGNATION OF SOURCE; AND ADVERTISEMENT Procedures for Particular Claims § 136.211...

  14. 45 CFR 618.515 - Compensation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Compensation. 618.515 Section 618.515 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION NONDISCRIMINATION... of which requires equal skill, effort, and responsibility, and that are performed under...

  15. 45 CFR 618.515 - Compensation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 3 2011-10-01 2011-10-01 false Compensation. 618.515 Section 618.515 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION NONDISCRIMINATION... of which requires equal skill, effort, and responsibility, and that are performed under...

  16. 7 CFR 930.133 - Compensation rate.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Compensation rate. 930.133 Section 930.133 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES...

  17. 29 CFR 1207.3 - Compensation of neutrals.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Compensation of neutrals. 1207.3 Section 1207.3 Labor Regulations Relating to Labor (Continued) NATIONAL MEDIATION BOARD ESTABLISHMENT OF SPECIAL ADJUSTMENT BOARDS § 1207.3 Compensation of neutrals. (a) Neutrals appointed by the National Mediation Board. All...

  18. 7 CFR 966.33 - Expenses and compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Expenses and compensation. 966.33 Section 966.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... Regulating Handling Committee § 966.33 Expenses and compensation. Committee members and alternates may...

  19. 29 CFR 1207.3 - Compensation of neutrals.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 4 2012-07-01 2012-07-01 false Compensation of neutrals. 1207.3 Section 1207.3 Labor Regulations Relating to Labor (Continued) NATIONAL MEDIATION BOARD ESTABLISHMENT OF SPECIAL ADJUSTMENT BOARDS § 1207.3 Compensation of neutrals. (a) Neutrals appointed by the National Mediation Board. All...

  20. 5 CFR 844.105 - Relationship to workers' compensation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Relationship to workers' compensation. 844.105 Section 844.105 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL... Provisions § 844.105 Relationship to workers' compensation. (a) Except as provided in paragraph (b) of...

  1. 5 CFR 844.105 - Relationship to workers' compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 2 2011-01-01 2011-01-01 false Relationship to workers' compensation. 844.105 Section 844.105 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL... Provisions § 844.105 Relationship to workers' compensation. (a) Except as provided in paragraph (b) of...

  2. 28 CFR 104.41 - Amount of compensation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Amount of compensation. 104.41 Section 104.41 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION...-related aircraft crashes of September 11, 2001. In no event shall an award (before collateral...

  3. 28 CFR 104.41 - Amount of compensation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Amount of compensation. 104.41 Section 104.41 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION...-related aircraft crashes of September 11, 2001. In no event shall an award (before collateral...

  4. 28 CFR 104.41 - Amount of compensation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Amount of compensation. 104.41 Section 104.41 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) SEPTEMBER 11TH VICTIM COMPENSATION...-related aircraft crashes of September 11, 2001. In no event shall an award (before collateral...

  5. Large birefringence and polarization holographic gratings formed in photocross-linkable polymer liquid crystals comprising bistolane mesogenic side groups

    SciTech Connect

    Emoto, Akira; Matsumoto, Taro; Shioda, Tatsutoshi; Ono, Hiroshi; Yamashita, Ayumi; Kawatsuki, Nobuhiro

    2009-10-01

    Polarization gratings with large birefringence are formed in photoreactive polymer liquid crystals with bistolane moiety and terminal cinnamic acid moiety by the use of polarized ultraviolet interference light and subsequent annealing. The polarized ultraviolet light causes the axis-selective photoreaction between the cinnamic acid groups and subsequent annealing induce the reorientation of peripheral molecules without cross-linking along the cross-linked groups. Long bistolane mesogenic moiety exhibits large birefringence in comparison with a biphenyl mesogenic moiety, the value of the induced birefringence in the bistolane mesogenic liquid crystalline (LC) polymer is strongly dependent on both the grating constant and the wavelength of the reconstruction light.

  6. Vibration sensor based on highly birefringent Bragg gratings written in standard optical fiber by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Chah, Karima; Bueno, Antonio; Kinet, Damien; Caucheteur, Christophe; Chluda, Cédric; Mégret, Patrice; Wuilpart, Marc

    2014-05-01

    We present a vibration sensor based on highly birefringent fiber Bragg gratings written in standard single mode optical fiber and realized with UV femtosecond pulses. This vibration sensor takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes which induces intensity distribution changes in the two fiber Bragg grating reflection modes. The gratings are inscribed with the femtosecond line by line technique and have a birefringence value of 6 10-4. We demonstrate that theses gratings are temperature birefringence insensitive and ideal for vibration measurements.

  7. Use of retinal nerve fiber layer birefringence as an addition to absorption in retinal scanning for biometric purposes

    NASA Astrophysics Data System (ADS)

    Agopov, Mikael; Gramatikov, Boris I.; Wu, Yi-Kai; Irsch, Kristina; Guyton, David L.

    2008-03-01

    We built a device sensitive to the birefringence of the retinal nerve fiber layer for biometric purposes. A circle of 20° diameter on the retina was scanned around the optic disk with a spot of light from a 785 nm laser diode. The nonbirefringent blood vessels indenting or displacing the retinal nerve fiber layer were seen as “blips” in the measured birefringence-derived signal. For comparison, the reflection-absorption signature of the blood vessel pattern in the scanned circle was also measured. The birefringence-derived signal proved to add useful information to the reflectance-absorption signature for retinal biometric scanning.

  8. PCF Based Sensor with High Sensitivity, High Birefringence and Low Confinement Losses for Liquid Analyte Sensing Applications

    PubMed Central

    Ademgil, Huseyin; Haxha, Shyqyri

    2015-01-01

    In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped V-PCF and horizontally-shaped H-PCF. The full vectorial Finite Element Method (FEM) simulations performed to examine the sensitivity, the confinement losses, the effective refractive index and the modal birefringence features of the proposed elliptical air hole PCF structures. We show that the proposed PCF structures exhibit high relative sensitivity, high birefringence and low confinement losses simultaneously for various analytes. PMID:26694408

  9. Temperature and strain discrimination based on a temperature-insensitive birefringent interferometer incorporating an erbium-doped fiber.

    PubMed

    Han, Young-Geun; Chung, Youngjoo; Lee, Sang Bae; Kim, Chang-Seok; Jeong, Myung Yung; Kim, Moon Ki

    2009-04-20

    A simple configuration for simultaneous measurement of temperature and strain exploiting a temperature-insensitive birefringent interferometer based on a photonic crystal fiber incorporating an erbium-doped fiber (EDF) is investigated. The transmission peak power of the birefringent interferometer incorporating the EDF is changed by the temperature variation because the amplified spontaneous emission of the EDF strongly depends on temperature. The applied strain changes the peak wavelength of the birefringent interferometer connecting with the EDF, which can make it possible to discriminate concurrent sensitivities like temperature and strain. The temperature and strain sensitivities were -0.04 dB/ degrees C and 1.3 pm/microepsilon, respectively.

  10. Use of retinal nerve fiber layer birefringence as an addition to absorption in retinal scanning for biometric purposes.

    PubMed

    Agopov, Mikael; Gramatikov, Boris I; Wu, Yi-Kai; Irsch, Kristina; Guyton, David L

    2008-03-10

    We built a device sensitive to the birefringence of the retinal nerve fiber layer for biometric purposes. A circle of 20 degrees diameter on the retina was scanned around the optic disk with a spot of light from a 785 nm laser diode. The nonbirefringent blood vessels indenting or displacing the retinal nerve fiber layer were seen as "blips" in the measured birefringence-derived signal. For comparison, the reflection-absorption signature of the blood vessel pattern in the scanned circle was also measured. The birefringence-derived signal proved to add useful information to the reflectance-absorption signature for retinal biometric scanning.

  11. Workers' Compensation and Teacher Stress.

    ERIC Educational Resources Information Center

    Nisbet, Michael K.

    1999-01-01

    Examines the Workers' Compensation system and teacher stress to determine if a burned-out teacher should be eligible for Workers' Compensation benefits. Concludes that although most states do not allow Workers' Compensation benefits to burned-out teachers, compensation should be granted because the injuries are real and work-related. (Contains 48…

  12. Real-time measurement system for tracking birefringence, weight, thickness, and surface temperature during drying of solution cast coatings and films.

    PubMed

    Unsal, E; Drum, J; Yucel, O; Nugay, I I; Yalcin, B; Cakmak, M

    2012-02-01

    This paper describes the design and performance of a new instrument to track temporal changes in physical parameters during the drying behavior of solutions, as well as curing of monomers. This real-time instrument follows in-plane and out-of-plane birefringence, weight, thickness, and surface temperature during the course of solidification of coatings and films through solvent evaporation and thermal or photocuring in a controlled atmosphere. It is specifically designed to simulate behavior of polymer solutions inside an industrial size, continuous roll-to-roll solution casting line and other coating operations where resins are subjected to ultraviolet (UV) curing from monomer precursors. Controlled processing parameters include air speed, temperature, initial cast thickness, and solute concentration, while measured parameters are thickness, weight, film temperature, in-plane and out-of-plane birefringence. In this paper, we illustrate the utility of this instrument with solution cast and dried poly (amide-imide)∕DMAc (Dimethylacetamide) solution, water based black paint, and organo-modified clay∕NMP (N-Methylpyrrolidone) solution. In addition, the physical changes that take place during UV photo polymerization of a monomer are tracked. This instrument is designed to be generic and it can be used for tracking any drying∕swelling∕solidification systems including paper, foodstuffs such as; grains, milk as well as pharmaceutical thin paste and slurries.

  13. Parametric approaches to micro-scale characterization of tissue volumes in vivo and ex vivo: Imaging microvasculature, attenuation, birefringence, and stiffness (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sampson, David D.; Chin, Lixin; Gong, Peijun; Wijesinghe, Philip; Es'haghian, Shaghayegh; Allen, Wesley M.; Klyen, Blake R.; Kirk, Rodney W.; Kennedy, Brendan F.; McLaughlin, Robert A.

    2016-03-01

    INVITED TALK Advances in imaging tissue microstructure in living subjects, or in freshly excised tissue with minimum preparation and processing, are important for future diagnosis and surgical guidance in the clinical setting, particularly for application to cancer. Whilst microscopy methods continue to advance on the cellular scale and medical imaging is well established on the scale of the whole tumor or organ, it is attractive to consider imaging the tumor environment on the micro-scale, between that of cells and whole tissues. Such a scenario is ideally suited to optical coherence tomography (OCT), with the twin attractions of requiring little or no tissue preparation, and in vivo capability. OCT's intrinsic scattering contrast reveals many morphological features of tumors, but is frequently ineffective in revealing other important aspects, such as microvasculature, or in reliably distinguishing tumor from uninvolved stroma. To address these shortcomings, we are developing several advances on the basic OCT approach. We are exploring speckle fluctuations to image tissue microvasculature and we have been developing several parametric approaches to tissue micro-scale characterization. Our approaches extract, from a three-dimensional OCT data set, a two-dimensional image of an optical parameter, such as attenuation or birefringence, or a mechanical parameter, such as stiffness, that aids in characterizing the tissue. This latter method, termed optical coherence elastography, parallels developments in ultrasound and magnetic resonance imaging. Parametric imaging of birefringence and of stiffness both show promise in addressing the important issue of differentiating cancer from uninvolved stroma in breast tissue.

  14. Real-time measurement system for tracking birefringence, weight, thickness, and surface temperature during drying of solution cast coatings and films

    NASA Astrophysics Data System (ADS)

    Unsal, E.; Drum, J.; Yucel, O.; Nugay, I. I.; Yalcin, B.; Cakmak, M.

    2012-02-01

    This paper describes the design and performance of a new instrument to track temporal changes in physical parameters during the drying behavior of solutions, as well as curing of monomers. This real-time instrument follows in-plane and out-of-plane birefringence, weight, thickness, and surface temperature during the course of solidification of coatings and films through solvent evaporation and thermal or photocuring in a controlled atmosphere. It is specifically designed to simulate behavior of polymer solutions inside an industrial size, continuous roll-to-roll solution casting line and other coating operations where resins are subjected to ultraviolet (UV) curing from monomer precursors. Controlled processing parameters include air speed, temperature, initial cast thickness, and solute concentration, while measured parameters are thickness, weight, film temperature, in-plane and out-of-plane birefringence. In this paper, we illustrate the utility of this instrument with solution cast and dried poly (amide-imide)/DMAc (Dimethylacetamide) solution, water based black paint, and organo-modified clay/NMP (N-Methylpyrrolidone) solution. In addition, the physical changes that take place during UV photo polymerization of a monomer are tracked. This instrument is designed to be generic and it can be used for tracking any drying/swelling/solidification systems including paper, foodstuffs such as; grains, milk as well as pharmaceutical thin paste and slurries.

  15. Compensation neurosis rides again.

    PubMed

    Levy, A

    1992-01-01

    Compensation neurosis (CN), also known as accident neurosis, has generally not been considered to be a 'real' disorder. In 1961 it was seemingly laid to rest by Henry Miller, a distinguished neurologist, in a sharp article which appeared in the British Medical Journal. Miller's view of patients who presented psychological symptoms following accidents or traumas was suspicious. Compensated or not, his view seemed to be that they should have their legal process finished as quickly as possible and then they will miraculously convalescence. Miller's work, it appeared, was the coup de grâce for this ill-defined diagnosis. Today, however, compensation neurosis seems to ride again. After a prolonged silence in the psychiatric literature, new papers are emerging, strongly suggesting that this vanishing diagnosis be reconsidered. This new trend will be presented.

  16. 7 CFR 1160.207 - Compensation and reimbursement.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ....207 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Milk), DEPARTMENT OF AGRICULTURE FLUID MILK PROMOTION PROGRAM Fluid Milk Promotion Order National Fluid Milk Processor Promotion Board § 1160.207 Compensation...

  17. Noise stochastic corrected maximum a posteriori estimator for birefringence imaging using polarization-sensitive optical coherence tomography

    PubMed Central

    Kasaragod, Deepa; Makita, Shuichi; Hong, Young-Joo; Yasuno, Yoshiaki

    2017-01-01

    This paper presents a noise-stochastic corrected maximum a posteriori estimator for birefringence imaging using Jones matrix optical coherence tomography. The estimator described in this paper is based on the relationship between probability distribution functions of the measured birefringence and the effective signal to noise ratio (ESNR) as well as the true birefringence and the true ESNR. The Monte Carlo method is used to numerically describe this relationship and adaptive 2D kernel density estimation provides the likelihood for a posteriori estimation of the true birefringence. Improved estimation is shown for the new estimator with stochastic model of ESNR in comparison to the old estimator, both based on the Jones matrix noise model. A comparison with the mean estimator is also done. Numerical simulation validates the superiority of the new estimator. The superior performance of the new estimator was also shown by in vivo measurement of optic nerve head. PMID:28270974

  18. Surface birefringence of self-assembly periodic nanostructures induced on 6H-SiC surface by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Song, Juan; Dai, Ye; Tao, Wenjun; Gong, Min; Ma, Guohong; Zhao, Quanzhong; Qiu, Jianrong

    2016-02-01

    In this paper, we report the birefringence effect of surface self-assembly periodic nanostructures induced on 6H-SiC by femtosecond laser irradiation. Birefringence characteristic (e.g. cross-polarized image), measured by cross polarized microscopy, was found to be controlled by both single pulse energy and scanning velocity. Comparing birefringence measurement results of nanostructures and morphology characterization by Scanning electron microscopy, it is shown that ∼200 nm-period deep-subwavelength periodic ripples (DSWR) plays a dominating role in the birefringence effect. Raman spectra show that the change of retardance with pulse energy and scanning velocity is most possibly caused by the thickness variation of DSWR. Finally, a light attenuator based on a single layer of DSWR structure on 6H-SiC surface was constructed and tested by light source of 800 nm to have a tunable attenuating ratio of 69-100%.

  19. Adaptive continuous twisting algorithm

    NASA Astrophysics Data System (ADS)

    Moreno, Jaime A.; Negrete, Daniel Y.; Torres-González, Victor; Fridman, Leonid

    2016-09-01

    In this paper, an adaptive continuous twisting algorithm (ACTA) is presented. For double integrator, ACTA produces a continuous control signal ensuring finite time convergence of the states to zero. Moreover, the control signal generated by ACTA compensates the Lipschitz perturbation in finite time, i.e. its value converges to the opposite value of the perturbation. ACTA also keeps its convergence properties, even in the case that the upper bound of the derivative of the perturbation exists, but it is unknown.

  20. Effect of thermally induced birefringence on performance of KD*P electro-optics crystal with rectangular shape.

    PubMed

    Yin, Xingliang; Jiang, Menghua; Sun, Zhe; Hui, Yongling; Lei, Hong; Li, Qiang

    2017-04-01

    In this paper, we present what we believe is the first demonstration of a new rectangular KD*P crystal as an electro-optic switch and calculations of the stress-induced birefringence and depolarization loss in the crystal. We simulated and experimentally demonstrate the thermal depolarization loss of crystal in both cylindrical and rectangular shape. The results show that by using a rectangular KD*P crystal, the effects of the thermally induced birefringence and depolarization can be lessened.

  1. 3-D TECATE/BREW: Thermal, stress, and birefringent ray-tracing codes for solid-state laser design

    NASA Astrophysics Data System (ADS)

    Gelinas, R. J.; Doss, S. K.; Nelson, R. G.

    1994-07-01

    This report describes the physics, code formulations, and numerics that are used in the TECATE (totally Eulerian code for anisotropic thermo-elasticity) and BREW (birefringent ray-tracing of electromagnetic waves) codes for laser design. These codes resolve thermal, stress, and birefringent optical effects in 3-D stationary solid-state systems. This suite of three constituent codes is a package referred to as LASRPAK.

  2. Three-parameter error analysis method based on rotating coordinates in rotating birefringent polarizer system

    SciTech Connect

    Cao, Junjie; Jia, Hongzhi

    2015-11-15

    We propose error analysis using a rotating coordinate system with three parameters of linearly polarized light—incidence angle, azimuth angle on the front surface, and angle between the incidence and vibration planes—and demonstrate the method on a rotating birefringent prism system. The transmittance and angles are calculated plane-by-plane using a birefringence ellipsoid model and the final transmitted intensity equation is deduced. The effects of oblique incidence, light interference, beam convergence, and misalignment of the rotation and prism axes are discussed. We simulate the entire error model using MATLAB and conduct experiments based on a built polarimeter. The simulation and experimental results are consistent and demonstrate the rationality and validity of this method.

  3. Birefringence and residual stress induced by CO2 laser mitigation of damage growth in fused silica

    NASA Astrophysics Data System (ADS)

    Gallais, L.; Cormont, P.; Rullier, J. L.

    2009-10-01

    We investigate the residual stress field created near mitigated sites and its influence on the efficiency on the CO2 laser mitigation of damage growth process. A numerical model of CO2 laser interaction with fused silica is developed that take into account laser energy absorption, heat transfer, thermally-induced stress and birefringence. Specific photoelastic methods are developed to characterize the residual stress near mitigated sites in fused silica samples. The stress distribution and quantitative values of stress levels are obtained for sites treated with the CO2 laser in various conditions of energy deposition (beam size, pulse duration, incident power). The results obtained also show that the presence of birefringence/residual stress around the mitigated sites has a critical effect on their laser damage resistance.

  4. Three-parameter error analysis method based on rotating coordinates in rotating birefringent polarizer system.

    PubMed

    Cao, Junjie; Jia, Hongzhi

    2015-11-01

    We propose error analysis using a rotating coordinate system with three parameters of linearly polarized light--incidence angle, azimuth angle on the front surface, and angle between the incidence and vibration planes--and demonstrate the method on a rotating birefringent prism system. The transmittance and angles are calculated plane-by-plane using a birefringence ellipsoid model and the final transmitted intensity equation is deduced. The effects of oblique incidence, light interference, beam convergence, and misalignment of the rotation and prism axes are discussed. We simulate the entire error model using MATLAB and conduct experiments based on a built polarimeter. The simulation and experimental results are consistent and demonstrate the rationality and validity of this method.

  5. Correction of large birefringent effect of windows for in situ ellipsometry measurements.

    PubMed

    Jin, Lianhua; Kondoh, Eiichi

    2014-03-15

    To extract true optical properties of samples in a chamber with entrance and exit optical windows, oftentimes the windows were approximated as simple retarders where the retardation was small and premeasured under a given condition. The proposed method allows to cope with large birefringent effect of chamber windows thanks to its capability of extracting ellipsometric parameters (Δ, Ψ) of isotropic samples as well as measuring birefringent parameters (δ, θ) of each window separately and simultaneously. This method is, however, not valid for anisotropic samples. Ex situ results and extracted ellipsometric parameters results from in situ measurements of a silicon substrate and a SiO2 film thermally grown on the silicon substrate exhibited excellent agreement and provided significance of this method.

  6. Three-parameter error analysis method based on rotating coordinates in rotating birefringent polarizer system

    NASA Astrophysics Data System (ADS)

    Cao, Junjie; Jia, Hongzhi

    2015-11-01

    We propose error analysis using a rotating coordinate system with three parameters of linearly polarized light—incidence angle, azimuth angle on the front surface, and angle between the incidence and vibration planes—and demonstrate the method on a rotating birefringent prism system. The transmittance and angles are calculated plane-by-plane using a birefringence ellipsoid model and the final transmitted intensity equation is deduced. The effects of oblique incidence, light interference, beam convergence, and misalignment of the rotation and prism axes are discussed. We simulate the entire error model using MATLAB and conduct experiments based on a built polarimeter. The simulation and experimental results are consistent and demonstrate the rationality and validity of this method.

  7. Design of a highly-birefringent microstructured photonic crystal fiber for pressure monitoring.

    PubMed

    Jewart, Charles M; Quintero, Sully Mejía; Braga, Arthur M B; Chen, Kevin P

    2010-12-06

    We present the design of an air hole microstructured photonic crystal fiber for pressure sensing applications. The air-hole photonic crystal lattices were designed to produce a large intrinsic birefringence of 1.16 x 10(-3). The impact of the surrounding air holes for pressure sensing to the propagation mode profiles and indices were studied and improved, which ensures single mode propagation in the fiber core defined by the photonic crystal lattice. An air hole matrix and a practical chemical etching process during the fiber perform preparation stage is proposed to produce an optical fiber with a birefringence-pressure coefficient of 43.89 x 10 (-6)MPa(-1) or a fiber Bragg grating pressure responsivity of 44.15 pm/MPa, which is a 17 times improvement over previous photonic crystal fiber designs.

  8. Anomalous birefringence in andradite-grossular solid solutions: a quantum-mechanical approach

    NASA Astrophysics Data System (ADS)

    Lacivita, Valentina; D'Arco, Philippe; Orlando, Roberto; Dovesi, Roberto; Meyer, Alessio

    2013-11-01

    The static linear optical properties (refractive indices, birefringence and axial angle) of andradite-grossular (Ca3Fe2Si3O12-Ca3Al2Si3O12) solid solutions have been computed at the ab initio quantum-mechanical level through the Coupled Perturbed Kohn-Sham scheme, using an all-electron Gaussian-type basis set. Geometry relaxation after substitution of 1-8 Al for Fe atoms in the primitive cell of andradite yields 23 non-equivalent configurations ranging from cubic to triclinic symmetry. Refractive indices vary quite regularly between the andradite (1.860) and grossular (1.671) end-members; the birefringence δ and the axial angle 2 V at intermediate compositions can be as large as 0.02° and 89°, respectively. Comparison with experiments suffers from inhomogeneities and impurities of natural samples; however, semi-quantitative agreement is observed.

  9. Characterization of temperature-dependent birefringence in polarization maintaining fibers based on Brillouin dynamic gratings

    NASA Astrophysics Data System (ADS)

    Kim, Yong Hyun; Song, Kwang Yong

    2015-07-01

    Temperature dependence of birefringence in various types of polarization-maintaining fibers (PMF's) is rigorously investigated by the spectral analysis of Brillouin dynamic grating (BDG). PANDA, Bowtie, and PM photonic crystal fibers are tested in the temperature range of -30 to 150 ºC, where nonlinear temperature dependence is quantified for each fiber to an accuracy of ±7.6 × 10-8. It is observed that the amount of deviation from the linearity varies according to the structural parameters of the PMF's and the existence of acrylate jacket. Experimental confirmation of the validity of the BDG-based birefringence measurement is also presented in comparison to the periodic lateral force method.

  10. A novel synthesis approach for birefringent filters having arbitrarily amplitude transmittances

    NASA Astrophysics Data System (ADS)

    Halassi, Abde Rezzaq; Hamdi, Rachid; Bendimerad, Djalal Falih; Benkelfat, Badr-Eddine

    2016-06-01

    In this paper, we present a novel procedure for the synthesis of a filter having an arbitrarily specified amplitude transmittance. The filter configuration consists of N birefringent stages placed between a polarizer and an analyzer, with each stage containing an identical section and a variable section. An additional variable section is placed in front of the analyzer. The synthesis procedure is based on the resolution of a generalized nonlinear equation system directly deducted from the Jones matrix formalism to determine the angles of each stage, the angle of the analyzer and the phase shifts of the variable sections. A typical example of a 6-stage birefringent filter having an arbitrarily non-symmetric amplitude transmittance is shown and the opto-geometrical parameters are given to demonstrate the efficiency of the proposed synthesis procedure. The results obtained show an excellent agreement with those developed in the literature.

  11. Modulational Instability and Stimulated Raman Scattering in Normally Dispersive Highly Birefringent Fibers

    NASA Astrophysics Data System (ADS)

    Millot, G.; Dinda, P. Tchofo; Seve, E.; Wabnitz, S.

    2001-07-01

    The nonlinear interaction of two laser beams in normally dispersive highly birefringent optical fibers leads to a large set of fascinating physical effects such as modulational instability (MI) and stimulated Raman scattering (SRS). These two nonlinear phenomena have a positive role as a mechanism for the generation of short optical pulses and represent a drawback in fiber-optics transmissions. Indeed, we will show that an induced process of modulational instability may be exploited for the generation of THz train of vector dark solitons. The technique of frequency-resolved optical gating is used to completely characterize the intensity and phase of the dark soliton trains. On the other hand, we shall discuss control processes for MI and SRS in birefringent optical fibers. In particular, we analyze experiments showing that with dual-frequency, orthogonal polarization pumping one may achieve the simultaneous suppression of modulational instability and substantial reduction of stimulated Raman scattering.

  12. Real-time imaging of action potentials in nerves using changes in birefringence

    PubMed Central

    Badreddine, Ali H.; Jordan, Tomas; Bigio, Irving J.

    2016-01-01

    Polarized light can be used to measure the electrical activity associated with action potential propagation in nerves, as manifested in simultaneous dynamic changes in their intrinsic optical birefringence. These signals may serve as a tool for minimally invasive neuroimaging in various types of neuroscience research, including the study of neuronal activation patterns with high spatiotemporal resolution. A fast linear photodiode array was used to image propagating action potentials in an excised portion of the lobster walking leg nerve. We show that the crossed-polarized signal (XPS) can be reliably imaged over a ≥2 cm span in our custom nerve chamber, by averaging multiple-stimulation signals, and also in single-scan real-time “movies”. This demonstration paves the way toward utilizing changes in the optical birefringence to image more complex neuronal activity in nerve fibers and other organized neuronal tissue. PMID:27231635

  13. Measurement of stress-induced birefringence in glasses based on reflective laser feedback effect

    NASA Astrophysics Data System (ADS)

    Haisha, Niu; YanXiong, Niu; Jiyang, Li

    2017-02-01

    A glass birefringence measurement system utilizing the reflective laser feedback (RLF) effect is presented. The measurement principle is analyzed based on the equivalent cavity of a Fabry-Perot interferometer, and the experiments are conducted with a piece of quartz glass with applied extrusion force. In the feedback system, aluminum film used as a feedback mirror is affixed to the back of the sample. When the light is reflected back into the cavity, as the reinjected light is imprinted with the birefringence information in the sample, the gain and polarization states of the laser are modulated. The variation of optical power and polarization states hopping is monitored to obtain the magnitude of the stress. The system has advantages such as simplicity and low-cost with a precision of 1.9 nm. Moreover, by adjusting the position of the aluminum, large-area samples can be measured anywhere at any place.

  14. A note on the birefringence angle estimation in CMB data analysis

    NASA Astrophysics Data System (ADS)

    Gruppuso, A.; Maggio, G.; Molinari, D.; Natoli, P.

    2016-05-01

    Parity violating physics beyond the standard model of particle physics induces a rotation of the linear polarization of photons. This effect, also known as cosmological birefringence (CB), can be tested with the observations of the cosmic microwave background (CMB) anisotropies which are linearly polarized at the level of 5-10%. In particular CB produces non-null CMB cross correlations between temperature and B mode-polarization, and between E- and B-mode polarization. Here we study the properties of the so called D-estimators, often used to constrain such an effect. After deriving the framework of both frequentist and Bayesian analysis, we discuss the interplay between birefringence and weak-lensing, which, albeit parity conserving, modifies pre-existing TB and EB cross correlation.

  15. Suppression of Brewster delocalization anomalies in an alternating isotropic-birefringent random layered medium

    NASA Astrophysics Data System (ADS)

    Jordan, T. M.; Partridge, J. C.; Roberts, N. W.

    2013-07-01

    We investigate the polarization dependence of localization length in alternating isotropic-birefringent stacks with uncorrelated thickness disorder. The birefringent layers can be positive uniaxial, negative uniaxial, or a mixture of both. Stacks which contain a mixture are shown to suppress the Brewster delocalization anomalies and, over all incident angles, exhibit p-polarization localization length maxima that are of similar magnitude to normal incidence. Furthermore, we propose a parameter set that enables the p-polarization localization length to monotonically decrease with angle of incidence. This investigation was inspired by weakly polarizing mirrors on the sides of silvery fish and provides a generic means to produce polarization-insensitive, broadband reflections from a random, all-dielectric layered medium.

  16. Competition of Faraday rotation and birefringence in femtosecond laser direct written waveguides in magneto-optical glass.

    PubMed

    Liu, Qiang; Gross, S; Dekker, P; Withford, M J; Steel, M J

    2014-11-17

    We consider the process of Faraday rotation in femtosecond laser direct-write waveguides. The birefringence commonly associated with such waveguides may be expected to impact the observable Faraday rotation. Here, we theoretically calculate and experimentally verify the competition between Faraday rotation and birefringence in two waveguides created by laser writing in a commercial magneto-optic glass. The magnetic field applied to induce Faraday rotation is nonuniform, and as a result, we find that the two effects can be clearly separated and used to accurately determine even weak birefringence. The birefringence in the waveguides was determined to be on the scale of Δn = 10(-6) to 10(-5). The reduction in Faraday rotation caused by birefringence of order Δn = 10(-6) was moderate and we obtained approximately 9° rotation in an 11 mm waveguide. In contrast, for birefringence of order 10(-5), a significant reduction in the polarization azimuth change was found and only 6° rotation was observed.

  17. Semiconductor laser with a birefringent external cavity for information systems with wavelength division multiplexing

    SciTech Connect

    Paranin, V D; Matyunin, S A; Tukmakov, K N

    2013-10-31

    The spectrum of a semiconductor laser with a birefringent external Gires – Tournois cavity is studied. The generation of two main laser modes corresponding to the ordinary and extraordinary wave resonances is found. It is shown that the radiation spectrum is controlled with a high energy efficiency without losses for spectral filtration. The possibility of using two-mode lasing in optical communication systems with wavelength division multiplexing is shown. (control of laser radiation parameters)

  18. Advancements in the Interferometric Measurements of Real Time Finishing Birefringent Filter's Crystal Plates

    NASA Astrophysics Data System (ADS)

    Gan, Ma; Mgan, Ya; Kushtal Skomorovsky, Gi, Vi; Domyshev, Gn; Sadokhin, Vp

    2006-10-01

    The finishing of birefringent plates consists of two processes: polishing and evaluation of a surface, which have been performed separately till now. The purpose of this work is achieving of high accuracy of the evaluation and machining of the plane-parallel plates from birefringent crystals, in particular of crystal plates of birefringent filters during their finishing. The developed process combines evaluation and polishing in an interactive way. We have found modes of treatment, shape of polisher, have designed interferometer, with a mirror arranged in polisher. Visual checking of optical thickness comparatively with reference plate was carried out using the interference fringes of equal birefringence, and checking of an optical wedge - by interference rings of an equal inclination. The automated processing of TV camera interference fringes was impossible, because of gaps of interference fringes on polishing cells above the mirror. Therefore a special software was developed for processing of a complex fringe pattern interferogram. Software FastInterf uses furrier analysis technique which allows to process an interferogram with multiply gaps. Interferograms are registered by a high resolution TV camera (1280 ×1024). Automatic processing of a fringe interferogram using FastInterf software takes less then one second. The influence of gaps is excluded, and the flat field is taken into account. Software provides full 3D surface and wavefront maps. Aberration analysis of a wavefront gives information on thickness of a plate comparatively with a reference one, optical wedge of plate and azimuth of an inclination of wave front. Moreover, software provides a control of surface quality. The measuring device, features of the software are described and process of interferometric evaluation during polishing is illustrated.

  19. Non-osteoporotic women with low-trauma fracture present altered birefringence in cortical bone.

    PubMed

    Ascenzi, Maria-Grazia; Chin, Jesse; Lappe, Joan; Recker, Robert

    2016-03-01

    Areal bone mineral density (BMD) by DXA, although an important index, does not accurately assess risk of fragility fracture. Another bone structural parameter, the orientation of type I collagen, is known to add to risk determination, independently of BMD. Accordingly, we investigated the Haversian systems of transiliac crest biopsies from non-osteoporotic women with low-trauma fractures, matched to healthy women without fracture by age and BMD. We employed circularly polarized light (CPL) microscopy because 1) each of the extinct and bright birefringent signals of CPL corresponds to a specific collagen arrangement; and 2) CPL can employ magnification suitable to provide data, of manageable size, from the whole cortical component of a section of biopsy. Under CPL, the coaxial layers of osteons, called lamellae, appear either birefringent extinct or bright. On a section transverse to the Haversian system, the extinct lamella comprises mainly collagen forming small angles, and the bright lamella comprises mainly collagen forming large angles, relative to the general orientation of the Haversian system. We performed semi-automatic morphometry for birefringent and structural parameters for which we computed intra- and inter-observer errors. The statistical analysis used a linear mixed model to compare fracturing and non-fracturing groups while addressing pairing of fracturing and non-fracturing subjects, and linear regression to assess differences between matched subjects. We found significant reduction in 1) lamellar width and area for extinct lamella and bright lamella; 2) percentage of extinct birefringence in osteons, and 3) single osteon area; in the fracturing group; and in lamellar width in the fracturing subject of all pairs. Our results evidence the need to investigate, in a larger sample of subjects, the distribution of collagen orientation as a parameter diagnostic of increased fracture risk.

  20. Production of single-mode fibres with negligible intrinsic birefringence and polarisation mode dispersion

    NASA Astrophysics Data System (ADS)

    Barlow, A. J.; Payne, D. N.; Hadley, M. R.; Mansfield, R. J.

    1981-10-01

    A method is reported whereby fibers can be reproducibly manufactured with negligible intrinsic birefringence or polarization mode dispersion (less than 0.02 ps/km). The fibers are produced by rotating the preform during drawing to impact a permanent twist and are referred to as spun fibers to distinguish them from fibers twisted after drawing. Such fibers will find application in the Faraday current monitor and for high-bandwidth telecommunications.

  1. Zona pellucida birefringence and meiotic spindle visualisation of human oocytes are not influenced by IVM technology.

    PubMed

    Omidi, Marjan; Khalili, Mohammad Ali; Ashourzadeh, Sareh; Rahimipour, Marzieh

    2014-03-01

    The aim of the present study was to investigate the relationship between the presence of the meiotic spindle and zona pellucida (ZP) birefringence with morphology of in vivo- and in vitro-matured human oocytes. Germinal vesicles (n=47) and MI (n=38) oocytes obtained from stimulated ovaries of patients undergoing intracytoplasmic sperm injection (ICSI) underwent IVM. Using a PolScope (OCTAX PolarAID; Octax, Herbon, Germany), the presence of spindles and ZP birefringence was assessed in both in vivo-matured (n=56) and IVM (n=56) oocytes. In addition, the morphology of each matured oocyte was evaluated microscopically. There were insignificant differences for ZP birefringence and meiotic spindle between the in vivo-matured and IVM MII oocytes. Subanalysis revealed that the rates of morphologically abnormal oocytes did not differ significantly between the two groups, except in the case of irregular shape (P=0.001), refractile body (P=0.001) and fragmented polar body (P=0.03), which were higher in IVM oocytes. In the case of in vivo-matured oocytes, a significantly higher percentage of oocytes with intracytoplasmic and both intra- and extracytoplasmic abnormalities have a low birefringent ZP (P=0.007 and P=0.02, respectively). There was no relationship between morphological abnormalities and spindle detection. The findings suggest that clinical IVM is a safe technology that maintains the high maturation rate and integrity of oocytes. In addition, the use of the non-invasive PolScope is recommended for the detection of oocytes most suitable for ICSI.

  2. Evolution of dosage compensation.

    PubMed

    Steinemann, M; Steinemann, S; Turner, B M

    1996-04-01

    In polytene chromosome squashes from the fruit fly Drosophila melanogaster, the single, dosage-compensated X chromosome in males can be distinguished from the autosomes by the presence of an isoform of histone H4 acetylated at lysine 16, H4.Ac16. We have used H4.Ac16 as a marker to examine the evolving relationship between dosage compensation and sex chromosome composition in species of Drosophila with one (D. melanogaster), two (D. pseudoobscura) or three (D. miranda) identifiable X chromosome arms. In each case, we find that H4.Ac16 is distributed as discrete, closely spaced bands along the entire length of each X chromosome, the only exception being the X2 chromosome of D. miranda in which a terminal region constituting about 10% of the chromosome by length is not labelled with anti-H4.Ac16 antibodies. We conclude that, with this exception, dosage compensation extends along the X chromosomes of all three species. As D. pseudoobscura and D. miranda diverged only about 2 Mya, the spread of dosage-compensated loci along X2 has been rapid, suggesting that regional changes rather than piecemeal, gene-by-gene, changes may have been involved.

  3. AACC CEO Survey: Compensation

    ERIC Educational Resources Information Center

    Phillippe, Kent A.

    2016-01-01

    In 2015, the American Association of Community Colleges (AACC) conducted a survey of community college chief executive officers (CEOs) to collect their opinions on current issues, and gather information on their compensation. This report provides the results from this survey. The AACC CEO Survey was sent to 960 public community college presidents.…

  4. Reactive Power Compensating System.

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1985-01-04

    The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

  5. Backlash compensator mechanism

    DOEpatents

    Chrislock, Jerry L.

    1979-01-01

    Mechanism which compensates for backlash error in a lead screw position indicator by decoupling the indicator shaft from the lead screw when reversing rotation. The position indicator then displays correct information regardless of the direction of rotation of the lead screw.

  6. The Compensation Question

    ERIC Educational Resources Information Center

    Richwine, Jason; Biggs, Andrew; Mishel, Lawrence; Roy, Joydeep

    2012-01-01

    Over the past few years, as cash-strapped states and school districts have faced tough budget decisions, spending on teacher compensation has come under the microscope. The underlying question is whether, when you take everything into account, today's teachers are fairly paid, underpaid, or overpaid. In this forum, two pairs of respected…

  7. Nucleosome and DNA-protein condensed structures in solution from flow birefringence and intrinsic viscosity

    SciTech Connect

    Harrington, R.E.

    1980-10-01

    Highly sensitive streaming birefringence measurements combined with intrinsic viscosity are used to characterize the shape anisometry and optical anisotropy of nucleosomes over a range of salt concentration > 30 mM KCl and of structures obtained by the condensation of high molecular weight DNA with polylysine. These measurements appear useful for several reasons. Both streaming birefringence and intrinsic viscosity are hydrodynamic properties based upon the rotational diffusion of macromolecular particles and hence are inherently more sensitive to details of particle anisometry than are hydrodynamic properties based upon translational diffusion. An established body of both hydrodynamic and continuum dielectric optical theory is available with which to interpret streaming birefringence results. Extinction angles (i.e., mean orientation angles of particles in a velocity gradient) are entirely hydrodynamic properties, and hence can be interpreted through the rotational coefficient to characterize particle anisometry and to estimate absolute dimensions. The ratio of Maxwell coefficient to intrinsic viscosity is proportional to the absolute particle anisotropy. The high optical anisotropy of DNA relative to that of associated protein permits certain details of tertiary structure and shape anisometry to be estimated from the observed optical anisotropy compared to optical models involving the DNA alone. The method is essentially independent of solvent.

  8. Effects of birefringence on Fizeau interferometry that uses a polarization phase-shifting technique.

    PubMed

    Zhao, Chunyu; Kang, Dongyel; Burge, James H

    2005-12-10

    Interferometers that use different states of polarization for the reference and the test beams can modulate the relative phase shift by using polarization optics in the imaging system. Thus the interferometer can capture simultaneous images that have a fixed phase shift, which can be used for phase-shifting interferometry. As all measurements are made simultaneously, the interferometer is not sensitive to vibration. Fizeau interferometers of this type have an advantage compared with Twyman-Green-type systems because they are common-path interferometers. However, a polarization Fizeau interferometer is not strictly common path when both wavefronts are transmitted by an optic that suffers from birefringence. The two polarized beams see different phases owing to birefringence; as a result, an error can be introduced in the measurement. We study the effect of birefringence on measurement accuracy when different polarization techniques are used in Fizeau interferometers. We demonstrate that measurement error is reduced dramatically and can be eliminated if the reference and test beams are circularly polarized rather than linearly polarized.

  9. Dispersion of linearly polarized light propagating in a thin birefringent plate.

    PubMed

    Yang, Xifeng; Jia, Yaqing; Zhao, Youbo; Zhang, Tiequn; Zhu, Xiaonong

    2005-04-01

    We analyze theoretically the dispersion of linearly polarized light propagating in a uniaxial anisotropic medium where multibeam interference is present. Explicit expressions of the group-delay dispersion for transmitting waves are derived for the simplest situation, and the effect of dispersion on pulse broadening is analyzed for a few selected cases. Our results reveal that at normal incidence and in the situation where the optic axis is parallel to the surface of birefringent plate (in the x-y plane), the dispersion of the refracted wave decreases with the extent of birefringence. In particular, the dispersion for the electric field parallel to the polarization direction of the incident light changes with the rotation angle between the optic axis and the polarization direction of the incident field, whereas the dispersion for the refracted field whose direction is vertical to the polarization of incident light is independent of this angle. For oblique incidence, dispersion varies substantially for different incident angles. In the situation where the optic axis is in the x-z plane at either normal or oblique incidence, the dispersion increases in a periodically oscillating manner as a function of the relative thickness of the birefringent plate.

  10. Digital Beam Steering Device Based on Decoupled Birefringent Prism Deflector and Polarization Rotator

    NASA Technical Reports Server (NTRS)

    Pishnyak, Oleg; Kreminska, Lyubov; Laventovich, Oleg D.; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.

    2004-01-01

    We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal (LC) or a solid crystal such as yttrium orthovanadate (YVO4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2(sup N) directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of +/- 56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells.

  11. Retardance of bilayer anisotropic samples consisting of well-aligned cylindrical scatterers and birefringent media

    NASA Astrophysics Data System (ADS)

    Guo, Yihong; Zeng, Nan; He, Honghui; Liu, Celong; Du, E.; He, Yonghong; Ma, Hui

    2016-05-01

    Both cylindrical scatterers and birefringent media may contribute to the anisotropy of tissue, where anisotropy can be characterized using polarization techniques. Our previous studies have shown that a layer of well-aligned cylindrical scatterers displays anisotropic properties similar to those of a piece of birefringent media, whose equivalent extraordinary axis is along the axial direction of the cylinders. We focused on a sample consisting of two layers of anisotropic media, with each layer having a different orientation; the characteristics of this sample were representative of the properties of multilayer fibrous tissues. Using a Mueller matrix decomposition method, we examined in detail how the total retardance and the equivalent extraordinary axis of the bilayered sample varied with changes in the retardance of the two layers and the direction of the extraordinary axis. The results of this study showed that, in such bilayer samples, a layer of well-aligned cylindrical scatterers generated a retardance that behaved exactly like the retardance generated by a piece of birefringent media. The simulated results were also confirmed by the results of experiments using aligned glass fibers.

  12. Microwave birefringent metamaterials for polarization conversion based on spoof surface plasmon polariton modes

    PubMed Central

    Li, Yongfeng; Zhang, Jieqiu; Ma, Hua; Wang, Jiafu; Pang, Yongqiang; Feng, Dayi; Xu, Zhuo; Qu, Shaobo

    2016-01-01

    We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and y-polarized components of incident waves. Since the dispersion curve of SSPPs is nonlinear, frequency-dependent phase differences can be obtained between the two orthogonal components of transmitted waves. As an example, we demonstrate a microwave birefringent metamaterials composed of fishbone structures. The full-polarization-state conversions on the zero-longitude line of Poincaré sphere can be fulfilled twice in 6–20 GHz for both linearly polarized (LP) and circularly polarized (CP) waves incidence. Besides, at a given frequency, the full-polarization-state conversion can be achieved by changing the polarization angle of the incident LP waves. Both the simulation and experiment results verify the high-efficiency polarization conversion functions of the birefringent metamaterial, including circular-to-circular, circular-to-linear(linear-to-circular), linear-to-linear polarization conversions. PMID:27698443

  13. Polarization birefringence measurements for characterizing the myocardium, including healthy, infarcted, and stem-cell-regenerated tissues

    NASA Astrophysics Data System (ADS)

    Wood, Michael F. G.; Ghosh, Nirmalya; Wallenburg, Marika A.; Li, Shu-Hong; Weisel, Richard D.; Wilson, Brian C.; Li, Ren-Ke; Vitkin, I. Alex

    2010-07-01

    Myocardial infarction leads to structural remodeling of the myocardium, in particular to the loss of cardiomyocytes due to necrosis and an increase in collagen with scar formation. Stem cell regenerative treatments have been shown to alter this remodeling process, resulting in improved cardiac function. As healthy myocardial tissue is highly fibrous and anisotropic, it exhibits optical linear birefringence due to the different refractive indices parallel and perpendicular to the fibers. Accordingly, changes in myocardial structure associated with infarction and treatment-induced remodeling will alter the anisotropy exhibited by the tissue. Polarization-based linear birefringence is measured on the myocardium of adult rat hearts after myocardial infarction and compared with hearts that had received mesenchymal stem cell treatment. Both point measurement and imaging data show a decrease in birefringence in the region of infarction, with a partial rebound back toward the healthy values following regenerative treatment with stem cells. These results demonstrate the ability of optical polarimetry to characterize the micro-organizational state of the myocardium via its measured anisotropy, and the potential of this approach for monitoring regenerative treatments of myocardial infarction.

  14. Novel laser machining of optical fibers for long cavities with low birefringence.

    PubMed

    Takahashi, Hiroki; Morphew, Jack; Oručević, Fedja; Noguchi, Atsushi; Kassa, Ezra; Keller, Matthias

    2014-12-15

    We present a novel method of machining optical fiber surfaces with a CO₂ laser for use in Fiber-based Fabry-Perot Cavities (FFPCs). Previously FFPCs were prone to large birefringence and limited to relatively short cavity lengths (≤ 200 μm). These characteristics hinder their use in some applications such as cavity quantum electrodynamics with trapped ions. We optimized the laser machining process to produce large, uniform surface structures. This enables the cavities to achieve high finesse even for long cavity lengths. By rotating the fibers around their axis during the laser machining process the asymmetry resulting from the laser's transverse mode profile is eliminated. Consequently we are able to fabricate fiber mirrors with a high degree of rotational symmetry, leading to remarkably low birefringence. Through measurements of the cavity finesse over a range of cavity lengths and the polarization dependence of the cavity linewidth, we confirmed the quality of the produced fiber mirrors for use in low-birefringence FFPCs.

  15. Magneto-optical circular birefringence of a chiral medium in high magnetic field

    NASA Astrophysics Data System (ADS)

    Surma, M.

    Measurements are reported of the magneto-optical circular birefringence of an intracentrifuged blood. The blood plasma is optically active. Under the influence of external magnetic field magnetooptical circular birefri2ngence of the in 3vestigated medium is observed as a superposition of linear (B), quadratic (B ) and cubic (B ) field dependence. The quantitative result of the observed effect is different for parallel ( ) and antiparallel ( ) light propagation k, to the direction of the magneti2c field B 3 acting on the medium. These results are the first experimental observation of the B and B effects and the different circular birefringence for a chiral medium in a magnetic field parallel and antiparallel to the light beam propagation. The parallel (k,B) and antiparallel (k,- B) effects are obse2rved clea 3rly for a magnetic field of induction B above 10T acting on the plasma. The B and B dependent effects are unambiguously recorded for B values above 20T. For different sources of human plasma the magneto-optical data differ slightly. The magneto-optical circular birefringence of the plasma investigated has been measured in high magnetic fields of up to 30T and with a 488nm wavelength laser beam.

  16. Feasibility of a compact fiber optic probe for real time tracing of subsurface skin birefringence

    NASA Astrophysics Data System (ADS)

    Tugbaev, Vitaly; Myllyla, Risto

    2005-08-01

    A novel approach anticipates real time acquisition of spatially resolved polarization data to facilitate fast cross-sectional tracing collagen-related birefringence in skin down to reticular dermis, i.e. up to the depth of a few hundreds micrometers. It is based on a unique integration of a static-type interferometer in a time domain system intended for polarization-sensitive optical coherence tomography (PS-OCT). The design concept avoids any movable parts to evolve fringes over the traced depth, and exploits liquid crystal bistable switches to rapidly discriminate between orthogonal polarization components of the analyzable signal. The signal is transmitted through a polarization maintaining fiber and detected, by turns, in the single optical channel by the same line camera of appropriate format. The approach relies on the statements proven in the art. In particular, time-domain PS-OCT based on coherent detection of the fringe intensity in orthogonal polarization components of reflected signal allows identifying at least qualitatively collagen depletion regions in subsurface skin layers. Polarization state of light backscattered from sufficiently shallow depth in skin is defined mostly by linear birefringence of collagen fibers. Propagation of light in such linearly birefringent medium satisfies the reciprocity principle in optics.

  17. Measurement of birefringence of optical materials using a wedged plate interferometer

    NASA Technical Reports Server (NTRS)

    Shukla, R. P.; Perera, G. M.; George, M. C.; Venkateswarlu, Putcha

    1990-01-01

    A nondestructive technique for measuring the birefringence of optical materials such as calcite using wedged plate interferometer is presented. The sample needed for measuring the refractive index must be polished in the form of a parallel plate. The method is based on the measurement of the longitudinal displacement of the focus when the parallel plate is inserted in a converging beam of light. The displacement of the focus is a measure of the refractive index of the optical material. In the case of a uniaxial crystal, the displacement of the focus for the extraordinary ray is different from the displacement of the focus for the ordinary ray. Hence the birefringence of the crystal is determined by measuring the difference between the two focii. It is possible to obtain an accuracy up to 0.0002 in the measurement of birefringence depending on the sample thickness. The method should find its application for the characterization of new crystals in various material research and crystal growth laboratories.

  18. Wavelength-tunable mid-infrared femtosecond Raman soliton generation in birefringent ZBLAN photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Sharma, Sneha; Kumar, Jitendra

    2016-03-01

    A solid core high birefringent ZrF4-BaF2-LaF3-AlF3-NaF photonic crystal fiber (PCF) with low confinement loss is proposed for the generation of Raman soliton source in the mid-infrared region. The birefringence value of the PCF reaches the magnitude of 10- 3 and confinement loss is 0.05 dB/m at 3000 nm wavelength. Numerical simulation of femtosecond Raman soliton generation based on soliton self-frequency shift in the birefringent PCF is analyzed using the coupled nonlinear Schrodinger equation and split-step Fourier method. We investigate the dependence of output pulse width, wavelength shift, and conversion efficiency of Raman soliton formation on several input parameters. A femtosecond Raman soliton source with its wavelength tunable from 1500 to 3600 nm can be obtained. It is found that the maximum conversion efficiency is 93% when the wavelength is tuned by varying the initial input chirp.

  19. Transmission imaging polarimetry for a linear birefringent medium using a carrier fringe method.

    PubMed

    Drobczynski, Slawomir; Bueno, Juan M; Artal, Pablo; Kasprzak, Henryk

    2006-08-01

    We present an imaging polarimeter in transmission mode that is based on a carrier frequency method and allows a spatially resolved polarimetric description of nondichroic linear birefringent media. The apparatus incorporates a generator of polarization states in the incoming pathway and a Wollaston prism and a linear polarizer as the analyzer unit. A series of two fringe pattern images of the birefringent sample under study, corresponding to two independent polarization states of the generator unit, were recorded. From these images and by using Fourier analysis, the 2D distribution of azimuth angle and retardation were calculated. Two alternative generator units were used: (i) a linear polarizer combined with a rotatory quarter-wave plate and (ii) a liquid-crystal variable retarder. A uniform quarter-wave plate at different orientations was measured with both generator units to demonstrate the effectiveness and the accuracy of the method. The mean absolute deviations were 1.8 degrees and 4.1 degrees for the azimuth and the retardation, respectively, with the first generator unit, and 2.9 degrees and 4.4 degrees for the second one. Moreover, some nonuniform birefringent samples presenting wider ranges of azimuth and retardation were also tested.

  20. Transient magnetic birefringence for determining magnetic nanoparticle diameters in dense, highly light scattering media

    NASA Astrophysics Data System (ADS)

    Köber, Mariana; Moros, Maria; Grazú, Valeria; de la Fuente, Jesus M.; Luna, Mónica; Briones, Fernando

    2012-04-01

    The increasing use of biofunctionalized magnetic nanoparticles in biomedical applications calls for further development of characterization tools that allow for determining the interactions of the nanoparticles with the biological medium in situ. In cell-incubating conditions, for example, nanoparticles may aggregate and serum proteins adsorb on the particles, altering the nanoparticles’ performance and their interaction with cell membranes. In this work we show that the aggregation of spherical magnetite nanoparticles can be detected with high sensitivity in dense, highly light scattering media by making use of magnetically induced birefringence. Moreover, the hydrodynamic particle diameter distribution of anisometric nanoparticle aggregates can be determined directly in these media by monitoring the relaxation time of the magnetically induced birefringence. As a proof of concept, we performed measurements on nanoparticles included in an agarose gel, which scatters light in a similar way as a more complex biological medium but where particle-matrix interactions are weak. Magnetite nanoparticles were separated by agarose gel electrophoresis and the hydrodynamic diameter distribution was determined in situ. For the different particle functionalizations and agarose concentrations tested, we could show that gel electrophoresis did not yield a complete separation of monomers and small aggregates, and that the electrophoretic mobility of the aggregates decreased linearly with the hydrodynamic diameter. Furthermore, the rotational particle diffusion was not clearly affected by nanoparticle-gel interactions. The possibility to detect nanoparticle aggregates and their hydrodynamic diameters in complex scattering media like cell tissue makes transient magnetic birefringence an interesting technique for biological applications.

  1. Microwave birefringent metamaterials for polarization conversion based on spoof surface plasmon polariton modes

    NASA Astrophysics Data System (ADS)

    Li, Yongfeng; Zhang, Jieqiu; Ma, Hua; Wang, Jiafu; Pang, Yongqiang; Feng, Dayi; Xu, Zhuo; Qu, Shaobo

    2016-10-01

    We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and y-polarized components of incident waves. Since the dispersion curve of SSPPs is nonlinear, frequency-dependent phase differences can be obtained between the two orthogonal components of transmitted waves. As an example, we demonstrate a microwave birefringent metamaterials composed of fishbone structures. The full-polarization-state conversions on the zero-longitude line of Poincaré sphere can be fulfilled twice in 6-20 GHz for both linearly polarized (LP) and circularly polarized (CP) waves incidence. Besides, at a given frequency, the full-polarization-state conversion can be achieved by changing the polarization angle of the incident LP waves. Both the simulation and experiment results verify the high-efficiency polarization conversion functions of the birefringent metamaterial, including circular-to-circular, circular-to-linear(linear-to-circular), linear-to-linear polarization conversions.

  2. Perfect Optical Compensator With 1:1 Shutter Ratio Used For High Speed Camera

    NASA Astrophysics Data System (ADS)

    Zhihong, Rong

    1983-03-01

    An optical compensator used for high speed camera is described. The method of compensation, the analysis of the imaging quality and the result of experiment are introduced. The compensator consists of pairs of parallel mirrors. It can perform perfect compensation even at 1:1 shutter ratio. Using this compensator a high speed camera can be operated with no shutter and can obtain the same image sharpness as that of the intermittent camera. The advantages of this compensator are summarized as follows: . While compensating, the aberration correction of the objective would not be damaged. . There is no displacement and defocussing between the scanning image and the film in frame center during compensation. Increasing the exposure angle doesn't reduce the resolving power. . The compensator can also be used in the projector in place of the intermittent mechanism to practise continuous (non-intermittent) projection without shutter.

  3. The Federal Employees' Compensation Act.

    ERIC Educational Resources Information Center

    Nordlund, Willis J.

    1991-01-01

    The 1916 Federal Employees' Compensation Act is still the focal point around which the federal workers compensation program works today. The program has gone through many changes on its way to becoming a modern means of compensating workers for job-related injury, disease, and death. (Author)

  4. Deferred Compensation Becomes More Common

    ERIC Educational Resources Information Center

    June, Audrey Williams

    2006-01-01

    A key part of the compensation package for some college and university presidents is money that they do not receive in their paychecks. Formally known as deferred compensation, such payments can take many forms, including supplemental retirement pay, severance pay, or even bonuses. With large institutions leading the way, deferred compensation has…

  5. CGI delay compensation

    NASA Technical Reports Server (NTRS)

    Mcfarland, Richard E.

    1986-01-01

    Computer-generated graphics in real-time helicopter simulation produces objectionable scene-presentation time delays. In the flight simulation laboratory at Ames Research Center, it has been determined that these delays have an adverse influence on pilot performance during aggressive tasks such as nap-of-the-earth (NOE) maneuvers. Using contemporary equipment, computer-generated image (CGI) time delays are an unavoidable consequence of the operations required for scene generation. However, providing that magnitide distortions at higher frequencies are tolerable, delay compensation is possible over a restricted frequency range. This range, assumed to have an upper limit of perhaps 10 or 15 rad/sec, conforms approximately to the bandwidth associated with helicopter handling qualities research. A compensation algorithm is introduced here and evaluated in terms of tradeoffs in frequency responses. The algorithm has a discrete basis and accommodates both a large, constant transport delay interval and a periodic delay interval, as associated with asynchronous operations.

  6. High-resolution birefringence investigation of octylcyanobiphenyl (8CB): An upper bound on the discontinuity at the smectic-A to nematic phase transition

    NASA Astrophysics Data System (ADS)

    Çetinkaya, M. C.; Yildiz, S.; Özbek, H.; Losada-Pérez, P.; Leys, J.; Thoen, J.

    2013-10-01

    We report optical birefringence data by two different methods with high temperature resolution for octylcyanobiphenyl (8CB) near the smectic-A to nematic (Sm-A-N) phase transition temperature TAN. Within the resolution of our experiments, we find that the Sm-A-N phase transition is continuous. For a possible discontinuity in the orientational order parameter S(T) at TAN, we arrive at an upper limit of 0.0002, which is substantially smaller than other estimates in literature, but consistent with the value of 0.00008 derived from the upper limit of the latent heat from high-resolution adiabatic scanning calorimetry (ASC), which is itself consistent with the Halperin-Lubensky-Ma theory. The temperature derivative of the order parameter exhibits a power law divergence with a critical exponent that is consistent with the value α=0.31±0.03 for the specific heat capacity obtained by ASC.

  7. Contribution of counterions and degree of ionization for birefringence creation and relaxation kinetics parameters of PAH/PAZO films

    SciTech Connect

    Raposo, Maria Monteiro Timóteo, Ana Rita; Ribeiro, Paulo A.; Ferreira, Quirina; Botelho do Rego, Ana Maria

    2015-09-21

    Photo induced birefringent materials can be used to develop optical and conversion energy devices, and consequently, the study of the variables that influences the creation and relaxation of birefringence should be carefully analyzed. In this work, the parameters of birefringence creation and relaxation kinetics curves obtained on layer-by-layer (LBL) films, prepared from azo-polyectrolyte poly[1-[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and poly(allylamine hydrochloride)(PAH), are related with the presence of counterions and the degree of ionization of the polyelectrolytes. Those kinetics curves obtained on PAH/PAZO LBL films, prepared from PAH solutions with different pHs and maintaining the pH of PAZO solution constant at pH = 9, were analyzed taking into account the films composition which was characterized by X-ray photoelectron spectroscopy. The creation and relaxation birefringence curves are justified by two processes: one associated to local mobility of the azobenzene with a characteristic time 30 s and intensity constant and other associated with polymeric chains mobility with the characteristic time and intensity decreasing with pH. These results allow us to conclude that the birefringence creation process, associated to local mobility of azobenzenes is independent of the degree of ionization and of number of counterions or co-ions present while the birefringence creation process associated to mobility of chains have its characteristic time and intensity dependent of both degree of ionization and number of counterions. The birefringence relaxation processes are dependent of the degree of ionization. The analysis of the films composition revealed, in addition, the presence of a protonated secondary or tertiary amine revealing that PAZO may have positive charges and consequently a zwitterionic behavior.

  8. Contribution of counterions and degree of ionization for birefringence creation and relaxation kinetics parameters of PAH/PAZO films

    NASA Astrophysics Data System (ADS)

    Raposo, Maria; Ferreira, Quirina; Monteiro Timóteo, Ana Rita; Ribeiro, Paulo A.; do Rego, Ana Maria Botelho

    2015-09-01

    Photo induced birefringent materials can be used to develop optical and conversion energy devices, and consequently, the study of the variables that influences the creation and relaxation of birefringence should be carefully analyzed. In this work, the parameters of birefringence creation and relaxation kinetics curves obtained on layer-by-layer (LBL) films, prepared from azo-polyectrolyte poly[1-[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and poly(allylamine hydrochloride)(PAH), are related with the presence of counterions and the degree of ionization of the polyelectrolytes. Those kinetics curves obtained on PAH/PAZO LBL films, prepared from PAH solutions with different pHs and maintaining the pH of PAZO solution constant at pH = 9, were analyzed taking into account the films composition which was characterized by X-ray photoelectron spectroscopy. The creation and relaxation birefringence curves are justified by two processes: one associated to local mobility of the azobenzene with a characteristic time 30 s and intensity constant and other associated with polymeric chains mobility with the characteristic time and intensity decreasing with pH. These results allow us to conclude that the birefringence creation process, associated to local mobility of azobenzenes is independent of the degree of ionization and of number of counterions or co-ions present while the birefringence creation process associated to mobility of chains have its characteristic time and intensity dependent of both degree of ionization and number of counterions. The birefringence relaxation processes are dependent of the degree of ionization. The analysis of the films composition revealed, in addition, the presence of a protonated secondary or tertiary amine revealing that PAZO may have positive charges and consequently a zwitterionic behavior.

  9. Ground difference compensating system

    DOEpatents

    Johnson, Kris W.; Akasam, Sivaprasad

    2005-10-25

    A method of ground level compensation includes measuring a voltage of at least one signal with respect to a primary ground potential and measuring, with respect to the primary ground potential, a voltage level associated with a secondary ground potential. A difference between the voltage level associated with the secondary ground potential and an expected value is calculated. The measured voltage of the at least one signal is adjusted by an amount corresponding to the calculated difference.

  10. Corneal birefringence measured by spectrally resolved Mueller matrix ellipsometry and implications for non-invasive glucose monitoring.

    PubMed

    Westphal, Peter; Kaltenbach, Johannes-Maria; Wicker, Kai

    2016-04-01

    A good understanding of the corneal birefringence properties is essential for polarimetric glucose monitoring in the aqueous humor of the eye. Therefore, we have measured complete 16-element Mueller matrices of single-pass transitions through nine porcine corneas in-vitro, spectrally resolved in the range 300…1000 nm. These ellipsometric measurements have been performed at several angles of incidence at the apex and partially at the periphery of the corneas. The Mueller matrices have been decomposed into linear birefringence, circular birefringence (i.e. optical rotation), depolarization, and diattenuation. We found considerable circular birefringence, strongly increasing with decreasing wavelength, for most corneas. Furthermore, the decomposition revealed significant dependence of the linear retardance (in nm) on the wavelength below 500 nm. These findings suggest that uniaxial and biaxial crystals are insufficient models for a general description of the corneal birefringence, especially in the blue and in the UV spectral range. The implications on spectral-polarimetric approaches for glucose monitoring in the eye (for diabetics) are discussed.

  11. Corneal birefringence measured by spectrally resolved Mueller matrix ellipsometry and implications for non-invasive glucose monitoring

    PubMed Central

    Westphal, Peter; Kaltenbach, Johannes-Maria; Wicker, Kai

    2016-01-01

    A good understanding of the corneal birefringence properties is essential for polarimetric glucose monitoring in the aqueous humor of the eye. Therefore, we have measured complete 16-element Mueller matrices of single-pass transitions through nine porcine corneas in-vitro, spectrally resolved in the range 300…1000 nm. These ellipsometric measurements have been performed at several angles of incidence at the apex and partially at the periphery of the corneas. The Mueller matrices have been decomposed into linear birefringence, circular birefringence (i.e. optical rotation), depolarization, and diattenuation. We found considerable circular birefringence, strongly increasing with decreasing wavelength, for most corneas. Furthermore, the decomposition revealed significant dependence of the linear retardance (in nm) on the wavelength below 500 nm. These findings suggest that uniaxial and biaxial crystals are insufficient models for a general description of the corneal birefringence, especially in the blue and in the UV spectral range. The implications on spectral-polarimetric approaches for glucose monitoring in the eye (for diabetics) are discussed. PMID:27446644

  12. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...

  13. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...

  14. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...

  15. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...

  16. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...

  17. Surrogacy, Compensation, and Legal Parentage: Against the Adoption Model.

    PubMed

    van Zyl, Liezl; Walker, Ruth

    2015-09-01

    Surrogate motherhood is treated as a form of adoption in many countries: the birth mother and her partner are presumed to be the parents of the child, while the intended parents have to adopt the baby once it is born. Other than compensation for expenses related to the pregnancy, payment to surrogates is not permitted. We believe that the failure to compensate surrogate mothers for their labour as well as the significant risks they undertake is both unfair and exploitative. We accept that introducing payment for surrogates would create a significant tension in the adoption model. However, we recommend rejecting the adoption model altogether rather than continuing to prohibit compensation to surrogates.

  18. Computer-controlled near-infrared polarimeter featuring a new type of stress-birefringent modulator

    SciTech Connect

    West, S.C.; Schmidt, G.D.; Pawlicki, R.; Rieke, G.H.; Angel, R.P.

    1988-07-01

    The development of an astronomical polarimeter for the spectral region 1-2.6 microns is reported. The instrument incorporates a fused silica stress-birefringent modulator capable of producing square-wave polarimetric modulation of over 95 percent efficiency from dc to 2 Hz and quarter-wave retardation at wavelengths up to the K photometric bands. Possible applications of this instrument are examined, including the search for comparatively weak magnetic fields in white dwarf accretion binaries, the study of the nature of polarization in faint active galactic nuclei, and near-IR survey of isolated magnetic white dwarfs. 32 references.

  19. Design of infrared imaging birefringent interferometers for small-UAVs and handheld scanning systems (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Pola Fossi, Armande; Ferrec, Yann; Guerineau, Nicolas; Roux, Nicolas; Kling, Emmanuel; Sauer, Hervé

    2016-10-01

    Hyperspectral imaging from unmanned aerial vehicles arouses a growing interest, as well for agriculture management as pollution monitoring or security purposes. Most of current instruments are in the visible or near infrared spectral range, but the midwave or longwave infrared may also be interesting. Among the available solutions for compact imaging spectrometers in this spectral range, static imaging Fourier transform spectrometers are well adapted, thanks to the absence of moving part, a 2D snapshot imaging, which can be useful for image registration, and a high flux collection efficiency. To reach a high compactness compliant with small UAVs, birefringent interferometers are good candidates. Indeed, they can be roughly seen as a plate which comes in front of the camera lens. We propose here firstly to expose the design rules of such instruments in the midwave or longwave infrared. The first point is about the material: highly birefringent uniaxial crystals materials are not so common in this spectral domain. For MWIR spectral imagers, TeO2 or YVO4 can be used. For LWIR instruments, current materials, like ZnGeP2 or AgGaS2 are available, but their birefringence is not so high. Calomel is a promising way, but not still available. The second point consists in defining the type of interferometer, like Savart interferometer, Wollaston interferometer, or other designs. To help this choice, we have developed a software tool to calculate the propagation of plane waves in a stack of birefringent plates. This allows us to choose the optimal assembly of the plates to reach the required spectral resolution. We will then present experimental results obtained with a MWIR prototype. This prototype, called SIBI,, works in the [3.7µm-4.8µm] spectral domain (or [2050cm 1-2700cm 1]), with a spectral resolution about 13cm 1. A first ground campaign was led in June 2015, on Mount Etna (Italy). This campaign was useful to emphasize the assets and drawbacks of this instrument

  20. Repeating pulsed magnet system for axion-like particle searches and vacuum birefringence experiments

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Inada, T.; Namba, T.; Asai, S.; Kobayashi, T.; Matsuo, A.; Kindo, K.; Nojiri, H.

    2016-10-01

    We have developed a repeating pulsed magnet system which generates magnetic fields of about 10 T in a direction transverse to an incident beam over a length of 0.8 m with a repetition rate of 0.2 Hz. Its repetition rate is by two orders of magnitude higher than usual pulsed magnets. It is composed of four low resistance racetrack coils and a 30 kJ transportable capacitor bank as a power supply. The system aims at axion-like particle searches with a pulsed light source and vacuum birefringence measurements. We report on the details of the system and its performances.

  1. Reversible change of birefringence sign by optical and thermal processes in an azobenzene polymethacrylate

    SciTech Connect

    Rodriguez, F.J.; Sanchez, C.; Villacampa, B.; Alcala, R.; Cases, R.; Millaruelo, M.; Oriol, L.

    2005-01-10

    Birefringence ({delta}n) induced in an azobenzene polymethacrylate by combination of biphotonic and thermotropic processes has subsequently been changed in sign by room temperature illumination with linearly polarized blue light. The sign of {delta}n can be reversed again, by simply heating up the film to 100 deg. C. This change of {delta}n between positive and negative values can be repeated several times. Besides, by appropriate choice of film thickness and blue light irradiation conditions the same absolute value for positive and negative {delta}n values can be obtained.

  2. Crystalline perfection, birefringence and laser damage threshold properties of piperidinium p-hydroxybenzoate

    SciTech Connect

    Sudhahar, S.; Zahid, I. MD; Kumar, M. Krishna; Kumar, R. Mohan

    2015-06-24

    Piperidinium p-hydroxybenzoate (PPHB) crystal was grown by slow evaporation method. Single crystal X-ray diffraction studies confirm that PPHB crystallizes in monoclinic crystal system with noncentrosymmetric space group Cc. The crystalline perfection of the grown crystal was evaluated by using high resolution X-ray diffractometry. UV-Visible transmission and birefringence studies were employed on the grown PPHB crystal. The laser induced damage threshold value was estimated using Nd:YAG laser. Thermal behavior of PPHB crystal has been investigated by TG-DTA analyses. Etching studies have been performed to assess the growth pattern of PPHB crystal.

  3. Pump Spectral Bandwidth, Birefringence, and Entanglement in Type-II Parametric Down Conversion

    DOE PAGES

    Erenso, Daniel

    2009-01-01

    The twin photons produced by a type-II spontaneous parametric down conversion are well know as a potential source of photons for quantum teleportation due to the strong entanglement in polarization. This strong entanglement in polarization, however, depends on the spectral composition of the pump photon and the nature of optical isotropy of the crystal. By exact numerical calculation of the concurrence, we have shown that how pump photons spectral width and the birefringence nature of the crystal directly affect the degree of polarization entanglement of the twin photons.

  4. Numerical analysis of stress distribution in embedded highly birefringent PANDA fibers

    NASA Astrophysics Data System (ADS)

    Lesiak, Piotr; Woliński, Tomasz

    2015-09-01

    The paper presents numerical analysis compared with experimental data of influence of polymerization shrinkage on highly birefringent (HB) PANDA optical fibers embedded in a composite material. Since polymerization is a chemical process consisting in combining single molecules in a macromolecular compound [1], principal directions of the polymerization shrinkage depend on a number of the composite layers associated with this process. In this paper a detailed analysis of the piezo-optic effects occurring in HB optical fibers before and after the lamination process answers the question to what extent a degree of the material degradation can be properly estimated.

  5. Stretched exponential kinetics for photoinduced birefringence in azo dye doped PVA films

    NASA Astrophysics Data System (ADS)

    Yang, Hye Ri; Kim, Eun Ju; Lee, Sang Jo; Kim, Gun Yeup; Kwak, Chong Hoon

    2009-05-01

    We fabricated azo dye (methylorange) doped poly vinyl alcohol (MO/PVA) thin films and measured the photoinduced birefringence (PIB) kinetics for several pump beam intensities and for various MO concentrations by using the pump-probe technique. A novel approach to explain the transient behaviors of the photoinduced anisotropy is presented by employing an empirical stretched exponential time response in the course of the trans-cis-trans photoisomerization of azo molecules and is compared with the experimental data, showing excellent agreement. The stretched exponent is estimated to be β = 0.34 ± 0.04, revealing amorphous nature of the MO/PVA system.

  6. Effect of grain size on optical transmittance of birefringent polycrystalline ceramics

    NASA Astrophysics Data System (ADS)

    Wen, Tzu-Chien

    Polycrystalline ceramics are increasingly used for fabricating windows and domes for the mid infra-red regime (3-5 mum) due to their superior durability as compared to glass and the lower cost of their fabrication and finishing relative to single crystals without significant compromise in optical properties. Due to the noncubic structure, MgF2 and Al2O3 are birefringent ceramics. Birefringence causes scatter of light at the grain boundaries and diminishes in-line transmittance and optical performance. This dissertation presents experimental results and analyses of the grain-size and wavelength dependence of the in-line transmittance of polycrystalline MgF2 and Al2O3. Chapter 2 presents experimental results and analyses of light transmission in polycrystalline MgF2 as a function of the mean grain size at different wavelengths. The scattering coefficient of polycrystalline MgF 2 increased linearly with the mean grain size and inversely with the square of the wavelength of light. These trends are consistent with theoretical models based on both a limiting form of the Raleigh-Gans-Debye theory of particle scattering and light retardation theories that take refractive-index variations along the light path. Chapter 3 investigates the applicability of particle light scattering theories to light attenuation in birefringent polycrystalline ceramics by measuring light transmittance in a model two-phase system. The system consisted of microspheres of silica dispersed in a solution of glycerol in water. It was found that RGD theory showed the systematic deviation for higher particle volume fraction (φ > 0.2) and larger particle size (d p > 1 mum). This result suggested that light scattering models based on single particle scattering are unlikely to provide viable physical explanation for the effect of grain size on light transmittance in birefringent polycrystalline ceramics due to the high volume fraction in dense polycrystalline ceramics. Chapter 4 analyses light

  7. Polarization sensitive localization based super-resolution microscopy with a birefringent wedge

    NASA Astrophysics Data System (ADS)

    Sinkó, József; Gajdos, Tamás; Czvik, Elvira; Szabó, Gábor; Erdélyi, Miklós

    2017-03-01

    A practical method has been presented for polarization sensitive localization based super-resolution microscopy using a birefringent dual wedge. The measurement of the polarization degree at the single molecule level can reveal the chemical and physical properties of the local environment of the fluorescent dye molecule and can hence provide information about the sub-diffraction sized structure of biological samples. Polarization sensitive STORM imaging of the F-Actins proved correlation between the orientation of fluorescent dipoles and the axis of the fibril.

  8. Single negative birefringence in stacked spoof plasmon metasurfaces by prism experiment.

    PubMed

    Beruete, M; Navarro-Cía, M; Falcone, F; Campillo, I; Sorolla, M

    2010-03-01

    We report negative and positive refraction in a prism made of stacked perforated thin surfaces for s and p polarization, respectively. By corrugating the subwavelength slits of a free-standing periodic arrangement, geometrically induced surface-plasmon-like currents are excited and transmission is allowed under s polarization (electric-field vector parallel to the slit). When several of those corrugated slit arrays are subwavelength stacked, the stack behaves as a negative effective index medium (because of double negativity) under s polarization, whereas it behaves as a positive effective index medium under p polarization. The birefringence has been confirmed by the usual wedge experiment in the millimeter-wave range.

  9. Enhanced transverse load sensitivity by using a highly birefringent photonic crystal fiber with larger air holes on one axis.

    PubMed

    Kim, Hyun-Min; Kim, Tae-Hun; Kim, Bongkyun; Chung, Youngjoo

    2010-07-10

    We report on a transverse load sensor with enhanced sensitivity through the use of a birefringent interferometer based on a highly birefringent photonic crystal fiber (HB-PCF). The transverse load sensitivity can be enhanced by using a fabricated HB-PCF having larger air holes on its fast axis. The transverse load sensitivity was measured to be high: approximately 2.17 nm/(N/cm). The temperature-induced undesirable effects can be ignored because transmission outputs of our HB-PCF were stable with the change of the temperature. The sensing probe can be compact because of its high birefringence with the order of 10(-3) and no bending loss.

  10. Dispersion of group and phase modal birefringence in elliptical-core fiber measured by white-light spectral interferometry.

    PubMed

    Hlubina, Petr; Martynkien, Tadeusz; Urbańczyk, Waclaw

    2003-11-03

    We present a white-light spectral interferometric technique employing a low-resolution spectrometer for measurement of the dispersion of the group and phase modal birefringence in an elliptical-core optical fi ber over a wide spectral range. The technique utilizes a tandem con fi guration of a Michelson interferometer and the optical fi ber to record a series of spectral interferograms and to measure the equalization wavelengths as a function of the optical path difference in the Michelson interferometer, or equivalently, the wavelength dependence of the group modal birefringence in the optical fi ber. Applying a polynomial fi t to the measured data, the wavelength dependence of the phase modal birefringence can also be determined.

  11. 26 CFR 1.414(s)-1 - Definition of compensation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 5 2010-04-01 2010-04-01 false Definition of compensation. 1.414(s)-1 Section 1.414(s)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(s)-1 Definition...

  12. Distributed temperature sensing based on birefringence effect on transient Brillouin grating in a polarization-maintaining photonic crystal fiber.

    PubMed

    Dong, Yongkang; Bao, Xiaoyi; Chen, Liang

    2009-09-01

    We demonstrate a time-domain distributed temperature sensing based on birefringence effect on transient Brillouin grating (TBG) in a polarization-maintaining photonic crystal fiber (PM-PCF), which uses two short pump pulses (2 ns) to excite a TBG and a long probe pulse (6 ns) to map the transient Brillouin grating spectrum (TBGS) associated with the birefringence. The 2 ns pump pulses defines a spatial resolution of 20 cm and a temperature measurement range of a few hundred degrees Celsius, and the long probe pulse provides a narrow TBGS with a temperature resolution of 0.07 degrees C.

  13. Smectic A Filled Birefringent Elements and Fast Switching Twisted Dual Frequency Nematic Cells Used for Digital Light Deflection

    NASA Technical Reports Server (NTRS)

    Pishnyak, Oleg; Golovin, Andrii; Kreminskia, Liubov; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.; Lavrentovich, Oleg D.

    2006-01-01

    We describe the application of smectic A (SmA) liquid crystals for beam deflection. SmA materials can be used in digital beam deflectors (DBDs) as fillers for passive birefringent prisms. SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Fast rotation of the incident light polarization in DBDs is achieved by an electrically switched 90 twisted nematic (TN) cell.

  14. Birefringence and second harmonic generation on tendon collagen following red linearly polarized laser irradiation.

    PubMed

    Silva, Daniela Fátima Teixeira; Gomes, Anderson Stevens Leonidas; de Campos Vidal, Benedicto; Ribeiro, Martha Simões

    2013-04-01

    Regarding the importance of type I collagen in understanding the mechanical properties of a range of tissues, there is still a gap in our knowledge of how proteins perform such work. There is consensus in literature that the mechanical characteristics of a tissue are primarily determined by the organization of its molecules. The purpose of this study was to characterize the organization of non-irradiated and irradiated type I collagen. Irradiation was performed with a linearly polarized HeNe laser (λ = 632.8 nm) and characterization was undertaken using polarized light microscopy to investigate the birefringence and second harmonic generation to analyze nonlinear susceptibility. Rats received laser irradiation (P = 6.0 mW, I = 21.2 mW/cm(2), E ≈ 0.3 J, ED = 1.0 J/cm(2)) on their healthy Achilles tendons, which after were extracted to prepare the specimens. Our results show that irradiated samples present higher birefringence and greater non-linear susceptibility than non-irradiated samples. Under studied conditions, we propose that a red laser with polarization direction aligned in parallel to the tendon long axis promotes further alignment on the ordered healthy collagen fibrils towards the electric field incident. Thus, prospects for biomedical applications for laser polarized radiation on type I collagen are encouraging since it supports greater tissue organization.

  15. Modeling optical behavior of birefringent biological tissues for evaluation of quantitative polarized light microscopy

    NASA Astrophysics Data System (ADS)

    van Turnhout, Mark C.; Kranenbarg, Sander; van Leeuwen, Johan L.

    2009-09-01

    Quantitative polarized light microscopy (qPLM) is a popular tool for the investigation of birefringent architectures in biological tissues. Collagen, the most abundant protein in mammals, is such a birefringent material. Interpretation of results of qPLM in terms of collagen network architecture and anisotropy is challenging, because different collagen networks may yield equal qPLM results. We created a model and used the linear optical behavior of collagen to construct a Jones or Mueller matrix for a histological cartilage section in an optical qPLM train. Histological sections of tendon were used to validate the basic assumption of the model. Results show that information on collagen densities is needed for the interpretation of qPLM results in terms of collagen anisotropy. A parameter that is independent of the optical system and that measures collagen fiber anisotropy is introduced, and its physical interpretation is discussed. With our results, we can quantify which part of different qPLM results is due to differences in collagen densities and which part is due to changes in the collagen network. Because collagen fiber orientation and anisotropy are important for tissue function, these results can improve the biological and medical relevance of qPLM results.

  16. Birefringence by a smoothly inhomogeneous locally isotropic medium: Three-dimensional case

    NASA Astrophysics Data System (ADS)

    Savchenko, A. Yu.; Zel'dovich, B. Ya.

    1994-09-01

    The propagation problem for electromagnetic waves in a smoothly inhomogeneous locally isotropic medium, which was considered for a layered case in V. S. Liberman and B. Ya. Zel'dovich, Phys. Rev. E 49, 2389 (1994) is generalized to a three-dimensional situation. Effective ``linear'' birefringence, i.e., coherent transformation of a right circularly polarized wave into the left one with the amplitude ~(λ/a) is predicted and calculated. It corresponds to the corrections δn~(λ/a)2 to the effective refractive index tensor, where a>>λ is the size of smooth inhomogeneity. An important feature is that linear birefringence appears only in the presence of gradients of impedance ρ(r)= √μ(r)/ɛ(r) , whereas the gradients of refractive index n(r)= √ɛ(r)μ(r) are not necessary in a general three-dimensional case. This is in contrast with a layered medium (one-dimensional case) where the net effect was proportional to the product (d lnρ/dz)(d lnn/dz).

  17. Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon

    SciTech Connect

    Ganapati, Vidya; Schoenfelder, Stephan; Castellanos, Sergio; Oener, Sebastian; Koepge, Ringo; Sampson, Aaron; Marcus, Matthew A.; Lai, Barry; Morhenn, Humphrey; Hahn, Giso; Bagdahn, Joerg; Buonassisi1, Tonio

    2010-05-05

    This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: {beta}-SiC and {beta}-Si{sub 3}N{sub 4} microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing.

  18. An Elimination Method of Temperature-Induced Linear Birefringence in a Stray Current Sensor

    PubMed Central

    Xu, Shaoyi; Li, Wei; Xing, Fangfang; Wang, Yuqiao; Wang, Ruilin; Wang, Xianghui

    2017-01-01

    In this work, an elimination method of the temperature-induced linear birefringence (TILB) in a stray current sensor is proposed using the cylindrical spiral fiber (CSF), which produces a large amount of circular birefringence to eliminate the TILB based on geometric rotation effect. First, the differential equations that indicate the polarization evolution of the CSF element are derived, and the output error model is built based on the Jones matrix calculus. Then, an accurate search method is proposed to obtain the key parameters of the CSF, including the length of the cylindrical silica rod and the number of the curve spirals. The optimized results are 302 mm and 11, respectively. Moreover, an effective factor is proposed to analyze the elimination of the TILB, which should be greater than 7.42 to achieve the output error requirement that is not greater than 0.5%. Finally, temperature experiments are conducted to verify the feasibility of the elimination method. The results indicate that the output error caused by the TILB can be controlled less than 0.43% based on this elimination method within the range from −20 °C to 40 °C. PMID:28282953

  19. Irregular spin angular momentum transfer from light to small birefringent particles

    SciTech Connect

    Rothmayer, M.; Tierney, D.; Schmitzer, H.; Frins, E.; Dultz, W.

    2009-10-15

    The transfer of spin angular momentum from photons to small particles is a key experiment of quantum physics. The particles rotate clockwise or counterclockwise depending on the polarization of the light beam which holds them in an optical trap. We show that even perfectly disk shaped particles will in general not rotate with a constant angular speed. The particles will periodically accelerate and decelerate their rotational motion due to a varying spin angular momentum transfer from the light. Using the Poincare sphere we derive the equation of motion of a birefringent plate and verify the results by measuring the time dependent rotation of small crystals of Hg(I) iodide and 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) in the trap of polarized optical tweezers. For small ellipticities of the polarized light in the tweezers the plate stops in a fixed orientation relative to the axes of the light ellipse. We discuss the origin of this halt and propose an application of small birefringent plates as self-adjusting optical retarders in micro-optics.

  20. Numerical simulation of polarization-resolved second-harmonic microscopy in birefringent media

    NASA Astrophysics Data System (ADS)

    Gusachenko, Ivan; Schanne-Klein, Marie-Claire

    2013-11-01

    Polarization-resolved second-harmonic microscopy has recently emerged as a valuable technique for in situ imaging of collagen structure in tissues. Nevertheless, collagen-rich tissues such as tendon, ligament, skin dermis, bone, cornea, or artery exhibit a heterogeneous and anisotropic architecture that results in complex optical properties. While experimental evidence of polarization distortions has been reported in various tissues, the physics of second-harmonic imaging within such tissues is not fully understood yet. In this work, we performed numerical simulations of polarization-resolved second-harmonic generation in a strongly focused regime within a birefringent tissue. We show that vectorial components due to strong focusing have a rather small effect on the measurement of the second-harmonic tensorial response, while birefringence and optical dispersion may affect these measurements dramatically. We show indeed that a difference in the focal field distribution for ordinary and extraordinary waves results in different phase-matching conditions, which strongly affects the relative efficacy of second-harmonic generation for different polarizations. These results are of great interest for extracting reliable quantitative parameters from second-harmonic images.

  1. High-magnification super-resolution FINCH microscopy using birefringent crystal lens interferometers

    NASA Astrophysics Data System (ADS)

    Siegel, Nisan; Lupashin, Vladimir; Storrie, Brian; Brooker, Gary

    2016-12-01

    Fresnel incoherent correlation holography (FINCH) microscopy is a promising approach for high-resolution biological imaging but has so far been limited to use with low-magnification, low-numerical-aperture configurations. We report the use of in-line incoherent interferometers made from uniaxial birefringent α-barium borate (α-BBO) or calcite crystals that overcome the aberrations and distortions present with previous implementations that employed spatial light modulators or gradient refractive index lenses. FINCH microscopy incorporating these birefringent elements and high-numerical-aperture oil immersion objectives could outperform standard wide-field fluorescence microscopy, with, for example, a 149 nm lateral point spread function at a wavelength of 590 nm. Enhanced resolution was confirmed with sub-resolution fluorescent beads. Taking the Golgi apparatus as a biological example, three different proteins labelled with GFP and two other fluorescent dyes in HeLa cells were resolved with an image quality that is comparable to similar samples captured by structured illumination microscopy.

  2. Annealing of linear birefringence in single-mode fiber coils - Application to optical fiber current sensors

    NASA Technical Reports Server (NTRS)

    Tang, Dingding; Rose, A. H.; Day, G. W.; Etzel, Shelley M.

    1991-01-01

    Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850 C. The residual birefringence and induced loss are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of 8.4 x 10 to the -5th/K over the range from -75 to 145 C has been demonstrated. This is approximately 20 percent greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about 1.6 + 10 to the -4th/K over the range from -20 to 120 C has also been demonstrated.

  3. Linear birefringence and dichroism measurement in oil-based Fe3O4 magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Lin, Jing-Fung; Wang, Chia-Hung; Lee, Meng-Zhe

    2013-04-01

    To prepare dispersed Fe3O4 magnetic nanoparticles (MNPs), we adopt a co-precipitation method and consider surfactant amount, stirring speed, dispersion mode, and molar ratio of Fe3+/Fe2+. Via transmission electronic microscopy and X-ray diffractometry, we characterize the dispersibility and size of the products and determine the appropriate values of experimental parameters. The stirring speed is 1000 rpm in titration. There is simultaneous ultrasonic vibration and mechanical stirring in the titration and surface coating processes. The surfactant amount of oleic acid is 1.2 ml for molar ratios of Fe3+/Fe2+ as 1.7:1, 1.8:1, and 1.9:1. The average diameters of these Fe3O4 MNPs are 11 nm, and the ratios of saturation magnetization for these MNPs to that of bulk magnetite range from 45% to 65%, with remanent magnetization close to zero and low coercivity. Above all, the linear birefringence and dichroism measurements of the kerosene-based ferrofluid (FF) samples are investigated by a Stokes polarimeter. The influences of particle size distribution and magnetization in the birefringence and dichroism measurements of FFs are discussed.

  4. The system spatial-frequency filtering of birefringence images of human blood layers

    NASA Astrophysics Data System (ADS)

    Ushenko, A. G.; Boychuk, T. M.; Mincer, O. P.; Angelsky, P. O.; Bodnar, N. B.; Oleinichenko, B. P.; Bizer, L. I.

    2013-09-01

    Among various opticophysical methods [1 - 3] of diagnosing the structure and properties of the optical anisotropic component of various biological objects a specific trend has been singled out - multidimensional laser polarimetry of microscopic images of the biological tissues with the following statistic, correlative and fractal analysis of the coordinate distributions of the azimuths and ellipticity of polarization in approximating of linear birefringence polycrystalline protein networks [4 - 10]. At the same time, in most cases, experimental obtaining of tissue sample is a traumatic biopsy operation. In addition, the mechanisms of transformation of the state of polarization of laser radiation by means of the opticoanisotropic biological structures are more varied (optical dichroism, circular birefringence). Hereat, real polycrystalline networks can be formed by different types, both in size and optical properties of biological crystals. Finally, much more accessible for an experimental investigation are biological fluids such as blood, bile, urine, and others. Thus, further progress of laser polarimetry can be associated with the development of new methods of analysis and processing (selection) of polarization- heterogeneous images of biological tissues and fluids, taking into account a wider set of mechanisms anisotropic mechanisms. Our research is aimed at developing experimental method of the Fourier polarimetry and a spatialfrequency selection for distributions of the azimuth and the ellipticity polarization of blood plasma laser images with a view of diagnosing prostate cancer.

  5. Multiple scattering of polarized light in turbid birefringent media: a Monte Carlo simulation.

    PubMed

    Otsuki, Soichi

    2016-07-20

    Multiple scattering of polarized light in a birefringent turbid plane medium was studied using a Monte Carlo simulation. The reduced effective scattering Mueller matrix obtained in the simulation was factorized in two dimensions using the Lu-Chipman decomposition, yielding polarization parameters that exhibited dependences on the azimuth and the radial distance around the illumination point. We propose a double-scattering model for the propagation of polarized photons in turbid infinite plane media. When the birefringence slow axis is along the azimuth of 90° on the plane surface, the retardance becomes the largest negative along the azimuth of 0° and the largest positive along the azimuth of 90° and increases with increasing the azimuth from 0° to 90°. This azimuthal dependence may result from the overlap of the contributions from the light propagations vertical to, and lateral along, the plane surface. Thus, the dependences on the azimuth and the radial distance of the polarization parameters, such as the retardance, its orientation, optical rotation, and the depolarization coefficients, are correctly predicted.

  6. Macroscopic birefringence in liquid crystals from novel cyanobacterial polysaccharide with an extremely high molecular weight

    NASA Astrophysics Data System (ADS)

    Okajima-Kaneko, Maiko; Hayasaka-Kaneko, Daisaku; Miyazato, Shinji; Kaneko, Tatsuo

    2007-05-01

    We report an efficient method for extraction of anionic polysaccharides (PS) from cyanobacteria, Aphanothece sacrum; we used a hot alkaline solution (0.01 N NaOH) as an elution solvent in the first step of the extraction and isopropanol as a precipitation solvent in the last step. Thin fibers of PS were obtained at a high yield (50-80 % to the weight of the raw cyanobacterial sample). The spectroscopy and elemental analyses indicated the PS contains fucose, uronic acids (14.2 % by a carbazole-sulfuric acid method), a sugar unit containing amides. The solution of PS with a concentration of 1 wt% showed a very high viscosity (80 000cps) implying a high molecular weight, and a strong macroscopic birefringence with a texture typical of nematic liquid crystals was confirmed by crossed-polarizing microscopy (more than 0.5 wt%). The PS from A. sacrum may form a special structure rigid-rod enough to show LC phase and macroscopic birefringence.

  7. Density and birefringence of a highly stable α,α,β-trisnaphthylbenzene glass

    NASA Astrophysics Data System (ADS)

    Dalal, Shakeel S.; Sepúlveda, A.; Pribil, Greg K.; Fakhraai, Zahra; Ediger, M. D.

    2012-05-01

    Spectroscopic ellipsometry has been used to understand the properties of α,α,β-trisnaphthylbenzene (ααβ-TNB) glasses vapor-deposited at a substrate temperature of 295 K (0.85 Tg). In a single temperature ramping experiment, a range of properties of the as-deposited glass can be measured, including density, fictive temperature, onset temperature, thermal expansion coefficient, and birefringence. The vapor-deposited ααβ-TNB glass is 1.3% more dense than the ordinary glass prepared by cooling at 1 K/min, is found to be birefringent, has a fictive temperature 35 K below that of the ordinary glass, and an onset temperature 20 K above that of the ordinary glass. The thermal expansion coefficient of the vapor-deposited ααβ-TNB glass is 14% lower than that of the ordinary glass, indicating that lower portions of the potential energy landscape have more harmonic potential minima than the parts accessible to the ordinary glass.

  8. Novel pressure sensor by diode-pumped birefringent Nd:YAG dual-frequency laser

    NASA Astrophysics Data System (ADS)

    Huang, Chunning; Li, Yan; Zhang, Shulian; Guo, Hui

    2002-09-01

    The prototype of a novel sensor based on laser frequency splitting technology is presented in this paper and the results of a series of experiments are reported. A scheme of the novel pressure sensor by diode-pumped birefringent Nd:YAG dual-frequency laser is brought forward. As a result of the stress birefringence the laser's longitudinal mode is split to two with frequency difference. Both the theoretical analysis and the experiments indicate that there is a direct ratio relation between the frequency difference and the pressure imposed on the Nd:YAG crystal. Therefore when the external pressure is sensed by the Nd:YAG dual-frequency laser and the beat frequency is measured by the frequency counter, the pressure value can be obtained from the magnitude of the beat frequency. The laser can operate under single mode or complex modes with little error to the experiment results. Some research work under different pumping ways is finished and it indicates that the beat frequency has little relation with pumping ways. The experiment has a good linearity (R greater than 0.999) with satisfied precision, sensitivity (5.27 MHz/kPa) and stability, which provides a good academic and experimental foundation for further research.

  9. [Temperature-dependent optical activity and birefringence study of D-alanine single crystal].

    PubMed

    Li, Zong-Sheng; Gong, Yan; Wang, Wen-Qing; Du, Wei-Min

    2006-02-01

    The measurement of the anisotropy of optical acitivity and birefringence is one of the most important clues to studying physical properties of a biaxial crystal of D-alanine. In order to investigate a second-order phase transition predicted by A. Salam between two states of D-alanine, the behavior of birefringence and optical activity is useful for the phenomenological approach to the transition mechanism. The optical activity as a peculiar quantity can respond to the modulation of the crystal lattice and to the change in the bonding nature of constituent atoms. In the present paper, the authors use the PEM-90 photoelastic modulator to study the conformation change of D-alanine at the temperature ranging from 220 to 290 K. The temperature dependence of I(2f)/I(dc) showed that the conformation of D-alanine molecule in single crystal changed around 250 K. The obtained results provide an obvious evidence of optical rotation phase transition predicted by Salam.

  10. Active Wireline Heave Compensation for Ocean Drilling

    NASA Astrophysics Data System (ADS)

    Goldberg, D.; Liu, T.; Swain, K.; Furman, C.; Iturrino, G. J.

    2014-12-01

    , with additional advantages that include upgradable compensation control software and the capability for continued assessment under varying environmental conditions. Future integration of downhole cable dynamics as an input feedback could further improve CE during logging operations.­

  11. Temperature compensated photovoltaic array

    DOEpatents

    Mosher, Dan Michael

    1997-11-18

    A temperature compensated photovoltaic module (20) comprised of a series of solar cells (22) having a thermally activated switch (24) connected in parallel with several of the cells (22). The photovoltaic module (20) is adapted to charge conventional batteries having a temperature coefficient (TC) differing from the temperature coefficient (TC) of the module (20). The calibration temperatures of the switches (24) are chosen whereby the colder the ambient temperature for the module (20), the more switches that are on and form a closed circuit to short the associated solar cells (22). By shorting some of the solar cells (22) as the ambient temperature decreases, the battery being charged by the module (20) is not excessively overcharged at lower temperatures. PV module (20) is an integrated solution that is reliable and inexpensive.

  12. Temperature compensated photovoltaic array

    DOEpatents

    Mosher, D.M.

    1997-11-18

    A temperature compensated photovoltaic module comprises a series of solar cells having a thermally activated switch connected in parallel with several of the cells. The photovoltaic module is adapted to charge conventional batteries having a temperature coefficient differing from the temperature coefficient of the module. The calibration temperatures of the switches are chosen whereby the colder the ambient temperature for the module, the more switches that are on and form a closed circuit to short the associated solar cells. By shorting some of the solar cells as the ambient temperature decreases, the battery being charged by the module is not excessively overcharged at lower temperatures. PV module is an integrated solution that is reliable and inexpensive. 2 figs.

  13. Alternative Teacher Compensation: A Primer

    ERIC Educational Resources Information Center

    Koppich, Julia E.; Rigby, Jessica

    2009-01-01

    This policy primer is designed to provide base-line information about new forms of teacher pay that are emerging around the country, to support the local conversations and negotiations that will lead to the development of innovative compensation systems. It identifies reasons why teacher compensation is high on local, state, and federal policy…

  14. Compensation: The Impact of Policy.

    ERIC Educational Resources Information Center

    Morrell, Louis R.

    1994-01-01

    Complexity of employee compensation policy is examined as it applies to colleges and universities. It is argued that sound compensation policy helps the institution attract and retain qualified, skilled employees. New approaches that shift the focus from job to employee are outlined, and their implications for institutions of higher education are…

  15. 28 CFR Appendix C to Part 79 - Radiation Exposure Compensation Act Offset Worksheet-On Site Participants

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Radiation Exposure Compensation Act... JUSTICE (CONTINUED) CLAIMS UNDER THE RADIATION EXPOSURE COMPENSATION ACT Pt. 79, App. C Appendix C to Part 79—Radiation Exposure Compensation Act Offset Worksheet—On Site Participants Radiation...

  16. 28 CFR Appendix C to Part 79 - Radiation Exposure Compensation Act Offset Worksheet-On Site Participants

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Radiation Exposure Compensation Act... JUSTICE (CONTINUED) CLAIMS UNDER THE RADIATION EXPOSURE COMPENSATION ACT Pt. 79, App. C Appendix C to Part 79—Radiation Exposure Compensation Act Offset Worksheet—On Site Participants Radiation...

  17. 28 CFR Appendix C to Part 79 - Radiation Exposure Compensation Act Offset Worksheet-On Site Participants

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Radiation Exposure Compensation Act... JUSTICE (CONTINUED) CLAIMS UNDER THE RADIATION EXPOSURE COMPENSATION ACT Pt. 79, App. C Appendix C to Part 79—Radiation Exposure Compensation Act Offset Worksheet—On Site Participants Radiation...

  18. 28 CFR Appendix C to Part 79 - Radiation Exposure Compensation Act Offset Worksheet-On Site Participants

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Radiation Exposure Compensation Act... JUSTICE (CONTINUED) CLAIMS UNDER THE RADIATION EXPOSURE COMPENSATION ACT Pt. 79, App. C Appendix C to Part 79—Radiation Exposure Compensation Act Offset Worksheet—On Site Participants Radiation...

  19. 28 CFR Appendix C to Part 79 - Radiation Exposure Compensation Act Offset Worksheet-On Site Participants

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Radiation Exposure Compensation Act... JUSTICE (CONTINUED) CLAIMS UNDER THE RADIATION EXPOSURE COMPENSATION ACT Pt. 79, App. C Appendix C to Part 79—Radiation Exposure Compensation Act Offset Worksheet—On Site Participants Radiation...

  20. New Perspectives on Compensation Strategies for the Out-of-School Time Workforce. Working Paper Series. Report.

    ERIC Educational Resources Information Center

    Morgan, Gwen; Harvey, Brooke

    Noting that the quality, continuity, and stability of out-of-school time programs depend, in part, on the presence of a well-trained and fairly compensated staff, this paper examines the unique characteristics of the out-of-school time workforce that contribute to inadequate compensation and explores workforce compensation from an economic…

  1. Workers' compensation law: an overview.

    PubMed

    Yorker, B

    1994-09-01

    1. The workers' compensation system provides benefits to workers who are injured or made ill in the course of employment or their dependents regardless of fault. 2. The current workers' compensation laws benefit both the employer and the employee; however, workers' compensation is an exclusive remedy which bars recovery through a negligence lawsuit. 3. Workers' compensation regulations interact with other federal statutes such as the Americans With Disabilities Act and the Family Medical Leave Act. 4. Workers' compensation covers occupational injuries and occupational diseases, which may include cumulative trauma and mental stress claims. Nurses may be instrumental in evaluating and planning for an injured employee's return to work and occasionally in detecting fraudulent claims.

  2. Compensation of thermal lensing effect and TEM00-mode generation in cw Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Jang, Won Kweon; Shin, Seong Sook; Lee, Sungman

    2003-11-01

    The thermally induced birefringence was successfully compensated by placing a quarter-wave plate into a plane parallel Nd:YAG laser resonator of 130 W output power in multi-mode. The optimal conversion efficiency was 38.3% and the slope efficiency was 58.2% with output coupler of 80% reflectance, and the beam quality factor of M2 was 26.7. For higher modes elimination, an aperture of 1.5 mm in diameter was inserted into resonator, and M2 was decreased to 1.8. However, the insertion of quarter-wave plate made an additional improvement to 1.15 of M2 value by alternating their radial and tangential polarization directions every bouncing feedback. We report the experimental results with theoretical analysis for high power solid-state laser fabrication with better beam quality.

  3. Trying to compensate. Latest ranking of CEO compensation finds stock options still key to pay as experts monitor for effects of SEC rule changes.

    PubMed

    Galloro, Vince; Vesely, Rebecca; Zigmond, Jessica

    2007-07-30

    Despite past outcries from critics, stock options continue to play a starring, albeit smaller, role in compensation for CEOs at top companies, based on research by accounting professor Steven Balsam, left. Read about the 30 healthcare executives who brought home the biggest pay packages in our annual ranking of CEOs' compensation.

  4. Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

    PubMed Central

    Villiger, Martin; Lorenser, Dirk; McLaughlin, Robert A.; Quirk, Bryden C.; Kirk, Rodney W.; Bouma, Brett E.; Sampson, David D.

    2016-01-01

    Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex vivo imaging of breast tumour samples revealed excellent contrast between lowly birefringent malignant regions, and stromal tissue, which is rich in oriented collagen and exhibits higher birefringence, as confirmed with co-located histology. The ability to clearly differentiate between tumour and uninvolved stroma based on intrinsic contrast could prove decisive for the intraoperative assessment of tumour margins. PMID:27364229

  5. Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

    NASA Astrophysics Data System (ADS)

    Villiger, Martin; Lorenser, Dirk; McLaughlin, Robert A.; Quirk, Bryden C.; Kirk, Rodney W.; Bouma, Brett E.; Sampson, David D.

    2016-07-01

    Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex vivo imaging of breast tumour samples revealed excellent contrast between lowly birefringent malignant regions, and stromal tissue, which is rich in oriented collagen and exhibits higher birefringence, as confirmed with co-located histology. The ability to clearly differentiate between tumour and uninvolved stroma based on intrinsic contrast could prove decisive for the intraoperative assessment of tumour margins.

  6. Efficiency of four-wave mixing between orthogonally polarized linear waves and solitons in a birefringent fiber

    NASA Astrophysics Data System (ADS)

    Mas Arabí, C.; Bessin, F.; Kudlinski, A.; Mussot, A.; Skryabin, D.; Conforti, M.

    2016-12-01

    We analyze the interaction between orthogonally polarized solitons and dispersive waves via four-wave mixing in a birefringent fiber. We calculate analytically the efficiency of the phase-sensitive scattering between orthogonally polarized solitons and dispersive waves. Experiments performed by using a photonic crystal fiber perfectly match the analytical predictions.

  7. All-solid birefringent hybrid photonic crystal fiber based interferometric sensor for measurement of strain and temperature

    NASA Astrophysics Data System (ADS)

    Gu, Bobo; Yuan, Wu; Zhang, A. Ping; Bang, Ole

    2011-12-01

    A highly sensitive fiber-optic interferometric sensor based on an all-solid birefringent hybrid photonic crystal fiber (PCF) is demonstrated for measuring strain and temperature. A strain sensitivity of ~23.8 pm/μɛ and a thermal sensitivity of ~- 1.12 nm/°C are demonstrated in the experiment.

  8. STUDIES ON THE ANOMALOUS VISCOSITY AND FLOW-BIREFRINGENCE OF PROTEIN SOLUTIONS

    PubMed Central

    Lawrence, A. S. C.; Miall, Margaret; Needham, Joseph; Shen, Shih-Chang

    1944-01-01

    1. An extensive investigation has been made of protein particle shape using the methods of flow-birefringence and anomalous viscosity measurement in the coaxial cell. 2. As a result of investigations on a number of proteins, it is concluded that they may be divided into four groups. Group A consists of those which show flow-anomaly both in the bulk phase and in the surface film. These also show flow-birefringence in the bulk phase. Examples: tobacco mosaic disease virus nucleoprotein; myosin. Though corpuscular proteins, they have elongated particles before denaturation. Group B consists of those which show flow-anomaly only (in the first instance) in the surface film, and no flow-birefringence in the bulk phase. They are probably close to spherical in shape in solution, but form elongated particles as they denature in the surface film. After this process has been completed, they may show flow-anomaly also in the bulk phase. Some proteins show flow-anomaly in the surface film immediately it forms, others only show it after a certain time has elapsed for the building up of the film. We designate the former as group B1 and the latter as group B2. Group B1, immediate surface film flow-anomaly. Examples: serum euglobulin, amphibian embryo euglobulin b. Group B2, slowly appearing surface film flow-anomaly. After the film has once been fully formed and then dispersed by shaking, the solution may have the properties of that of a protein in group B1; i.e., anomalous flow in the film may occur immediately on testing in the viscosimeter. Examples: avian ovalbumin, amphibian embryo pseudoglobulin. Group C consists of those proteins which show flow-anomaly neither in the bulk phase nor in the surface film, under the conditions used by us. They are probably close to spherical in shape. Examples: insulin, methaemoglobin, amphibian embryo euglobulin c, mucoproteins. 3. The theoretical significance of protein fibre molecules, whether native or formed by denaturation in the living

  9. [Vestibular compensation studies]. [Vestibular Compensation and Morphological Studies

    NASA Technical Reports Server (NTRS)

    Perachio, Adrian A. (Principal Investigator)

    1996-01-01

    The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging.

  10. Separating the Siamese twins: using a π-shifted Sagnac interferometer to control the relative weight/influence of circular and linear birefringence on the loop transmission facilitating their measurement.

    PubMed

    Want-Gauthier, Eric; Golub, Ilya

    2017-03-01

    We demonstrate a novel method to measure circular birefringence (CB) and linear birefringence (LB) present simultaneously in the device under study. By using a π-shifted Sagnac interferometer, the scheme eliminates the dependence on incoming polarization and on the orientation angle of the linear birefringence. Moreover, due to different handedness symmetry/response of CB and LB to counter-propagating waves, the technique allows us to control the relative influence of the two birefringences leading to a requirement of only two measurements to determine both of them. Thus, comparing to Stokes polarimeters and other methods, our scheme has advantages when characterizing media containing both birefringences. Our findings are experimentally confirmed.

  11. Compensated pulsed alternator

    DOEpatents

    Weldon, William F.; Driga, Mircea D.; Woodson, Herbert H.

    1980-01-01

    This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

  12. Growth and birefringence studies of semi organic non-linear optical LHB single crystal

    NASA Astrophysics Data System (ADS)

    Jayaramakrishnan, V.; Prasanyaa, T.; Haris, M.; Bhoopathi, G.

    2015-02-01

    In the last few decades nonlinear optical materials are getting attention in the field of optical data storage, telecommunication, second harmonic generation (SHG) and optical signal processing, etc. In the present work we are reporting the single crystal growth of L-Histidine with hydro-bromic acid. The L-Histidine bromide (LHB) single crystals have been harvested from the solution in a span of 34 days by adopting slow cooling solution growth technique. The grown crystals have been subjected to powder X-ray diffraction studies to identify the cell parameters and structure. The crystalline perfection has been defined by rocking curve (HRXRD) analysis. Optical transmission spectra reveal the optical properties of the grown crystals. The Modified channel spectrum (MCS) method has been adopted for the study of spectral dependence of linear birefringence over the wavelength range 480-620 nm. The second harmonic generation efficiency was tested by using Kurtz and Perry method, keeping KDP as reference.

  13. Generation of a train of ultrashort pulses from a compact birefringent crystal array

    NASA Astrophysics Data System (ADS)

    Dromey, B.; Zepf, M.; Landreman, M.; O'Keeffe, K.; Robinson, T.; Hooker, S. M.

    2007-08-01

    A linear array of n calcite crystals is shown to allow the generation of a high contrast (>10:1) train of 2n high energy (>100 μJ) pulses from a single ultrafast laser pulse. Advantage is taken of the pulse-splitting properties of a single birefringent crystal, where an incident laser pulse can be split into two pulses with orthogonal polarizations and equal intensity, separated temporally in proportion to the thickness of the crystal traversed and the difference in refractive indices of the two optic axes. In the work presented here an array of seven calcite crystals of sequentially doubled thickness is used to produce a train of 128 pulses, each of femtosecond duration. Readily versatile properties such as the number of pulses in the train and variable mark-space ratio are realized from such a setup.

  14. Femtosecond laser direct-write waveplates based on stress-induced birefringence.

    PubMed

    McMillen, Ben; Athanasiou, Christos; Bellouard, Yves

    2016-11-28

    The use of femtosecond lasers to introduce controlled stress states has recently been demonstrated in silica glass. We use this technique, in combination with chemical etching, to generate and control stress-induced birefringence over a well-defined region of interest, demonstrating direct-write wave plates with precisely tailored retardance levels. This tailoring enables the fabrication of laser-written polarization optics that can be tuned to any wavelength for which silica is transparent, and with a clear aperture free of any laser modifications. Using this approach, we achieve sufficient retardance to act as a quarter-wave plate. The stress distribution within the clear aperture is analyzed and modeled, providing a generic template that can be used as a set of design rules for laser-machined polarization devices.

  15. A quantitative collagen fibers orientation assessment using birefringence measurements: Calibration and application to human osteons

    PubMed Central

    Spiesz, Ewa M.; Kaminsky, Werner; Zysset, Philippe K.

    2011-01-01

    Even though mechanical properties depend strongly on the arrangement of collagen fibers in mineralized tissues, it is not yet well resolved. Only a few semi-quantitative evaluations of the fiber arrangement in bone, like spectroscopic techniques or circularly polarized light microscopy methods are available. In this study the out-of-plane collagen arrangement angle was calibrated to the linear birefringence of a longitudinally fibered mineralized turkey leg tendon cut at variety of angles to the main axis. The calibration curve was applied to human cortical bone osteons to quantify the out-of-plane collagen fibers arrangement. The proposed calibration curve is normalized to sample thickness and wavelength of the probing light to enable a universally applicable quantitative assessment. This approach may improve our understanding of the fibrillar structure of bone and its implications on mechanical properties. PMID:21970947

  16. Hygroscopic study of hydroxypropylcellulose : Structure and strain-induced birefringence of capillary bridges.

    PubMed

    Godinho, M H; Pieranski, P; Sotta, P

    2016-09-01

    The hygroscopic method developed previously for studies of lyotropic liquid crystals is used for the first time in experiments with millimetric capillary bridges made of a hydroxypropylcellulose/water mixture. Composition of such very small samples is controlled via humidity of the surrounding air. By a slow and well-controlled drying of initially isotropic samples, the isotropic/anisotropic phase transition is crossed and polydomain pseudo-isotropic capillary bridges are prepared. Kept in an atmosphere of constant humidity, these bridges are stretched and the strain-induced birefringence [Formula: see text] n is measured as a function of the draw ratio [Formula: see text] . The variation of [Formula: see text] n with [Formula: see text] is interpreted in terms of an affine uniaxial deformation of the initial pseudo-isotropic texture.

  17. Interrogation cradle and insertable containment fixture for detecting birefringent microcrystals in bile

    DOEpatents

    Darrow, Chris; Seger, Tino

    2003-09-30

    A transparent flow channel fluidly communicates a fluid source and a collection reservoir. An interrogating light beam passes through a first polarizer having a first plane of polarization. The flow channel is orthogonal to the light beam. The light beam passes through a fluid sample as it flows through the flow channel, and is then filtered through a second polarizer having a second plane of polarization rotated 90.degree. from the first plane of polarization. An electronic photo-detector is aligned with the light beam, and signals the presence of birefringent microcrystals in the fluid sample by generating voltage pulses. A disposable containment fixture includes the flow channel and the collection reservoir. The fixture is adapted for removable insertion into an interrogation cradle that includes optical and data processing components. The cradle rigidly positions the centerline of the flow channel orthogonal to the light beam.

  18. Spatiotemporal solitons in birefringent media near the zero-dispersion point

    NASA Astrophysics Data System (ADS)

    Fitrakis, E. P.; Nistazakis, H. E.; Malomed, B. A.; Frantzeskakis, D. J.; Kevrekidis, P. G.

    2006-09-01

    We present a new species of spatiotemporal solitons (STSs, alias light bullets) that may be formed through the interaction of two waves with different polarizations in a birefringent Kerr medium near the point at which the second-order group-velocity dispersion (GVD) vanishes in the presence of a uniform cw background in one component. The analysis is based on an asymptotic reduction of the two cross-phase, modulation-coupled (2+1)-dimensional nonlinear Schrödinger equations, incorporating the third-order GVD to the Davey-Stewartson (DS) systems of type I or II for the self-defocusing and focusing Kerr nonlinearity, respectively. The STSs are then predicted following the pattern of the dromion solutions of the DS-I system and lump solitons of the DS-II system. Strictly speaking, the solitons are unstable, but they are shown to be stable objects on experimentally relevant scales of the propagation distance.

  19. An ab initio investigation of the Buckingham birefringence of furan, thiophene, and selenophene in cyclohexane solution

    NASA Astrophysics Data System (ADS)

    Rizzo, Antonio; Frediani, Luca; Ruud, Kenneth

    2007-10-01

    Using a recently developed quadratic response methodology for the calculation of frequency-dependent third-order properties of molecules in solution, we investigate the Buckingham birefringence of furan, thiophene, and selenophene in cyclohexane solution. These systems are chosen since accurate experimental data are available, allowing for a direct comparison of experimental observations with our theoretical estimates. Our model for describing the solvent effects is based on a dielectric continuum approach for the solvent, and uses a molecule-shaped cavity. Our results show qualitatively different Buckingham constants and effective quadrupole centers calculated with and without the solvent, and only when the solvent is included are the qualitative trends observed experimentally reproduced. It is demonstrated that a significant part of this effect arises from the geometry relaxation of the molecules in the solvent.

  20. Mid-infrared dispersive waves generation in a birefringent fluorotellurite microstructured fiber

    NASA Astrophysics Data System (ADS)

    Yao, Chuanfei; Zhao, Zhipeng; Jia, Zhixu; Li, Qing; Hu, Minglie; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

    2016-09-01

    Tunable mid-infrared dispersive waves are generated in a birefringent fluorotellurite microstructured fiber (FTMF) pumped by a 1560 nm femtosecond fiber laser. The FTMF have two zero-dispersion wavelengths (ZDWs) for each polarization axis. The second ZDWs for the fast and slow axes of the FTMF are 2224 and 2042 nm, respectively. As the pump laser is polarized along the fast (or slow) axis of the FTMF, tunable mid-infrared dispersive waves from 2680 to 2725 nm (or from 2260 to 2400 nm) are generated in the FTMF when the Raman soliton meets the second zero-dispersion wavelength of the fast (or slow) axis with increasing the pump power. Our results show that the designed FTMFs are promising nonlinear media for generating tunable mid-infrared light sources.

  1. Dynamical decoupling in optical fibers: Preserving polarization qubits from birefringent dephasing

    NASA Astrophysics Data System (ADS)

    Roy Bardhan, Bhaskar; Anisimov, Petr M.; Gupta, Manish K.; Brown, Katherine L.; Jones, N. Cody; Lee, Hwang; Dowling, Jonathan P.

    2012-02-01

    One of the major challenges in quantum computation has been to preserve the coherence of a quantum system against dephasing effects of the environment. The information stored in photon polarization, for example, is quickly lost due to such dephasing, and it is crucial to preserve the input states when one tries to transmit quantum information encoded in the photons through a communication channel. We propose a dynamical decoupling sequence, to protect photonic qubits from dephasing, by integrating wave plates into optical fiber at prescribed locations. We simulate random birefringent noise along realistic lengths of optical fiber and study preservation of polarization qubits through such fibers enhanced with Carr-Purcell-Meiboom-Gill (CPMG) dynamical decoupling. This technique can maintain photonic qubit coherence at high fidelity, making a step toward achieving scalable and useful quantum communication with photonic qubits.

  2. Manipulating full photonic band gaps in two dimensional birefringent photonic crystals.

    PubMed

    Proietti Zaccaria, Remo; Verma, Prabhat; Kawaguchi, Satoshi; Shoji, Satoru; Kawata, Satoshi

    2008-09-15

    The probability to realize a full photonic band gap in two-dimensional birefringent photonic crystals can be readily manipulated by introducing symmetry reduction or air holes in the crystal elements. The results lie in either creation of new band gaps or enlargement of existing band gaps. In particular, a combination of the two processes produces an effect much stronger than a simple summation of their individual contributions. Materials with both relatively low refractive index (rutile) and high refractive index (tellurium) were considered. The combined effect of introduction of symmetry reduction and air holes resulted in a maximum enlargement of the band gaps by 8.4% and 20.2%, respectively, for the two materials.

  3. Mueller-matrices polarization selection of two-dimensional linear and circular birefringence images

    NASA Astrophysics Data System (ADS)

    Ushenko, V. A.; Zabolotna, N. I.; Pavlov, S. V.; Burcovets, D. M.; Novakovska, O. Yu.

    2013-12-01

    The work consists of investigation results of diagnostic efficiency of a new azimuthally stable Mueller-matrix method of analysis of laser autofluorescence coordinate distributions of biological tissues histological sections. A new model of generalized optical anisotropy of biological tissues protein networks is proposed in order to define the processes of laser autofluorescence. The influence of complex mechanisms of both phase anisotropy (linear birefringence and optical activity) and linear (circular) dichroism is taken into account. The interconnections between the azimuthally stable Mueller-matrix elements characterizing laser autofluorescence and different mechanisms of optical anisotropy are determined. The complex statistic, correlation and fractal analysis of coordinate distributions of such Mueller-matrix rotation invariants is proposed. Thereupon the quantitative criteria (statistic moments of the 1st to the 4th order, correlation moment, fratal parameters) of differentiation of histological sections of uterus wall tumor - group 1 (polypus) and group 2 (adenocarcinoma) are estimated.

  4. Temperature independent torsion sensor based on modal interferometry in ultra high-birefringent photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Frazão, Orlando; Jesus, C.; Baptista, José M.; Santos, José L.; Roy, Philippe

    2009-10-01

    A fiber-optic sensor for torsion measurement, based on a two-LP-mode operation in ultra high birefringent photonic crystal fiber (PCF) is described. The structure of the photonic crystal fiber presents two large asymmetric holes adjacent to the core fiber. When linearly polarized light is injected in x or in y directions, respectively, two different interferometers can be obtained. In one of these cases, as torsion is applied to the ultra Hi-Bi PCF a beat between the two interferometers is formed due to the simultaneous excitation of the two polarization states. The detection technique to read the torsion sensor is based on the analysis of the Fast Fourier Transform (FFT), which is an alternative and simple solution. The sensor exhibited reduced sensitivity to temperature and also to strain.

  5. Relationship between birefringence and neurotubule density in the primate retinal nerve fiber layer

    NASA Astrophysics Data System (ADS)

    Aranibar, R. G.; Kemp, N. J.; Dwelle, J. C.; Byers, S. E.; Markey, M. K.; Milner, T. E.; Rylander, H. G.

    2007-02-01

    The relationship between retinal nerve fiber layer (RNFL) birefringence (Δn) and neurotubule density (NTD, retinal ganglion cell (RGC) neurotubules per unit RNFL area) was investigated by correlating measurements of these two parameters in 1 eye of a healthy cynomolgus monkey. Phase retardation per unit depth (PR/UD, proportional to Δn) was measured at 5.6-15 ° intervals around the optic nerve head (ONH) with an enhanced polarization-sensitive optical coherence tomography (EPS-OCT) instrument. Transverse tissue sections containing 3 RGC nerve fiber bundles from each peripapillary RNFL octant were imaged with a transmission electron microscope (TEM). Morphological measurements taken in TEM images were used by a novel algorithm to estimate NTD. Registered PR/UD and NTD data were then correlated using single- and multi-level models, yielding correlation coefficients in the range 0.49 <= r <= 0.61 (0.06 <= P <= 0.11). It was found that in order for the single-level correlation coefficient (r = 0.61) to be statistically significant (P <= 0.05) and powerful (Power >= 80%), NTD measurements in at least 16, rather than 8, RNFL sectors were needed. Interestingly, a single-level correlation coefficient of r = 0.81 (P = 0.01) was calculated between octant-averaged PR/UD and RGC axoplasmic area (A x, axon area less non-cytoskeletal organelle area) mode. A x represents a RGC axon's neurotubule-inhabitable area. Intuitively, a strong relationship should exist between A x and neurotubule number if neurotubules provide the primary structural support for RGC axons and structural requirements are the same in all RGC axons. If this relationship exists, error resulting from NTD estimation methods or preservation artifacts may have caused lower observed correlations of PR/UD with NTD than with A x mode, and more accurate methods of measuring in vivo NTD may be required to determine an accurate relationship between RNFL birefringence and NTD.

  6. Postural Compensation for Unilateral Vestibular Loss

    PubMed Central

    Peterka, Robert J.; Statler, Kennyn D.; Wrisley, Diane M.; Horak, Fay B.

    2011-01-01

    Postural control of upright stance was investigated in well-compensated, unilateral vestibular loss (UVL) subjects compared to age-matched control subjects. The goal was to determine how sensory weighting for postural control in UVL subjects differed from control subjects, and how sensory weighting related to UVL subjects’ functional compensation, as assessed by standardized balance and dizziness questionnaires. Postural control mechanisms were identified using a model-based interpretation of medial–lateral center-of-mass body-sway evoked by support-surface rotational stimuli during eyes-closed stance. The surface-tilt stimuli consisted of continuous pseudorandom rotations presented at four different amplitudes. Parameters of a feedback control model were obtained that accounted for each subject’s sway response to the surface-tilt stimuli. Sensory weighting factors quantified the relative contributions to stance control of vestibular sensory information, signaling body-sway relative to earth-vertical, and proprioceptive information, signaling body-sway relative to the surface. Results showed that UVL subjects made significantly greater use of proprioceptive, and therefore less use of vestibular, orientation information on all tests. There was relatively little overlap in the distributions of sensory weights measured in UVL and control subjects, although UVL subjects varied widely in the amount they could use their remaining vestibular function. Increased reliance on proprioceptive information by UVL subjects was associated with their balance being more disturbed by the surface-tilt perturbations than control subjects, thus indicating a deficiency of balance control even in well-compensated UVL subjects. Furthermore, there was some tendency for UVL subjects who were less able to utilize remaining vestibular information to also indicate worse functional compensation on questionnaires. PMID:21922014

  7. Power Compensation for ICRF Heating in EAST

    NASA Astrophysics Data System (ADS)

    Chen, Gen; Qin, Chengming; Mao, Yuzhou; Zhao, Yanping; Yuan, Shuai; Zhang, Xinjun

    2016-08-01

    The source system covering a working frequency range of 24 MHz to 70 MHz with a total maximum output power of 12 MW has already been fabricated for Ion Cyclotron Range of Frequency (ICRF) heating in EAST from 2012. There are two continuous wave (CW) antennas consisting of four launching elements each fed by a separate 1.5 MW transmitter. Due to the strong mutual coupling among the launching elements, the injection power for launching elements should be imbalance to keep the k‖ (parallel wave number) spectrum of the launcher symmetric for ICRF heating. Cross power induced by the mutual coupling will also induce many significant issues, such as an uncontrollable phase of currents in launching elements, high voltage standing wave ratio (VSWR), and impedance mismatching. It is necessary to develop a power compensation system for antennas to keep the power balance between the feed points. The power balance system consists of two significant parts: a decoupler and phase control. The decoupler helps to achieve ports isolation to make the differential phase controllable and compensate partly cross power. After that, the differential phase of 0 or π will keep the power balance of two feed points completely. The first power compensation system consisting of four decouplers was assembled and tested for the port B antenna at the working frequency of 35 MHz. With the application of the power compensation system, the power balance, phase feedback control, and voltage standing wave ratio (VSWR) had obviously been improved in the 2015 EAST campaign. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2015GB101001) and National Natural Science Foundation of China (Nos. 11575237, 11375235, 11375236)

  8. Delay compensation in integrated communication and control systems. II - Implementation and verification

    NASA Technical Reports Server (NTRS)

    Luck, Rogelio; Ray, Asok

    1990-01-01

    The implementation and verification of the delay-compensation algorithm are addressed. The delay compensator has been experimentally verified at an IEEE 802.4 network testbed for velocity control of a DC servomotor. The performance of the delay-compensation algorithm was also examined by combined discrete-event and continuous-time simulation of the flight control system of an advanced aircraft that uses the SAE (Society of Automotive Engineers) linear token passing bus for data communications.

  9. Temperature-compensating dc restorer

    NASA Technical Reports Server (NTRS)

    Thomas, H. M.

    1980-01-01

    Circuit provides stable references restoration in addition to temperature compensation. Possible TV monitor applications include traffic and security surveillance systems, where cameras are subject to environmental extremes, as in unheated warehouses or outdoors.

  10. 7 CFR 929.33 - Expenses and compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Expenses and compensation. 929.33 Section 929.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  11. 7 CFR 929.33 - Expenses and compensation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Expenses and compensation. 929.33 Section 929.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  12. 7 CFR 929.33 - Expenses and compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Expenses and compensation. 929.33 Section 929.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  13. 7 CFR 929.33 - Expenses and compensation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Expenses and compensation. 929.33 Section 929.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  14. 7 CFR 929.33 - Expenses and compensation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Expenses and compensation. 929.33 Section 929.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  15. Connecting Compensation and Evaluation to Build Professional Development

    ERIC Educational Resources Information Center

    Morey, Natalie

    2008-01-01

    At Maryknoll School in Honolulu, Hawaii, a Coalition of Essential Schools affiliate since 1995, teachers and administrators are continually working on the issue of building capacity for leadership. This has led to implementation of an alternative to the traditional salary scale. The Compensation Committee, made up of teachers, administrators, and…

  16. 7 CFR 930.33 - Expenses and compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Expenses and compensation. 930.33 Section 930.33 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE...

  17. 47 CFR 76.60 - Compensation for carriage.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Compensation for carriage. 76.60 Section 76.60 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND... bear the costs associated with delivering a good quality signal or a baseband video signal to...

  18. 47 CFR 76.60 - Compensation for carriage.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Compensation for carriage. 76.60 Section 76.60 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND... bear the costs associated with delivering a good quality signal or a baseband video signal to...

  19. 47 CFR 76.60 - Compensation for carriage.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Compensation for carriage. 76.60 Section 76.60 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND... bear the costs associated with delivering a good quality signal or a baseband video signal to...

  20. 47 CFR 76.60 - Compensation for carriage.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Compensation for carriage. 76.60 Section 76.60 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND... bear the costs associated with delivering a good quality signal or a baseband video signal to...