Radio polarization properties of quasars and active galaxies at high redshifts

NASA Astrophysics Data System (ADS)

Vernstrom, T.; Gaensler, B. M.; Vacca, V.; Farnes, J. S.; Haverkorn, M.; O'Sullivan, S. P.

2018-04-01

We present the largest ever sample of radio polarization properties for z > 4 sources, with 14 sources having significant polarization detections. Using wide-band data from the Karl G. Jansky Very Large Array, we obtained the rest-frame total intensity and polarization properties of 37 radio sources, nine of which have spectroscopic redshifts in the range 1 ≤ z ≤ 1.4, with the other 28 having spectroscopic redshifts in the range 3.5 ≤ z ≤ 6.21. Fits are performed for the Stokes I and fractional polarization spectra, and Faraday rotation measures are derived using rotation measure synthesis and QU fitting. Using archival data of 476 polarized sources, we compare high-redshift (z > 3) source properties to a 15 GHz rest-frame luminosity matched sample of low-redshift (z < 3) sources to investigate if the polarization properties of radio sources at high redshifts are intrinsically different than those at low redshift. We find a mean of the rotation measure absolute values, corrected for Galactic rotation, of 50 ± 22 rad m-2 for z > 3 sources and 57 ± 4 rad m-2 for z < 3. Although there is some indication of lower intrinsic rotation measures at high-z possibly due to higher depolarization from the high-density environments, using several statistical tests we detect no significant difference between low- and high-redshift sources. Larger samples are necessary to determine any true physical difference.

Revealing the Faraday depth structure of radio galaxy NGC 612 with broad-band radio polarimetric observations

NASA Astrophysics Data System (ADS)

Kaczmarek, J. F.; Purcell, C. R.; Gaensler, B. M.; Sun, X.; O'Sullivan, S. P.; McClure-Griffiths, N. M.

2018-05-01

We present full-polarization, broad-band observations of the radio galaxy NGC 612 (PKS B0131-637) from 1.3 to 3.1 GHz using the Australia Telescope Compact Array. The relatively large angular scale of the radio galaxy makes it a good candidate with which to investigate the polarization mechanisms responsible for the observed Faraday depth structure. By fitting complex polarization models to the polarized spectrum of each pixel, we find that a single polarization component can adequately describe the observed signal for the majority of the radio galaxy. While we cannot definitively rule out internal Faraday rotation, we argue that the bulk of the Faraday rotation is taking place in a thin skin that girts the polarized emission. Using minimum energy estimates, we find an implied total magnetic field strength of 4.2 μG.

Parsec-scale Faraday rotation and polarization of 20 active galactic nuclei jets

NASA Astrophysics Data System (ADS)

Kravchenko, E. V.; Kovalev, Y. Y.; Sokolovsky, K. V.

2017-05-01

We perform polarimetry analysis of 20 active galactic nuclei jets using the very long baseline array at 1.4, 1.6, 2.2, 2.4, 4.6, 5.0, 8.1, 8.4 and 15.4 GHz. The study allowed us to investigate linearly polarized properties of the jets at parsec scales: distribution of the Faraday rotation measure (RM) and fractional polarization along the jets, Faraday effects and structure of Faraday-corrected polarization images. Wavelength dependence of the fractional polarization and polarization angle is consistent with external Faraday rotation, while some sources show internal rotation. The RM changes along the jets, systematically increasing its value towards synchrotron self-absorbed cores at shorter wavelengths. The highest core RM reaches 16 900 rad m-2 in the source rest frame for the quasar 0952+179, suggesting the presence of highly magnetized, dense media in these regions. The typical RM of transparent jet regions has values of an order of a hundred rad m-2. Significant transverse RM gradients are observed in seven sources. The magnetic field in the Faraday screen has no preferred orientation, and is observed to be random or regular from source to source. Half of the sources show evidence for the helical magnetic fields in their rotating magneto-ionic media. At the same time jets themselves contain large-scale, ordered magnetic fields and tend to align its direction with the jet flow. The observed variety of polarized signatures can be explained by a model of spine-sheath jet structure.

Polarization Angle Calibration and B-Mode Characterization with the BICEP and Keck Array CMB Telescopes

NASA Astrophysics Data System (ADS)

Bullock, Eric

Since its discovery in 1964, the Cosmic Microwave Background (CMB) has led to widespread acceptance of the Big Bang cosmological paradigm as an explanation for the evolution of the Universe. However, this paradigm does not explain the origin of the initial conditions, leading to such issues as the "horizon problem" and "flatness problem." In the early 1980's, the inflationary paradigm was introduced as a possible source for the initial conditions. This theory postulates that the Universe underwent a period of exponential expansion within a tiny fraction of a second after the beginning. Such an expansion is predicted to inject a stochastic background of gravitational waves that could imprint a detectable B-mode (curl-like) signal in the polarization of the CMB. It is this signal that the family of telescopes used by the B ICEP1, BICEP2, and Keck Array collaborations were designed to detect. These telescopes are small aperture, on-axis, refracting telescopes. We have used the data from these telescopes, particularly BICEP2 and the Keck Array, to place the tightest constraints, as of March 2016, on the tensor-to-scalar ratio of the CMB of r 0.05 < 0.07. In this dissertation, we provide an overview of the Keck Array telescopes and analysis of the data. We also investigate, as the main focus of this dissertation, a device we call the Dielectric Sheet Calibrator (DSC) that is used to measure the polarization angles of our detectors as projected on the sky. With these measurements, we gain the potential to separate the polarization rotation effects of parity-violating physics, such as cosmic birefringence, from a systematic uncertainty on our detectors' polarization angles. Current calibration techniques for polarization sensitive CMB detectors claim an accuracy of +/-0.5°, which sets a limit for determining the usefulness of the DSC. Through a series of consistency tests on a single Keck Array receiver, we demonstrate a statistical uncertainty on the DSC measurements of +/-0.03° and estimate a systematic uncertainty of +/-0.2°. which meets the minimum goal. We also conclude that there is no conflict between the DSC-derived polarization angles of this single receiver and the rotation derived from that receiver's CMB data under the hypothesis of no cosmic birefringence.

Giant optical activity in quasi-2D planar nanostructures

NASA Astrophysics Data System (ADS)

Kuwata-Gonokami, Makoto; Saito, Nobuyoshi; Ino, Yusuke; Konishi, Kuniaki; Kauranen, Martti; Jefimovs, Konstantins; Vallius, Tuomas; Turunen, Jari; Svirko, Yuri P.

2006-01-01

Planar chirality can lead to interesting polarization effects whose interpretation has invoked possible violation of reciprocity and time reversality. We show that a quasi-two-dimensional array consisting of gold nanoparticles with no symmetry plane and having sub-wavelength periodicity and thickness exhibits giant specific rotation (~10 4 °/mm) at normal incidence. The rotation is the same for light incident on the front and back sides of the sample. Such reciprocity manifests three-dimensionality of the structure arising from the asymmetry of light-plasmon coupling at the air-metal and substrate-metal interfaces of the structure. The structures thus enable nanoscale polarization control but violate no symmetry principle.

Faraday rotation at low frequencies: magnetoionic material of the large FRII radio galaxy PKS J0636-2036

NASA Astrophysics Data System (ADS)

O'Sullivan, S. P.; Lenc, E.; Anderson, C. S.; Gaensler, B. M.; Murphy, T.

2018-04-01

We present a low-frequency, broad-band polarization study of the FRII radio galaxy PKS J0636-2036 (z = 0.0551), using the Murchison Widefield Array (MWA) from 70 to 230 MHz. The northern and southern hotspots (separated by ˜14.5 arcmin on the sky) are resolved by the MWA (3.3 arcmin resolution) and both are detected in linear polarization across the full frequency range. A combination of Faraday rotation measure (RM) synthesis and broad-band polarization model fitting is used to constrain the Faraday depolarization properties of the source. For the integrated southern hotspot emission, two-RM-component models are strongly favoured over a single RM component, and the best-fitting model requires Faraday dispersions of approximately 0.7 and 1.2 rad m-2 (with a mean RM of ˜50 rad m-2). High-resolution imaging at 5 arcsec with the Australia Telescope Compact Array shows significant sub-structure in the southern hotspot and highlights some of the limitations in the polarization modelling of the MWA data. Based on the observed depolarization, combined with extrapolations of gas density scaling relations for group environments, we estimate magnetic field strengths in the intergalactic medium between ˜0.04 and 0.5 μG. We also comment on future prospects of detecting more polarized sources at low frequencies.

MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday Rotation in Parsec-scale AGN Jets

NASA Astrophysics Data System (ADS)

Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.; Aller, Hugh D.; Homan, Daniel C.; Kovalev, Yuri Y.; Pushkarev, Alexander B.; Savolainen, Tuomas

2012-10-01

We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure and the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal Faraday rotation is needed.

Split-Block Waveguide Polarization Twist for 220 to 325 GHz

NASA Technical Reports Server (NTRS)

Ward, John; Chattopadhyay, Goutam

2008-01-01

A split-block waveguide circuit that rotates polarization by 90 has been designed with WR-3 input and output waveguides, which are rectangular waveguides used for a nominal frequency range of 220 to 325 GHz. Heretofore, twisted rectangular waveguides equipped with flanges at the input and output have been the standard means of rotating the polarizations of guided microwave signals. However, the fabrication and assembly of such components become difficult at high frequency due to decreasing wavelength, such that twisted rectangular waveguides become impractical at frequencies above a few hundred gigahertz. Conventional twisted rectangular waveguides are also not amenable to integration into highly miniaturized subassemblies of advanced millimeter- and submillimeter-wave detector arrays now undergoing development. In contrast, the present polarization- rotating waveguide can readily be incorporated into complex integrated waveguide circuits such as miniaturized detector arrays fabricated by either conventional end milling of metal blocks or by deep reactive ion etching of silicon blocks. Moreover, the present split-block design can be scaled up in frequency to at least 5 THz. The main step in fabricating a splitblock polarization-rotating waveguide of the present design is to cut channels having special asymmetrically shaped steps into mating upper and lower blocks (see Figure 1). The dimensions of the steps are chosen to be consistent with the WR-3 waveguide cross section, which is 0.864 by 0.432 mm. The channels are characterized by varying widths with constant depths of 0.432, 0.324, and 0.216 mm and by relatively large corner radii to facilitate fabrication. The steps effect both a geometric transition and the corresponding impedance-matched electromagnetic-polarization transition between (1) a WR-3 rectangular waveguide oriented with the electric field vector normal to the block mating surfaces and (2) a corresponding WR-3 waveguide oriented with its electric field vector parallel to the mating surfaces of the blocks. A prototype has been built and tested. Figure 2 presents test results indicative of good performance over nearly the entire WR-3 waveguide frequency band.

Polarization-selective optical transmission through a plasmonic metasurface.

PubMed

Pelzman, Charles; Cho, Sang-Yeon

2015-06-22

We present the design, fabrication, and experimental characterization of a nanoslit-based metasurface that offers polarization-selective optical transmission for advanced imaging applications. The metasurface consists of an array of meta-atoms, constructed with two orthogonally coupled subwavelength apertures. Highly enhanced optical transmission was achieved by selective excitation of surface plasmon waves on the metasurface. By rotating the orientation of the linearly polarized incident beam, switching of enhanced optical transmission bands through the metasurface was experimentally demonstrated. This demonstration is a significant step towards developing advanced multispectral imaging devices.

Polarization-selective optical transmission through a plasmonic metasurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelzman, Charles; Cho, Sang-Yeon, E-mail: sangycho@nmsu.edu

2015-06-22

We present the design, fabrication, and experimental characterization of a nanoslit-based metasurface that offers polarization-selective optical transmission for advanced imaging applications. The metasurface consists of an array of meta-atoms, constructed with two orthogonally coupled subwavelength apertures. Highly enhanced optical transmission was achieved by selective excitation of surface plasmon waves on the metasurface. By rotating the orientation of the linearly polarized incident beam, switching of enhanced optical transmission bands through the metasurface was experimentally demonstrated. This demonstration is a significant step towards developing advanced multispectral imaging devices.

Constraining Polarized Foregrounds for EoR Experiments. II. Polarization Leakage Simulations in the Avoidance Scheme

NASA Astrophysics Data System (ADS)

Nunhokee, C. D.; Bernardi, G.; Kohn, S. A.; Aguirre, J. E.; Thyagarajan, N.; Dillon, J. S.; Foster, G.; Grobler, T. L.; Martinot, J. Z. E.; Parsons, A. R.

2017-10-01

A critical challenge in the observation of the redshifted 21 cm line is its separation from bright Galactic and extragalactic foregrounds. In particular, the instrumental leakage of polarized foregrounds, which undergo significant Faraday rotation as they propagate through the interstellar medium, may harmfully contaminate the 21 cm power spectrum. We develop a formalism to describe the leakage due to instrumental widefield effects in visibility-based power spectra measured with redundant arrays, extending the delay-spectrum approach presented in Parsons et al. We construct polarized sky models and propagate them through the instrument model to simulate realistic full-sky observations with the Precision Array to Probe the Epoch of Reionization. We find that the leakage due to a population of polarized point sources is expected to be higher than diffuse Galactic polarization at any k mode for a 30 m reference baseline. For the same reference baseline, a foreground-free window at k > 0.3 h Mpc-1 can be defined in terms of leakage from diffuse Galactic polarization even under the most pessimistic assumptions. If measurements of polarized foreground power spectra or a model of polarized foregrounds are given, our method is able to predict the polarization leakage in actual 21 cm observations, potentially enabling its statistical subtraction from the measured 21 cm power spectrum.

Highly efficient all-dielectric optical tensor impedance metasurfaces for chiral polarization control.

PubMed

Kim, Minseok; Eleftheriades, George V

2016-10-15

We propose a highly efficient (nearly lossless and impedance-matched) all-dielectric optical tensor impedance metasurface that mimics chiral effects at optical wavelengths. By cascading an array of rotated crossed silicon nanoblocks, we realize chiral optical tensor impedance metasurfaces that operate as circular polarization selective surfaces. Their efficiencies are maximized through a nonlinear numerical optimization process in which the tensor impedance metasurfaces are modeled via multi-conductor transmission line theory. From rigorous full-wave simulations that include all material losses, we show field transmission efficiencies of 94% for right- and left-handed circular polarization selective surfaces at 800 nm.

Teleseismic P-wave polarization analysis at the Gräfenberg array

NASA Astrophysics Data System (ADS)

Cristiano, L.; Meier, T.; Krüger, F.; Keers, H.; Weidle, C.

2016-12-01

P-wave polarization at the Gräfenberg array (GRF) in southern Germany is analysed in terms of azimuthal deviations and deviations in the vertical polarization using 20 yr of broad-band recordings. An automated procedure for estimating P-wave polarization parameters is suggested, based on the definition of a characteristic function, which evaluates the polarization angles and their time variability as well as the amplitude, linearity and the signal-to-noise ratio of the P wave. P-wave polarization at the GRF array is shown to depend mainly on frequency and backazimuth and only slightly on epicentral distance indicating depth-dependent local anisotropy and lateral heterogeneity. A harmonic analysis is applied to the azimuthal anomalies to analyse their periodicity as a function of backazimuth. The dominant periods are 180° and 360°. At low frequencies, between 0.03 and 0.1 Hz, the observed fast directions of azimuthal anisotropy inferred from the 180° periodicity are similar across the array. The average fast direction of azimuthal anisotropy at these frequencies is N20°E with an uncertainty of about 8° and is consistent with fast directions of Pn-wave propagation. Lateral velocity gradients determined for the low-frequency band are compatible with the Moho topography of the area. A more complex pattern in the horizontal fast axis orientation beneath the GRF array is observed in the high-frequency band between 0.1 and 0.5 Hz, and is attributed to anisotropy in the upper crust. A remarkable rotation of the horizontal fast axis orientation across the suture between the geological units Moldanubicum and Saxothuringicum is observed. In contrast, the 360° periodicity at high frequencies is rather consistent across the array and may either point to lower velocities in the upper crust towards the Bohemian Massif and/or to anisotropy dipping predominantly in the NE-SW direction. Altogether, P-wave polarization analysis indicates the presence of layered lithospheric anisotropy in the area of the GRF array. Seismic anisotropy is more variable in the brittle upper crust compared to lower crustal and subcrustal depths.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, David F.; Aguirre, James E.; Parsons, Aaron R.

Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using themore » delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.« less

Mechanically Reconfigurable Single-Arm Spiral Antenna Array for Generation of Broadband Circularly Polarized Orbital Angular Momentum Vortex Waves.

PubMed

Li, Long; Zhou, Xiaoxiao

2018-03-23

In this paper, a mechanically reconfigurable circular array with single-arm spiral antennas (SASAs) is designed, fabricated, and experimentally demonstrated to generate broadband circularly polarized orbital angular momentum (OAM) vortex waves in radio frequency domain. With the symmetrical and broadband properties of single-arm spiral antennas, the vortex waves with different OAM modes can be mechanically reconfigurable generated in a wide band from 3.4 GHz to 4.7 GHz. The prototype of the circular array is proposed, conducted, and fabricated to validate the theoretical analysis. The simulated and experimental results verify that different OAM modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The proposed method paves a reconfigurable way to generate multiple OAM vortex waves with spin angular momentum (SAM) in radio and microwave satellite communication applications.

MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VIII. FARADAY ROTATION IN PARSEC-SCALE AGN JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.

2012-10-01

We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure andmore » the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal Faraday rotation is needed.« less

Source finding in linear polarization for LOFAR, and SKA predecessor surveys, using Faraday moments

NASA Astrophysics Data System (ADS)

Farnes, J. S.; Heald, G.; Junklewitz, H.; Mulcahy, D. D.; Haverkorn, M.; Van Eck, C. L.; Riseley, C. J.; Brentjens, M.; Horellou, C.; Vacca, V.; Jones, D. I.; Horneffer, A.; Paladino, R.

2018-03-01

The optimal source-finding strategy for linear polarization data is an unsolved problem, with many inhibitive factors imposed by the technically challenging nature of polarization observations. Such an algorithm is essential for Square Kilometre Array (SKA) pathfinder surveys, such as the Multifrequency Snapshot Sky Survey with the LOw Frequency ARray (LOFAR), as data volumes are significant enough to prohibit manual inspection. We present a new strategy of `Faraday Moments' for source-finding in linear polarization with LOFAR, using the moments of the frequency-dependent full-Stokes data (i.e. the mean, standard deviation, skewness, and excess kurtosis). Through simulations of the sky, we find that moments can identify polarized sources with a high completeness: 98.5 per cent at a signal to noise of 5. While the method has low reliability, rotation measure (RM) synthesis can be applied per candidate source to filter out instrumental and spurious detections. This combined strategy will result in a complete and reliable catalogue of polarized sources that includes the full sensitivity of the observational bandwidth. We find that the technique can reduce the number of pixels on which RM Synthesis needs to be performed by a factor of ≈1 × 105 for source distributions anticipated with modern radio telescopes. Through tests on LOFAR data, we find that the technique works effectively in the presence of diffuse emission. Extensions of this method are directly applicable to other upcoming radio surveys such as the POlarization Sky Survey of the Universe's Magnetism with the Australia Square Kilometre Array Pathfinder, and the SKA itself.

Optical manipulation and catalytic activity enhanced by surface plasmon effect

NASA Astrophysics Data System (ADS)

Zou, Ningmu; Min, Jiang; Jiao, Wenxiang; Wang, Guanghui

2017-02-01

For optical manipulation, a nano-optical conveyor belt consisting of an array of gold plasmonic non-concentric nano-rings (PNNRs) is demonstrated for the realization of trapping and unidirectional transportation of nanoparticles by polarization rotation of excitation beam. These hot spots of an asymmetric plasmonic nanostructure are polarization dependent, therefore, one can use the incident polarization state to manipulate the trapped targets. Trapped particles could be transferred between adjacent PNNRs in a given direction just by rotating the polarization of incident beam due to unbalanced potential. The angular dependent distribution of electric field around PNNR has been solved using the three- dimensional finite-difference time-domain (FDTD) technique. For optical enhanced catalytic activity, the spectral properties of dimers of Au nanorod-Au nanorod nanostructures under the excitation of 532nm photons have been investigated. With a super-resolution catalytic mapping technique, we identified the existence of "hot spot" in terms of catalytic reactivity at the gap region within the twined plasmonic nanostructure. Also, FDTD calculation has revealed an intrinsic correlation between hot electron transfer.

Stronger net posterior cortical forces and asymmetric microtubule arrays produce simultaneous centration and rotation of the pronuclear complex in the early Caenorhabditis elegans embryo

PubMed Central

Coffman, Valerie C.; McDermott, Matthew B. A.; Shtylla, Blerta; Dawes, Adriana T.

2016-01-01

Positioning of microtubule-organizing centers (MTOCs) incorporates biochemical and mechanical cues for proper alignment of the mitotic spindle and cell division site. Current experimental and theoretical studies in the early Caenorhabditis elegans embryo assume remarkable changes in the origin and polarity of forces acting on the MTOCs. These changes must occur over a few minutes, between initial centration and rotation of the pronuclear complex and entry into mitosis, and the models do not replicate in vivo timing of centration and rotation. Here we propose a model that incorporates asymmetry in the microtubule arrays generated by each MTOC, which we demonstrate with in vivo measurements, and a similar asymmetric force profile to that required for posterior-directed spindle displacement during mitosis. We find that these asymmetries are capable of and important for recapitulating the simultaneous centration and rotation of the pronuclear complex observed in vivo. The combination of theoretical and experimental evidence provided here offers a unified framework for the spatial organization and forces needed for pronuclear centration, rotation, and spindle displacement in the early C. elegans embryo. PMID:27733624

Radio observations of a few selected blazars

NASA Technical Reports Server (NTRS)

Saikia, D. J.; Salter, C. J.; Neff, S. G.; Gower, A. C.; Sinha, R. P.

1987-01-01

The paper presents total-intensity and linear-polarization observations of four selected blazars, 0716+714, 0752+258, 1156+295 and 1400+162, with the VLA A-array, and MERLIN and EVN observations of 1400+162. The sources 0752+258 and 1400+162 which have nearly constant optical polarization, have well-defined double-lobed radio structure, with relatively weak radio cores, and are likely to be at large viewing angles. In addition, 0752+258 appears to be a twin-jet blazar. The position angle (PA) of the VLBI jet in 1400+162 is close to that of the arcsec-scale jet near the nucleus, as well as the optical and 2-cm core polarization PAs. The blazars 0716+714 and 1156+295, which exhibit strongly variable optical polarization, have a core-dominated radio structure and perhaps have their jet axes close to the line-of-sight. From polarization observations at 20, 18, 6, and 2 cm, it is found that the rotation measure of the radio core in 0716+714 is about -20 rad/sq m. It is suggested that low values of core rotation measure in core-dominated sources could be consistent with the relativistic beaming models.

Advanced ACTPol Cryogenic Detector Arrays and Readout

NASA Astrophysics Data System (ADS)

Henderson, S. W.; Allison, R.; Austermann, J.; Baildon, T.; Battaglia, N.; Beall, J. A.; Becker, D.; De Bernardis, F.; Bond, J. R.; Calabrese, E.; Choi, S. K.; Coughlin, K. P.; Crowley, K. T.; Datta, R.; Devlin, M. J.; Duff, S. M.; Dunkley, J.; Dünner, R.; van Engelen, A.; Gallardo, P. A.; Grace, E.; Hasselfield, M.; Hills, F.; Hilton, G. C.; Hincks, A. D.; Hloẑek, R.; Ho, S. P.; Hubmayr, J.; Huffenberger, K.; Hughes, J. P.; Irwin, K. D.; Koopman, B. J.; Kosowsky, A. B.; Li, D.; McMahon, J.; Munson, C.; Nati, F.; Newburgh, L.; Niemack, M. D.; Niraula, P.; Page, L. A.; Pappas, C. G.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Sehgal, N.; Sherwin, B. D.; Sievers, J. L.; Simon, S. M.; Spergel, D. N.; Staggs, S. T.; Stevens, J. R.; Thornton, R.; Van Lanen, J.; Vavagiakis, E. M.; Ward, J. T.; Wollack, E. J.

2016-08-01

Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies—imaged in intensity and polarization at few arcminute-scale resolution—will enable precision cosmological constraints and also a wide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the Advanced ACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the Advanced ACTPol cryogenic detector arrays.

Advanced ACTPol Cryogenic Detector Arrays and Readout

NASA Technical Reports Server (NTRS)

Henderson, S.W.; Allison, R.; Austermann, J.; Baildon, T.; Battaglia, N.; Beall, J. A.; Becker, D.; De Bernardis, F.; Bond, J. R.; Wollack, E. J.

2016-01-01

Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies-imaged in intensity and polarization at few arcminute-scale resolution-will enable precision cosmological constraints and also awide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the AdvancedACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the AdvancedACTPol cryogenic detector arrays.

High Performance Circularly Polarized Microstrip Antenna

NASA Technical Reports Server (NTRS)

Bondyopadhyay, Probir K. (Inventor)

1997-01-01

A microstrip antenna for radiating circularly polarized electromagnetic waves comprising a cluster array of at least four microstrip radiator elements, each of which is provided with dual orthogonal coplanar feeds in phase quadrature relation achieved by connection to an asymmetric T-junction power divider impedance notched at resonance. The dual fed circularly polarized reference element is positioned with its axis at a 45 deg angle with respect to the unit cell axis. The other three dual fed elements in the unit cell are positioned and fed with a coplanar feed structure with sequential rotation and phasing to enhance the axial ratio and impedance matching performance over a wide bandwidth. The centers of the radiator elements are disposed at the corners of a square with each side of a length d in the range of 0.7 to 0.9 times the free space wavelength of the antenna radiation and the radiator elements reside in a square unit cell area of sides equal to 2d and thereby permit the array to be used as a phased array antenna for electronic scanning and is realizable in a high temperature superconducting thin film material for high efficiency.

Reliable low-power control of ultrafast vortex-core switching with the selectivity in an array of vortex states by in-plane circular-rotational magnetic fields and spin-polarized currents

NASA Astrophysics Data System (ADS)

Kim, Sang-Koog; Lee, Ki-Suk; Yu, Young-Sang; Choi, Youn-Seok

2008-01-01

The authors investigated the technological utility of counterclockwise (CCW) and clockwise (CW) circular-rotating fields (HCCW and HCW) and spin-polarized currents with an angular frequency ωH close to the vortex eigenfrequency ωD, for the reliable, low-power, and selective switching of the bistate magnetization (M) orientations of a vortex core (VC) in an array of soft magnetic nanoelements. CCW and CW circular gyrotropic motions in response to HCCW and HCW, respectively, show remarkably contrasting resonant behaviors, (i.e., extremely large-amplitude resonance versus small-amplitude nonresonance), depending on the M orientation of a given VC. Owing to this asymmetric resonance characteristics, the HCCW(HCW) with ωH˜ωD can be used to effectively switch only the up (down) core to its downward (upward) M orientation, selectively, by sufficiently low field (˜10Oe) and current density (˜107A/cm2). This work provides a reliable, low power, effective means of information storage, information recording, and information readout in vortex-based random access memory, simply called VRAM.

Ultra-sensing with slit-enhanced infrared spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Mayerhöfer, Thomas G.; Knipper, Richard; Hübner, Uwe; Cialla-May, Dana; Weber, Karina; Popp, Jürgen

2017-02-01

Infrared spectroscopy enables the label-free detection of structure specific fingerprints of analytes. The sensitivity of corresponding methods can strongly be enhanced by attaching analytes on plasmonic active surfaces. We introduce a slit array metamaterial perfect absorber (SAMPA) [1] consisting of a dielectric layer sandwiched between two Au layers of which the upper layer is perforated with a periodic array of slits. This structure combines the principle of Extraordinary Optical Transmission (more light is transmitted through a hole than is incident on its surface) with that of Perfect Absorption (reflectance and transmittance are virtually zero). Accordingly, within the slights the electric fields are strongly enhanced and light-matter interaction is correspondingly greatly amplified. Thus, already small concentrations of analytes down to a monolayer can be detected and identified by their spectral fingerprints with a standard mid-infrared spectrometer. Closely related to the SAMPAs are plasmonic slit absorbers, which simply consist of slit arrays in thin gold layers deposited on a layer of Si3N4.[2] These slit arrays operate like unstructured gold layers if the incident light is polarized parallel to the long slit axes. In contrast, for light polarized perpendicular to the long slit axis, the plasmon is excited. By the introduction of a second slit, which is rotated relative to the first slit, both principal polarization states excite plasmon resonances which can be made to differ in wavelength. As a consequence, the operating wavelength range of this slit array can be tuned by adjusting the polarization state of the incoming light. [1] Mayerhöfer, T.G., et al.. ACS Photonics, 2015. 2(11): p. 1567-1575. [2] Knipper, R., et. al., in preparation.

METimage: an innovative multi-spectral imaging radiometer for the EUMETSAT polar system follow-on satellite mission

NASA Astrophysics Data System (ADS)

Alpers, Matthias; Brüns, Christian; Pillukat, Alexander

2017-11-01

The evolving needs of the meteorological community concerning the EUMETSAT Polar System follow-on satellite mission (Post-EPS) require the development of a high-performance multi-spectral imaging radiometer. Recognizing these needs, Jena Optronik GmbH proposed an innovative instrument concept, which comprises a high flexibility to adapt to user requirements as a very important feature. Core parameters like ground sampling distance (GSD), number and width of spectral channels, signal-to-noise ratio, polarization control and calibration facilities can be chosen in a wide range without changing the basic instrument configuration. Core item of the METimage instrument is a rotating telescope scanner to cover the large swath width of about 2800 km, which all polar platforms need for global coverage. The de-rotated image facilitates use of in-field spectral channel separation, which allows tailoring individual channel GSD (ground sampling distance) and features like TDI (time delay and integration). State-of-the-art detector arrays and readout electronics can easily be employed. Currently, the German DLR Space Agency, Jena- Optronik GmbH and AIM Infrarot Module GmbH work together implementing core assemblies of METimage: the rotating telescope scanner and the infrared detectors. The METimage instrument phase B study was kicked-off in September 2008. Germany intents to provide METimage as an in-kind contribution of the first METimage flight model to the EUMETSAT Post-EPS Programme.

Direction-dependent Corrections in Polarimetric Radio Imaging. I. Characterizing the Effects of the Primary Beam on Full-Stokes Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagannathan, P.; Bhatnagar, S.; Rau, U.

Next generation radio telescope arrays are being designed and commissioned to accurately measure polarized intensity and rotation measures (RMs) across the entire sky through deep, wide-field radio interferometric surveys. Radio interferometer dish antenna arrays are affected by direction-dependent (DD) gains due to both instrumental and atmospheric effects. In this paper, we demonstrate the effect of DD errors of the parabolic dish antenna array on the measured polarized intensities of radio sources in interferometric images. We characterize the extent of polarimetric image degradation due to the DD gains through wide-band VLA simulations of representative point-source simulations of the radio sky atmore » L band (1–2 GHz). We show that at the 0.5 gain level of the primary beam there is significant flux leakage from Stokes I to Q , U amounting to 10% of the total intensity. We further demonstrate that while the instrumental response averages down for observations over large parallactic angle intervals, full-polarization DD correction is required to remove the effects of DD leakage. We also explore the effect of the DD beam on the RM signals and show that while the instrumental effect is primarily centered around 0 rad-m{sup −2}, the effect is significant over a broad range of RM requiring full polarization DD correction to accurately reconstruct the RM synthesis signal.« less

Polarization Observations with the Cosmic Background Imager

NASA Astrophysics Data System (ADS)

Cartwright, J. K.; Padin, S.; Pearson, T. J.; Readhead, A. C. S.; Shepherd, M. C.; Taylor, G. B.

2001-05-01

We describe polarization observations of the CMBR with the Cosmic Background Imager, a 13 element interferometer which operates in the 26-36 GHz band from a site at 5000m in northern Chile. The array consists of 90-cm Cassegrain antennas mounted on a single, fully steerable platform; this platform can be rotated about the optical axis to facilitate polarization observations. The CBI employs single mode circularly polarized receivers, of which 12 are configured for LCP and one is configured for RCP. The 12 cross polarized baselines sample multipoles from l 600 to l 3500. The instrumental polarization of the CBI was calibrated with observations of 3C279, a bright polarized source which is unresolved by the CBI. Because the centimeter flux of 3C279 is variable, it was monitored twice per month for 8 months in 2000 with the VLA at 22 and 43 GHz. These observations also established the stability of the polarization characteristics of the CBI. This work was made possible by NSF grant AST-9802989

Microstrip Patch Antenna And Method

NASA Technical Reports Server (NTRS)

Fink, Patrick W. (Inventor)

2001-01-01

Method and apparatus are provided for a microstrip feeder structure for supplying properly phased signals to each radiator element in a microstrip antenna array that may be utilized for radiating circularly polarized electromagnetic waves. In one disclosed embodiment. the microstrip feeder structure includes a plurality of microstrip sections many or all of which preferably have an electrical length substantially equal to one-quarter wavelength at the antenna operating frequency. The feeder structure provides a low loss feed structure that may be duplicated multiple times through a set of rotations and translations to provide a radiating array of the desired size.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Namikawa, Toshiya

We study the reconstruction of the cosmic rotation power spectrum produced by parity-violating physics, with an eye to ongoing and near future cosmic microwave background (CMB) experiments such as BICEP Array, CMBS4, LiteBIRD and Simons Observatory. In addition to the inflationary gravitational waves and gravitational lensing, measurements of other various effects on CMB polarization open new window into the early Universe. One of these is anisotropies of the cosmic polarization rotation which probes the Chern-Simons term generally predicted by string theory. The anisotropies of the cosmic rotation are also generated by the primordial magnetism and in the Standard Model extentionmore » framework. The cosmic rotation anisotropies can be reconstructed as quadratic in CMB anisotropies. However, the power of the reconstructed cosmic rotation is a CMB four-point correlation and is not directly related to the cosmic-rotation power spectrum. Understanding all contributions in the four-point correlation is required to extract the cosmic rotation signal. Here, assuming inflationary motivated cosmic-rotation models, we employ simulation to quantify each contribution to the four-point correlation and find that (1) a secondary contraction of the trispectrum increases the total signal-to-noise, (2) a bias from the lensing-induced trispectrum is significant compared to the statistical errors in, e.g., LiteBIRD and CMBS4-like experiments, (3) the use of a realization-dependent estimator decreases the statistical errors by 10%–20%, depending on experimental specifications, and (4) other higher-order contributions are negligible at least for near future experiments.« less

VLA Measurements of Faraday Rotation through Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Kooi, Jason E.; Fischer, Patrick D.; Buffo, Jacob J.; Spangler, Steven R.

2017-04-01

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun, which play an important role in space weather. Faraday rotation is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. Faraday rotation is proportional to the path integral through the plasma of the electron density and the line-of-sight component of the magnetic field. Faraday-rotation observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1 - 2 GHz frequencies of a constellation of radio sources through the solar corona at heliocentric distances that ranged from 6 - 15 R_{⊙}. Two sources (0842+1835 and 0900+1832) were occulted by a single CME, and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. ( Solar Phys., 98, 341, 1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the Large Angle and Spectrometric Coronagraph (LASCO) C3 instrument to determine the Thomson-scattering brightness [BT], providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant-density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and Faraday rotation. The plasma densities (6 - 22×103 cm^{-3}) and axial magnetic-field strengths (2 - 12 mG) inferred from our models are consistent with the modeling work of Liu et al. ( Astrophys. J., 665, 1439, 2007) and Jensen and Russell ( Geophys. Res. Lett., 35, L02103, 2008), as well as previous CME Faraday-rotation observations by Bird et al. (1985).

Magnetically coupled gear based drive mechanism for contactless continuous rotation using superconducting magnetic bearing below 10 K

NASA Astrophysics Data System (ADS)

Matsumura, T.; Sakurai, Y.; Kataza, H.; Utsunomiya, S.; Yamamoto, R.

2016-11-01

We present the design and mechanical performances of a magnetically coupled gear mechanism to drive a levitating rotor magnet of a superconducting magnetic bearing (SMB). The SMB consists of a ring-shaped high-temperature superconducting array (YBCO) and a ring-shaped permanent magnet. This rotational system is designed to operate below 10 K, and thus the design philosophy is to minimize any potential source of heat dissipation. While an SMB provides only a functionality of namely a bearing, it requires a mechanism to drive a rotational motion. We introduce a simple implementation of a magnetically coupled gears between a stator and a rotor. This enables to achieve enough torque to drive a levitating rotor without slip at the rotation frequency of about 1 Hz below 10 K. The rotational variation between the rotor and the drive gear is synchronised within σ = 0.019 Hz. The development of this mechanism is a part of the program to develop a testbed in order to evaluate a prototype half-wave plate based polarization modulator for future space missions. The successful development allows this modulator to be a candidate for an instrument to probe the cosmic inflation by measuring the cosmic microwave background polarization.

Recent VLA Measurements of CME-Induced Faraday Rotation

NASA Astrophysics Data System (ADS)

Kooi, Jason; Thomas, Najma; Guy, Michael; Spangler, Steven R.

2018-01-01

Observations of Faraday rotation, the change in polarization position angle of linearly polarized radiation as it propagates through a magnetized plasma, have been used for decades to determine the strength and structure of the coronal magnetic field and plasma density. Similarly, observations of Faraday rotation through a coronal mass ejection (CME) have the potential to improve our understanding of the CME’s plasma structure. We report recent results from simultaneous white-light coronagraph and radio observations made of a CME in July 2015. We made radio observations using the Karl G. Jansky Very Large Array (VLA) at 1 - 2 GHz frequencies of a set of cosmic radio sources through the solar corona at heliocentric distances that ranged between 8 - 23 solar radii. A unique aspect of these observations is that the CME occulted several of these radio sources and, therefore, our Faraday rotation measurements provide information on the plasma structure in different regions of the CME. We successfully measured CME-induced Faraday rotation along multiple lines of sight because we made special arrangements with the staff at the National Radio Astronomy Observatory to trigger VLA observations when a candidate CME appeared low in the corona in near real-time images from the Large Angle and Spectrometric Coronagraph (LASCO) C2 instrument.

Faraday signature of magnetic helicity from reduced depolarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandenburg, Axel; Stepanov, Rodion

2014-05-10

Using one-dimensional models, we show that a helical magnetic field with an appropriate sign of helicity can compensate the Faraday depolarization resulting from the superposition of Faraday-rotated polarization planes from a spatially extended source. For radio emission from a helical magnetic field, the polarization as a function of the square of the wavelength becomes asymmetric with respect to zero. Mathematically speaking, the resulting emission occurs then either at observable or at unobservable (imaginary) wavelengths. We demonstrate that rotation measure (RM) synthesis allows for the reconstruction of the underlying Faraday dispersion function in the former case, but not in the latter.more » The presence of positive magnetic helicity can thus be detected by observing positive RM in highly polarized regions in the sky and negative RM in weakly polarized regions. Conversely, negative magnetic helicity can be detected by observing negative RM in highly polarized regions and positive RM in weakly polarized regions. The simultaneous presence of two magnetic constituents with opposite signs of helicity is shown to possess signatures that can be quantified through polarization peaks at specific wavelengths and the gradient of the phase of the Faraday dispersion function. Similar polarization peaks can tentatively also be identified for the bi-helical magnetic fields that are generated self-consistently by a dynamo from helically forced turbulence, even though the magnetic energy spectrum is then continuous. Finally, we discuss the possibility of detecting magnetic fields with helical and non-helical properties in external galaxies using the Square Kilometre Array.« less

NGC 7538 IRS. 1. Interaction of a Polarized Dust Spiral and a Molecular Outflow

NASA Astrophysics Data System (ADS)

Wright, M. C. H.; Hull, Charles L. H.; Pillai, Thushara; Zhao, Jun-Hui; Sandell, Göran

2014-12-01

We present dust polarization and CO molecular line images of NGC 7538 IRS 1. We combined data from the Submillimeter Array, the Combined Array for Research in Millimeter-wave Astronomy, and the James Clerk Maxwell Telescope to make images with ~2.''5 resolution at 230 and 345 GHz. The images show a remarkable spiral pattern in both the dust polarization and molecular outflow. These data dramatically illustrate the interplay between a high infall rate onto IRS 1 and a powerful outflow disrupting the dense, clumpy medium surrounding the star. The images of the dust polarization and the CO outflow presented here provide observational evidence for the exchange of energy and angular momentum between the infall and the outflow. The spiral dust pattern, which rotates through over 180° from IRS 1, may be a clumpy filament wound up by conservation of angular momentum in the infalling material. The redshifted CO emission ridge traces the dust spiral closely through the MM dust cores, several of which may contain protostars. We propose that the CO maps the boundary layer where the outflow is ablating gas from the dense gas in the spiral.

Defect-Induced Hedgehog Polarization States in Multiferroics

NASA Astrophysics Data System (ADS)

Li, Linze; Cheng, Xiaoxing; Jokisaari, Jacob R.; Gao, Peng; Britson, Jason; Adamo, Carolina; Heikes, Colin; Schlom, Darrell G.; Chen, Long-Qing; Pan, Xiaoqing

2018-03-01

Continuous developments in nanotechnology require new approaches to materials synthesis that can produce novel functional structures. Here, we show that nanoscale defects, such as nonstoichiometric nanoregions (NSNRs), can act as nano-building blocks for creating complex electrical polarization structures in the prototypical multiferroic BiFeO3 . An array of charged NSNRs are produced in BiFeO3 thin films by tuning the substrate temperature during film growth. Atomic-scale scanning transmission electron microscopy imaging reveals exotic polarization rotation patterns around these NSNRs. These polarization patterns resemble hedgehog or vortex topologies and can cause local changes in lattice symmetries leading to mixed-phase structures resembling the morphotropic phase boundary with high piezoelectricity. Phase-field simulations indicate that the observed polarization configurations are mainly induced by charged states at the NSNRs. Engineering defects thus may provide a new route for developing ferroelectric- or multiferroic-based nanodevices.

Defect-Induced Hedgehog Polarization States in Multiferroics.

PubMed

Li, Linze; Cheng, Xiaoxing; Jokisaari, Jacob R; Gao, Peng; Britson, Jason; Adamo, Carolina; Heikes, Colin; Schlom, Darrell G; Chen, Long-Qing; Pan, Xiaoqing

2018-03-30

Continuous developments in nanotechnology require new approaches to materials synthesis that can produce novel functional structures. Here, we show that nanoscale defects, such as nonstoichiometric nanoregions (NSNRs), can act as nano-building blocks for creating complex electrical polarization structures in the prototypical multiferroic BiFeO_{3}. An array of charged NSNRs are produced in BiFeO_{3} thin films by tuning the substrate temperature during film growth. Atomic-scale scanning transmission electron microscopy imaging reveals exotic polarization rotation patterns around these NSNRs. These polarization patterns resemble hedgehog or vortex topologies and can cause local changes in lattice symmetries leading to mixed-phase structures resembling the morphotropic phase boundary with high piezoelectricity. Phase-field simulations indicate that the observed polarization configurations are mainly induced by charged states at the NSNRs. Engineering defects thus may provide a new route for developing ferroelectric- or multiferroic-based nanodevices.

Design and performance of the spin asymmetries of the nucleon experiment

NASA Astrophysics Data System (ADS)

Maxwell, J. D.; Armstrong, W. R.; Choi, S.; Jones, M. K.; Kang, H.; Liyanage, A.; Meziani, Z.-E.; Mulholland, J.; Ndukum, L.; Rondón, O. A.; Ahmidouch, A.; Albayrak, I.; Asaturyan, A.; Ates, O.; Baghdasaryan, H.; Boeglin, W.; Bosted, P.; Brash, E.; Brock, J.; Butuceanu, C.; Bychkov, M.; Carlin, C.; Carter, P.; Chen, C.; Chen, J.-P.; Christy, M. E.; Covrig, S.; Crabb, D.; Danagoulian, S.; Daniel, A.; Davidenko, A. M.; Davis, B.; Day, D.; Deconinck, W.; Deur, A.; Dunne, J.; Dutta, D.; El Fassi, L.; Elaasar, M.; Ellis, C.; Ent, R.; Flay, D.; Frlez, E.; Gaskell, D.; Geagla, O.; German, J.; Gilman, R.; Gogami, T.; Gomez, J.; Goncharenko, Y. M.; Hashimoto, O.; Higinbotham, D. W.; Horn, T.; Huber, G. M.; Jones, M.; Kalantarians, N.; Kang, H. K.; Kawama, D.; Keith, C.; Keppel, C.; Khandaker, M.; Kim, Y.; King, P. M.; Kohl, M.; Kovacs, K.; Kubarovsky, V.; Li, Y.; Liyanage, N.; Luo, W.; Mamyan, V.; Markowitz, P.; Maruta, T.; Meekins, D.; Melnik, Y. M.; Mkrtchyan, A.; Mkrtchyan, H.; Mochalov, V. V.; Monaghan, P.; Narayan, A.; Nakamura, S. N.; Nuruzzaman; Pentchev, L.; Pocanic, D.; Posik, M.; Puckett, A.; Qiu, X.; Reinhold, J.; Riordan, S.; Roche, J.; Sawatzky, B.; Shabestari, M.; Slifer, K.; Smith, G.; Soloviev, L.; Solvignon, P.; Tadevosyan, V.; Tang, L.; Vasiliev, A. N.; Veilleux, M.; Walton, T.; Wesselmann, F.; Wood, S. A.; Yao, H.; Ye, Z.; Zhu, L.

2018-03-01

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2 . 5

Testing parity-violating physics from cosmic rotation power reconstruction

DOE PAGES

Namikawa, Toshiya

2017-02-22

We study the reconstruction of the cosmic rotation power spectrum produced by parity-violating physics, with an eye to ongoing and near future cosmic microwave background (CMB) experiments such as BICEP Array, CMBS4, LiteBIRD and Simons Observatory. In addition to the inflationary gravitational waves and gravitational lensing, measurements of other various effects on CMB polarization open new window into the early Universe. One of these is anisotropies of the cosmic polarization rotation which probes the Chern-Simons term generally predicted by string theory. The anisotropies of the cosmic rotation are also generated by the primordial magnetism and in the Standard Model extentionmore » framework. The cosmic rotation anisotropies can be reconstructed as quadratic in CMB anisotropies. However, the power of the reconstructed cosmic rotation is a CMB four-point correlation and is not directly related to the cosmic-rotation power spectrum. Understanding all contributions in the four-point correlation is required to extract the cosmic rotation signal. Here, assuming inflationary motivated cosmic-rotation models, we employ simulation to quantify each contribution to the four-point correlation and find that (1) a secondary contraction of the trispectrum increases the total signal-to-noise, (2) a bias from the lensing-induced trispectrum is significant compared to the statistical errors in, e.g., LiteBIRD and CMBS4-like experiments, (3) the use of a realization-dependent estimator decreases the statistical errors by 10%–20%, depending on experimental specifications, and (4) other higher-order contributions are negligible at least for near future experiments.« less

Application Research of Horn Array Multi-Beam Antenna in Reference Source System for Satellite Interference Location

NASA Astrophysics Data System (ADS)

Zhou, Ping; Lin, Hui; Zhang, Qi

2018-01-01

The reference source system is a key factor to ensure the successful location of the satellite interference source. Currently, the traditional system used a mechanical rotating antenna which leaded to the disadvantages of slow rotation and high failure-rate, which seriously restricted the system’s positioning-timeliness and became its obvious weaknesses. In this paper, a multi-beam antenna scheme based on the horn array was proposed as a reference source for the satellite interference location, which was used as an alternative to the traditional reference source antenna. The new scheme has designed a small circularly polarized horn antenna as an element and proposed a multi-beamforming algorithm based on planar array. Moreover, the simulation analysis of horn antenna pattern, multi-beam forming algorithm and simulated satellite link cross-ambiguity calculation have been carried out respectively. Finally, cross-ambiguity calculation of the traditional reference source system has also been tested. The comparison between the results of computer simulation and the actual test results shows that the scheme is scientific and feasible, obviously superior to the traditional reference source system.

VANDENBERG AIR FORCE BASE, CALIF. - With its cover removed, the SciSat-1 spacecraft is rotated. The solar arrays will be attached and the communications systems checked out. The SciSat-1 weighs approximately 330 pounds and after launch will be placed in a 400-mile-high polar orbit to investigate processes that control the distribution of ozone in the upper atmosphere. The data from the satellite will provide Canadian and international scientists with improved measurements relating to global ozone processes and help policymakers assess existing environmental policy and develop protective measures for improving the health of our atmosphere, preventing further ozone depletion. The mission is designed to last two years.

NASA Image and Video Library

2003-07-29

VANDENBERG AIR FORCE BASE, CALIF. - With its cover removed, the SciSat-1 spacecraft is rotated. The solar arrays will be attached and the communications systems checked out. The SciSat-1 weighs approximately 330 pounds and after launch will be placed in a 400-mile-high polar orbit to investigate processes that control the distribution of ozone in the upper atmosphere. The data from the satellite will provide Canadian and international scientists with improved measurements relating to global ozone processes and help policymakers assess existing environmental policy and develop protective measures for improving the health of our atmosphere, preventing further ozone depletion. The mission is designed to last two years.

Optical anisotropy in micromechanically rolled carbon nanotube forest

NASA Astrophysics Data System (ADS)

Razib, Mohd Asyraf bin Mohd; Rana, Masud; Saleh, Tanveer; Fan, Harrison; Koch, Andrew; Nojeh, Alireza; Takahata, Kenichi; Muthalif, Asan Gani Bin Abdul

2017-09-01

The bulk appearance of arrays of vertically aligned carbon nanotubes (VACNT arrays or CNT forests) is dark as they absorb most of the incident light. In this paper, two postprocessing techniques have been described where the CNT forest can be patterned by selective bending of the tips of the nanotubes using a rigid cylindrical tool. A tungsten tool was used to bend the vertical structure of CNTs with predefined parameters in two different ways as stated above: bending using the bottom surface of the tool (micromechanical bending (M2B)) and rolling using the side of the tool (micromechanical rolling (M2R)). The processed zone was investigated using a Field Emission Scanning Electron Microscope (FESEM) and optical setup to reveal the surface morphology and optical characteristics of the patterned CNTs on the substrate. Interestingly, the polarized optical reflection from the micromechanical rolled (M2R) sample was found to be significantly influenced by the rotation of the sample. It was observed that, if the polarization of the light is parallel to the alignment of the CNTs, the reflectance is at least 2 x higher than for the perpendicular direction. Furthermore, the reflectance varied almost linearly with good repeatability ( 10%) as the processed CNT forest sample was rotated from 0° to 90°. [Figure not available: see fulltext.

Broad-band, radio spectro-polarimetric study of 100 radiative-mode and jet-mode AGN

NASA Astrophysics Data System (ADS)

O'Sullivan, S. P.; Purcell, C. R.; Anderson, C. S.; Farnes, J. S.; Sun, X. H.; Gaensler, B. M.

2017-08-01

We present the results from a broad-band (1 to 3 GHz), spectro-polarimetry study of the integrated emission from 100 extragalactic radio sources with the Australia Telescope Compact Array, selected to be highly linearly polarized at 1.4 GHz. We use a general-purpose, polarization model-fitting procedure that describes the Faraday rotation measure (RM) and intrinsic polarization structure of up to three distinct polarized emission regions or `RM components' of a source. Overall, 37 per cent/52 per cent/11 per cent of sources are best fitted by one/two/three RM components. However, these fractions are dependent on the signal-to-noise ratio (S/N) in polarization (more RM components more likely at higher S/N). In general, our analysis shows that sources with high integrated degrees of polarization at 1.4 GHz have low Faraday depolarization, are typically dominated by a single RM component, have a steep spectral index and have a high intrinsic degree of polarization. After classifying our sample into radiative-mode and jet-mode AGN, we find no significant difference between the Faraday rotation or Faraday depolarization properties of jet-mode and radiative-mode AGN. However, there is a statistically significant difference in the intrinsic degree of polarization between the two types, with the jet-mode sources having more intrinsically ordered magnetic field structures than the radiative-mode sources. We also find a preferred perpendicular orientation of the intrinsic magnetic field structure of jet-mode AGN with respect to the jet direction, while no clear preference is found for the radiative-mode sources.

Computational polarization difference underwater imaging based on image fusion

NASA Astrophysics Data System (ADS)

Han, Hongwei; Zhang, Xiaohui; Guan, Feng

2016-01-01

Polarization difference imaging can improve the quality of images acquired underwater, whether the background and veiling light are unpolarized or partial polarized. Computational polarization difference imaging technique which replaces the mechanical rotation of polarization analyzer and shortens the time spent to select the optimum orthogonal ǁ and ⊥axes is the improvement of the conventional PDI. But it originally gets the output image by setting the weight coefficient manually to an identical constant for all pixels. In this paper, a kind of algorithm is proposed to combine the Q and U parameters of the Stokes vector through pixel-level image fusion theory based on non-subsample contourlet transform. The experimental system built by the green LED array with polarizer to illuminate a piece of flat target merged in water and the CCD with polarization analyzer to obtain target image under different angle is used to verify the effect of the proposed algorithm. The results showed that the output processed by our algorithm could show more details of the flat target and had higher contrast compared to original computational polarization difference imaging.

First Season QUIET Observations: Measurements of CMB Polarization Power Spectra at 43 GHz in the Multipole Range 25 <= ell <= 475

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bischoff, C.; /Chicago U., EFI /Harvard-Smithsonian Ctr. Astrophys.; Brizius, A.

2010-12-01

The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43GHz and 95GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the CMB. QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000 hours of data were collected, first with the 19-element 43-GHz array (3458 hours) and then with the 90-element 95-GHz array. Each array observes the same four fields, selected for low foregrounds, together covering {approx}more » 1000 square degrees. This paper reports initial results from the 43-GHz receiver which has an array sensitivity to CMB fluctuations of 69 {mu}K{radical}s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range {ell} = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3-{sigma} significance, the E-mode spectrum is consistent with the {Lambda}CDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35{sub -0.87}{sup +1.06}. The combination of a new time-stream 'double-demodulation' technique, Mizuguchi-Dragone optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1.« less

Faraday Rotation and Models for the Plasma Structure of the Solar Corona

NASA Astrophysics Data System (ADS)

Mancuso, Salvatore; Spangler, Steven R.

2000-08-01

Faraday rotation observations of polarized radiation from natural radio sources are unique among remote diagnostics of the solar corona in that they provide information on the coronal magnetic field. Dual frequency radio polarization measurements yield the rotation measure, a quantity that is proportional to the integral along the line of sight of the product of the electron density and the line-of-sight component of the magnetic field. We made linear polarization observations with the NRAO Very Large Array of 13 polarized radio sources occulted by the solar corona. The observations were made at frequencies of 1465 and 1665 MHz on four days in 1997 May and cover a 20 day period, sampling elongations ranging from about 5 to 14 Rsolar. The magnitudes of the rotation measures observed range from about 11 to 0 rad m-2. The relatively low values for the rotation measures are due to the solar minimum configuration of the corona at the time of the observations, with the lines of sight to the sources generally not crossing sector boundaries. The largest rotation measure was observed for the extended radio source 3C 79 on 1997 May 11 and corresponds to a case in which the line of sight passed next to the streamer belt at small solar elongations. We have developed a three-dimensional model of the solar corona that is in excellent agreement with the observed rotation measures, as well as being completely consistent with other coronal diagnostics such as coronagraph images. In particular, our observations support the coronal magnetic field model of Pätzold et al. (1987) they would be inconsistent with coronal magnetic fields significantly weaker or stronger than this model. The plasma density distribution in the corona is successfully modeled by a dense streamer belt component and a more tenuous coronal hole component. Details of these models are given in § 3 of this paper. The principal disagreement between the model and observations occurs for three lines of sight for which the model predicts nearly zero rotation measure but for which we measure small but significant values of -1 to -2 rad m-2. These lines of sight passed over the solar polar regions. We discuss the possibility that these residual rotation measures are due to static coronal plasma structures, not described by global coronal models, or to very long wavelength coronal Alfvén waves. Fluctuations in the rotation measure on timescales of a few hours were observed for some sources and not others. When detected, they were of order 1-2 rad m-2 and occurred on timescales of several hours.

Freely-tunable broadband polarization rotator for terahertz waves

NASA Astrophysics Data System (ADS)

Peng, Ru-Wen; Fan, Ren-Hao; Zhou, Yu; Jiang, Shang-Chi; Xiong, Xiang; Huang, Xian-Rong; Wang, Mu

It is known that commercially-available terahertz (THz) emitters usually generate linearly polarized waves only along certain directions, but in practice, a polarization rotator that is capable of rotating the polarization of THz waves to any direction is particularly desirable and it will have various important applications. In this work, we demonstrate a freely tunable polarization rotator for broadband THz waves using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized THz wave to any desired direction with nearly perfect conversion efficiency. The device performance has been experimentally demonstrated by both THz transmission spectra and direct imaging. The polarization rotation originates from multi wave interference in the three-layer grating structure based on the scattering-matrix analysis. We can expect that this active broadband polarization rotator has wide applications in analytical chemistry, biology, communication technology, imaging, etc.. Reference: R. H. Fan, Y. Zhou, X. P. Ren, R. W. Peng, S. C. Jiang, D. H. Xu, X. Xiong, X. R. Huang, and Mu Wang, Advanced Materials 27,1201(2015). Freely-tunable broadband polarization rotator for terahertz waves.

Microstrip Antenna for Remote Sensing of Soil Moisture and Sea Surface Salinity

NASA Technical Reports Server (NTRS)

Ramhat-Samii, Yahya; Kona, Keerti; Manteghi, Majid; Dinardo, Steven; Hunter, Don; Njoku, Eni; Wilson, Wiliam; Yueh, Simon

2009-01-01

This compact, lightweight, dual-frequency antenna feed developed for future soil moisture and sea surface salinity (SSS) missions can benefit future soil and ocean studies by lowering mass, volume, and cost of the antenna system. It also allows for airborne soil moisture and salinity remote sensors operating on small aircraft. While microstrip antenna technology has been developed for radio communications, it has yet to be applied to combined radar and radiometer for Earth remote sensing. The antenna feed provides a key instrument element enabling high-resolution radiometric observations with large, deployable antennas. The design is based on the microstrip stacked-patch array (MSPA) used to feed a large, lightweight, deployable, rotating mesh antenna for spaceborne L-band (approximately equal to 1 GHz) passive and active sensing systems. The array consists of stacked patches to provide dual-frequency capability and suitable radiation patterns. The stacked-patch microstrip element was designed to cover the required L-band center frequencies at 1.26 GHz (lower patch) and 1.413 GHz (upper patch), with dual-linear polarization capabilities. The dimension of patches produces the required frequencies. To achieve excellent polarization isolation and control of antenna sidelobes for the MSPA, the orientation of each stacked-patch element within the array is optimized to reduce the cross-polarization. A specialized feed-distribution network was designed to achieve the required excitation amplitude and phase for each stacked-patch element.

Diagnostics of the solar corona from comparison between Faraday rotation measurements and magnetohydrodynamic simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Chat, G.; Cohen, O.; Kasper, J. C.

Polarized natural radio sources passing behind the Sun experience Faraday rotation as a consequence of the electron density and magnetic field strength in coronal plasma. Since Faraday rotation is proportional to the product of the density and the component of the magnetic field along the line of sight of the observer, a model is required to interpret the observations and infer coronal structures. Faraday rotation observations have been compared with relatively ad hoc models of the corona. Here for the first time we compare these observations with magnetohydrodynamic (MHD) models of the solar corona driven by measurements of the photosphericmore » magnetic field. We use observations made with the NRAO Very Large Array of 34 polarized radio sources occulted by the solar corona between 5 and 14 solar radii. The measurements were made during 1997 May, and 2005 March and April. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona. We find that (1) using a synoptic map of the solar magnetic field just one Carrington rotation off produces poorer agreements, meaning that the outer corona changes in the course of one month, even in solar minimum; (2) global MHD models of the solar corona driven by photospheric magnetic field measurements are generally able to reproduce Faraday rotation observations; and (3) some sources show significant disagreement between the model and the observations, which appears to be a function of the proximity of the line of sight to the large-scale heliospheric current sheet.« less

Multifrequency observations of the radio continuum emission from NGC 253. 1: Magnetic fields and rotation measures in the bar and halo

NASA Astrophysics Data System (ADS)

Beck, R.; Carilli, C. L.; Holdaway, M. A.; Klein, U.

1994-12-01

Radio continuum observations of the spiral galaxy NGC 253 with the Effelsberg and Very Large Array (VLA) telescopes reveal polarized emission from the bar and halo regions. Within the bar Faraday depolarization is strong at 1.5 and 5 GHz, due to ionized gas with ne approximately equal 0.1 - 3/cu cm which is mixed with turbulent magnetic fields of approximately equal 17 microG estimated strength. Even at 10 GHz the degree of polarization in the bar is low (only approximately equal 5% east and approximately equal 2% west of the nucleus) due to beam depolarization by unresolved tangled fields. In contrast, the magnetic fields in the halo are highly uniform, as indicated by fractional polarizations up to 40% at 10 GHz. Faraday depolarization in the halo at 1.5 GHz calls for a warm, clumpy gas component with ne approximately equal 0.02/cu cm and approximately equal 6 microG turbulent fields. We detected Faraday rotation in the bar, with rotation measures absolute value of RM approximately equal 100 rad/sq m (between 10 and 5 GHz) having different signs east and west of the nucleus. Below 5 GHz Faraday rotation is strongly reduced by the limited transparency for polarized emission in the bar. Faraday rotation in the halo in two regions at approximately 5 kpc above and below the plane with RM approximately equal -7 rad/sq m between 10 and 1.5 GHz can be ascribed to hot gas with mean value of ne approximately equal 0.002/cu cm and uniform fields along the line of sight of mean value of Bu parallel approximately equal -2 microG. The magnetic field structure in the bar and halo of NGC 253 is best described by the quadrupole-type dynamo mode SO, with a ring-like field in the bar and a field mainly parallel to the plane in a co-rotating halo. A major perturbation occurs in the east where the field is perpendicular to the plane and follows a 'spur'. The galactic wind is suppressed by the dominating plane-parallel field, except along the spur.

Polarization rotation in meteor burst communication systems

NASA Astrophysics Data System (ADS)

Cannon, P. S.

1986-06-01

Theoretical modeling of several meteor burst communication (MBC) paths indicates that polarization rotation losses are significant for a linearly polarized system operating near 40 MHz. Losses for a hybrid system with physical installation problems, consisting of linearly polarized transmitting and circularly polarized receiving antennas, were found to be less. Both ionospheric Faraday rotation polarization changes, and underdense meteor trail scattering wave polarization rotation, are considered. These losses are found to cause a 15-70 percent data throughput reduction of the value predicted for the situation without polarization rotation, in the two 40-MHz linearly polarized links considered for noon summer solstice conditions during high solar sunspot number periods. Qualitative experimental confirmation is provided through a cross polarization approach.

Laser Oscillator Incorporating a Wedged Polarization Rotator and a Porro Prism as Cavity Mirror

NASA Technical Reports Server (NTRS)

Li, Steven

2011-01-01

A laser cavity was designed and implemented by using a wedged polarization rotator and a Porro prism in order to reduce the parts count, and to improve the laser reliability. In this invention, a z-cut quartz polarization rotator is used to compensate the wavelength retardance introduced by the Porro prism. The polarization rotator rotates the polarization of the linear polarized beam with a designed angle that is independent of the orientation of the rotator. This unique property was used to combine the retardance compensation and a Risley prism to a single optical component: a wedged polarization rotator. This greatly simplifies the laser alignment procedure and reduces the number of the laser optical components.

From Cores to Envelopes to Disks: A Multi-scale View of Magnetized Star Formation

NASA Astrophysics Data System (ADS)

Hull, Charles L. H.

2014-12-01

Observations of polarization in star forming regions have been made across many wavelengths, many size scales, and many stages of stellar evolution. One of the overarching goals of these observations has been to determine the importance of magnetic fields -- which are the cause of the polarization -- in the star formation process. We begin by describing the commissioning and the calibration of the 1.3 mm dual-polarization receiver system we built for CARMA (the Combined Array for Research in Millimeter-wave Astronomy), a radio telescope in the eastern Sierra region of California. One of the primary science drivers behind the polarization system is to observe polarized thermal emission from dust grains in the dense clumps of dust and gas where the youngest, Class 0 protostars are forming. We go on to describe the CARMA TADPOL survey -- the largest high-resolution (~1000 AU scale) survey to date of dust polarization in low-mass protostellar cores -- and discuss our main findings: (1) Magnetic fields (B-fields) on scales of ~1000 AU are not tightly aligned with protostellar outflows. Rather, the data are consistent both with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular) and where they are randomly aligned. (2) Sources with high CARMA polarization fractions have consistent B-field orientations on large scales (~20'', measured using single-dish submillimeter telescopes) and small scales (~2.5'', measured by CARMA). We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ~1000 AU scales of protostellar envelopes. Finally, (3) While on the whole outflows appear to be randomly aligned with B-fields, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. This work shows that the ~1000 AU protostellar envelope may be a turning point: at larger scales B-fields may still retain the memory of the global B-field drawn in from the ambient medium; but at smaller scales the B-fields may be affected by the dynamics of both envelope and disk rotation. This sets the stage for ALMA (the Atacama Large Millimeter/submillimeter Array), which will soon reveal the morphology of B-fields in circumstellar disks themselves.

Design and performance of the spin asymmetries of the nucleon experiment

DOE PAGES

Maxwell, J. D.; Armstrong, W. R.; Choi, S.; ...

2018-03-01

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1, A 2, g 1, gmore » 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.« less

Design and performance of the spin asymmetries of the nucleon experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, J. D.; Armstrong, W. R.; Choi, S.

The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1, A 2, g 1, gmore » 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.« less

Vibrational characteristics of a superconducting magnetic bearing employed for a prototype polarization modulator

NASA Astrophysics Data System (ADS)

Sakurai, Yuki; Matsumura, Tomotake; Sugai, Hajime; Katayama, Nobuhiko; Ohsaki, Hiroyuki; Terao, Yutaka; Terachi, Yusuke; Kataza, Hirokazu; Utsunomiya, Shin; Yamamoto, Ryo

2017-07-01

We present the vibrational characteristics of a levitating rotor in a superconducting magnetic bearing (SMB) system operating at below 10 K. We develop a polarization modulator that requires a continuously rotating optical element, called half-wave plate (HWP), for a cosmic microwave background polarization experiment. The HWP has to operate at the temperature below 10 K, and thus an SMB provides a smooth rotation of the HWP at the cryogenic temperature of about 10 K with minimal heat dissipation. In order to understand the potential interference to the cosmological observations due to the vibration of the HWP, it is essential to characterize the vibrational properties of the levitating rotor of the SMB. We constructed a prototype model that consists of an SMB with an array of high temperature superconductors, YBCO, and a permanent magnet ring, NdFeB. The rotor position is monitored by a laser displacement gauge, and a cryogenic Hall sensor via the magnetic field. In this presentation, we present the measurement results of the vibration characteristics using our prototype SMB system. We characterize the vibrational properties as the spring constant and the damping, and discuss the projected performance of this technology toward the use in future space missions.

VARIABLE AND POLARIZED RADIO EMISSION FROM THE T6 BROWN DWARF WISEP J112254.73+255021.5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, P. K. G.; Berger, E.; Gizis, J. E., E-mail: pwilliams@cfa.harvard.edu

2017-01-10

Route and Wolszczan recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ∼17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission. Assuming that the radio emission of this T dwarf is periodically variable on ∼hour timescales, like other radio-active ultracool dwarfs, we infer a likely period of 116 minutes. However, our observation lasted only 162 minutes and so more data are needed to test thismore » hypothesis. The handedness of the circular polarization switches twice and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object’s magnetic dipole axis may be highly misaligned relative to its rotation axis.« less

Polarization Observations with the Cosmic Background Imager

NASA Astrophysics Data System (ADS)

Cartwright, J. K.; Padin, S.; Pearson, T. J.; Readhead, A. C. S.; Shepherd, M. C.; Taylor, G. B.

2000-12-01

The linear polarization of the Cosmic Microwave Background Radiation is a fundamental prediction of the standard model. We report a limit on the polarization of the CMBR for l ~660. This limit was obtained with the Cosmic Background Imager, a 13 element interferometer which operates in the 26-36 GHz band from a site at 5000m in northern Chile. The array consists of 90-cm Cassegrain antennas mounted on a single, fully steerable platform; this platform can be rotated about the optical axis to facilitate polarization observations. The CBI employs single mode circularly polarized receivers, of which 12 are configured for LCP and one is configured for RCP. The 12 cross polarized baselines sample multipoles from l ~600 to l ~3500. The instrumental polarization of the CBI was calibrated with observations of 3C279, a bright polarized source which is unresolved by the CBI. Because the centimeter flux of 3C279 is variable, it was monitored twice per month for 8 months in '00 with the VLA at 22 and 43 GHz. These observations also established the stability of the polarization characteristics of the CBI. This work was made possible by NSF grant AST-9802989

Coherent Optical Adaptive Techniques (COAT)

DTIC Science & Technology

1973-02-01

quarter wave plate and frequency shifter twice. The polarization-rotated wave is then partially reflected by the beam - splitters B,, B2 , B to provide a...between the beam splitters B, and Bp. This causes a change in the relative phase of the local oscillator to the detectors and, consequently, a change in...trackinr. The basic method is illustrated in Figure T-l. There, an array of laser beams , derived from a single laser source, is shown with provision

Optical second harmonic generation from V-shaped chromium nanohole arrays

NASA Astrophysics Data System (ADS)

Khoa Quang, Ngo; Miyauchi, Yoshihiro; Mizutani, Goro; Charlton, Martin D.; Chen, Ruiqi; Boden, Stuart; Rutt, Harvey

2014-02-01

We observed rotational anisotropy of optical second harmonic generation (SHG) from an array of V-shaped chromium nanoholes fabricated by electron beam lithography. Phenomenological analysis indicated that the effective nonlinear susceptibility element \\chi _{313}^{(2)} had a characteristic contribution to the observed anisotropic SHG intensity patterns. Here, coordinate 1 is in the direction of the tip of V shapes in the substrate plane, and 3 indicates the direction perpendicular to the sample surface. The SHG intensity for the S-polarized output light was very weak, probably owing to the cancellation effect of the image dipoles generated at the metal-air boundary. The possible origin of the observed nonlinearity is discussed in terms of the susceptibility elements obtained.

VANDENBERG AIR FORCE BASE, CALIF. - At Vandenberg Air Force Base, Calif. a covered SciSat-1 spacecraft is lifted onto a rotation stand. The solar arrays will be attached and the communications systems checked out. The SciSat-1 weighs approximately 330 pounds and after launch will be placed in a 400-mile-high polar orbit to investigate processes that control the distribution of ozone in the upper atmosphere. The data from the satellite will provide Canadian and international scientists with improved measurements relating to global ozone processes and help policymakers assess existing environmental policy and develop protective measures for improving the health of our atmosphere, preventing further ozone depletion. The mission is designed to last two years.

NASA Image and Video Library

2003-07-29

VANDENBERG AIR FORCE BASE, CALIF. - At Vandenberg Air Force Base, Calif. a covered SciSat-1 spacecraft is lifted onto a rotation stand. The solar arrays will be attached and the communications systems checked out. The SciSat-1 weighs approximately 330 pounds and after launch will be placed in a 400-mile-high polar orbit to investigate processes that control the distribution of ozone in the upper atmosphere. The data from the satellite will provide Canadian and international scientists with improved measurements relating to global ozone processes and help policymakers assess existing environmental policy and develop protective measures for improving the health of our atmosphere, preventing further ozone depletion. The mission is designed to last two years.

Broadband integrated polarization rotator using three-layer metallic grating structures

DOE PAGES

Fan, Ren -Hao; Liu, Dong; Peng, Ru -Wen; ...

2018-01-05

In this work, we demonstrate broadband integrated polarization rotator (IPR) with a series of three-layer rotating metallic grating structures. This transmissive optical IPR can conveniently rotate the polarization of linearly polarized light to any desired directions at different spatial locations with high conversion efficiency, which is nearly constant for different rotation angles. The linear polarization rotation originates from multi-wave interference in the three-layer grating structure. As a result, we anticipate that this type of IPR will find wide applications in analytical chemistry, biology, communication technology, imaging, etc.

Broadband integrated polarization rotator using three-layer metallic grating structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Ren -Hao; Liu, Dong; Peng, Ru -Wen

In this work, we demonstrate broadband integrated polarization rotator (IPR) with a series of three-layer rotating metallic grating structures. This transmissive optical IPR can conveniently rotate the polarization of linearly polarized light to any desired directions at different spatial locations with high conversion efficiency, which is nearly constant for different rotation angles. The linear polarization rotation originates from multi-wave interference in the three-layer grating structure. As a result, we anticipate that this type of IPR will find wide applications in analytical chemistry, biology, communication technology, imaging, etc.

Polarization splitter and polarization rotator designs based on transformation optics.

PubMed

Kwon, Do-Hoon; Werner, Douglas H

2008-11-10

The transformation optics technique is employed in this paper to design two optical devices - a two-dimensional polarization splitter and a three-dimensional polarization rotator for propagating beams. The polarization splitter translates the TM- and the TE-polarized components of an incident beam in opposite directions (i.e., shifted up or shifted down). The polarization rotator rotates the polarization state of an incoming beam by an arbitrary angle. Both optical devices are reflectionless at the entry and exit interfaces. Design details and full-wave simulation results are provided.

An all-reflective polarization rotator

NASA Astrophysics Data System (ADS)

Bohus, J.; Budai, Judit; Kalashnikov, M.; Osvay, K.

2017-05-01

The conceptual design and proof of principle experimental results of a polarization rotator based on mirrors are presented. The device is suitable for any-angle, online rotation of the plane of polarization of high peak intensity ultrashort laser pulses. Controllable rotation of the polarization vector of short laser pulses with a broad bandwidth requires achromatic retarding plates which have a limited scalability and the substantial plate thickness can lead to pulse broadening and inaccurate polarization rotation. Polarization rotators based on reflective optical elements are preferable alternatives to wave plates especially when used in high average power or high peak intensity ultra-short laser systems. The control of the polarization state is desirable in many laser-matter interaction experiments e.g., high harmonic and attosecond pulse generation, electron, proton and ion acceleration, electron-positron pair creating, vacuum nonlinear polarization effect. The device can also serve as a beam attenuator, in combination with a linear polarizer.

Seismic anisotropy in the vicinity of the Alpine fault, New Zealand, estimated by seismic interferometry

NASA Astrophysics Data System (ADS)

Takagi, R.; Okada, T.; Yoshida, K.; Townend, J.; Boese, C. M.; Baratin, L. M.; Chamberlain, C. J.; Savage, M. K.

2016-12-01

We estimate shear wave velocity anisotropy in shallow crust near the Alpine fault using seismic interferometry of borehole vertical arrays. We utilized four borehole observations: two sensors are deployed in two boreholes of the Deep Fault Drilling Project in the hanging wall side, and the other two sites are located in the footwall side. Surface sensors deployed just above each borehole are used to make vertical arrays. Crosscorrelating rotated horizontal seismograms observed by the borehole and surface sensors, we extracted polarized shear waves propagating from the bottom to the surface of each borehole. The extracted shear waves show polarization angle dependence of travel time, indicating shear wave anisotropy between the two sensors. In the hanging wall side, the estimated fast shear wave directions are parallel to the Alpine fault. Strong anisotropy of 20% is observed at the site within 100 m from the Alpine fault. The hanging wall consists of mylonite and schist characterized by fault parallel foliation. In addition, an acoustic borehole imaging reveals fractures parallel to the Alpine fault. The fault parallel anisotropy suggest structural anisotropy is predominant in the hanging wall, demonstrating consistency of geological and seismological observations. In the footwall side, on the other hand, the angle between the fast direction and the strike of the Alpine fault is 33-40 degrees. Since the footwall is composed of granitoid that may not have planar structure, stress induced anisotropy is possibly predominant. The direction of maximum horizontal stress (SHmax) estimated by focal mechanisms of regional earthquakes is 55 degrees of the Alpine fault. Possible interpretation of the difference between the fast direction and SHmax direction is depth rotation of stress field near the Alpine fault. Similar depth rotation of stress field is also observed in the SAFOD borehole at the San Andreas fault.

Bio-sensing based on plasmon-coupling caused by rotated sub-micrometer gratings in metal-dielectric interfacial layers

NASA Astrophysics Data System (ADS)

Csete, M.; Sipos, Á.; Szalai, A.; Mathesz, A.; Deli, M. A.; Veszelka, Sz.; Schmatulla, A.; Kőházi-Kis, A.; Osvay, K.; Marti, O.; Bor, Zs.

2007-09-01

Novel plasmonic sensor chips are prepared by generating sub-micrometer periodic patterns in the interfacial layers of bimetal-polymer films via master-grating based interference method. Poly-carbonate films spin-coated onto vacuum evaporated silver-gold bimetallic layers are irradiated by the two interfering UV beams of a Nd:YAG laser. It is proven by pulsed force mode AFM that periodic adhesion pattern corresponds to the surface relief gratings, consisting of sub-micrometer droplet arrays and continuous polymer stripes, induced by p- and s-polarized beams, respectively. The characteristic periods are the same, but more complex and larger amplitude adhesion modulation is detectable on the droplet arrays. The polar and azimuthal angle dependence of the resonance characteristic of plasmons is studied by combining the prism- and grating-coupling methods in a modified Kretschmann arrangement, illuminating the structured metal-polymer interface by a frequency doubled Nd:YAG laser through a semi-cylinder. It is proven that the grating-coupling results in double-peaked plasmon resonance curves on both of the droplet arrays and line gratings, when the grooves are rotated to an appropriate azimuthal angle, and the modulation amplitude of the structure is sufficiently large. Streptavidin seeding is performed to demonstrate that small amount of protein can be detected monitoring the shift of the secondary resonance minima. The available high concentration sensitivity is explained by the promotion of protein adherence in the structure's valleys due to the enhanced adhesion. The line-shaped polymer gratings resulting in narrow resonance peaks are utilized to demonstrate the effect of therapeutic molecules on Amyloid-Β peptide, a pathogenic factor in Alzheimer disease.

Magnetization mechanisms in ordered arrays of polycrystalline Fe100-xCox nanowires

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

2015-05-01

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe100-xCox nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.

Anisotropies in the linear polarization of vacancy photoluminescence in diamond induced by crystal rotations and strong magnetic fields

NASA Astrophysics Data System (ADS)

Braukmann, D.; Popov, V. P.; Glaser, E. R.; Kennedy, T. A.; Bayer, M.; Debus, J.

2018-03-01

We study the linear polarization properties of the photoluminescence of ensembles of neutral and negatively charged nitrogen vacancies and neutral vacancies in diamond crystals as a function of their symmetry and their response to strong external magnetic fields. The linear polarization degree, which exceeds 10% at room temperature, and rotation of the polarization plane of their zero-phonon lines significantly depend on the crystal rotation around specific axes demonstrating anisotropic angular evolutions. The sign of the polarization plane rotation is changed periodically through the crystal rotation, which indicates a switching between electron excited states of orthogonal linear polarizations. At external magnetic fields of up to 10 T, the angular dependencies of the linear polarization degree experience a remarkable phase shift. Moreover, the rotation of the linear polarization plane increases linearly with rising magnetic field at 6 K and room temperature, for the negatively charged nitrogen vacancies, which is attributed to magneto-optical Faraday rotation.

Terahertz metamaterials and systems based on rolled-up 3D elements: designs, technological approaches, and properties

PubMed Central

Prinz, Victor Ya.; Naumova, Elena V.; Golod, Sergey V.; Seleznev, Vladimir A.; Bocharov, Andrey A.; Kubarev, Vitaliy V.

2017-01-01

Electromagnetic metamaterials opened the way to extraordinary manipulation of radiation. Terahertz (THz) and optical metamaterials are usually fabricated by traditional planar-patterning approaches, while the majority of practical applications require metamaterials with 3D resonators. Making arrays of precise 3D micro- and nanoresonators is still a challenging problem. Here we present a versatile set of approaches to fabrication of metamaterials with 3D resonators rolled-up from strained films, demonstrate novel THz metamaterials/systems, and show giant polarization rotation by several chiral metamaterials/systems. The polarization spectra of chiral metamaterials on semiconductor substrates exhibit ultrasharp quasiperiodic peaks. Application of 3D printing allowed assembling more complex systems, including the bianisotropic system with optimal microhelices, which showed an extreme polarization azimuth rotation of 85° with drop by 150° at a frequency shift of 0.4%. We refer the quasiperiodic peaks in the polarization spectra of metamaterial systems to the interplay of different resonances, including peculiar chiral waveguide resonance. Formed metamaterials cannot be made by any other presently available technology. All steps of presented fabrication approaches are parallel, IC-compatible and allow mass fabrication with scaling of rolled-up resonators up to visible frequencies. We anticipate that the rolled-up meta-atoms will be ideal building blocks for future generations of commercial metamaterials, devices and systems on their basis. PMID:28256587

Terahertz metamaterials and systems based on rolled-up 3D elements: designs, technological approaches, and properties

NASA Astrophysics Data System (ADS)

Prinz, Victor Ya.; Naumova, Elena V.; Golod, Sergey V.; Seleznev, Vladimir A.; Bocharov, Andrey A.; Kubarev, Vitaliy V.

2017-03-01

Electromagnetic metamaterials opened the way to extraordinary manipulation of radiation. Terahertz (THz) and optical metamaterials are usually fabricated by traditional planar-patterning approaches, while the majority of practical applications require metamaterials with 3D resonators. Making arrays of precise 3D micro- and nanoresonators is still a challenging problem. Here we present a versatile set of approaches to fabrication of metamaterials with 3D resonators rolled-up from strained films, demonstrate novel THz metamaterials/systems, and show giant polarization rotation by several chiral metamaterials/systems. The polarization spectra of chiral metamaterials on semiconductor substrates exhibit ultrasharp quasiperiodic peaks. Application of 3D printing allowed assembling more complex systems, including the bianisotropic system with optimal microhelices, which showed an extreme polarization azimuth rotation of 85° with drop by 150° at a frequency shift of 0.4%. We refer the quasiperiodic peaks in the polarization spectra of metamaterial systems to the interplay of different resonances, including peculiar chiral waveguide resonance. Formed metamaterials cannot be made by any other presently available technology. All steps of presented fabrication approaches are parallel, IC-compatible and allow mass fabrication with scaling of rolled-up resonators up to visible frequencies. We anticipate that the rolled-up meta-atoms will be ideal building blocks for future generations of commercial metamaterials, devices and systems on their basis.

Terahertz metamaterials and systems based on rolled-up 3D elements: designs, technological approaches, and properties.

PubMed

Prinz, Victor Ya; Naumova, Elena V; Golod, Sergey V; Seleznev, Vladimir A; Bocharov, Andrey A; Kubarev, Vitaliy V

2017-03-03

Electromagnetic metamaterials opened the way to extraordinary manipulation of radiation. Terahertz (THz) and optical metamaterials are usually fabricated by traditional planar-patterning approaches, while the majority of practical applications require metamaterials with 3D resonators. Making arrays of precise 3D micro- and nanoresonators is still a challenging problem. Here we present a versatile set of approaches to fabrication of metamaterials with 3D resonators rolled-up from strained films, demonstrate novel THz metamaterials/systems, and show giant polarization rotation by several chiral metamaterials/systems. The polarization spectra of chiral metamaterials on semiconductor substrates exhibit ultrasharp quasiperiodic peaks. Application of 3D printing allowed assembling more complex systems, including the bianisotropic system with optimal microhelices, which showed an extreme polarization azimuth rotation of 85° with drop by 150° at a frequency shift of 0.4%. We refer the quasiperiodic peaks in the polarization spectra of metamaterial systems to the interplay of different resonances, including peculiar chiral waveguide resonance. Formed metamaterials cannot be made by any other presently available technology. All steps of presented fabrication approaches are parallel, IC-compatible and allow mass fabrication with scaling of rolled-up resonators up to visible frequencies. We anticipate that the rolled-up meta-atoms will be ideal building blocks for future generations of commercial metamaterials, devices and systems on their basis.

The Evolving Polarized Jet of Black Hole Candidate Swift J1745-26

NASA Technical Reports Server (NTRS)

Curran, P. A.; Coriat, M.; Miller-Jones, J. C. A.; Armstrong, R. P.; Edwards, P. G.; Sivakoff, G. R.; Woudt, P.; Altamirano, D.; Belloni, T. M.; Corbel, S.;

CCAM: A novel millimeter-wave instrument using a close-packed TES bolometer array

NASA Astrophysics Data System (ADS)

Lau, Judy M.

This thesis describes CCAM, an instrument designed to map the Cosmic Microwave Background (CMB), and also presents some of the initial measurements made with CCAM on the Atacama Cosmology Telescope (ACT). CCAM uses a CCD-like camera of millimeter-wave TES bolometers. It employs new detector technology, read-out electronics, cold re-imaging optics, and cryogenics to obtain high sensitivity CMB anisotropy measurements. The free-standing 8×32 close-packed array of pop- up TES detectors is the first of its kind to observe the sky at 145 GHz. We present the design of the receiver including the antireflection coated silicon lens re-imaging system, construction and optimization of the pulse tube/ sorption refrigerator cryogenic system, as well as the technology developed to integrate eight 1×32 TES columns and accompanying read-out electronics in to an array of 256 millimeter-wave detectors into a focal plane area of 3.5 cm 2. The performance of the detectors and optics prior to deployment at the ACT site in Chile are reported as well as preliminary performance results of the instrument when optically paired with the ACT telescope in the summer of 2007. Here, we also report on the feasibility of the TES detector array to measure polarization when coupled to a rotating birefringent sapphire half wave plate and wire-grid polarizer.

6-C polarization analysis using point measurements of translational and rotational ground-motion: theory and applications

NASA Astrophysics Data System (ADS)

Sollberger, David; Greenhalgh, Stewart A.; Schmelzbach, Cedric; Van Renterghem, Cédéric; Robertsson, Johan O. A.

2018-04-01

We provide a six-component (6-C) polarization model for P-, SV-, SH-, Rayleigh-, and Love-waves both inside an elastic medium as well as at the free surface. It is shown that single-station 6-C data comprised of three components of rotational motion and three components of translational motion provide the opportunity to unambiguously identify the wave type, propagation direction, and local P- and S-wave velocities at the receiver location by use of polarization analysis. To extract such information by conventional processing of three-component (3-C) translational data would require large and dense receiver arrays. The additional rotational components allow the extension of the rank of the coherency matrix used for polarization analysis. This enables us to accurately determine the wave type and wave parameters (propagation direction and velocity) of seismic phases, even if more than one wave is present in the analysis time window. This is not possible with standard, pure-translational 3-C recordings. In order to identify modes of vibration and to extract the accompanying wave parameters, we adapt the multiple signal classification algorithm (MUSIC). Due to the strong nonlinearity of the MUSIC estimator function, it can be used to detect the presence of specific wave types within the analysis time window at very high resolution. We show how the extracted wavefield properties can be used, in a fully automated way, to separate the wavefield into its different wave modes using only a single 6-C recording station. As an example, we apply the method to remove surface wave energy while preserving the underlying reflection signal and to suppress energy originating from undesired directions, such as side-scattered waves.

Tunable Polarization Conversion and Rotation based on a Reconfigurable Metasurface.

PubMed

Zhang, M; Zhang, W; Liu, A Q; Li, F C; Lan, C F

2017-09-21

Polarization is an important property of electromagnetic (EM) wave and different polarization manipulations are required for varied optical applications. Here we report a reconfigurable metasurface which achieves both the polarization conversion and the polarization rotation in THz regime. The metasurface is reconfigured through the micro-electro-mechanical-systems (MEMS) actuation. The cross polarization transmittance from a linear polarized incidence is experimentally tuned from 0 to 28% at 2.66 THz. In addition, the polarization rotation angle is effectively changed from -12.8° to 13.1° at 1.78 THz. The tunable bi-functional metasurface for polarization conversion and the polarization rotation can be flexibly applied in various applications such as imaging, polarization microscopy and material analysis, etc.

Quantum interference of highly-dispersive surface plasmons (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tokpanov, Yury S.; Fakonas, James S.; Atwater, Harry A.

2016-09-01

Previous experiments have shown that surface plasmon polaritons (SPPs) preserve their entangled state and do not cause measurable decoherence. However, essentially all of them were done using SPPs whose dispersion was in the linear "photon-like" regime. We report in this presentation on experiments showing how transition to "true-plasmon" non-linear dispersion regime, which occurs near SPP resonance frequency, will affect quantum coherent properties of light. To generate a polarization-entangled state we utilize type-I parametric down-conversion, occurring in a pair of non-linear crystals (BiBO), glued together and rotated by 90 degrees with respect to each other. For state projection measurements, we use a pair of polarizers and single-photon avalanche diode coincidence count detectors. We interpose a plasmonic hole array in the path of down-converted light before the polarizer. Without the hole array, we measure visibility V=99-100% and Bell's number S=2.81±0.03. To study geometrical effects we fabricated plasmonic hole arrays (gold on optically polished glass) with elliptical holes (axes are 190nm and 240nm) using focused ion beam. When we put this sample in our system we measured the reduction of visibility V=86±5% using entangled light. However, measurement using classical light gave exactly the same visibility; hence, this reduction is caused only by the difference in transmission coefficients of different polarizations. As samples with non-linear dispersion we fabricated two-layer (a-Si - Au) and three-layer (a-Si - Au - a-Si) structures on optically polished glass with different pitches and circular holes. The results of measurements with these samples will be discussed along with the theoretical investigations.

Microstrip antenna developments at JPL

NASA Technical Reports Server (NTRS)

Huang, John

1991-01-01

The in-house development of microstrip antennas, initiated in 1981, when a spaceborne lightweight and low-profile planar array was needed for a satellite communication system, is described. The work described covers the prediction of finite-ground-plane effects by the geometric theory of diffraction, higher-order-mode circularly polarized circular patch antennas, circularly polarized microstrip arrays with linearly polarized elements, an impedance-matching teardrop-shaped probe feed, a dual-polarized microstrip array with high isolation and low cross-polarization, a planar microstrip Yagi array, a microstrip reflectarray, a Ka-band MMIC array, and a series-fed linear arrays.

Freely Tunable Broadband Polarization Rotator for Terahertz Waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Ren-Hao; Zhou, Yu; Ren, Xiao-Ping

2014-12-28

A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging.

THE EFFECT OF GRAVITATION ON THE POLARIZATION STATE OF A LIGHT RAY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Tanay; Sen, A. K.

In the present work, detailed calculations have been carried out on the rotation of the polarization vector of an electromagnetic wave due to the presence of a gravitational field of a rotating body. This has been done using the general expression of Maxwell’s equation in curved spacetime. Considering the far-field approximation (i.e., the impact parameter is greater than the Schwarzschild radius and rotation parameter), the amount of rotation of the polarization vector as a function of impact parameter has been obtained for a rotating body (considering Kerr geometry). The present work shows that the rotation of the polarization vector cannotmore » be observed in the case of Schwarzschild geometry. This work also calculates the rotational effect when considering prograde and retrograde orbits for the light ray. Although the present work demonstrates the effect of rotation of the polarization vector, it confirms that there would be no net polarization of an electromagnetic wave due to the curved spacetime geometry in a Kerr field.« less

Metasurface for multi-channel terahertz beam splitters and polarization rotators

NASA Astrophysics Data System (ADS)

Zang, XiaoFei; Gong, HanHong; Li, Zhen; Xie, JingYa; Cheng, QingQing; Chen, Lin; Shkurinov, Alexander P.; Zhu, YiMing; Zhuang, SongLin

2018-04-01

Terahertz beam splitters and polarization rotators are two typical devices with wide applications ranging from terahertz communication to system integration. However, they are faced with severe challenges in manipulating THz waves in multiple channels, which is desirable for system integration and device miniaturization. Here, we propose a method to design ultra-thin multi-channel THz beam splitters and polarization rotators simultaneously. The reflected beams are divided into four beams with nearly the same density under illumination of linear-polarized THz waves, while the polarization of reflected beams in each channel is modulated with a rotation angle or invariable with respect to the incident THz waves, leading to the multi-channel polarization rotator (multiple polarization rotation in the reflective channels) and beam splitter, respectively. Reflective metasurfaces, created by patterning metal-rods with different orientations on a polyimide film, were fabricated and measured to demonstrate these characteristics. The proposed approach provides an efficient way of controlling polarization of THz waves in various channels, which significantly simplifies THz functional devices and the experimental system.

Dependence of locked mode behavior on frequency and polarity of a rotating external magnetic perturbation

NASA Astrophysics Data System (ADS)

Inoue, S.; Shiraishi, J.; Takechi, M.; Matsunaga, G.; Isayama, A.; Hayashi, N.; Ide, S.

2018-02-01

Active control and stabilization of locked modes (LM) via rotating external magnetic perturbations are numerically investigated under a realistic low resistivity condition. To explore plasma responses to rotating and/or static external magnetic perturbations, we have developed a resistive magnetohydrodynamic code ‘AEOLUS-IT’. By using AEOLUS-IT, dependencies of mode behavior on frequency and polarity of the rotating magnetic perturbation are successfully clarified. Here, the rotational direction of the rotating magnetic perturbation to the equilibrium plasma rotation in the laboratory frame is referred to as ‘polarity’. The rotating magnetic perturbation acts on the background rotating plasma in the presence of a static field. Under such circumstances, there exist bifurcated states of the background rotating plasma, which should be taken into account when studying the dependence of the mode behavior on the rotating magnetic perturbation. It is found that there exist an optimum frequency and polarity of the rotating magnetic perturbation to control the LM, and that the LM is effectively stabilized by a co-polarity magnetic perturbation in comparison with a counter-polarity one.

Electro-optic voltage sensor for sensing voltage in an E-field

DOEpatents

Davidson, James R.; Crawford, Thomas M.; Seifert, Gary D.

2002-03-26

A miniature electro-optic voltage sensor and system capable of accurate operation at high voltages has a sensor body disposed in an E-field. The body receives a source beam of electromagnetic radiation. A polarization beam displacer separates the source light beam into two beams with orthogonal linear polarizations. A wave plate rotates the linear polarization to rotated polarization. A transducer utilizes Pockels electro-optic effect and induces a differential phase shift on the major and minor axes of the rotated polarization in response to the E-field. A prism redirects the beam back through the transducer, wave plate, and polarization beam displacer. The prism also converts the rotated polarization to circular or elliptical polarization. The wave plate rotates the major and minor axes of the circular or elliptical polarization to linear polarization. The polarization beam displacer separates the beam into two beams of orthogonal linear polarization representing the major and minor axes. The system may have a transmitter for producing the beam of electro-magnetic radiation; a detector for converting the two beams into electrical signals; and a signal processor for determining the voltage.

Radio Remote Sensing of Coronal Mass Ejections: Implications for Parker Solar Probe and Solar Orbiter

NASA Astrophysics Data System (ADS)

Kooi, J. E.; Thomas, N. C.; Guy, M. B., III; Spangler, S. R.

2017-12-01

Coronal mass ejections (CMEs) are fast-moving magnetic field structures of enhanced plasma density that play an important role in space weather. The Solar Orbiter and Parker Solar Probe will usher in a new era of in situ measurements, probing CMEs within distances of 60 and 10 solar radii, respectively. At the present, only remote-sensing techniques such as Faraday rotation can probe the plasma structure of CMEs at these distances. Faraday rotation is the change in polarization position angle of linearly polarized radiation as it propagates through a magnetized plasma (e.g. a CME) and is proportional to the path integral of the electron density and line-of-sight magnetic field. In conjunction with white-light coronagraph measurements, Faraday rotation observations have been used in recent years to determine the magnetic field strength of CMEs. We report recent results from simultaneous white-light and radio observations made of a CME in July 2015. We made radio observations using the Karl G. Jansky Very Large Array (VLA) at 1 - 2 GHz frequencies of a set of radio sources through the solar corona at heliocentric distances that ranged between 8 - 23 solar radii. These Faraday rotation observations provide a priori estimates for comparison with future in situ measurements made by the Solar Orbiter and Parker Solar Probe. Similar Faraday rotation observations made simultaneously with observations by the Solar Orbiter and Parker Solar Probe in the future could provide information about the global structure of CMEs sampled by these probes and, therefore, aid in understanding the in situ measurements.

Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

PubMed

Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

2015-04-17

Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole. Copyright © 2015, American Association for the Advancement of Science.

BROADBAND RADIO POLARIMETRY AND FARADAY ROTATION OF 563 EXTRAGALACTIC RADIO SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, C. S.; Gaensler, B. M.; Feain, I. J.

2015-12-10

We present a broadband spectropolarimetric survey of 563 discrete, mostly unresolved radio sources between 1.3 and 2.0 GHz using data taken with the Australia Telescope Compact Array. We have used rotation-measure synthesis to identify Faraday-complex polarized sources, those objects whose frequency-dependent polarization behavior indicates the presence of material possessing complicated magnetoionic structure along the line of sight (LOS). For sources classified as Faraday-complex, we have analyzed a number of their radio and multiwavelength properties to determine whether they differ from Faraday-simple polarized sources (sources for which LOS magnetoionic structures are comparatively simple) in these properties. We use this information tomore » constrain the physical nature of the magnetoionic structures responsible for generating the observed complexity. We detect Faraday complexity in 12% of polarized sources at ∼1′ resolution, but we demonstrate that underlying signal-to-noise limitations mean the true percentage is likely to be significantly higher in the polarized radio source population. We find that the properties of Faraday-complex objects are diverse, but that complexity is most often associated with depolarization of extended radio sources possessing a relatively steep total intensity spectrum. We find an association between Faraday complexity and LOS structure in the Galactic interstellar medium (ISM) and claim that a significant proportion of the Faraday complexity we observe may be generated at interfaces of the ISM associated with ionization fronts near neutral hydrogen structures. Galaxy cluster environments and internally generated Faraday complexity provide possible alternative explanations in some cases.« less

Interferometric Observation of the Highly Polarized SiO Maser Emission from the v = 1, J = 5-4 Transition Associated with VY Canis Majoris

NASA Astrophysics Data System (ADS)

Shinnaga, Hiroko; Moran, James M.; Young, Ken H.; Ho, Paul T. P.

2004-11-01

We used the Submillimeter Array to image the SiO maser emission in the v=1, J=5-4 transition associated with the peculiar red supergiant VY Canis Majoris. We identified seven maser components and measured their relative positions and linear polarization properties. Five of the maser components are coincident to within about 150 mas (~200 AU at the distance of 1.5 kpc); most of them may originate in the circumstellar envelope at a radius of about 50 mas from the star along with the SiO masers in the lowest rotational transitions. Our measurements show that two of the maser components may be offset from the inner stellar envelope (at the 3 σ level of significance) and may be part of a larger bipolar outflow associated with VY CMa identified by Shinnaga et al. The strongest maser feature at a velocity of 35.9 km s-1 has a 60% linear polarization, and its polarization direction is aligned with the bipolar axis. Such a high degree of polarization suggests that maser inversion is due to radiative pumping. Five of the other maser features have significant linear polarization.

Magnetization mechanisms in ordered arrays of polycrystalline Fe{sub 100−x}Co{sub x} nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viqueira, M. S.; Bajales, N.; Urreta, S. E.

2015-05-28

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe{sub 100−x}Co{sub x} nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, themore » alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.« less

"Axis of Universe" Not Seen in Data, Astronomers Say

NASA Astrophysics Data System (ADS)

1997-04-01

A claim that the universe has a preferred direction is not supported by recent observational evidence, according to three astronomers who analyzed data from the Very Large Array (VLA) radio telescope in New Mexico and the W.M. Keck Telescope in Hawaii. John Wardle of Brandeis University, Rick Perley of the National Radio Astronomy Observatory, and Marshall Cohen of the California Institute of Technology responded to an article in the April 21 issue of Physical Review Letters, in which Borge Nodland of the University of Rochester and John Ralston of the University of Kansas claimed to have found that the universe has a distinct axis that affects electromagnetic radiation (light, radio waves, etc.). Nodland and Ralston said that their analysis of previous radio observations of 160 galaxies, made in the 1970s and 1980s, showed that radiation coming from objects had its direction of polarization rotated by different amounts, depending on the direction of the galaxies. The amount of polarization rotation, they said, increases with the distance of the galaxies, and depends on direction, indicating that the universe has an axis along which more rotation occurs. Wardle, Perley and Cohen say that recent, high-quality observations with the VLA and the 10-meter W.M. Keck telescope show "that the radio and optical data directly refute" the contention of Nodland and Ralston. The more-recent data, consisting of polarization images of galaxies and quasars at a variety of distances and in different directions, simply do not show any evidence for Nodland and Ralston's "cosmic corkscrew" effect, the researchers say. Wardle, Perley and Cohen have submitted their results to Physical Review Letters. Galaxies and quasars, and the "jets" of subatomic particles ejected at great speeds by some of these objects, have definite patterns of polarized emission of light and radio waves. These patterns are well-known and established. If the polarization of their light were rotated by some cosmological effect, the known relationships between the objects and the direction of polarization of their light should be altered, Wardle, Perley and Cohen reasoned. They examined polarization images to seek evidence for such alteration. For example, the quasar PKS 2209+152, nearly 9 billion light-years distant, should, according to the Nodland and Ralston "corkscrew" hypothesis, have had the polarization of its radio emission rotated by about 90 degrees. Instead, VLA observations showed no rotation at all. After studying VLA and Keck data on 26 galaxies and quasars, Wardle, Perley and Cohen conclude that "the observational data at both optical and radio wavelengths show that any rotation of the plane of polarizaton over cosmological distances is unmeasurably small and is indistinguishable from zero." Wardle said, "The best fit to the high resolution optical and radio data shows that any effect is at least a hundred times smaller than that claimed by Nodland and Ralston." The VLA is an instrument of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The W.M. Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California and NASA; it was made possible by the generous financial support of the W.M. Keck Foundation.

Optical Modeling and Polarization Calibration for CMB Measurements with Actpol and Advanced Actpol

NASA Technical Reports Server (NTRS)

Koopman, Brian; Austermann, Jason; Cho, Hsiao-Mei; Coughlin, Kevin P.; Duff, Shannon M.; Gallardo, Patricio A.; Hasselfield, Matthew; Henderson, Shawn W.; Ho, Shuay-Pwu Patty; Hubmayr, Johannes;

Optical modeling and polarization calibration for CMB measurements with ACTPol and Advanced ACTPol

NASA Astrophysics Data System (ADS)

Koopman, Brian; Austermann, Jason; Cho, Hsiao-Mei; Coughlin, Kevin P.; Duff, Shannon M.; Gallardo, Patricio A.; Hasselfield, Matthew; Henderson, Shawn W.; Ho, Shuay-Pwu Patty; Hubmayr, Johannes; Irwin, Kent D.; Li, Dale; McMahon, Jeff; Nati, Federico; Niemack, Michael D.; Newburgh, Laura; Page, Lyman A.; Salatino, Maria; Schillaci, Alessandro; Schmitt, Benjamin L.; Simon, Sara M.; Vavagiakis, Eve M.; Ward, Jonathan T.; Wollack, Edward J.

2016-07-01

The Atacama Cosmology Telescope Polarimeter (ACTPol) is a polarization sensitive upgrade to the Atacama Cosmology Telescope, located at an elevation of 5190 m on Cerro Toco in Chile. ACTPol uses transition edge sensor bolometers coupled to orthomode transducers to measure both the temperature and polarization of the Cosmic Microwave Background (CMB). Calibration of the detector angles is a critical step in producing polarization maps of the CMB. Polarization angle offsets in the detector calibration can cause leakage in polarization from E to B modes and induce a spurious signal in the EB and TB cross correlations, which eliminates our ability to measure potential cosmological sources of EB and TB signals, such as cosmic birefringence. We calibrate the ACTPol detector angles by ray tracing the designed detector angle through the entire optical chain to determine the projection of each detector angle on the sky. The distribution of calibrated detector polarization angles are consistent with a global offset angle from zero when compared to the EB-nulling offset angle, the angle required to null the EB cross-correlation power spectrum. We present the optical modeling process. The detector angles can be cross checked through observations of known polarized sources, whether this be a galactic source or a laboratory reference standard. To cross check the ACTPol detector angles, we use a thin film polarization grid placed in front of the receiver of the telescope, between the receiver and the secondary reflector. Making use of a rapidly rotating half-wave plate (HWP) mount we spin the polarizing grid at a constant speed, polarizing and rotating the incoming atmospheric signal. The resulting sinusoidal signal is used to determine the detector angles. The optical modeling calibration was shown to be consistent with a global offset angle of zero when compared to EB nulling in the first ACTPol results and will continue to be a part of our calibration implementation. The first array of detectors for Advanced ACTPol, the next generation upgrade to ACTPol, will be deployed in 2016. We plan to continue using both techniques and compare them to astrophysical source measurements for the Advanced ACTPol polarization calibration.

Study of Rayleigh-Love coupling from Spatial Gradient Observation

NASA Astrophysics Data System (ADS)

Lin, C. J.; Hosseini, K.; Donner, S.; Vernon, F.; Wassermann, J. M.; Igel, H.

2017-12-01

We present a new method to study Rayleigh-Love coupling. Instead of using seismograms solely, where ground motion is recorded as function of time, we incorporate with rotation and strain, also called spatial gradient where ground is represented as function of distance. Seismic rotation and strain are intrinsic different observable wavefield so are helpful to indentify wave type and wave propagation. A Mw 7.5 earthquake on 29 March 2015 occurred in Kokopo, Papua New Guinea recorded by a dense seismic array at PFO, California are used to obtaint seismic spatial gradient. We firstly estimate time series of azimuthal direction and phase velocity of SH wave and Rayleigh wave by analyzing collocated seismograms and rotations. This result also compares with frequency wavenumber methods using a nearby ANZA seismic array. We find the direction of Rayleigh wave fits well with great-circle back azimuth during wave propagation, while the direction of Love wave deviates from that, especially when main energy of Rayleigh wave arrives. From the analysis of cross-correlation between areal strain and vertical rotation, it reveals that high coherence, either positive or negative, happens at the same time when Love wave deparate from great-circle path. We also find the observed azimuth of Love wave and polarized particle motion of Rayleigh wave fits well with the fast direction of Rayleigh wave, for the period of 50 secs. We conclude the cause of deviated azimuth of Love wave is due to Rayleigh-Love coupling, as surface wave propagates through the area with anisotropic structure.

Interferometric Gravity Darkening Observations of Vega with the CHARA Array

NASA Astrophysics Data System (ADS)

Aufdenberg, J. P.; Merand, A.; Coude Foresto, V.; Absil, O.; Di Folco, E.; Kervella, P.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.; Turner, N. H.; Berger, D. H.; McAlister, H. A.

2005-12-01

We have obtained high-precision interferometric measurements of the A0 V standard star Vega with the Center for High Angular Resolution Astronomy (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR) beam combiner in the K' band at projected baselines between 103 m and 273 m. The measured squared visibility amplitudes beyond the first lobe are significantly weaker than expected for a slowly rotating star and provide strong evidence for the model of Vega as a rapidly rotating star viewed very nearly pole on. We have constructed a Roche-von Zeipel gravity-darkened model atmosphere which is in generally good agreement with both our interferometric data and archival spectrophotometry. Our model indicates Vega is rotating at ˜92% of its angular break-up rate with an equatorial velocity of ˜275 km s-1. We find a polar effective temperature of ˜10150 K and a pole-to-equator effective temperature difference of ˜2500 K, much larger than the ˜300 K derived by Gulliver, Hill, and Adelman. Our model suggests that Vega's cool equatorial atmosphere may have significant convective flux and predicts a significantly cooler spectral energy distribution for Vega as seen by its surrounding debris disk. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology. The CHARA Array is operated by the Center for High Angular Resolution Astronomy with support from Georgia State University and the National Science Foundation, the Keck Foundation and the Packard Foundation.

Constraining Polarized Foregrounds for EoR Experiments. II. Polarization Leakage Simulations in the Avoidance Scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nunhokee, C. D.; Bernardi, G.; Foster, G.

A critical challenge in the observation of the redshifted 21 cm line is its separation from bright Galactic and extragalactic foregrounds. In particular, the instrumental leakage of polarized foregrounds, which undergo significant Faraday rotation as they propagate through the interstellar medium, may harmfully contaminate the 21 cm power spectrum. We develop a formalism to describe the leakage due to instrumental widefield effects in visibility-based power spectra measured with redundant arrays, extending the delay-spectrum approach presented in Parsons et al. We construct polarized sky models and propagate them through the instrument model to simulate realistic full-sky observations with the Precision Arraymore » to Probe the Epoch of Reionization. We find that the leakage due to a population of polarized point sources is expected to be higher than diffuse Galactic polarization at any k mode for a 30 m reference baseline. For the same reference baseline, a foreground-free window at k > 0.3 h Mpc{sup −1} can be defined in terms of leakage from diffuse Galactic polarization even under the most pessimistic assumptions. If measurements of polarized foreground power spectra or a model of polarized foregrounds are given, our method is able to predict the polarization leakage in actual 21 cm observations, potentially enabling its statistical subtraction from the measured 21 cm power spectrum.« less

Gamma-ray burster counterparts - Radio

NASA Technical Reports Server (NTRS)

Schaefer, Bradley E.; Cline, Thomas L.; Desai, U. D.; Teegarden, B. J.; Atteia, J.-L.; Barat, C.; Estulin, I. V.; Evans, W. D.; Fenimore, E. E.; Hurley, K.

1989-01-01

Many observers and theorists have suggested that gamma-ray bursters (GRBs) are related to highly magnetized rotating, neutron stars, in which case an analogy with pulsars implies that GRBs would be prodigious emitters of polarized radio emission during quiescence. The paper reports on a survey conducted with the Very Large Array radio telescope of 10 small GRB error regions for quiescent radio emission at wavelengths of 2, 6, and 20 cm. The sensitivity of the survey varied from 0.1 to 0.8 mJy. The observations did indeed reveal four radio sources inside the GRB error regions.

Probing microstructural information of anisotropic scattering media using rotation-independent polarization parameters.

PubMed

Sun, Minghao; He, Honghui; Zeng, Nan; Du, E; Guo, Yihong; Peng, Cheng; He, Yonghong; Ma, Hui

2014-05-10

Polarization parameters contain rich information on the micro- and macro-structure of scattering media. However, many of these parameters are sensitive to the spatial orientation of anisotropic media, and may not effectively reveal the microstructural information. In this paper, we take polarization images of different textile samples at different azimuth angles. The results demonstrate that the rotation insensitive polarization parameters from rotating linear polarization imaging and Mueller matrix transformation methods can be used to distinguish the characteristic features of different textile samples. Further examinations using both experiments and Monte Carlo simulations reveal that the residue rotation dependence in these polarization parameters is due to the oblique incidence illumination. This study shows that such rotation independent parameters are potentially capable of quantitatively classifying anisotropic samples, such as textiles or biological tissues.

CONSTRAINING POLARIZED FOREGROUNDS FOR EoR EXPERIMENTS. I. 2D POWER SPECTRA FROM THE PAPER-32 IMAGING ARRAY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohn, S. A.; Aguirre, J. E.; Moore, D. F.

2016-06-01

Current generation low-frequency interferometers constructed with the objective of detecting the high-redshift 21 cm background aim to generate power spectra of the brightness temperature contrast of neutral hydrogen in primordial intergalactic medium. Two-dimensional (2D) power spectra (power in Fourier modes parallel and perpendicular to the line of sight) that formed from interferometric visibilities have been shown to delineate a boundary between spectrally smooth foregrounds (known as the wedge ) and spectrally structured 21 cm background emission (the EoR window ). However, polarized foregrounds are known to possess spectral structure due to Faraday rotation, which can leak into the EoR window.more » In this work we create and analyze 2D power spectra from the PAPER-32 imaging array in Stokes I, Q, U, and V. These allow us to observe and diagnose systematic effects in our calibration at high signal-to-noise within the Fourier space most relevant to EoR experiments. We observe well-defined windows in the Stokes visibilities, with Stokes Q, U, and V power spectra sharing a similar wedge shape to that seen in Stokes I. With modest polarization calibration, we see no evidence that polarization calibration errors move power outside the wedge in any Stokes visibility to the noise levels attained. Deeper integrations will be required to confirm that this behavior persists to the depth required for EoR detection.« less

Measurements of the Structure of the Plasma Rotation in Slowly Rotating Tearing Modes in DIII-D

NASA Astrophysics Data System (ADS)

Taylor, N. Z.; Ferraro, N. M.; La Haye, R. J.; Petty, C. C.; Bowman, C.

2014-10-01

A helically modified ion flow by an island can lead to helical ion polarization currents which can affect tearing mode stability. This issue is of particular importance to ITER where large inertia and relatively low torque will likely result in low rotation. In DIII-D cases either (1) a m/n = 2/1 mode is slowed down to ~1 kHz (faster than the inverse wall time) by near balanced neutral beams or (2) an island is entrained by applied rotating n = 1 magnetic field at 10 Hz (slower than the inverse wall time). The n = 1 island structure is measured with electron cyclotron emission radiometry. The ion rotation and temperature are measured by fast resolution (274 μ s) charge exchange recombination (CER) spectroscopy in the 1 kHz freely rotating case and by standard CER (5 ms) in the 10 Hz entrainment. Tangential and vertical CER arrays allow for the radial profile of the helically perturbed rotation to be determined. A comparison of the measured nonlinear island structures with that from the linear resistive stability code M3D-C1 will be presented. Work supported in part by the US Department of Energy under DE-FG02-95ER54309 and DE-FC02-04ER54698.

Ultra-thin, single-layer polarization rotator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, T. V.; Truong, V. V., E-mail: Truong.Vo-Van@Concordia.Ca; Do, P. A.

We demonstrate light polarization control over a broad spectral range by a uniform layer of vanadium dioxide as it undergoes a phase transition from insulator to metal. Changes in refractive indices create unequal phase shifts on s- and p-polarization components of incident light, and rotation of linear polarization shows intensity modulation by a factor of 10{sup 3} when transmitted through polarizers. This makes possible polarization rotation devices as thin as 50 nm that would be activated thermally, optically or electrically.

Electrically-Generated Spin Polarization in Non-Magnetic Semiconductors

DTIC Science & Technology

2016-03-31

resolved Faraday rotation data due to electron spin polarization from previous pump pulses was characterized, and an analytic solution for this phase...electron spin polarization was shown to produce nuclear hyperpolarization through dynamic nuclear polarization. Time-resolved Faraday rotation...Distribution approved for public release. 3    Figure 3. Total magnetic field measured using time-resolved Faraday rotation with the electrically

Polarization splitting phenomenon of photonic crystals constructed by two-fold rotationally symmetric unit-cells

NASA Astrophysics Data System (ADS)

Yasa, U. G.; Giden, I. H.; Turduev, M.; Kurt, H.

2017-09-01

We present an intrinsic polarization splitting characteristic of low-symmetric photonic crystals (PCs) formed by unit-cells with C 2 rotational symmetry. This behavior emerges from the polarization sensitive self-collimation effect for both transverse-magnetic (TM) and transverse-electric (TE) modes depending on the rotational orientations of the unit-cell elements. Numerical analyzes are performed in both frequency and time domains for different types of square lattice two-fold rotational symmetric PC structures. At incident wavelength of λ = 1550 nm, high polarization extinction ratios with ˜26 dB (for TE polarization) and ˜22 dB (for TM polarization) are obtained with an operating bandwidth of 59 nm. Moreover, fabrication feasibilities of the designed structure are analyzed to evaluate their robustness in terms of the unit-cell orientation: for the selected PC unit-cell composition, corresponding extinction ratios for both polarizations still remain to be over 18 dB for the unit-cell rotation interval of θ = [40°-55°]. Taking all these advantages, two-fold rotationally symmetric PCs could be considered as an essential component in photonic integrated circuits for polarization control of light.

In-Flight Performance of the Polarization Modulator in the CLASP Rocket Experiment

NASA Technical Reports Server (NTRS)

Ishikawa, Shin-nosuke; Shimizu, Toshifumi; Kano, Ryohei; Bando, Takamasa; Ishikawa, Ryoko; Giono, Gabriel; Beabout, Dyana L.; Beabout, Brent L.; Nakayama, Satoshi; Tajima, Takao

2016-01-01

We developed a polarization modulation unit (PMU), a motor system to rotate a waveplate continuously. In polarization measurements, the continuous rotating waveplate is an important element as well as a polarization analyzer to record the incident polarization in a time series of camera exposures. The control logic of PMU was originally developed for the next Japanese solar observation satellite SOLAR-C by the SOLAR-C working group. We applied this PMU for the Chromospheric Lyman-alpha SpectroPolarimeter (CLASP). CLASP is a sounding rocket experiment to observe the linear polarization of the Lyman-alpha emission (121.6 nm vacuum ultraviolet) from the upper chromosphere and transition region of the Sun with a high polarization sensitivity of 0.1 % for the first time and investigate their vector magnetic field by the Hanle effect. The driver circuit was developed to optimize the rotation for the CLASP waveplate (12.5 rotations per minute). Rotation non-uniformity of the waveplate causes error in the polarization degree (i.e. scale error) and crosstalk between Stokes components. We confirmed that PMU has superior rotation uniformity in the ground test and the scale error and crosstalk of Stokes Q and U are less than 0.01 %. After PMU was attached to the CLASP instrument, we performed vibration tests and confirmed all PMU functions performance including rotation uniformity did not change. CLASP was successfully launched on September 3, 2015, and PMU functioned well as designed. PMU achieved a good rotation uniformity, and the high precision polarization measurement of CLASP was successfully achieved.

In-flight performance of the polarization modulator in the CLASP rocket experiment

NASA Astrophysics Data System (ADS)

Ishikawa, Shin-nosuke; Shimizu, Toshifumi; Kano, Ryohei; Bando, Takamasa; Ishikawa, Ryoko; Giono, Gabriel; Beabout, Dyana L.; Beabout, Brent L.; Nakayama, Satoshi; Tajima, Takao

2016-07-01

We developed a polarization modulation unit (PMU), a motor system to rotate a waveplate continuously. In polarization measurements, the continuous rotating waveplate is an important element as well as a polarization analyzer to record the incident polarization in a time series of camera exposures. The control logic of PMU was originally developed for the next Japanese solar observation satellite SOLAR-C by the SOLAR-C working group. We applied this PMU for the Chromospheric Lyman-alpha SpectroPolarimeter (CLASP). CLASP is a sounding rocket experiment to observe the linear polarization of the Lyman-alpha emission (121.6 nm vacuum ultraviolet) from the upper chromosphere and transition region of the Sun with a high polarization sensitivity of 0.1 % for the first time and investigate their vector magnetic field by the Hanle effect. The driver circuit was developed to optimize the rotation for the CLASP waveplate (12.5 rotations per minute). Rotation non- uniformity of the waveplate causes error in the polarization degree (i.e. scale error) and crosstalk between Stokes components. We confirmed that PMU has superior rotation uniformity in the ground test and the scale error and crosstalk of Stokes Q and U are less than 0.01 %. After PMU was attached to the CLASP instrument, we performed vibration tests and confirmed all PMU functions performance including rotation uniformity did not change. CLASP was successfully launched on September 3, 2015, and PMU functioned well as designed. PMU achieved a good rotation uniformity, and the high precision polarization measurement of CLASP was successfully achieved.

OCAPI: a multidirectional multichannel polarizing imager

NASA Astrophysics Data System (ADS)

Le Naour, C.; Eichen, G.; Léon, J. F.

2017-11-01

OCAPI (Optical Carbonaceous and anthropogenic Aerosols Pathfinder Instrument) is an imager dedicated to the observation of the spectral, directional and polarized signatures of the solar radiance reflected by the Earth-Atmosphere system. The measurements are used to study air quality and pollution by tracking aerosol quantity, types and circulation at various scales in the visible range. The main characteristics of OCAPI are a 110° along track and cross track field of view, eight polarized channels distributed between 320 and 2130 nm. The resolution is 4 x 4 km2 in the visible and the shortwave infrared (SWIR) range, and 10 x 10 km2 in the UV. The instrumental concept is derived from POLDER and PARASOL with additional channels in the UV and SWIR to better determine aerosol properties and constrain Earth surface and cloud contributions in the detected signal. It is based on three wide field-ofview telecentric optics (UV, Visible and SWIR), a rotating wheel bearing spectral and polarized filters and two dimensional detector arrays at the focal plane of the optics. The instrument requirements, concept and budgets are presented.

Polarimetry at millimeter wavelengths with the NIKA camera: calibration and performance

NASA Astrophysics Data System (ADS)

Ritacco, A.; Ponthieu, N.; Catalano, A.; Adam, R.; Ade, P.; André, P.; Beelen, A.; Benoît, A.; Bideaud, A.; Billot, N.; Bourrion, O.; Calvo, M.; Coiffard, G.; Comis, B.; Désert, F.-X.; Doyle, S.; Goupy, J.; Kramer, C.; Leclercq, S.; Macías-Pérez, J. F.; Mauskopf, P.; Maury, A.; Mayet, F.; Monfardini, A.; Pajot, F.; Pascale, E.; Perotto, L.; Pisano, G.; Rebolo-Iglesias, M.; Revéret, V.; Rodriguez, L.; Romero, C.; Ruppin, F.; Savini, G.; Schuster, K.; Sievers, A.; Thum, C.; Triqueneaux, S.; Tucker, C.; Zylka, R.

2017-03-01

Magnetic fields, which play a major role in a large number of astrophysical processes can be traced via observations of dust polarization. In particular, Planck low-resolution observations of dust polarization have demonstrated that Galactic filamentary structures, where star formation takes place, are associated to well organized magnetic fields. A better understanding of this process requires detailed observations of galactic dust polarization on scales of 0.01 to 0.1 pc. Such high-resolution polarization observations can be carried out at the IRAM 30 m telescope using the recently installed NIKA2 camera, which features two frequency bands at 260 and 150 GHz (respectively 1.15 and 2.05 mm), the 260 GHz band being polarization sensitive. NIKA2 so far in commissioning phase, has its focal plane filled with 3300 detectors to cover a Field of View (FoV) of 6.5 arcmin diameter. The NIKA camera, which consisted of two arrays of 132 and 224 Lumped Element Kinetic Inductance Detectors (LEKIDs) and a FWHM (Full-Width-Half-Maximum) of 12 and 18.2 arcsec at 1.15 and 2.05 mm respectively, has been operated at the IRAM 30 m telescope from 2012 to 2015 as a test-bench for NIKA2. NIKA was equipped of a room temperature polarization system (a half wave plate (HWP) and a grid polarizer facing the NIKA cryostat window). The fast and continuous rotation of the HWP permits the quasi simultaneous reconstruction of the three Stokes parameters, I, Q, and U at 150 and 260 GHz. This paper presents the first polarization measurements with KIDs and reports the polarization performance of the NIKA camera and the pertinence of the choice of the polarization setup in the perspective of NIKA2. We describe the polarized data reduction pipeline, specifically developed for this project and how the continuous rotation of the HWP permits to shift the polarized signal far from any low frequency noise. We also present the dedicated algorithm developed to correct systematic leakage effects. We report results on compact and extended sources obtained duringthe February 2015 technical campaign. These results demonstrate a good understanding of polarization systematics and state-of-the-art performance in terms of photometry, polarization degree and polarization angle reconstruction.

Circumstellar Disks Around Rapidly Rotating Be-type Stars

NASA Astrophysics Data System (ADS)

Touhami, Yamina

2012-01-01

Be stars are rapidly rotating B-type stars that eject large amounts of gaseous material into a circumstellar equatorial disk. The existence of this disk has been confirmed through the presence of several observational signatures such as the strong hydrogen emission lines, the IR flux excess, and the linear polarization detected from these systems. Here we report simultaneous near-IR interferometric and spectroscopic observations of circumstellar disks around Be stars obtained with the CHARA Array long baseline interferometer and the Mimir spectrograph at Lowell observatory. The goal of this project was to measure precise angular sizes and to characterize the fundamental geometrical and physical properties of the circumstellar disks. We were able to determine spatial extensions, inclinations, and position angles, as well as the gas density profile of the circumstellar disks using an elliptical Gaussian model and a physical thick disk model, and we show that the K-band interferometric angular sizes of the circumstellar disks are correlated with the H-alpha angular sizes. By combining the projected rotational velocity of the Be star with the disk inclination derived from interferometry, we provide estimates of the equatorial rotational velocities of these rapidly rotating Be stars.

A Translational Polarization Rotator

NASA Technical Reports Server (NTRS)

Chuss, David T.; Wollack, Edward J.; Pisano, Giampaolo; Ackiss, Sheridan; U-Yen, Kongpop; Ng, Ming wah

2012-01-01

We explore a free-space polarization modulator in which a variable phase introduction between right- and left-handed circular polarization components is used to rotate the linear polarization of the outgoing beam relative to that of the incoming beam. In this device, the polarization states are separated by a circular polarizer that consists of a quarter-wave plate in combination with a wire grid. A movable mirror is positioned behind and parallel to the circular polarizer. As the polarizer-mirror distance is separated, an incident liear polarization will be rotated through an angle that is proportional to the introduced phase delay. We demonstrate a prototype device that modulates Stokes Q and U over a 20% bandwidth.

Polarization measurements made on LFRA and OASIS emitter arrays

NASA Astrophysics Data System (ADS)

Geske, Jon; Sparkman, Kevin; Oleson, Jim; Laveigne, Joe; Sieglinger, Breck; Marlow, Steve; Lowry, Heard; Burns, James

2008-04-01

Polarization is increasingly being considered as a method of discrimination in passive sensing applications. In this paper the degree of polarization of the thermal emission from the emitter arrays of two new Santa Barbara Infrared (SBIR) micro-bolometer resistor array scene projectors was characterized at ambient temperature and at 77 K. The emitter arrays characterized were from the Large Format Resistive Array (LFRA) and the Optimized Arrays for Space-Background Infrared Simulation (OASIS) scene projectors. This paper reports the results of this testing.

Practical method for transversely measuring the spin polarization of optically pumped alkali atoms

NASA Astrophysics Data System (ADS)

Ding, Zhichao; Yuan, Jie; Long, Xingwu

2018-06-01

A practical method to measure the spin polarization of optically pumped alkali atoms is demonstrated. In order to realize transverse measurement, the transverse spin component of spin-polarized alkali atoms is created by a rotating exciting magnetic field, and detected using the optical rotation of a near-resonant probe beam for realizing a high detection sensitivity. The dependency of the optical rotation on the spin polarization of 133Cs atoms is derived theoretically and verified experimentally. By changing the direction of the rotating magnetic field, we realize the transverse measurement of the spin polarization of 133Cs atoms in either ground-state hyperfine level.

Rotation of the cosmic microwave background polarization from weak gravitational lensing.

PubMed

Dai, Liang

2014-01-31

When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection.

Enhanced Polarized Emission from the One-parsec-scale Hotspot of 3C 84 as a Result of the Interaction with the Clumpy Ambient Medium

NASA Astrophysics Data System (ADS)

Nagai, H.; Fujita, Y.; Nakamura, M.; Orienti, M.; Kino, M.; Asada, K.; Giovannini, G.

2017-11-01

We present Very Long Baseline Array polarimetric observations of the innermost jet of 3C 84 (NGC 1275) at 43 GHz. A significant polarized emission is detected at the hotspot of the innermost restarted jet, which is located 1 pc south from the radio core. While the previous report presented a hotspot at the southern end of the western limb, the hotspot location has been moved to the southern end of the eastern limb. Faraday rotation is detected within an entire bandwidth of the 43 GHz band. The measured rotation measure (RM) is at most (6.3 ± 1.9) × 105 rad m-2 and might be slightly time variable on the timescale of a month by a factor of a few. Our measured RM and the RM previously reported by the CARMA and SMA observations cannot be consistently explained by the spherical accretion flow with a power-law profile. We propose that a clumpy/inhomogeneous ambient medium is responsible for the observed RM. Using an equipartition magnetic field, we derive the electron density of 2 × 104 cm-3. Such an electron density is consistent with the cloud of the narrow line emission region around the central engine. We also discuss the magnetic field configuration from the black hole scale to the parsec scale and the origin of low polarization.

Seismic shear waves as Foucault pendulum

NASA Astrophysics Data System (ADS)

Snieder, Roel; Sens-Schönfelder, Christoph; Ruigrok, Elmer; Shiomi, Katsuhiko

2016-03-01

Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of ScS and ScS2 waves, we show that the Foucault-like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed SKS splitting.

Polarization digital holographic microscopy using low-cost liquid crystal polarization rotators

NASA Astrophysics Data System (ADS)

Dovhaliuk, Rostyslav Yu

2018-02-01

Polarization imaging methods are actively used to study anisotropic objects. A number of methods and systems, such as imaging polarimeters, were proposed to measure the state of polarization of light that passed through the object. Digital holographic and interferometric approaches can be used to quantitatively measure both amplitude and phase of a wavefront. Using polarization modulation optics, the measurement capabilities of such interference-based systems can be extended to measure polarization-dependent parameters, such as phase retardation. Different kinds of polarization rotators can be used to alternate the polarization of a reference beam. Liquid crystals are used in a rapidly increasing number of different optoelectronic devices. Twisted nematic liquid crystals are widely used as amplitude modulators in electronic displays and light valves or shutter glass. Such devices are of particular interest for polarization imaging, as they can be used as polarization rotators, and due to large-scale manufacturing have relatively low cost. A simple Mach-Zehnder polarized holographic setup that uses modified shutter glass as a polarization rotator is demonstrated. The suggested approach is experimentally validated by measuring retardation of quarter-wave film.

Planar composite chiral metamaterial with broadband dispersionless polarization rotation and high transmission

NASA Astrophysics Data System (ADS)

Song, Kun; Ding, Changlin; Su, Zhaoxian; Liu, Yahong; Luo, Chunrong; Zhao, Xiaopeng; Bhattarai, Khagendra; Zhou, Jiangfeng

2016-12-01

We propose a planar composite chiral metamaterial (CCMM) by symmetrically inserting a metallic mesh between two layers of conjugated gammadion resonators. As the elaborate CCMM operates at off-resonance frequencies, it therefore presents low-loss and low-dispersion polarization rotation features. The results show that the proposed CCMM can achieve pure and dispersionless polarization rotation with efficient transmission for a linearly polarized wave within a broad bandwidth. This off-resonance CCMM overcomes the drawbacks of high transmission losses and highly dispersive polarization rotation that exist in the previous resonance-type chiral metamaterials and also exhibits more simplicity of fabrication than the three-dimensional CMMs. The intriguing properties greatly improve the performance of chiral metamaterials in controlling the polarization state of electromagnetic waves.

RoboPol: first season rotations of optical polarization plane in blazars

DOE PAGES

Blinov, D.; Pavlidou, V.; Papadakis, I.; ...

2015-08-26

Here, we present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events. A possible connection of polarization swing events with periods of high activity in gamma-rays is investigated using the data set obtained during the first season of operation. It was found that the brightest gamma-ray flares tend to be located closer in time to rotation events, which may be an indication of two separate mechanisms responsible for the rotations. Blazars with detected rotations during non-rotating periodsmore » have significantly larger amplitude and faster variations of polarization angle than blazars without rotations. Our simulations show that the full set of observed rotations is not a likely outcome (probability ≤1.5 × 10 -2) of a random walk of the polarization vector simulated by a multicell model. Furthermore, it is highly unlikely (~5 × 10 -5) that none of our rotations is physically connected with an increase in gamma-ray activity.« less

Process and apparatus for measuring degree of polarization and angle of major axis of polarized beam of light

DOEpatents

Decker, Derek E.; Toeppen, John S.

1994-01-01

Apparatus and process are disclosed for calibrating measurements of the phase of the polarization of a polarized beam and the angle of the polarized optical beam's major axis of polarization at a diagnostic point with measurements of the same parameters at a point of interest along the polarized beam path prior to the diagnostic point. The process is carried out by measuring the phase angle of the polarization of the beam and angle of the major axis at the point of interest, using a rotatable polarizer and a detector, and then measuring these parameters again at a diagnostic point where a compensation apparatus, including a partial polarizer, which may comprise a stack of glass plates, is disposed normal to the beam path between a rotatable polarizer and a detector. The partial polarizer is then rotated both normal to the beam path and around the axis of the beam path until the detected phase of the beam polarization equals the phase measured at the point of interest. The rotatable polarizer at the diagnostic point may then be rotated manually to determine the angle of the major axis of the beam and this is compared with the measured angle of the major axis of the beam at the point of interest during calibration. Thereafter, changes in the polarization phase, and in the angle of the major axis, at the point of interest can be monitored by measuring the changes in these same parameters at the diagnostic point.

Tip-localized actin polymerization and remodeling, reflected by the localization of ADF, profilin and villin, are fundamental for gravity-sensing and polar growth in characean rhizoids.

PubMed

Braun, Markus; Hauslage, Jens; Czogalla, Aleksander; Limbach, Christoph

2004-07-01

Polar organization and gravity-oriented, polarized growth of characean rhizoids are dependent on the actin cytoskeleton. In this report, we demonstrate that the prominent center of the Spitzenkörper serves as the apical actin polymerization site in the extending tip. After cytochalasin D-induced disruption of the actin cytoskeleton, the regeneration of actin microfilaments (MFs) starts with the reappearance of a flat, brightly fluorescing actin array in the outermost tip. The actin array rounds up, produces actin MFs that radiate in all directions and is then relocated into its original central position in the center of the Spitzenkörper. The emerging actin MFs rearrange and cross-link to form the delicate, subapical meshwork, which then controls the statolith positioning, re-establishes the tip-high calcium gradient and mediates the reorganization of the Spitzenkörper with its central ER aggregate and the accumulation of secretory vesicles. Tip growth and gravitropic sensing, which includes control of statolith positioning and gravity-induced sedimentation, are not resumed until the original polar actin organization is completely restored. Immunolocalization of the actin-binding proteins, actin-depolymerizing factor (ADF) and profilin, which both accumulate in the center of the Spitzenkörper, indicates high actin turnover and gives additional support for the actin-polymerizing function of this central, apical area. Association of villin immunofluorescence with two populations of thick undulating actin cables with uniform polarity underlying rotational cytoplasmic streaming in the basal region suggests that villin is the major actin-bundling protein in rhizoids. Our results provide evidence that the precise coordination of apical actin polymerization and dynamic remodeling of actin MFs by actin-binding proteins play a fundamental role in cell polarization, gravity sensing and gravity-oriented polarized growth of characean rhizoids.

A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

NASA Astrophysics Data System (ADS)

Ruan, Juan; Zhang, Wei-Gang; Zhang, Hao; Geng, Peng-Cheng; Bai, Zhi-Yong

2013-06-01

A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.

RoboPol: connection between optical polarization plane rotations and gamma-ray flares in blazars

NASA Astrophysics Data System (ADS)

Blinov, D.; Pavlidou, V.; Papadakis, I.; Kiehlmann, S.; Liodakis, I.; Panopoulou, G. V.; Angelakis, E.; Baloković, M.; Hovatta, T.; King, O. G.; Kus, A.; Kylafis, N.; Mahabal, A.; Maharana, S.; Myserlis, I.; Paleologou, E.; Papamastorakis, I.; Pazderski, E.; Pearson, T. J.; Ramaprakash, A.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Zensus, J. A.

2018-02-01

We use results of our 3 yr polarimetric monitoring programme to investigate the previously suggested connection between rotations of the polarization plane in the optical emission of blazars and their gamma-ray flares in the GeV band. The homogeneous set of 40 rotation events in 24 sources detected by RoboPol is analysed together with the gamma-ray data provided by Fermi-LAT. We confirm that polarization plane rotations are indeed related to the closest gamma-ray flares in blazars and the time lags between these events are consistent with zero. Amplitudes of the rotations are anticorrelated with amplitudes of the gamma-ray flares. This is presumably caused by higher relativistic boosting (higher Doppler factors) in blazars that exhibit smaller amplitude polarization plane rotations. Moreover, the time-scales of rotations and flares are marginally correlated.

A technique for measuring vertically and horizontally polarized microwave brightness temperatures using electronic polarization-basis rotation

NASA Technical Reports Server (NTRS)

Gasiewski, Albin J.

1992-01-01

This technique for electronically rotating the polarization basis of an orthogonal-linear polarization radiometer is based on the measurement of the first three feedhorn Stokes parameters, along with the subsequent transformation of this measured Stokes vector into a rotated coordinate frame. The technique requires an accurate measurement of the cross-correlation between the two orthogonal feedhorn modes, for which an innovative polarized calibration load was developed. The experimental portion of this investigation consisted of a proof of concept demonstration of the technique of electronic polarization basis rotation (EPBR) using a ground based 90-GHz dual orthogonal-linear polarization radiometer. Practical calibration algorithms for ground-, aircraft-, and space-based instruments were identified and tested. The theoretical effort consisted of radiative transfer modeling using the planar-stratified numerical model described in Gasiewski and Staelin (1990).

Artificial intelligence applications of fast optical memory access

NASA Astrophysics Data System (ADS)

Henshaw, P. D.; Todtenkopf, A. B.

The operating principles and performance of rapid laser beam-steering (LBS) techniques are reviewed and illustrated with diagrams; their applicability to fast optical-memory (disk) access is evaluated; and the implications of fast access for the design of expert systems are discussed. LBS methods examined include analog deflection (source motion, wavefront tilt, and phased arrays), digital deflection (polarization modulation, reflectivity modulation, interferometric switching, and waveguide deflection), and photorefractive LBS. The disk-access problem is considered, and typical LBS requirements are listed as 38,000 beam positions, rotational latency 25 ms, one-sector rotation time 1.5 ms, and intersector space 87 microsec. The value of rapid access for increasing the power of expert systems (by permitting better organization of blocks of information) is illustrated by summarizing the learning process of the MVP-FORTH system (Park, 1983).

Polarity mechanisms such as contact inhibition of locomotion regulate persistent rotational motion of mammalian cells on micropatterns

PubMed Central

Camley, Brian A.; Zhang, Yunsong; Zhao, Yanxiang; Li, Bo; Ben-Jacob, Eshel; Levine, Herbert; Rappel, Wouter-Jan

2014-01-01

Pairs of endothelial cells on adhesive micropatterns rotate persistently, but pairs of fibroblasts do not; coherent rotation is present in normal mammary acini and kidney cells but absent in cancerous cells. Why? To answer this question, we develop a computational model of pairs of mammalian cells on adhesive micropatterns using a phase field method and study the conditions under which persistent rotational motion (PRM) emerges. Our model couples the shape of the cell, the cell’s internal chemical polarity, and interactions between cells such as volume exclusion and adhesion. We show that PRM can emerge from this minimal model and that the cell-cell interface may be influenced by the nucleus. We study the effect of various cell polarity mechanisms on rotational motion, including contact inhibition of locomotion, neighbor alignment, and velocity alignment, where cells align their polarity to their velocity. These polarity mechanisms strongly regulate PRM: Small differences in polarity mechanisms can create significant differences in collective rotation. We argue that the existence or absence of rotation under confinement may lead to insight into the cell’s methods for coordinating collective cell motility. PMID:25258412

Elliptical polarization of near-resonant linearly polarized probe light in optically pumped alkali metal vapor

PubMed Central

Li, Yingying; Wang, Zhiguo; Jin, Shilong; Yuan, Jie; Luo, Hui

2017-01-01

Optically pumped alkali metal atoms currently provide a sensitive solution for magnetic microscopic measurements. As the most practicable plan, Faraday rotation of linearly polarized light is extensively used in spin polarization measurements of alkali metal atoms. In some cases, near-resonant Faraday rotation is applied to improve the sensitivity. However, the near-resonant linearly polarized probe light is elliptically polarized after passing through optically pumped alkali metal vapor. The ellipticity of transmitted near-resonant probe light is numerically calculated and experimentally measured. In addition, we also analyze the negative impact of elliptical polarization on Faraday rotation measurements. From our theoretical estimate and experimental results, the elliptical polarization forms an inevitable error in spin polarization measurements. PMID:28216649

Spoof surface plasmon polaritons excitation and wavefront control by Pancharatnam–Berry phase manipulating metasurface

NASA Astrophysics Data System (ADS)

Meng, Yueyu; Ma, Hua; Li, Yongfeng; Feng, Mingde; Wang, Jiafu; Li, Zhiqiang; Qu, Shaobo

2018-05-01

Realizing fine control of surface plasmon polaritons (SPPs) and spoof surface plasmon polaritons (SSPPs) is highly desired in many integrated photonic and microwave applications, but the flexibility to control the wavefront of SPPs and SSPPs still need addressing. In this paper, a Pancharatnam–Berry (PB) phase manipulating metasurface (PMM) was designed to achieve SSPPs excitation and wavefront control. Under circular polarization (CP) incidence, simply by designing the rotation angle of the unit cells the reflection phase spatial distribution can be manipulated. By means of different phase profiles on the 2D unit cells array, the SSPPs can be excited with various wavefront shapes, without the need of special excitation structure pattern. Meanwhile, a plasmonic metal is also designed to support SSPPs with both TE and TM polarizations, which can efficiently guide out the energies from the input CP waves. As a proof of concept, a PB PMM composed of N-shape metallic structure was designed. Through designing the rotation of the unit cells, two typical phase profiles were designed to excite SSPPs in arbitrary slant direction or focusing. This scheme could be used to achieve SSPPs excitation with many other wavefront shapes, and would also enable promising applications in other spectra.

Development of a Precise Polarization Modulator for UV Spectropolarimetry

NASA Astrophysics Data System (ADS)

Ishikawa, S.; Shimizu, T.; Kano, R.; Bando, T.; Ishikawa, R.; Giono, G.; Tsuneta, S.; Nakayama, S.; Tajima, T.

2015-10-01

We developed a polarization modulation unit (PMU) to rotate a waveplate continuously in order to observe solar magnetic fields by spectropolarimetry. The non-uniformity of the PMU rotation may cause errors in the measurement of the degree of linear polarization (scale error) and its angle (crosstalk between Stokes-Q and -U), although it does not cause an artificial linear polarization signal (spurious polarization). We rotated a waveplate with the PMU to obtain a polarization modulation curve and estimated the scale error and crosstalk caused by the rotation non-uniformity. The estimated scale error and crosstalk were {<} 0.01 % for both. This PMU will be used as a waveplate motor for the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) rocket experiment. We confirm that the PMU performs and functions sufficiently well for CLASP.

Polarization rotation locking of vector solitons in a fiber ring laser.

PubMed

Zhao, L M; Tang, D Y; Zhang, H; Wu, X

2008-07-07

Polarization rotation of vector solitons in a fiber ring laser was experimentally studied. It was observed that the period of vector soliton polarization rotation could be locked to the cavity roundtrip time or multiple of it. We further show that multiple vector solitons can be formed in a fiber laser, and all the vector solitons have the same group velocity in cavity, however, their instantaneous polarization ellipse orientations could be orthogonal.

Apodised aperture using rotation of plane of polarization

DOEpatents

Simmons, W.W.; Leppelmeier, G.W.; Johnson, B.C.

1975-09-01

An apodised aperture based on the rotation of plane of polarization producing desirable characteristics on a transmitted light beam such as beam profiling in high flux laser amplifier chains is described. The apodised aperture is made with a lossless element by using one or more polarizers and/or analyzers and magneto-optical Faraday means for selectively rotating the plane of polarized radiation over the cross section to effect the desired apodisation. (auth)

Control of π-Electron Rotations in Chiral Aromatic Molecules Using Intense Laser Pulses

NASA Astrophysics Data System (ADS)

Kanno, Manabu; Kono, Hirohiko; Fujimura, Yuichi

Our recent theoretical studies on laser-induced π-electron rotations in chiral aromatic molecules are reviewed. π electrons of a chiral aromatic molecule can be rotated along its aromatic ring by a nonhelical, linearly polarized laser pulse. An ansa aromatic molecule with a six-membered ring, 2,5-dichloro[n](3,6) pyrazinophane, which belongs to a planar-chiral molecule group, and its simplified molecule 2,5-dichloropyrazine are taken as model molecules. Electron wavepacket simulations in the frozen-molecular-vibration approximation show that the initial direction of π-electron rotation depends on the polarization direction of a linearly polarized laser pulse applied. Consecutive unidirectional rotation can be achieved by applying a sequence of linearly polarized pump and dump pulses to prevent reverse rotation. Optimal control simulations of π-electron rotation show that another controlling factor for unidirectional rotation is the relative optical phase between the different frequency components of an incident pulse in addition to photon polarization direction. Effects of nonadiabatic coupling between π-electron rotation and molecular vibrations are also presented, where the constraints of the frozen approximation are removed. The angular momentum gradually decays mainly owing to nonadiabatic coupling, while the vibrational amplitudes greatly depend on their rotation direction. This suggests that the direction of π-electron rotation on an attosecond timescale can be identified by detecting femtosecond molecular vibrations.

Dynamic polarization vision in mantis shrimps

PubMed Central

Daly, Ilse M.; How, Martin J.; Partridge, Julian C.; Temple, Shelby E.; Marshall, N. Justin; Cronin, Thomas W.; Roberts, Nicholas W.

2016-01-01

Gaze stabilization is an almost ubiquitous animal behaviour, one that is required to see the world clearly and without blur. Stomatopods, however, only fix their eyes on scenes or objects of interest occasionally. Almost uniquely among animals they explore their visual environment with a series pitch, yaw and torsional (roll) rotations of their eyes, where each eye may also move largely independently of the other. In this work, we demonstrate that the torsional rotations are used to actively enhance their ability to see the polarization of light. Both Gonodactylus smithii and Odontodactylus scyllarus rotate their eyes to align particular photoreceptors relative to the angle of polarization of a linearly polarized visual stimulus, thereby maximizing the polarization contrast between an object of interest and its background. This is the first documented example of any animal displaying dynamic polarization vision, in which the polarization information is actively maximized through rotational eye movements. PMID:27401817

Role of flexoelectric coupling in polarization rotations at the a-c domain walls in ferroelectric perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Ye; Chen, Long-Qing; Kalinin, Sergei V.

Ferroelectric and ferroelastic domain walls play important roles in ferroelectric properties. However, their couplings with flexoelectricity have been less understood. Here, we applied phase-field simulation to investigate the flexoelectric coupling with ferroelectric a/c twin structures in lead ziconate titanate thin films. Local stress gradients were found to exist near twin walls that created both lateral and vertical electric fields through the flexoelectric effect, resulting in polarization inclinations from either horizontal or normal orientation, polarization rotation angles deviated from 90°, and consequently highly asymmetric a/c twin walls. Furthermore, by tuning the flexoelectric strengths in a reasonable range from first-principles calculations, wemore » found that the transverse flexoelectric coefficient has a larger influence on the polarization rotation than longitudinal and shear coefficients. And as polar rotations that commonly occur at compositional morphotropic phase boundaries contribute to the piezoelectric enhancement, this work calls for further exploration of alternative strain-engineered polar rotations via flexoelectricity in ferroelectric thin films.« less

Role of flexoelectric coupling in polarization rotations at the a-c domain walls in ferroelectric perovskites

DOE PAGES

Cao, Ye; Chen, Long-Qing; Kalinin, Sergei V.

2017-05-16

Ferroelectric and ferroelastic domain walls play important roles in ferroelectric properties. However, their couplings with flexoelectricity have been less understood. Here, we applied phase-field simulation to investigate the flexoelectric coupling with ferroelectric a/c twin structures in lead ziconate titanate thin films. Local stress gradients were found to exist near twin walls that created both lateral and vertical electric fields through the flexoelectric effect, resulting in polarization inclinations from either horizontal or normal orientation, polarization rotation angles deviated from 90°, and consequently highly asymmetric a/c twin walls. Furthermore, by tuning the flexoelectric strengths in a reasonable range from first-principles calculations, wemore » found that the transverse flexoelectric coefficient has a larger influence on the polarization rotation than longitudinal and shear coefficients. And as polar rotations that commonly occur at compositional morphotropic phase boundaries contribute to the piezoelectric enhancement, this work calls for further exploration of alternative strain-engineered polar rotations via flexoelectricity in ferroelectric thin films.« less

A STUDY OF BROADBAND FARADAY ROTATION AND POLARIZATION BEHAVIOR OVER 1.3–10 GHz IN 36 DISCRETE RADIO SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, C. S.; Gaensler, B. M.; Feain, I. J., E-mail: craiga@physics.usyd.edu.au

We present a broadband polarization analysis of 36 discrete polarized radio sources over a very broad, densely sampled frequency band. Our sample was selected on the basis of polarization behavior apparent in narrowband archival data at 1.4 GHz: half the sample shows complicated frequency-dependent polarization behavior (i.e., Faraday complexity) at these frequencies, while half shows comparatively simple behavior (i.e., they appear Faraday simple ). We re-observed the sample using the Australia Telescope Compact Array in full polarization, with 6 GHz of densely sampled frequency coverage spanning 1.3–10 GHz. We have devised a general polarization modeling technique that allows us tomore » identify multiple polarized emission components in a source, and to characterize their properties. We detect Faraday complex behavior in almost every source in our sample. Several sources exhibit particularly remarkable polarization behavior. By comparing our new and archival data, we have identified temporal variability in the broadband integrated polarization spectra of some sources. In a number of cases, the characteristics of the polarized emission components, including the range of Faraday depths over which they emit, their temporal variability, spectral index, and the linear extent of the source, allow us to argue that the spectropolarimetric data encode information about the magneto-ionic environment of active galactic nuclei themselves. Furthermore, the data place direct constraints on the geometry and magneto-ionic structure of this material. We discuss the consequences of restricted frequency bands on the detection and interpretation of polarization structures, and the implications for upcoming spectropolarimetric surveys.« less

Rotational inertia of continents: A proposed link between polar wandering and plate tectonics

USGS Publications Warehouse

Kane, M.F.

1972-01-01

A mechanism is proposed whereby displacement between continents and the earth's pole of rotation (polar wandering) gives rise to latitudinal transport of continental plates (continental drift) because of their relatively greater rotational inertia. When extended to short-term polar wobble, the hypothesis predicts an energy change nearly equivalent to the seismic energy rate.

Detailed study of upper mantle anisotropy in the upper mantle of eastern North America

NASA Astrophysics Data System (ADS)

Chen, X.; Levin, V. L.; Li, Y.

2016-12-01

We collected observations of core-refracted shear waves on a 1300 km long array crossing the eastern part of the North American continent from James Bay to the Fundy Basin. We combine data from the Earthscope Transportable Array, Canadian and US permanent observatories, and the recently completed Earthscope FlexArray QMIII.Past studies found ample evidence for directional dependence (anisotropy) of seismic wave speed in the upper mantle of this region. However, to date the lateral spacing of seismic observatories made direct comparisons between anisotropic structure and tectonic divisions evident on the surface challenging. With instruments spacing 50 km, and less near major tectonic boundaries such as the Grenville Front and the Appalachian Front, we can discriminate between gradual changes in anisotropic properties due to asthenospheric flow variations, and abrupt and localized changes likely to arise from juxtaposition of distinct lithospheric blocks.To insure lateral consistency of measurements we selected core-refracted shear waves that were observed over the entire length of our array. Also, since directional dependence of splitting parameters is a well recognized signature of vertical changes in anisotropic properties we examine observations from different directions, and look for systematic changes.Most locations show evidence for some degree of splitting in observed shear waves. Delays between fast and slow components estimated using rotation-correlation method range from 0.3 to 1.5 s. At most sites delay values vary considerably between individual phases measured. Fast polarizations are predominantly NE-SW, which agrees with numerous past studies of the region. Systematic directional dependence of fast polarization is seen at all sites we studied. Furthermore, the values of fast polarization appear to be similar along the entire array for individual events but vary from event to event. Both of these observations are consistent with the previously proposed notion of layered anisotropy in the upper mantle of the North American continent. We find localized changes in splitting parameters at the Grenville Front. The Appalachian Front, or the internal divisions of the Appalachian Orogen do not have obvious changes in splitting parameters associated with them.

Scalable Direct Writing of Lanthanide-Doped KMnF3 Perovskite Nanowires into Aligned Arrays with Polarized Up-Conversion Emission.

PubMed

Shi, Shuo; Sun, Ling-Dong; Xue, Ying-Xian; Dong, Hao; Wu, Ke; Guo, Shi-Chen; Wu, Bo-Tao; Yan, Chun-Hua

2018-05-09

The use of one-dimensional nano- and microstructured semiconductor and lanthanide materials is attractive for polarized-light-emission studies. Up-conversion emission from single-nanorod or anisotropic nanoparticles with a degree of polarization has also been discussed. However, microscale arrays of nanoparticles, especially well-aligned one-dimensional nanostructures as well as their up-conversion polarization characterization, have not been investigated yet. Herein, we present a novel and facile paradigm for preparing highly aligned arrays of lanthanide-doped KMnF 3 (KMnF 3 :Ln) perovskite nanowires, which are good candidates for polarized up-conversion emission studies. These perovskite nanowires, with a width of 10 nm and length of a few micrometers, are formed through the oriented attachment of KMnF 3 :Ln nanocubes along the [001] direction. By the employment of KMnF 3 :Ln nanowire gel as nanoink, a direct-writing method is developed to obtain diverse types of aligned patterns from the nanoscale to the wafer scale. Up-conversion emissions from the highly aligned nanowire arrays are polarized along the array direction with a polarization degree up to 60%. Taking advantage of microscopic nanowire arrays, these polarized up-conversion emissions should offer potential applications in light or information transportation.

Polarization rotation vector solitons in a graphene mode-locked fiber laser.

PubMed

Song, Yu Feng; Zhang, Han; Tang, Ding Yuan; Shen, De Yuan

2012-11-19

Polarization rotation vector solitons formed in a fiber laser passively mode locked with atomic layer graphene were experimentally investigated. It was found that different from the case of the polarization locked vector soliton formed in the laser, two extra sets of spectral sidebands always appear on the soliton spectrum of the polarization rotating vector solitons. We confirm that the new sets of spectral sidebands have the same formation mechanism as that of the Kelly sidebands.

The 20 GHz circularly polarized, high temperature superconducting microstrip antenna array

NASA Technical Reports Server (NTRS)

Morrow, Jarrett D.; Williams, Jeffery T.; Long, Stuart A.; Wolfe, John C.

1994-01-01

The primary goal was to design and characterize a four-element, 20 GHz, circularly polarized microstrip patch antenna fabricated from YBa2Cu3O(x) superconductor. The purpose is to support a high temperature superconductivity flight communications experiment between the space shuttle orbiter and the ACTS satellite. This study is intended to provide information into the design, construction, and feasibility of a circularly polarized superconducting 20 GHz downlink or cross-link antenna. We have demonstrated that significant gain improvements can be realized by using superconducting materials for large corporate fed array antennas. In addition, we have shown that when constructed from superconducting materials, the efficiency, and therefore the gain, of microstrip patches increases if the substrate is not so thick that the dominant loss mechanism for the patch is radiation into the surface waves of the conductor-backed substrate. We have considered two design configurations for a superconducting 20 GHz four-element circularly polarized microstrip antenna array. The first is the Huang array that uses properly oriented and phased linearly polarized microstrip patch elements to realize a circularly polarized pattern. The second is a gap-coupled array of circularly polarized elements. In this study we determined that although the Huang array operates well on low dielectric constant substrates, its performance becomes extremely sensitive to mismatches, interelement coupling, and design imperfections for substrates with high dielectric constants. For the gap-coupled microstrip array, we were able to fabricate and test circularly polarized elements and four-element arrays on LaAlO3 using sputtered copper films. These antennas were found to perform well, with relatively good circular polarization. In addition, we realized a four-element YBa2Cu3O(x) array of the same design and measured its pattern and gain relative to a room temperature copper array. The patterns were essentially the same as that for the copper array. The measured gain of the YBCO antenna was greater than that for the room temperature copper design at temperatures below 82K, reaching a value of 3.4 dB at the lowest temperatures.

ON THE ROTATION OF SUNSPOTS AND THEIR MAGNETIC POLARITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianchuan; Yang, Zhiliang; Guo, Kaiming

2016-07-20

The rotation of sunspots of 2 yr in two different solar cycles is studied with the data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory and the Michelson Doppler Imager instrument on board the Solar and Heliospheric Observataory . We choose the α sunspot groups and the relatively large and stable sunspots of complex active regions in our sample. In the year of 2003, the α sunspot groups and the preceding sunspots tend to rotate counterclockwise and have positive magnetic polarity in the northern hemisphere. In the southern hemisphere, the magnetic polarity and rotational tendency ofmore » the α sunspot groups and the preceding sunspots are opposite to the northern hemisphere. The average rotational speed of these sunspots in 2003 is about 0.°65 hr{sup 1}. From 2014 January to 2015 February, the α sunspot groups and the preceding sunspots tend to rotate clockwise and have negative magnetic polarity in the northern hemisphere. The patterns of rotation and magnetic polarity of the southern hemisphere are also opposite to those of the northern hemisphere. The average rotational speed of these sunspots in 2014/2015 is about 1.°49 hr{sup 1}. The rotation of the relatively large and stable preceding sunspots and that of the α sunspot groups located in the same hemisphere have opposite rotational direction in 2003 and 2014/2015.« less

Variable-delay Polarization Modulators for the CLASS Telescope

NASA Astrophysics Data System (ADS)

Harrington, Kathleen; Ali, A.; Amiri, M.; Appel, J. W.; Araujo, D.; Bennett, C. L.; Boone, F.; Chan, M.; Cho, H.; Chuss, D. T.; Colazo, F.; Crowe, E.; Denis, K.; Dünner, R.; Eimer, J.; Essinger-Hileman, T.; Gothe, D.; Halpern, M.; Hilton, G.; Hinshaw, G. F.; Huang, C.; Irwin, K.; Jones, G.; Karakla, J.; Kogut, A. J.; Larson, D.; Limon, M.; Lowry, L.; Marriage, T.; Mehrle, N.; Miller, A. D.; Miller, N.; Mirel, P.; Moseley, S. H.; Novak, G.; Reintsema, C.; Rostem, K.; Stevenson, T.; Towner, D.; U-Yen, K.; Wagner, E.; Watts, D.; Wollack, E.; Xu, Z.; Zeng, L.

2014-01-01

The challenges of measuring faint polarized signals at microwave wavelengths have motivated the development of rapid polarization modulators. One scalable technique, called a Variable-delay Polarization Modulator (VPM), consists of a stationary wire array in front of a movable mirror. The mirror motion creates a changing phase difference between the polarization modes parallel and orthogonal to the wire array. The Cosmology Large Angular Scale Surveyor (CLASS) will use a VPM as the first optical element in a telescope array that will search for the signature of inflation through the “B-mode” pattern in the polarization of the cosmic microwave background. In the CLASS VPMs, parallel transport of the mirror is maintained by a voice-coil actuated flexure system which will translate the mirror in a repeatable manner while holding tight parallelism constraints with respect to the wire array. The wire array will use 51 μm diameter copper-plated tungsten wire with 160 μm pitch over a 60 cm clear aperture. We present the status of the construction and testing of the mirror transport mechanism and wire arrays for the CLASS VPMs.

Three-dimensional vectorial multifocal arrays created by pseudo-period encoding

NASA Astrophysics Data System (ADS)

Zeng, Tingting; Chang, Chenliang; Chen, Zhaozhong; Wang, Hui-Tian; Ding, Jianping

2018-06-01

Multifocal arrays have been attracting considerable attention recently owing to their potential applications in parallel optical tweezers, parallel single-molecule orientation determination, parallel recording and multifocal multiphoton microscopy. However, the generation of vectorial multifocal arrays with a tailorable structure and polarization state remains a great challenge, and reports on multifocal arrays have hitherto been restricted either to scalar focal spots without polarization versatility or to regular arrays with fixed spacing. In this work, we propose a specific pseudo-period encoding technique to create three-dimensional (3D) vectorial multifocal arrays with the ability to manipulate the position, polarization state and intensity of each focal spot. We experimentally validated the flexibility of our approach in the generation of 3D vectorial multiple spots with polarization multiplicity and position tunability.

Design and performance of dual-polarization lumped-element kinetic inductance detectors for millimeter-wave polarimetry

NASA Astrophysics Data System (ADS)

McCarrick, H.; Jones, G.; Johnson, B. R.; Abitbol, M. H.; Ade, P. A. R.; Bryan, S.; Day, P.; Essinger-Hileman, T.; Flanigan, D.; Leduc, H. G.; Limon, M.; Mauskopf, P.; Miller, A.; Tucker, C.

2018-02-01

Aims: Lumped-element kinetic inductance detectors (LEKIDs) are an attractive technology for millimeter-wave observations that require large arrays of extremely low-noise detectors. We designed, fabricated and characterized 64-element (128 LEKID) arrays of horn-coupled, dual-polarization LEKIDs optimized for ground-based CMB polarimetry. Our devices are sensitive to two orthogonal polarizations in a single spectral band centered on 150 GHz with Δν/ν = 0.2. The 65 × 65 mm square arrays are designed to be tiled into the focal plane of an optical system. We demonstrate the viability of these dual-polarization LEKIDs with laboratory measurements. Methods: The LEKID modules are tested with an FPGA-based readout system in a sub-kelvin cryostat that uses a two-stage adiabatic demagnetization refrigerator. The devices are characterized using a blackbody and a millimeter-wave source. The polarization properties are measured with a cryogenic stepped half-wave plate. We measure the resonator parameters and the detector sensitivity, noise spectrum, dynamic range, and polarization response. Results: The resonators have internal quality factors approaching 1 × 106. The detectors have uniform response between orthogonal polarizations and a large dynamic range. The detectors are photon-noise limited above 1 pW of absorbed power. The noise-equivalent temperatures under a 3.4 K blackbody load are <100 μK √s. The polarization fractions of detectors sensitive to orthogonal polarizations are >80%. The entire array is multiplexed on a single readout line, demonstrating a multiplexing factor of 128. The array and readout meet the requirements for 4 arrays to be read out simultaneously for a multiplexing factor of 512. Conclusions: This laboratory study demonstrates the first dual-polarization LEKID array optimized specifically for CMB polarimetry and shows the readiness of the detectors for on-sky observations.

Structure and symmetry in coherent perfect polarization rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Zhou, Chuanhong; Andrews, James H.; Baker, Michael A.

2015-01-01

Theoretical investigations of different routes to coherent perfect polarization rotation illustrate its phenomenological connection with coherent perfect absorption. Our study of systems with broken parity, layering, combined Faraday rotation and optical activity, or a rotator-loaded optical cavity highlights their similarity and suggests alternate approaches to improving and miniaturizing optical devices.

Anomalous complete opaqueness in a sparse array of gold nanoparticle chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai Benfeng; Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084; Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu

2011-08-22

We report on an anomalous polarization-switching extinction effect in a sparse array of gold nanoparticle chains: under normal incidence of light, the array is almost transparent for one polarization; whereas it is fully opaque (with nearly zero transmittance) for the orthogonal polarization within a narrow band, even though the nanoparticles cover only a tiny fraction (say, 3.5%) of the transparent substrate surface. We reveal that the strong polarization-dependent short-range dipolar coupling and long-range radiative coupling of gold nanoparticles in this highly asymmetric array is responsible for this extraordinary effect.

How to derotate the cosmic microwave background polarization.

PubMed

Kamionkowski, Marc

2009-03-20

If the linear polarization of the cosmic microwave background is rotated in a frequency-independent manner as it propagates from the surface of last scatter, it may introduce a B-mode polarization. Here I show that measurement of higher-order TE, EE, EB, and TB correlations induced by this rotation can be used to reconstruct the rotation angle as a function of position on the sky. This technique can be used to distinguish primordial B modes from those induced by rotation. The effects of rotation can be distinguished geometrically from similar effects due to cosmic shear.

Simple Analytic Model for Nanowire Array Polarizers

NASA Astrophysics Data System (ADS)

Pelletier, Vincent; Asakawa, Koji; Wu, Mingshaw; Register, Richard; Chaikin, Paul

2006-03-01

Cylinder-forming diblock copolymers can be used to pattern nanowire arrays on a transparent substrate to be used as a polarizer, as described by Koji Asakawa in a complementary talk at this meeting. With a 33nm period, these wire arrays can polarize UV radiation, which is of great interest in lithography, astronomy and other areas. One can gain an analytical understanding of such an array made of non-perfectly conducting material of finite thickness using a model with an appropriately averaged complex dielectric function in an infinite wavelength approximation. This analysis predicts that the grid can go from an E-polarizer to an H-polarizer as the wavelength decreases below a cross-over wavelength, and experimental data confirm this cross-over. The overall response of the polarizing grid depends primarily on the plasma frequency of the metal used and the volume fraction of the nanowires, as well as the grid thickness. A numerical approach is also used to confirm the analytical model and assess departure from infinite wavelength effects. For our array dimensions, the polarization is only slightly different from this approximation for wavelengths down to 150nm.

Polarization due to rotational distortion in the bright star Regulus

NASA Astrophysics Data System (ADS)

Cotton, Daniel V.; Bailey, Jeremy; Howarth, Ian D.; Bott, Kimberly; Kedziora-Chudczer, Lucyna; Lucas, P. W.; Hough, J. H.

2017-10-01

Polarization in stars was first predicted by Chandrasekhar1, who calculated a substantial linear polarization at the stellar limb for a pure electron-scattering atmosphere. This polarization will average to zero when integrated over a spherical star but could be detected if the symmetry was broken, for example, by the eclipse of a binary companion. Nearly 50 years ago, Harrington and Collins2 modelled another way of breaking the symmetry and producing net polarization—the distortion of a rapidly rotating hot star. Here we report the first detection of this effect. Observations of the linear polarization of Regulus, with two different high-precision polarimeters, range from +42 ppm at a wavelength of 741 nm to -22 ppm at 395 nm. The reversal from red to blue is a distinctive feature of rotation-induced polarization. Using a new set of models for the polarization of rapidly rotating stars, we find that Regulus is rotating at 96.5-0.8+0.6% of its critical angular velocity for break-up, and has an inclination greater than 76.5°. The rotation axis of the star is at a position angle of 79.5 ± 0.7°. The conclusions are independent of, but in good agreement with, the results of previously published interferometric observations of Regulus3. The accurate measurement of rotation in early-type stars is important for understanding their stellar environments4 and the course of their evolution5.

Scanning Miniature Microscopes without Lenses

NASA Technical Reports Server (NTRS)

Wang, Yu

2009-01-01

The figure schematically depicts some alternative designs of proposed compact, lightweight optoelectronic microscopes that would contain no lenses and would generate magnified video images of specimens. Microscopes of this type were described previously in Miniature Microscope Without Lenses (NPO - 20218), NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 43 and Reflective Variants of Miniature Microscope Without Lenses (NPO 20610), NASA Tech Briefs, Vol. 26, No. 9 (September 1999), page 6a. To recapitulate: In the design and construction of a microscope of this type, the focusing optics of a conventional microscope are replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. Elimination of focusing optics reduces the size and weight of the instrument and eliminates the need for the time-consuming focusing operation. The microscopes described in the cited prior articles contained two-dimensional CCDs registered with two-dimensional arrays of microchannels and, as such, were designed to produce full two-dimensional images, without need for scanning. The microscopes of the present proposal would contain one-dimensional (line image) CCDs registered with linear arrays of microchannels. In the operation of such a microscope, one would scan a specimen along a line perpendicular to the array axis (in other words, one would scan in pushbroom fashion). One could then synthesize a full two-dimensional image of the specimen from the line-image data acquired at one-pixel increments of position along the scan. In one of the proposed microscopes, a beam of unpolarized light for illuminating the specimen would enter from the side. This light would be reflected down onto the specimen by a nonpolarizing beam splitter attached to the microchannels at their lower ends. A portion of the light incident on the specimen would be reflected upward, through the beam splitter and along the microchannels, to form an image on the CCD. If the nonpolarizing beam splitter were replaced by a polarizing one, then the specimen would be illuminated by s-polarized light. Upon reflection from the specimen, some of the s-polarized light would become p-polarized. Only the p-polarized light would contribute to the image on the CCD; in other words, the image would contain information on the polarization rotating characteristic of the specimen.

In-Flight Performance of the Polarization Modulator in the CLASP Rocket Experiment

NASA Technical Reports Server (NTRS)

Ishikawa, S.; Shimizu, T.; Kano, R.; Bando, T.; Ishikawa, R.; Giono, G.; Beabout, D.; Beabout, B.; Nakayama, S.; Tajima, T.

2016-01-01

We developed a polarization modulation unit (PMU), a motor system to rotate a waveplate continuously. We applied this PMU for the Chromospheric Lyman-alpha SpectroPolarimeter (CLASP), a sounding rocket experiment to observe the linear polarization of the Lyman-alpha emission (121.6 nm vacuum ultraviolet) from the upper chromosphere and transition region of the Sun with a high polarization sensitivity of 0.1% for the first time and investigate the vector magnetic field. Rotation non-uniformity of the waveplate causes error in the polarization degree (i.e. scale error) and crosstalk between Stokes components. In the ground tests, we confirmed that PMU has superior rotation uniformity. CLASP was successfully launched on September 3, 2015, and PMU functioned well as designed. PMU achieved a good rotation uniformity during the flight and the high precision polarization measurement of CLASP was successfully achieved.

Rotation Detection Using the Precession of Molecular Electric Dipole Moment

NASA Astrophysics Data System (ADS)

Ke, Yi; Deng, Xiao-Bing; Hu, Zhong-Kun

2017-11-01

We present a method to detect the rotation by using the precession of molecular electric dipole moment in a static electric field. The molecular electric dipole moments are polarized under the static electric field and a nonzero electric polarization vector emerges in the molecular gas. A resonant radio-frequency pulse electric field is applied to realize a 90° flip of the electric polarization vector of a particular rotational state. After the pulse electric field, the electric polarization vector precesses under the static electric field. The rotation induces a shift in the precession frequency which is measured to deduce the angular velocity of the rotation. The fundamental sensitivity limit of this method is estimated. This work is only a proposal and does not involve experimental results.

Lunar Science from Lunar Laser Ranging

NASA Technical Reports Server (NTRS)

Williams, J. G.; Boggs, D. H.; Ratcliff, J. T.

2013-01-01

Variations in rotation and orientation of the Moon are sensitive to solid-body tidal dissipation, dissipation due to relative motion at the fluid-core/solid-mantle boundary, tidal Love number k2, and moment of inertia differences. There is weaker sensitivity to flattening of the core/mantle boundary (CMB) and fluid core moment of inertia. Accurate Lunar Laser Ranging (LLR) measurements of the distance from observatories on the Earth to four retroreflector arrays on the Moon are sensitive to variations in lunar rotation, orientation and tidal displacements. Past solutions using the LLR data have given results for Love numbers plus dissipation due to solid-body tides and fluid core. Detection of the fluid core polar minus equatorial moment of inertia difference due to CMB flattening is weakly significant. This strengthens the case for a fluid lunar core. Future approaches are considered to detect a solid inner core.

Control of polarization rotation in nonlinear propagation of fully structured light

NASA Astrophysics Data System (ADS)

Gibson, Christopher J.; Bevington, Patrick; Oppo, Gian-Luca; Yao, Alison M.

2018-03-01

Knowing and controlling the spatial polarization distribution of a beam is of importance in applications such as optical tweezing, imaging, material processing, and communications. Here we show how the polarization distribution is affected by both linear and nonlinear (self-focusing) propagation. We derive an analytical expression for the polarization rotation of fully structured light (FSL) beams during linear propagation and show that the observed rotation is due entirely to the difference in Gouy phase between the two eigenmodes comprising the FSL beams, in excellent agreement with numerical simulations. We also explore the effect of cross-phase modulation due to a self-focusing (Kerr) nonlinearity and show that polarization rotation can be controlled by changing the eigenmodes of the superposition, and physical parameters such as the beam size, the amount of Kerr nonlinearity, and the input power. Finally, we show that by biasing cylindrical vector beams to have elliptical polarization, we can vary the polarization state from radial through spiral to azimuthal using nonlinear propagation.

Electrostrictive Graft Elastomers

NASA Technical Reports Server (NTRS)

Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor); St.Clair, Terry L. (Inventor)

2003-01-01

An electrostrictive graft elastomer has a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules. The polar graft moieties have been rotated by an applied electric field, e.g., into substantial polar alignment. The rotation is sustained until the electric field is removed. In another embodiment, a process for producing strain in an elastomer includes: (a) providing a graft elastomer having a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules; and (b) applying an electric field to the graft elastomer to rotate the polar graft moieties, e.g., into substantial polar alignment.

Microwave probe stations with three-dimensional control of the magnetic field to study high-frequency dynamics in nanoscale devices

NASA Astrophysics Data System (ADS)

Banuazizi, Seyed Amir Hossein; Åkerman, Johan

2018-06-01

We present two microwave probe stations with motorized rotary stages for adjusting the magnitude and angle of the applied magnetic field. In the first system, the magnetic field is provided by an electromagnet and can be adjusted from 0 to ˜1.4 T while its polar angle (θ) can be varied from 0° to 360°. In the second system, the magnetic field is provided by a Halbach array permanent magnet, which can be rotated and translated to cover the full range of polar (θ) and azimuthal (φ) angles with a tunable field magnitude up to ˜1 T. Both systems are equipped with microwave probes, bias-Ts, amplifiers, and spectrum analyzers to allow for microwave characterization up to 40 GHz, as well as software to automatically perform continuous large sets of electrical and microwave measurements.

KSC-2011-7025

NASA Image and Video Library

2011-09-08

VANDENBERG AIR FORCE BASE, Calif. – In a clean room inside the Astrotech Payload Processing Facility at Vandenberg Air Force Base in California, Ball Aerospace technicians rotate NASA’s National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) into the vertical position during a solar array frangible bolt pre-load verification test. NPP represents a critical first step in building the next-generation of Earth-observing satellites. NPP will carry the first of the new sensors developed for this satellite fleet, now known as the Joint Polar Satellite System (JPSS), to be launched in 2016. NPP is the bridge between NASA’s Earth Observing System (EOS) satellites and the forthcoming series of JPSS satellites. The mission will test key technologies and instruments for the JPSS missions. NPP is targeted to launch Oct. 25 from Space Launch Complex-2 aboard a United Launch Alliance Delta II rocket. For more information, visit http://www.nasa.gov/NPP. Photo credit: NASA/30th Communications Squadron, VAFB

KSC-2011-7027

NASA Image and Video Library

2011-09-08

VANDENBERG AIR FORCE BASE, Calif. – In a clean room inside the Astrotech Payload Processing Facility at Vandenberg Air Force Base in California, Ball Aerospace technicians rotate NASA’s National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) into the vertical position during a solar array frangible bolt pre-load verification test. NPP represents a critical first step in building the next-generation of Earth-observing satellites. NPP will carry the first of the new sensors developed for this satellite fleet, now known as the Joint Polar Satellite System (JPSS), to be launched in 2016. NPP is the bridge between NASA’s Earth Observing System (EOS) satellites and the forthcoming series of JPSS satellites. The mission will test key technologies and instruments for the JPSS missions. NPP is targeted to launch Oct. 25 from Space Launch Complex-2 aboard a United Launch Alliance Delta II rocket. For more information, visit http://www.nasa.gov/NPP. Photo credit: NASA/30th Communications Squadron, VAFB

KSC-2011-7026

NASA Image and Video Library

2011-09-08

VANDENBERG AIR FORCE BASE, Calif. – In a clean room inside the Astrotech Payload Processing Facility at Vandenberg Air Force Base in California, Ball Aerospace technicians rotate NASA’s National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) into the vertical position during a solar array frangible bolt pre-load verification test. NPP represents a critical first step in building the next-generation of Earth-observing satellites. NPP will carry the first of the new sensors developed for this satellite fleet, now known as the Joint Polar Satellite System (JPSS), to be launched in 2016. NPP is the bridge between NASA’s Earth Observing System (EOS) satellites and the forthcoming series of JPSS satellites. The mission will test key technologies and instruments for the JPSS missions. NPP is targeted to launch Oct. 25 from Space Launch Complex-2 aboard a United Launch Alliance Delta II rocket. For more information, visit http://www.nasa.gov/NPP. Photo credit: NASA/30th Communications Squadron, VAFB

THE OUTBURST OF THE BLAZAR S5 0716+71 IN 2011 OCTOBER: SHOCK IN A HELICAL JET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larionov, V. M.; Jorstad, S. G.; Morozova, D. A.

We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5 0716+714 along with Fermi {gamma}-ray data during a multi-waveband outburst in 2011 October. We analyze total and polarized intensity images of the blazar obtained with the VLBA at 43 GHz during and after the outburst. Monotonic rotation of the linear polarization vector at a rate of {approx}> 50 Degree-Sign per night coincided with a sharp maximum in {gamma}-ray and optical flux. At the same time, within the uncertainties, a new superluminal knot appeared with an apparent speedmore » of 21 {+-} 2c. The general multi-frequency behavior of the outburst can be explained within the framework of a shock wave propagating along a helical path in the blazar's jet.« less

Deformations and Rotational Ground Motions Inferred from Downhole Vertical Array Observations

NASA Astrophysics Data System (ADS)

Graizer, V.

2017-12-01

Only few direct reliable measurements of rotational component of strong earthquake ground motions are obtained so far. In the meantime, high quality data recorded at downhole vertical arrays during a number of earthquakes provide an opportunity to calculate deformations based on the differences in ground motions recorded simultaneously at different depths. More than twenty high resolution strong motion downhole vertical arrays were installed in California with primary goal to study site response of different geologic structures to strong motion. Deformation or simple shear strain with the rate γ is the combination of pure shear strain with the rate γ/2 and rotation with the rate of α=γ/2. Deformations and rotations were inferred from downhole array records of the Mw 6.0 Parkfield 2004, the Mw 7.2 Sierra El Mayor (Mexico) 2010, the Mw 6.5 Ferndale area in N. California 2010 and the two smaller earthquakes in California. Highest amplitude of rotation of 0.60E-03 rad was observed at the Eureka array corresponding to ground velocity of 35 cm/s, and highest rotation rate of 0.55E-02 rad/s associated with the S-wave was observed at a close epicentral distance of 4.3 km from the ML 4.2 event in Southern California at the La Cienega array. Large magnitude Sierra El Mayor earthquake produced long duration rotational motions of up to 1.5E-04 rad and 2.05E-03 rad/s associated with shear and surface waves at the El Centro array at closest fault distance of 33.4km. Rotational motions of such levels, especially tilting can have significant effect on structures. High dynamic range well synchronized and properly oriented instrumentation is necessary for reliable calculation of rotations from vertical array data. Data from the dense Treasure Island array near San Francisco demonstrate consistent change of shape of rotational motion with depth and material. In the frequency range of 1-15 Hz Fourier amplitude spectrum of vertical ground velocity is similar to the scaled tilt spectrum. Amplitudes of rotations at the site depend upon the size of the base and usually decrease with depth. They are also amplified by soft material. Earthquake data used in this study were downloaded from the Center for Engineering Strong Motion Data at http://www.strongmotioncenter.org/.

Enhanced Polarized Emission from the One-parsec-scale Hotspot of 3C 84 as a Result of the Interaction with the Clumpy Ambient Medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagai, H.; Kino, M.; Fujita, Y.

2017-11-01

We present Very Long Baseline Array polarimetric observations of the innermost jet of 3C 84 (NGC 1275) at 43 GHz. A significant polarized emission is detected at the hotspot of the innermost restarted jet, which is located 1 pc south from the radio core. While the previous report presented a hotspot at the southern end of the western limb, the hotspot location has been moved to the southern end of the eastern limb. Faraday rotation is detected within an entire bandwidth of the 43 GHz band. The measured rotation measure (RM) is at most (6.3 ± 1.9) × 10{sup 5}more » rad m{sup −2} and might be slightly time variable on the timescale of a month by a factor of a few. Our measured RM and the RM previously reported by the CARMA and SMA observations cannot be consistently explained by the spherical accretion flow with a power-law profile. We propose that a clumpy/inhomogeneous ambient medium is responsible for the observed RM. Using an equipartition magnetic field, we derive the electron density of 2 × 10{sup 4} cm{sup −3}. Such an electron density is consistent with the cloud of the narrow line emission region around the central engine. We also discuss the magnetic field configuration from the black hole scale to the parsec scale and the origin of low polarization.« less

Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology

PubMed Central

Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrik; Cohen, Oren; Plaja, Luis; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret

2016-01-01

Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date. PMID:26989782

Nonlinear polarization rotation and orthogonal polarization generation experienced in a single-beam configuration

NASA Astrophysics Data System (ADS)

Minkovski, N.; Petrov, G. I.; Saltiel, S. M.; Albert, O.; Etchepare, J.

2004-09-01

Nonlinear polarization rotation and generation of a polarization component orthogonal to the input beam were observed along fourfold axes of YVO4 and BaF2 crystals. We demonstrate experimentally that in both crystals the angle of rotation is proportional, at low intensities, to the square of the product of the input intensity and the crystal length and is the result of simultaneous action of two third-order processes. This type of nonlinear polarization rotation is driven by the real part of the cubic susceptibility. The recorded energy exchange between the two orthogonal components can exceed 10%. It is to our knowledge the highest energy-conversion efficiency achieved in a single beam nonresonant χ(3) interaction. A simple theoretical model is elaborated to describe the dependence of nonlinear polarization rotation and orthogonal polarization generation on the intensity of the input beam at both low- and high-intensity levels. It reveals the potential contributions from the real and the imaginary parts of the susceptibility tensor. Moreover, this kind of measurement is designed to permit the determination of the magnitude and the sign of the anisotropy of the real part of third-order nonlinearity in crystals with cubic or tetragonal symmetry on the basis of polarization-rotation measurements. The χxxxx(3) component of the third-order susceptibility tensor and its anisotropy sign and amplitude value for BaF2 and YVO4 crystals are estimated and discussed.

Micro-position sensor using faraday effect

DOEpatents

McElfresh, Michael [Livermore, CA; Lucas, Matthew [Pittsburgh, PA; Silveira, Joseph P [Tracy, CA; Groves, Scott E [Brentwood, CA

2007-02-27

A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent magnet to provide a magnetic field, and a magneto-optic material positioned in the magnetic field for rotating the plane of polarization of polarized light transmitted through the magneto-optic material. The magnet is independently movable relative to the magneto-optic material so as to rotate the plane of polarization of the polarized light as a function of the relative position of the magnet. In this manner, the position of the magnet relative to the magneto-optic material may be determined from the rotated polarized light. The sensing system also includes a light source, such as a laser or LED, for producing polarized light, and an optical fiber which is connected to the light source and to the magneto-optic material at a sensing end of the optical fiber. Processing electronics, such as a polarimeter, are also provided for determining the Faraday rotation of the plane of polarization of the back-reflected polarized light to determine the position of the magnet relative to the sensing end of the optical fiber.

Rotating fiber array molecular driver and molecular momentum transfer device constructed therewith

DOEpatents

Milleron, Norman

1983-01-01

A rotating fiber array molecular driver is disclosed which includes a magnetically suspended and rotated central hub to which is attached a plurality of elongated fibers extending radially therefrom. The hub is rotated so as to straighten and axially extend the fibers and to provide the fibers with a tip speed which exceeds the average molecular velocity of fluid molecules entering between the fibers. Molecules colliding with the sides of the rotating fibers are accelerated to the tip speed of the fiber and given a momentum having a directional orientation within a relatively narrow distribution angle at a point radially outward of the hub, which is centered and peaks at the normal to the fiber sides in the direction of fiber rotation. The rotating fiber array may be used with other like fiber arrays or with other stationary structures to form molecular momentum transfer devices such as vacuum pumps, molecular separators, molecular coaters, or molecular reactors.

Rotational displacement skills in rhesus macaques (Macaca mulatta).

PubMed

Hughes, Kelly D; Santos, Laurie R

2012-11-01

Rotational displacement tasks, in which participants must track an object at a hiding location within an array while the array rotates, exhibit a puzzling developmental pattern in humans. Human children take an unusually long time to master this task and tend to solve rotational problems through the use of nongeometric features or landmarks as opposed to other kinds of spatial cues. We investigated whether these developmental characteristics are unique to humans by testing rotational displacement skills in a monkey species, the rhesus macaque (Macaca mulatta), using a looking-time method. Monkeys first saw food hidden in two differently colored boxes within an array. The array was then rotated 180° and the boxes reopened to reveal the food in an expected or unexpected location. Our first two experiments explored the developmental time-course of performance on this rotational displacement task. We found that adult macaques looked longer at the unexpected event, but such performance was not mirrored in younger-aged macaques. In a third study, we systematically varied featural information and visible access to the array to investigate which strategies adult macaques used in solving rotational displacements. Our results show that adult macaques need both sets of information to solve the task. Taken together, these results suggest both similarities and differences in mechanisms by which human and nonhuman primates develop this spatial skill.

Transverse low frequency wave in a two fluid solar wind. M.S. Thesis

NASA Technical Reports Server (NTRS)

Solodyna, G. V.

1973-01-01

Investigation is made of the properties of low frequency transverse waves in a two-fluid solar wind having a radial magnetic field and radial streaming velocity. In order to examine what effects this streaming medium has on the waves, linearly polarized waves are decomposed into left and right circularly polarized waves. Computation is made of analytic expressions valid to first order for the radial amplitude and phase dependence of these constituent waves. It is shown that after travelling a given distance r, these waves have different amplitudes and phases. The former result causes their superposition to become elliptical rather than linear. The latter causes the axis of the ellipse of polarization to rotate through a well-defined angle. Analytic expressions are obtained for the eccentricity of the ellipse and for the angle of rotation. In analogy with regular Faraday rotation, in which the plane of polarization of a linear polarized wave rotates, the effect is denoted as generalized Faraday rotation.

Linearly polarized light emission from quantum dots with plasmonic nanoantenna arrays.

PubMed

Ren, Mengxin; Chen, Mo; Wu, Wei; Zhang, Lihui; Liu, Junku; Pi, Biao; Zhang, Xinzheng; Li, Qunqing; Fan, Shoushan; Xu, Jingjun

2015-05-13

Polarizers provide convenience in generating polarized light, meanwhile their adoption raises problems of extra weight, cost, and energy loss. Aiming to realize polarizer-free polarized light sources, herein, we present a plasmonic approach to achieve direct generation of linearly polarized optical waves at the nanometer scale. Periodic slot nanoantenna arrays are fabricated, which are driven by the transition dipole moments of luminescent semiconductor quantum dots. By harnessing interactions between quantum dots and scattered fields from the nanoantennas, spontaneous emission with a high degree of linear polarization is achieved from such hybrid antenna system with polarization perpendicular to antenna slot. We also demonstrate that the polarization is engineerable in aspects of both spectrum and magnitude by tailoring plasmonic resonance of the antenna arrays. Our findings will establish a basis for the development of innovative polarized light-emitting devices, which are useful in optical displays, spectroscopic techniques, optical telecommunications, and so forth.

Imagining physically impossible self-rotations: geometry is more important than gravity.

PubMed

Creem, S H; Wraga, M; Proffitt, D R

2001-08-01

Previous studies found that it is easier for observers to spatially update displays during imagined self-rotation versus array rotation. The present study examined whether either the physics of gravity or the geometric relationship between the viewer and array guided this self-rotation advantage. Experiments 1-3 preserved a real or imagined orthogonal relationship between the viewer and the array, requiring a rotation in the observer's transverse plane. Despite imagined self-rotations that defied gravity, a viewer advantage remained. Without this orthogonal relationship (Experiment 4), the viewer advantage was lost. We suggest that efficient transformation of the egocentric reference frame relies on the representation of body-environment relations that allow rotation around the observer's principal axis. This efficiency persists across different and conflicting physical and imagined postures.

Imagining physically impossible self-rotations: geometry is more important than gravity

NASA Technical Reports Server (NTRS)

Creem, S. H.; Wraga, M.; Proffitt, D. R.; Kaiser, M. K. (Principal Investigator)

2001-01-01

Previous studies found that it is easier for observers to spatially update displays during imagined self-rotation versus array rotation. The present study examined whether either the physics of gravity or the geometric relationship between the viewer and array guided this self-rotation advantage. Experiments 1-3 preserved a real or imagined orthogonal relationship between the viewer and the array, requiring a rotation in the observer's transverse plane. Despite imagined self-rotations that defied gravity, a viewer advantage remained. Without this orthogonal relationship (Experiment 4), the viewer advantage was lost. We suggest that efficient transformation of the egocentric reference frame relies on the representation of body-environment relations that allow rotation around the observer's principal axis. This efficiency persists across different and conflicting physical and imagined postures.

Vortex circulation and polarity patterns in closely packed cap arrays

DOE PAGES

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.; ...

2016-01-25

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

Soliton polarization rotation in fiber lasers

NASA Astrophysics Data System (ADS)

Afanasjev, V. V.

1995-02-01

I have found the approximate analytical solution in explicit form for a vector soliton with an arbitrary component ratio. My solution describes the dependence of soliton intensity on polarization angle and also nonlinear polarization rotation. The analytical results agree well with the numerical simulations.

Cooled particle accelerator target

DOEpatents

Degtiarenko, Pavel V.

2005-06-14

A novel particle beam target comprising: a rotating target disc mounted on a retainer and thermally coupled to a first array of spaced-apart parallel plate fins that extend radially inwardly from the retainer and mesh without physical contact with a second array of spaced-apart parallel plate fins that extend radially outwardly from and are thermally coupled to a cooling mechanism capable of removing heat from said second array of spaced-apart fins and located within the first array of spaced-apart parallel fins. Radiant thermal exchange between the two arrays of parallel plate fins provides removal of heat from the rotating disc. A method of cooling the rotating target is also described.

Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback.

PubMed

Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

2016-01-01

In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θp. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θp. The maximum value of the cross-correlation coefficient achieved is -0.99 with a zero time delay over a wide range of θp beyond 65° with a poor synchronization dynamic at θp less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θp. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

Polarization observations of broadband VHF signals by the FORTE satellite

NASA Astrophysics Data System (ADS)

Shao, Xuan-Min; Jacobson, Abram R.

2001-01-01

Coherent very high frequency (VHF) radio observations with the pair of orthogonal log-periodic array antennas of the FORTE satellite allow us to study thoroughly the polarization properties for a received signal. Eighty-one broadband VHF pulses that were generated by the Los Alamos Portable Pulser (LAPP) have been analyzed. The data are analyzed by computing the Stokes parameters in the time-frequency domain. We first examine the LAPP pulses at high time resolution so as to separate the ordinary and extraordinary ionospheric modes. The two modes have been found to be mirror images of each other in terms of polarization, as would be expected. For each mode the polarization degrades from circular toward elliptical as the nadir angle increases. Antenna pattern effects on this observation are discussed. The tilt of the detected polarization ellipse is found to be tightly associated with the azimuthal direction of the pulse source. The same set of data are then examined with much lower time resolution to intentionally mix together the two split modes, so that the ionospheric Faraday rotation can be detected. With the known geomagnetic field the total electron content (TEC) is computed, which shows good agreement with the TEC computed by dechirping the signal. A case study of an impulsive lightning emission shows that it is highly polarized, indicating that the associated breakdown processes are highly coherent and organized. Finally, we discuss the potential use of the polarization observations for locating terrestrial radio signals.

Rapid Mueller matrix polarimetry imaging based on four photoelastic modulators with no moving parts (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gribble, Adam; Alali, Sanaz; Vitkin, Alex

2016-03-01

Polarized light has many applications in biomedical imaging. The interaction of a biological sample with polarized light reveals information about its composition, both structural and functional. For example, the polarimetry-derived metric of linear retardance (birefringence) is dependent on tissue structural organization (anisotropy) and can be used to diagnose myocardial infarct; circular birefringence (optical rotation) can measure glucose concentrations. The most comprehensive type of polarimetry analysis is to measure the Mueller matrix, a polarization transfer function that completely describes how a sample interacts with polarized light. To derive this 4x4 matrix it is necessary to observe how a tissue interacts with different polarizations. A well-suited approach for tissue polarimetry is to use photoelastic modulators (PEMs), which dynamically modulate the polarization of light. Previously, we have demonstrated a rapid time-gated Stokes imaging system that is capable of characterizing the state of polarized light (the Stokes vector) over a large field, after interacting with any turbid media. This was accomplished by synchronizing CCD camera acquisition times relative to two PEMs using a field-programmable gate array (FPGA). Here, we extend this technology to four PEMs, yielding a polarimetry system that is capable of rapidly measuring the complete sample Mueller matrix over a large field of view, with no moving parts and no beam steering. We describe the calibration procedure and evaluate the accuracy of the measurements. Results are shown for tissue-mimicking phantoms, as well as initial biological samples.

Phase-Field Simulations of Topological Structures and Topological Phase Transitions in Ferroelectric Oxide Heterostructures

NASA Astrophysics Data System (ADS)

Zijian Hong

Ferroelectrics are materials that exhibit spontaneous electric polarization which can be switched between energy-degenerated states by external stimuli (e.g., mechanical force and electric field) that exceeds a critical value. They have wide potential applications in memories, capacitors, piezoelectric and pyroelectric sensors, and nanomechanical systems. Topological structures and topological phase transitions have been introduced to the condensed matter physics in the past few decades and have attracted broad attentions in various disciplines due to the rich physical insights and broad potential applications. Ferromagnetic topological structures such as vortex and skyrmion are known to be stabilized by the antisymmetric chiral interaction (e.g., Dzyaloshinskii-Moriya interaction). Without such interaction, ferroelectric topological structures (i.e., vortex, flux-closure, skyrmions, and merons) have been studied only recently with other designing strategies, such as reducing the dimension of the ferroelectrics. The overarching goal of this dissertation is to investigate the topological structures in ferroelectric oxide perovskites as well as the topological phase transitions under external applied forces. Pb(Zr,Ti)O3 (PZT) with morphotropic phase boundary is widely explored for high piezoelectric and dielectric properties. The domain structure of PZT tetragonal/rhombohedral (T/R) bilayer is investigated. Strong interfacial coupling is shown, with large polarization rotation to a lower symmetry phase near the T/R interface. Interlayer domain growth can also be captured, with T-domains in the R layer and R-domains in the T layer. For thin PZT bilayer with 5nm of T-layer and 20 nm of R-layer, the a1/a 2 twin domain structure is formed in the top T layer, which could be fully switched to R domains under applied bias. While a unique flux-closure pattern is observed both theoretically and experimentally in the thick bilayer film with 50 nm of thickness for both T and R layers. It is revealed that the bilayer system could facilitate the motion of the ferroelastic adomain in the top T-layer since the a-domain is not directly embedded in the substrate with high density of defects which can pin the domain wall. Excellent dielectric and piezoelectric responses are demonstrated due to the large polarization rotation and the highly mobile domain walls in both the thick and thin bilayer systems. density of defects which can pin the domain wall. Excellent dielectric and piezoelectric responses are demonstrated due to the large polarization rotation and the highly mobile domain walls in both the thick and thin bilayer systems. The long-range ordered polar vortex array is observed in the (PbTiO 3)n/(SrTiO3)n (PTOn/STOn with n=10˜20) superlattices with combined experimental and theoretical studies. Phase-field simulations reveal the three-dimensional textures of the polar vortex arrays. The neighboring vortices rotate in the opposite directions, which extended into tube-like vortex lines perpendicular to the vortex plane. The thickness-dependent phase diagram is predicted and verified by experimental observations. The energetics (the contributions from elastic, electrostatic, gradient and Landau chemical energies) accompanying the phase transitions are analyzed in details. The dominating depolarization energy at short periodicity (n<10) favors a1/ a2 twin domain, while the large elastic relaxation and Landau energy reduction at large periodicity (n>20) leads to the formation of flux-closure domain with both 90° a/c domain walls and 180° c+/c - domain walls, counterbalancing of the individual energies at intermediate periodicities (n=10˜20) gives rise to the formation of exotic vortex structure with continuous polarization rotation surrounding a singularity-like vortex core. Analytical calculations are performed, showing that the stability of the polar vortex structure is directly related to the length of Pi times bulk domain wall width, where vortex structure can be expected when the geometric length scale of the ferroelectrics is close to this value. The role of insulating STO is further revealed, which shows that a rich phase diagram can be formed by simply tuning the thickness of this layer. Wave-like polar spiral phase is simulated by substituting part of the PTO with BiFeO3 (BFO) in the PTO/STO superlattice (i.e., in a (PTO) 4/(BFO)4/(PTO)4/(STO)12 tricolor system) which has demonstrate ordered polar vortex lattice. This spiral phase is made up of semi-vortex cores that are floating up-down in the ferroelectric PTO layers, giving rise to a net in-plane polarization. An increase of Curie temperature and topological to regular domain transition temperature (over 200 K) is observed, due to the higher Curie temperature and larger spontaneous polarization in BFO layers. This unidirectional spiral state can be reversibly switched by experimentally feasible in-plane field, which evolves into a metastable vortex structure in-between two spiral phases with opposite in-plane directions. (Abstract shortened by ProQuest.).

Faraday effect on stimulated Raman scattering in the linear region

NASA Astrophysics Data System (ADS)

Liu, Z. J.; Li, B.; Xiang, J.; Cao, L. H.; Zheng, C. Y.; Hao, L.

2018-04-01

The paper presents the effect of Faraday rotation on stimulated Raman scattering (SRS). When light propagates along the magnetic field upon plasma, Faraday rotation occurs. The rotation angle can be expressed as {{d}}θ /{{d}}{s}=2.93× {10}-4B\\tfrac{{n}e/{n}c}{\\sqrt{1-{n}e/{n}c}} {cm}}-1 approximately, where θ is the rotation angle and s is distance, n e is the electron density, n c is the critical density and B is magnetic field in unit of Gauss. Both the incident light and Raman light have Faraday effects. The angle between the polarization directions of incident light and Raman light changes with position. The driven force of electron plasma wave also reduces, and then SRS scattering level is reduced. Faraday rotation effect can increase the laser intensity threshold of Raman scattering, even if the magnetic field strength is small. The circularly polarized light incident case is also compared with that of the linearly polarized light incident. The Raman scattering level of linearly polarized light is much smaller than that of circularly polarized light in the magnetized plasma. The difference between linearly and circularly polarized lights is also discussed.

Rotational Displacement Skills in Rhesus Macaques (Macaca mulatta)

PubMed Central

Hughes, Kelly D.; Santos, Laurie R.

2016-01-01

Rotational displacement tasks, in which participants must track an object at a hiding location within an array while the array rotates, exhibit a puzzling developmental pattern in humans. Human children take an unusually long time to master this task and tend to solve rotational problems through the use of nongeometric features or landmarks as opposed to other kinds of spatial cues. We investigated whether these developmental characteristics are unique to humans by testing rotational displacement skills in a monkey species, the rhesus macaque (Macaca mulatta), using a looking-time method. Monkeys first saw food hidden in two differently colored boxes within an array. The array was then rotated 180° and the boxes reopened to reveal the food in an expected or unexpected location. Our first two experiments explored the developmental time-course of performance on this rotational displacement task. We found that adult macaques looked longer at the unexpected event, but such performance was not mirrored in younger-aged macaques. In a third study, we systematically varied featural information and visible access to the array to investigate which strategies adult macaques used in solving rotational displacements. Our results show that adult macaques need both sets of information to solve the task. Taken together, these results suggest both similarities and differences in mechanisms by which human and nonhuman primates develop this spatial skill. PMID:22866770

Reducing parametric backscattering by polarization rotation

DOE PAGES

Barth, Ido; Fisch, Nathaniel J.

2016-10-01

When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. But, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction,more » it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Though the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.« less

A methodology for dosimetry audit of rotational radiotherapy using a commercial detector array.

PubMed

Hussein, Mohammad; Tsang, Yatman; Thomas, Russell A S; Gouldstone, Clare; Maughan, David; Snaith, Julia A D; Bolton, Steven C; Nisbet, Andrew; Clark, Catharine H

2013-07-01

To develop a methodology for the use of a commercial detector array in dosimetry audits of rotational radiotherapy. The methodology was developed as part of the development of a national audit of rotational radiotherapy. Ten cancer centres were asked to create a rotational radiotherapy treatment plan for a three-dimensional treatment-planning-system (3DTPS) test and audited. Phantom measurements using a commercial 2D ionisation chamber (IC) array were compared with measurements using 0.125 cm(3) IC, Gafchromic film and alanine pellets in the same plane. Relative and absolute gamma index (γ) comparisons were made for Gafchromic film and 2D-Array planes, respectively. Comparisons between individual detectors within the 2D-Array against the corresponding IC and alanine measurement showed a statistically significant concordance correlation coefficient (both ρc>0.998, p<0.001) with mean difference of -1.1 ± 1.1% and -0.8 ± 1.1%, respectively, in a high dose PTV. In the γ comparison between the 2D-Array and film it was that the 2D-Array was more likely to fail planes where there was a dose discrepancy due to the absolute analysis performed. It has been found that using a commercial detector array for a dosimetry audit of rotational radiotherapy is suitable in place of standard systems of dosimetry. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Transmission intensity disturbance in a rotating polarizer

NASA Astrophysics Data System (ADS)

Fan, J. Y.; Li, H. X.; Wu, F. Q.

2008-01-01

Random disturbance was observed in transmission intensity in various rotating prism polarizers when they were used in optical systems. As a result, the transmitted intensity exhibited cyclic significant deviation from the Malus cosine-squared law with rotation of prisms. The disturbance spoils the light quality transmitted through the polarizer thus dramatically depresses the accuracies of measurements when the prim polarizers were used in light path. A rigorous model is presented based on the solid basis of multi-beams interference, and theoretical results show good agreement with measured values and also indicate effective method for reducing the disturbance.

Optical super-resolution and periodical focusing effects by dielectric microspheres

NASA Astrophysics Data System (ADS)

Darafsheh, Arash

Optical microscopy is one of the oldest and most important imaging techniques; however, its far-field resolution is diffraction-limited. In this dissertation, we proposed and developed a novel method of optical microscopy with super-resolution by using high-index dielectric microspheres immersed in liquid and placed on the surface of the structures under study. We used barium titanate glass microspheres with diameters of D~2-220 mum and refractive indices n˜1.9-2.1 to discern minimal feature sizes ˜lambda/4 (down to ˜lambda/7) of various photonic and plasmonic nanostructures, where lambda is the illumination wavelength. We studied the magnification, field of view, and resolving power, in detail, as a function of sphere sizes. We studied optical coupling, transport, focusing, and polarization properties of linear arrays of dielectric spheres. We showed that in arrays of spheres with refractive index n=3, a special type of rays with transverse magnetic (TM) polarization incident on the spheres under the Brewster's angle form periodically focused modes with radial polarization and 2D period, where D is the diameter of the spheres. We showed that the formation of periodically focused modes in arrays of dielectric spheres gives a physical explanation for beam focusing and extraordinarily small attenuation of light in such chains. We showed that the light propagation in such arrays is strongly polarization-dependent, indicating that such arrays can be used as filters of beams with radial polarization. The effect of forming progressively smaller focused beams was experimentally observed in chains of sapphire spheres in agreement with the theory. We studied optical coupling,transport, focusing, and polarization properties of linear arrays of dielectric spheres. We showed that in arrays of spheres with refractive index n=a3, a special type of rays with transverse magnetic (TM) polarization incident on the spheres under the Brewster's angle form periodically focused modes with radial polarization and 2D period, where D is the diameter of the spheres. We showed that the formation of periodically focused modes in arrays of dielectric spheres gives a physical explanation for beam focusing and extraordinarily small attenuation of light in such chains. We showed that the light propagation in such arrays is strongly polarization-dependent, indicating that such arrays can be used as filters of beams with radial polarization. The effect of forming progressively smaller focused beams was experimentally observed in chains of sapphire spheres in agreement with the theory.

Self-Calibration of BICEP1 Three-Year Data and Constraints on Astrophysical Polarization Rotation

NASA Technical Reports Server (NTRS)

Kaufman, J. P.; Miller, N. J.; Shimon, M.; Barkats, D.; Bischoff, C.; Buder, I.; Keating, B. G.; Kovac, J. M.; Ade, P. A. R.; Aikin, R.;

Rotating reverse osmosis: a dynamic model for flux and rejection

NASA Technical Reports Server (NTRS)

Lee, S.; Lueptow, R. M.

2001-01-01

Reverse osmosis (RO) is a compact process for the removal of ionic and organic pollutants from contaminated water. However, flux decline and rejection deterioration due to concentration polarization and membrane fouling hinders the application of RO technology. In this study, a rotating cylindrical RO membrane is theoretically investigated as a novel method to reduce polarization and fouling. A dynamic model based on RO membrane transport incorporating concentration polarization is used to predict the performance of rotating RO system. Operating parameters such as rotational speed and transmembrane pressure play an important role in determining the flux and rejection in rotating RO. For a given geometry, a rotational speed sufficient to generate Taylor vortices in the annulus is essential to maintain high flux as well as high rejection. The flux and rejection were calculated for wide range of operating pressures and rotational speeds. c 2001 Elsevier Science B.V. All rights reserved.

Polar flagella rotation in Vibrio parahaemolyticus confers resistance to bacteriophage infection

PubMed Central

Zhang, Hui; Li, Lu; Zhao, Zhe; Peng, Daxin; Zhou, Xiaohui

2016-01-01

Bacteriophage has been recognized as a novel approach to treat bacterial infectious diseases. However, phage resistance may reduce the efficacy of phage therapy. Here, we described a mechanism of bacterial resistance to phage infections. In Gram-negative enteric pathogen Vibrio parahaemolyticus, we found that polar flagella can reduce the phage infectivity. Deletion of polar flagella, but not the lateral flagella, can dramatically promote the adsorption of phage to the bacteria and enhances the phage infectivity to V. parahaemolyticus, indicating that polar flagella play an inhibitory role in the phage infection. Notably, it is the rotation, not the physical presence, of polar flagella that inhibits the phage infection of V. parahaemolyticus. Strikingly, phage dramatically reduces the virulence of V. parahaemolyticus only when polar flagella were absent both in vitro and in vivo. These results indicated that polar flagella rotation is a previously unidentified mechanism that confers bacteriophage resistance. PMID:27189325

Polarization Ratio Determination with Two Identical Linearly Polarized Antennas

DTIC Science & Technology

2017-01-17

Fourier transform analysis of 21 measurements with one of the antennas rotating about its axis a circular polarization ratio is derived which can be...deter- mined directly from a discrete Fourier transform (DFT) of (5). However, leakage between closely spaced DFT bins requires improving the... Fourier transform and a mechanical antenna rotation to separate the principal and opposite circular polarization components followed by a basis

Vortex Generators in a Streamline-Traced, External-Compression Supersonic Inlet

NASA Technical Reports Server (NTRS)

Baydar, Ezgihan; Lu, Frank K.; Slater, John W.; Trefny, Charles J.

2017-01-01

Vortex generators within a streamline-traced, external-compression supersonic inlet for Mach 1.66 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. The vortex generators studied were rectangular vanes arranged in counter-rotating and co-rotating arrays. The vane geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The vanes were simulated using a vortex generator model. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the engine face. Design of experiments and statistical analysis methods were applied to quantify the effect of the geometric factors of the vanes and search for optimal vane arrays. Co-rotating vane arrays with negative angles-of-incidence positioned on the supersonic diffuser were effective in sweeping low-momentum flow from the top toward the sides of the subsonic diffuser. This distributed the low-momentum flow more evenly about the circumference of the subsonic diffuser and reduced distortion. Co-rotating vane arrays with negative angles-of-incidence or counter-rotating vane arrays positioned downstream of the terminal shock were effective in mixing higher-momentum flow with lower-momentum flow to increase recovery and decrease distortion. A strategy of combining a co-rotating vane array on the supersonic diffuser with a counter-rotating vane array on the subsonic diffuser was effective in increasing recovery and reducing distortion.

Large magnetic to electric field contrast in azimuthally polarized vortex beams generated by a metasurface (Presentation Recording)

NASA Astrophysics Data System (ADS)

Veysi, Mehdi; Guclu, Caner; Capolino, Filippo

2015-09-01

We investigate azimuthally E-polarized vortex beams with enhanced longitudinal magnetic field. Ideally, such beams possess strong longitudinal magnetic field on the beam axis where there is no electric field. First we formulate the electric field vector and the longitudinal magnetic field of an azimuthally E-polarized beam as an interference of right- and left-hand circularly polarized Laguerre Gaussian (LG) beams carrying the orbital angular momentum (OAM) states of -1 and +1, respectively. Then we propose a metasurface design that is capable of converting a linearly polarized Gaussian beam into an azimuthally E-polarized vortex beam with longitudinal magnetic field. The metasurface is composed of a rectangular array of double-layer double split-ring slot elements, though other geometries could be adopted as well. The element is specifically designed to have nearly a 180° transmission phase difference between the two polarization components along two orthogonal axes, similar to the optical axes of a half-wave plate. By locally rotating the optical axes of each metasurface element, the transmission phase profile of the circularly polarized waves over the metasurface can be tailored. Upon focusing of the generated vortex beam through a lens with a numerical aperture of 0.7, a 41-fold enhancement of the magnetic to electric field ratio is achieved on the beam axis with respect to that of a plane wave. Generation of beams with large magnetic field to electric field contrast can find applications in future spectroscopy systems based on magnetic dipole transitions, which are usually much weaker than electric dipole transitions.

A Ka-Band (26 GHz) Circularly Polarized 2x2 Microstrip Patch Sub-Array with Compact Feed

NASA Technical Reports Server (NTRS)

Chrysler, Andrew; Furse, Cynthia; Simons, Rainee N.; Miranda, Felix A.

2017-01-01

A Ka-band (26 GHz) 2x2 array consisting of square-shaped microstrip patch antenna elements with two truncated corners for circular polarization (CP) is presented. The array is being developed for satellite communications.

Improved Grid-Array Millimeter-Wave Amplifier

NASA Technical Reports Server (NTRS)

Rosenberg, James J.; Rutledge, David B.; Smith, R. Peter; Weikle, Robert

1993-01-01

Improved grid-array amplifiers operating at millimeter and submillimeter wavelengths developed for use in communications and radar. Feedback suppressed by making input polarizations orthogonal to output polarizations. Amplifier made to oscillate by introducing some feedback. Several grid-array amplifiers concatenated to form high-gain beam-amplifying unit.

High-Isolation Low Cross-Polarization Phased-Array Antenna for MPAR Application

NASA Astrophysics Data System (ADS)

Saeidi-Manesh, Hadi; Karimkashi, Shaya; Zhang, Guifu; Doviak, Richard J.

2017-12-01

The design and analysis of 12 × 12-element planar array of a dual-polarized aperture-coupled microstrip patch antenna operating in the frequency band of 2.7 GHz to 3.0 GHz for multifunction applications are presented. High-isolation between horizontal and vertical polarization ports and low cross-polarization are achieved through an aperture-coupled feed. The reflection coefficient and the isolation of horizontal and vertical ports at different scan angles are examined. The array antenna is fabricated and its radiation patterns are measured in the far-field and near-field chambers. The embedded element pattern of designed element is measured in the near-field chamber and is used for calculating the array scanning radiation pattern.

Generation of tunable radially polarized array beams by controllable coherence

NASA Astrophysics Data System (ADS)

Wang, Jing; Zhang, Jipeng; Zhu, Shijun; Li, Zhenhua

2017-05-01

In this paper, a new method for converting a single radial polarization beam into an arbitrary radially polarized array (RPA) beam such as a radial or rectangular symmetry array in the focal plane by modulating a periodic correlation structure is introduced. The realizability conditions for such source and the beam condition for radiation generated by such source are derived. It is illustrated that both the amplitude and the polarization are controllable by means of initial correlation structure and coherence parameter. Furthermore, by designing the source correlation structure, a tunable NUST-shaped RPA beam is demonstrated, which can find widespread applications in micro-nano engineering. Such a method for generation of arbitrary vector array beams is useful in beam shaping and optical tweezers.

Differently ordered TiO2 nanoarrays regulated by solvent polarity, and their photocatalytic performances

NASA Astrophysics Data System (ADS)

Hu, Wenyuan; Dong, Faqin; Zhang, Jing; Liu, Mingxue; He, Huichao; Wu, Yadong; Yang, Dingming; Deng, Hongquan

2018-06-01

Special TiO2 arrays with exposed facets were prepared in different solvents by low- temperature solvothermal synthesis. The morphology, phase and photocatalytic performance influenced by the various solvent polarities were characterized using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra and electrochemical testing. The results show that differences of solvent polarity are the main force driving differences in array growth; therefore, anatase TiO2 arrays with different crystal facets can be synthesized by tuning solvent polarity. TiO2 arrays prepared in cyclohexane are the best at oxidizing methyl orange through photocatalysis, followed by arrays prepared in toluene and ethanol. Arrays prepared in toluene are the best at reducing Cr(VI) photocatalytically, followed by those prepared in cyclohexane and ethanol. These differences in photocatalytic power are due to the ratio among the different crystal facets that are exposed, which affects the migration behavior of the photogenerated electrons and holes. In addition, the probable growth mechanisms of self-assembled ordered TiO2 arrays in different solvents are described.

Integrated polymer polarization rotator based on tilted laser ablation

NASA Astrophysics Data System (ADS)

Poulopoulos, Giannis; Kalavrouziotis, Dimitrios; Missinne, Jeroen; Bosman, Erwin; Van Steenberge, Geert; Apostolopoulos, Dimitrios; Avramopoulos, Hercules

2017-02-01

The ubiquitous need for compact, low-cost and mass production photonic devices, for next generation photonic enabled applications, necessitates the development of integrated components exhibiting functionalities that are, to date, carried out by free space elements or standard fiber equipment. The polarization rotator is a typical example of such tendency, as it is a crucial part of the PBS operation of future transceiver modules that leverage polarization multiplexing schemes for increasing the optical network capacity. Up to now, a variety of integrated polarization rotating concepts has been proposed and reported, relying, mainly, on special waveguide crossection configurations for achieving the rotation. Nevertheless, most of those concepts employ SiPh or III-V integration platforms, significantly increasing the fabrication complexity required for customizing the waveguide crossection, which in turn leads to either prohibitively increased cost or compromised quality and performance. In this manuscript we demonstrate the extensive design of a low-cost integrated polymer polarization rotator employing a right-trapezoidal waveguide interfaced to standard square polymer waveguides. First the crossection of the waveguide is defined by calculating and analyzing the components of the hybrid modes excited in the waveguide structure, using a Finite Difference mode solver. Mode overlaps between the fundamental polymer mode and each hybrid mode reveal the optimum lateral offset between the square polymer and the trapezoidal waveguide that ensures both minimum interface loss and maximized polarization rotation performance. The required trapezoidal waveguide length is obtained through EigenMode Expansion (EME) propagation simulations, while more than 95% maximum theoretical conversion efficiency is reported over the entire C-band, resulting to more than 13dB polarization extinction ratio. The polarization rotator design relies on the development of angled polymer waveguide sidewalls, employing the tilted laser ablation technology, currently available at CMST. Therefore, the aforementioned simulation steps adhere fully to the respective design rules, taking into account the anticipated fabrication variations

Angle-dependent rotation of calcite in elliptically polarized light

NASA Astrophysics Data System (ADS)

Herne, Catherine M.; Cartwright, Natalie A.; Cattani, Matthew T.; Tracy, Lucas A.

2017-08-01

Calcite crystals trapped in an elliptically polarized laser field exhibit intriguing rotational motion. In this paper, we show measurements of the angle-dependent motion, and discuss how the motion of birefringent calcite can be used to develop a reliable and efficient process for determining the polarization ellipticity and orientation of a laser mode. The crystals experience torque in two ways: from the transfer of spin angular momentum (SAM) from the circular polarization component of the light, and from a torque due to the linear polarization component of the light that acts to align the optic axis of the crystal with the polarization axis of the light. These torques alternatingly compete with and amplify each other, creating an oscillating rotational crystal velocity. We model the behavior as a rigid body in an angle-dependent torque. We experimentally demonstrate the dependence of the rotational velocity on the angular orientation of the crystal by placing the crystals in a sample solution in our trapping region, and observing their behavior under different polarization modes. Measurements are made by acquiring information simultaneously from a quadrant photodiode collecting the driving light after it passes through the sample region, and by imaging the crystal motion onto a camera. We finish by illustrating how to use this model to predict the ellipticity of a laser mode from rotational motion of birefringent crystals.

Dual polarized receiving steering antenna array for measurement of ultrawideband pulse polarization structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balzovsky, E. V.; Buyanov, Yu. I.; Koshelev, V. I., E-mail: koshelev@lhfe.hcei.tsc.ru

To measure simultaneously two orthogonal components of the electromagnetic field of nano- and subnano-second duration, an antenna array has been developed. The antenna elements of the array are the crossed dipoles of dimension 5 × 5 cm. The arms of the dipoles are connected to the active four-pole devices to compensate the frequency response variations of a short dipole in the frequency band ranging from 0.4 to 4 GHz. The dipoles have superimposed phase centers allowing measuring the polarization structure of the field in different directions. The developed antenna array is the linear one containing four elements. The pattern maximummore » position is controlled by means of the switched ultrawideband true time delay lines. Discrete steering in seven directions in the range from −40° to +40° has been realized. The error at setting the pattern maximum position is less than 4°. The isolation of the polarization exceeds 29 dB in the direction orthogonal to the array axis and in the whole steering range it exceeds 23 dB. Measurement results of the polarization structure of radiated and scattered pulses with different polarization are presented as well.« less

Status and Integrated Focal Plane Characterization of Simons Array - Cosmic Microwave Background Polarimetry Experiment

NASA Astrophysics Data System (ADS)

Roberts, Hayley; POLARBEAR

2018-06-01

Simons Array is a cosmic microwave background (CMB) polarization experiment located at 5,200 meter altitude site in the Atacama desert in Chile. The science goals of the Simons Array are to characterize the CMB B-mode signal from gravitational lensing, and search for B-mode polarization generated from inflationary gravitational waves.In 2012, POLARBEAR-1 (PB-1) began observations and the POLARBEAR team has published the first measurements of non-zero polarization B-mode polarization angular power spectrum where gravitational lensing of CMB is the dominant signal.POLARBEAR-2A (PB-2A), the first of three receivers of Simons Array, will have 7,588 polarization sensitive Transition Edge Sensor (TES) bolometers with frequencies 90 GHz and 150 GHz. This represents a factor of 6 increase in detector count compared to PB-1. Once Simons Array is fully deployed, the focal plane array will consist 22,764 TES bolometers across 90 GHz, 150 GHz, 220 GHz, and 270 GHz with a projected instantaneous sensitivity of 2.5 µK√s. Here we present the status of PB-2A and characterization of the integrated focal plane to be deployed summer of 2018.

Quantum-rotor-induced polarization.

PubMed

Meier, Benno

2018-07-01

Quantum-rotor-induced polarization is closely related to para-hydrogen-induced polarization. In both cases, the hyperpolarized spin order derives from rotational interaction and the Pauli principle by which the symmetry of the rotational ground state dictates the symmetry of the associated nuclear spin state. In quantum-rotor-induced polarization, there may be several spin states associated with the rotational ground state, and the hyperpolarization is typically generated by hetero-nuclear cross-relaxation. This review discusses preconditions for quantum-rotor-induced polarization for both the 1-dimensional methyl rotor and the asymmetric rotor H 2 17 O@C 60 , that is, a single water molecule encapsulated in fullerene C 60 . Experimental results are presented for both rotors. Copyright © 2018 John Wiley & Sons, Ltd.

Polarization rotation enhancement and scattering mechanisms in waveguide magnetophotonic crystals

NASA Astrophysics Data System (ADS)

Levy, Miguel; Li, Rong

2006-09-01

Intermodal coupling in photonic band gap optical channels in magnetic garnet films is found to leverage the nonreciprocal polarization rotation. Forward fundamental-mode to high-order mode backscattering yields the largest rotations. The underlying mechanism is traced to the dependence of the grating-coupling constant on the modal refractive index and profile of the propagating beam. Large changes in polarization near the band edges are observed in first and second orders. Extreme sensitivity to linear birefringence exists in second order.

Nonlinear and anisotropic polarization rotation in two-dimensional Dirac materials

NASA Astrophysics Data System (ADS)

Singh, Ashutosh; Ghosh, Saikat; Agarwal, Amit

2018-05-01

We predict nonlinear optical polarization rotation in two-dimensional massless Dirac systems including graphene and 8-P m m n borophene. When illuminated, a continuous-wave optical field leads to a nonlinear steady state of photoexcited carriers in the medium. The photoexcited population inversion and the interband coherence give rise to a finite transverse optical conductivity σx y(ω ) . This in turn leads to definitive signatures in associated Kerr and Faraday polarization rotation, which are measurable in a realistic experimental scenario.

Polarization-independent absorption enhancement in a graphene square array with a cascaded grating structure.

PubMed

Wu, Jun

2018-03-01

The polarization-independent enhanced absorption effect of graphene in the near-infrared range is investigated. This is achieved by placing a graphene square array on top of a dielectric square array backed by a two-dimensional multilayer grating. Total optical absorption in graphene can be attributed to critical coupling, which is achieved through the combined effect of guided-mode resonance with the dielectric square array and the photonic band gap with the two-dimensional multilayer grating. To reveal the physical origin of such a phenomenon, the electromagnetic field distributions for both polarizations are illustrated. The designed graphene absorber exhibits near-unity polarization-independent absorption at resonance with an ultra-narrow spectrum. Moreover, the polarization-independent absorption can be tuned simply by changing the geometric parameters. The results may have promising potential for the design of graphene-based optoelectronic devices.

Phased-array sources based on nonlinear metamaterial nanocavities

PubMed Central

Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil A.; Shaner, Eric A.; Klem, John F.; Sinclair, Michael B.; Brener, Igal

2015-01-01

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum. PMID:26126879

Slotted rotatable target assembly and systematic error analysis for a search for long range spin dependent interactions from exotic vector boson exchange using neutron spin rotation

NASA Astrophysics Data System (ADS)

Haddock, C.; Crawford, B.; Fox, W.; Francis, I.; Holley, A.; Magers, S.; Sarsour, M.; Snow, W. M.; Vanderwerp, J.

2018-03-01

We discuss the design and construction of a novel target array of nonmagnetic test masses used in a neutron polarimetry measurement made in search for new possible exotic spin dependent neutron-atominteractions of Nature at sub-mm length scales. This target was designed to accept and efficiently transmit a transversely polarized slow neutron beam through a series of long open parallel slots bounded by flat rectangular plates. These openings possessed equal atom density gradients normal to the slots from the flat test masses with dimensions optimized to achieve maximum sensitivity to an exotic spin-dependent interaction from vector boson exchanges with ranges in the mm - μm regime. The parallel slots were oriented differently in four quadrants that can be rotated about the neutron beam axis in discrete 90°increments using a Geneva drive. The spin rotation signals from the 4 quadrants were measured using a segmented neutron ion chamber to suppress possible systematic errors from stray magnetic fields in the target region. We discuss the per-neutron sensitivity of the target to the exotic interaction, the design constraints, the potential sources of systematic errors which could be present in this design, and our estimate of the achievable sensitivity using this method.

Wideband Microstrip Antenna-Feeding Array

NASA Technical Reports Server (NTRS)

Huang, John

1990-01-01

Special impedance-matching probes help reduce feed complexity. Lightweight array of microstrip antenna elements designed to transmit and illuminate reflector antenna with circularly polarized radiation at 1,545 to 1,550 MHz and to receive circularly polarized radiation at 1,646 to 1,660 MHz. Microstrip array is cluster of 7 subarrays containing total of 28 microstrip patches. Produces cicularly polarized beam with suitable edge taper to illuminate reflector antenna. Teardrop-shaped feed probe provides gradual change of field from coaxial transmission line into microstrip substrate. Intended to be part of larger overlapping-cluster array generating multiple contiguous beams.

Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

2016-01-15

In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θ{sub p}. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θ{sub p}. The maximum value of the cross-correlation coefficient achievedmore » is −0.99 with a zero time delay over a wide range of θ{sub p} beyond 65° with a poor synchronization dynamic at θ{sub p} less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θ{sub p}. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.« less

GINGER (Gyroscopes IN General Relativity), a ring lasers array to measure the Lense-Thirring effect

NASA Astrophysics Data System (ADS)

Di Virgilio, Angela D. V.

The purpose of the GINGER is to perform the first test of general relativity (not considering the gravitational redshift measurements) in a terrestrial laboratory, using light as a probe. The experiment will complement the ones in space, performed or under way, with an entirely different technique and at a far lower cost. The methodology is based on ring-lasers, which are extremely accurate rotation sensors and can not only sense purely kinematical rotations (Sagnac effect accounting for the Earth rotation, polar motion of the terrestrial axis, local rotational movements of the laboratory due to the Earth crust dynamics...), but also general relativistic contributions such as the de Sitter effect (coupling between the gravito-electric field of the earth and the kinematical rotation) and the Lense-Thirring effect (inertial frame dragging due to the angular momentum of the earth). In order to reveal the latter effects, ring-laser response must be improved to be able to measure the effective rotation vector (kinematic plus GR terms) with an accuracy of 1 part in 109 or better. This is a challenging technological aspect, which however has been accurately taken into account by designing a system of ring lasers that will be implemented in this project. A ring laser have been installed inside the underground laboratory of GranSasso, with the purpose to see if an underground location is the right choice for GINGER. The apparatus and the preliminary results will be discussed.

Two-dimensional arbitrary nano-manipulation on a plasmonic metasurface.

PubMed

Jiang, Min; Wang, Guanghui; Xu, Wenhao; Ji, Wenbin; Zou, Ningmu; Ho, Ho-Pui; Zhang, Xuping

2018-04-01

In this Letter, we report on a plasmonic nano-ellipse metasurface with the purpose of trapping and two-dimensional (2D) arbitrary transport of nanoparticles by means of rotating the polarization of an excitation beam. The locations of hot spots within a metasurface are polarization dependent, thus making it possible to turn on/off the adjacent hot spots and then convey the trapped target by rotating the incident polarization state. For the case of a metasurface with a unit cell of perpendicularly orientated nano-ellipses, the hot spots with higher intensities are located at both apexes of the nano-ellipse whose major axis is parallel to the direction of polarization. When the polarization gradually rotates to its counterpart direction, the trapped particle may move around the ellipse and transfer to the most adjacent ellipse, due to the unbalanced trap potentials around the nano-ellipse. Clockwise and counterclockwise rotation would guide the particle in a different direction, which makes it possible to convey the particle arbitrarily within the plasmonic metasurface by setting a time sequence of polarization rotation. As confirmed by the three-dimensional finite-difference time-domain analysis, our design offers a novel scheme of 2D arbitrary transport with nanometer accuracy, which could be used in many on-chip optofluidic applications.

Controlling electron quantum paths for generation of circularly polarized high-order harmonics by H2+ subject to tailored (ω , 2 ω ) counter-rotating laser fields

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2018-04-01

Recently, studies of high-order harmonics (HHG) from atoms driven by bichromatic counter-rotating circularly polarized laser fields as a source of coherent circularly polarized extreme ultraviolet (XUV) and soft-x-ray beams in a tabletop-scale setup have received considerable attention. Here, we demonstrate the ability to control the electron recollisions giving three returns per one cycle of the fundamental frequency ω by using tailored bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields with a molecular target. The full control of the electronic pathway is first analyzed by a classical trajectory analysis and then extended to a detailed quantum study of H2+ molecules in bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields. The radiation spectrum contains doublets of left- and right-circularly polarized harmonics in the XUV ranges. We study in detail the below-, near-, and above-threshold harmonic regions and describe how excited-state resonances alter the ellipticity and phase of the generated harmonic peaks.

An improved method for polarimetric image restoration in interferometry

NASA Astrophysics Data System (ADS)

Pratley, Luke; Johnston-Hollitt, Melanie

2016-11-01

Interferometric radio astronomy data require the effects of limited coverage in the Fourier plane to be accounted for via a deconvolution process. For the last 40 years this process, known as `cleaning', has been performed almost exclusively on all Stokes parameters individually as if they were independent scalar images. However, here we demonstrate for the case of the linear polarization P, this approach fails to properly account for the complex vector nature resulting in a process which is dependent on the axes under which the deconvolution is performed. We present here an improved method, `Generalized Complex CLEAN', which properly accounts for the complex vector nature of polarized emission and is invariant under rotations of the deconvolution axes. We use two Australia Telescope Compact Array data sets to test standard and complex CLEAN versions of the Högbom and SDI (Steer-Dwedney-Ito) CLEAN algorithms. We show that in general the complex CLEAN version of each algorithm produces more accurate clean components with fewer spurious detections and lower computation cost due to reduced iterations than the current methods. In particular, we find that the complex SDI CLEAN produces the best results for diffuse polarized sources as compared with standard CLEAN algorithms and other complex CLEAN algorithms. Given the move to wide-field, high-resolution polarimetric imaging with future telescopes such as the Square Kilometre Array, we suggest that Generalized Complex CLEAN should be adopted as the deconvolution method for all future polarimetric surveys and in particular that the complex version of an SDI CLEAN should be used.

METHOD AND APPARATUS FOR PRODUCING AND ANALYZING POLARIZED GAMMA RADIATION

DOEpatents

Hamermesh, M.; Hanna, S.S.; Perlow, G.J.

1964-04-21

A method of polarizing and resolving the plane of polarization of gamma rays is described. Polarization is produced by positioning a thin disc of ferromagnetic metal, cortaining /sup 57/Co, in a magnetic field. Resolution is accomplished by rotating a thin disc of iron enriched in /sup 57/Fe relative to a second magnetic field and noting the change of gamma absorption at each rotational position. (AEC)

Orientation and Polarisation Effects in Reactive Collisions

DTIC Science & Technology

1989-01-01

18 To clock the reaction, an ultrashort laser pulse initiates the experiment by photodis- sociating the HI, ejecting a translationally hot H atom in...the chamber and travels down; the pulsed , linearly polarized u.v. laser beam passes from right to left, going through a polarization rotator before... pulsed beam valve above the chamber; the pulsed linearly polarized laser beam passes through a polarization rotator before entering the chamber. Two

A Tikhonov Regularization Scheme for Focus Rotations with Focused Ultrasound Phased Arrays

PubMed Central

Hughes, Alec; Hynynen, Kullervo

2016-01-01

Phased arrays have a wide range of applications in focused ultrasound therapy. By using an array of individually-driven transducer elements, it is possible to steer a focus through space electronically and compensate for acoustically heterogeneous media with phase delays. In this paper, the concept of focusing an ultrasound phased array is expanded to include a method to control the orientation of the focus using a Tikhonov regularization scheme. It is then shown that the Tikhonov regularization parameter used to solve the ill-posed focus rotation problem plays an important role in the balance between quality focusing and array efficiency. Finally, the technique is applied to the synthesis of multiple foci, showing that this method allows for multiple independent spatial rotations. PMID:27913323

A Tikhonov Regularization Scheme for Focus Rotations With Focused Ultrasound-Phased Arrays.

PubMed

Hughes, Alec; Hynynen, Kullervo

2016-12-01

Phased arrays have a wide range of applications in focused ultrasound therapy. By using an array of individually driven transducer elements, it is possible to steer a focus through space electronically and compensate for acoustically heterogeneous media with phase delays. In this paper, the concept of focusing an ultrasound-phased array is expanded to include a method to control the orientation of the focus using a Tikhonov regularization scheme. It is then shown that the Tikhonov regularization parameter used to solve the ill-posed focus rotation problem plays an important role in the balance between quality focusing and array efficiency. Finally, the technique is applied to the synthesis of multiple foci, showing that this method allows for multiple independent spatial rotations.

Climatic impact of glacial cycle polar motion: Coupled oscillations of ice sheet mass and rotation pole position

USGS Publications Warehouse

Bills, Bruce G.; James, Thomas S.; Mengel, John G.

1999-01-01

Precessional motion of Earth's rotation axis relative to its orbit is a well-known source of long-period climatic variation. It is less well appreciated that growth and decay of polar ice sheets perturb the symmetry of the global mass distribution enough that the geographic location of the rotation axis will change by at least 15 km and possibly as much as 100 km during a single glacial cycle. This motion of the pole will change the seasonal and latitudinal pattern of temperatures. We present calculations, based on a diurnal average energy balance, which compare the summer and winter temperature anomalies due to a 1° decrease in obliquity with those due to a 1° motion of the rotation pole toward Hudson Bay. Both effects result in peak temperature perturbations of about 1° Celsius. The obliquity change primarily influences the amplitude of the seasonal cycle, while the polar motion primarily changes the annual mean temperatures. The polar motion induced temperature anomaly is such that it will act as a powerful negative feedback on ice sheet growth. We also explore the evolution of the coupled system composed of ice sheet mass and pole position. Oscillatory solutions result from the conflicting constraints of rotational and thermal stability. A positive mass anomaly on an otherwise featureless Earth is in rotational equilibrium only at the poles or the equator. The two polar equilibria are rotationally unstable, and the equatorial equilibrium, though rotationally stable, is thermally unstable. We find that with a plausible choice for the strength of coupling between the thermal and rotational systems, relatively modest external forcing can produce significant response at periods of 104–106 years, but it strongly attenuates polar motion at longer periods. We suggest that these coupled oscillations may contribute to the observed dominance of 100 kyr glacial cycles since the mid-Pleistocene and will tend to stabilize geographic patterns that are suitable to glaciations.

Polarimetric Imaging System for Automatic Target Detection and Recognition

DTIC Science & Technology

2000-03-01

technique shown in Figure 4(b) can also be used to integrate polarizer arrays with other types of imaging sensors, such as LWIR cameras and uncooled...vertical stripe pattern in this φ image is caused by nonuniformities in the particular polarizer array used. 2. CIRCULAR POLARIZATION IMAGING USING

Visible and infrared polarization ratio spectroreflectometer

NASA Technical Reports Server (NTRS)

Batten, C. E. (Inventor)

1980-01-01

The instrument assists in determining the refractive index and absorption index, at different spectral frequencies, of a solid sample by illuminating the sample at various angles in incidence and measuring the corresponding reflected intensities at various spectral frequencies and polarization angles. The ratio of the intensity of the reflected light for parallel polarized light to that for perpendicular polarized light at two different angles of incidence can be used to determine the optical constants of the sample. The invention involves an apparatus for facilitating the utilization of a wide variety of angles of incidence. The light source and polarizing element are positioned on an outer platform; the sample is positioned on an inner platform. The two platforms rotate about a common axis and cooperate in their rotation such that the sample is rotated one degree for every two degrees of rotation of the light source. This maintains the impingement of the reflected light upon the detector for any angle of incidence without moving or adjusting the detector which allows a continuous change in the angle of incidence.

Improved optical filter

NASA Technical Reports Server (NTRS)

Title, A. M.

1978-01-01

Filter includes partial polarizer between birefrigent elements. Plastic film on partial polarizer compensates for any polarization rotation by partial polarizer. Two quarter-wave plates change incident, linearly polarized light into elliptically polarized light.

Broadband radio spectro-polarimetric observations of high-Faraday-rotation-measure AGN

NASA Astrophysics Data System (ADS)

Pasetto, Alice; Carrasco-González, Carlos; O'Sullivan, Shane; Basu, Aritra; Bruni, Gabriele; Kraus, Alex; Curiel, Salvador; Mack, Karl-Heinz

2018-06-01

We present broadband polarimetric observations of a sample of high-Faraday-rotation-measure (high-RM) active galactic nuclei (AGN) using the Karl. G. Jansky Very Large Array (JVLA) telescope from 1 to 2 GHz, and 4 to 12 GHz. The sample (14 sources) consists of very compact sources (linear resolution smaller than ≈5 kpc) that are unpolarized at 1.4 GHz in the NRAO VLA Sky Survey (NVSS). Total intensity data have been modeled using a combination of synchrotron components, revealing complex structure in their radio spectra. Depolarization modeling, through the so-called qu-fitting (the modeling of the fractional quantities of the Stokes Q and U parameters), has been performed on the polarized data using an equation that attempts to simplify the process of fitting many different depolarization models. These models can be divided into two major categories: external depolarization (ED) and internal depolarization (ID) models. Understanding which of the two mechanisms is the most representative would help the qualitative understanding of the AGN jet environment and whether it is embedded in a dense external magneto-ionic medium or if it is the jet-wind that causes the high RM and strong depolarization. This could help to probe the jet magnetic field geometry (e.g., helical or otherwise). This new high-sensitivity data shows a complicated behavior in the total intensity and polarization radio spectrum of individual sources. We observed the presence of several synchrotron components and Faraday components in their total intensity and polarized spectra. For the majority of our targets (12 sources), the depolarization seems to be caused by a turbulent magnetic field. Thus, our main selection criteria (lack of polarization at 1.4 GHz in the NVSS) result in a sample of sources with very large RMs and depolarization due to turbulent magnetic fields local to the source. These broadband JVLA data reveal the complexity of the polarization properties of this class of radio sources. We show how the new qu-fitting technique can be used to probe the magnetized radio source environment and to spectrally resolve the polarized components of unresolved radio sources.

On-sky performance evaluation and calibration of a polarization-sensitive focal plane array

NASA Astrophysics Data System (ADS)

Vorobiev, Dmitry; Ninkov, Zoran; Brock, Neal; West, Ray

2016-07-01

The advent of pixelated micropolarizer arrays (MPAs) has facilitated the development of polarization-sensitive focal plane arrays (FPAs) based on charge-coupled devices (CCDs) and active pixel sensors (APSs), which are otherwise only able to measure the intensity of light. Polarization sensors based on MPAs are extremely compact, light-weight, mechanically robust devices with no moving parts, capable of measuring the degree and angle of polarization of light in a single snapshot. Furthermore, micropolarizer arrays based on wire grid polarizers (so called micro-grid polarizers) offer extremely broadband performance, across the optical and infrared regimes. These devices have potential for a wide array of commercial and research applications, where measurements of polarization can provide critical information, but where conventional polarimeters could be practically implemented. To date, the most successful commercial applications of these devices are 4D Technology's PhaseCam laser interferometers and PolarCam imaging polarimeters. Recently, MPA-based polarimeters have been identified as a potential solution for space-based telescopes, where the small size, snapshot capability and low power consumption (offered by these devices) are extremely desirable. In this work, we investigated the performance of MPA-based polarimeters designed for astronomical polarimetry using the Rochester Institute of Technology Polarization Imaging Camera (RITPIC). We deployed RITPIC on the 0.9 meter SMARTS telescope at the Cerro Tololo Inter-American Observatory and observed a variety of astronomical objects (calibration stars, variable stars, reflection nebulae and planetary nebulae). We use our observations to develop calibration procedures that are unique to these devices and provide an estimate for polarimetric precision that is achievable.

Novel wideband microwave polarization network using a fully-reconfigurable photonic waveguide interleaver with a two-ring resonator-assisted asymmetric Mach-Zehnder structure.

PubMed

Zhuang, Leimeng; Beeker, Willem; Leinse, Arne; Heideman, René; van Dijk, Paulus; Roeloffzen, Chris

2013-02-11

We propose and demonstrate a novel wideband microwave photonic polarization network for dual linear-polarized antennas. The polarization network is based on a waveguide-implemented fully-reconfigurable optical interleaver using a two-ring resonator-assisted asymmetric Mach-Zehnder structure. For microwave photonic signal processing, this structure is able to serve as a wideband 2 × 2 RF coupler with reconfigurable complex coefficients, and therefore can be used as a polarization network for wideband antennas. Such a device can equip the antennas with not only the polarization rotation capability for linear-polarization signals but also the capability to operate with and tune between two opposite circular polarizations. Operating together with a particular modulation scheme, the device is also able to serve for simultaneous feeding of dual-polarization signals. These photonic-implemented RF functionalities can be applied to wideband antenna systems to perform agile polarization manipulations and tracking operations. An example of such a interleaver has been realized in TriPleX waveguide technology, which was designed with a free spectral range of 20 GHz and a mask footprint of smaller than 1 × 1 cm. Using the realized device, the reconfigurable complex coefficients of the polarization network were demonstrated with a continuous bandwidth from 2 to 8 GHz and an in-band phase ripple of smaller than 5 degree. The waveguide structure of the device allows it to be further integrated with other functional building blocks of a photonic integrated circuit to realize on-chip, complex microwave photonic processors. Of particular interest, it can be included in an optical beamformer for phased array antennas, so that simultaneous wideband beam and polarization trackings can be achieved photonically. To our knowledge, this is the first-time on-chip demonstration of an integrated microwave photonic polarization network for dual linear-polarized antennas.

Levitation pressure and friction losses in superconducting bearings

DOEpatents

Hull, John R.

2001-01-01

A superconducting bearing having at least one permanent magnet magnetized with a vertical polarization. The lower or stator portion of the bearing includes an array of high-temperature superconducting elements which are comprised of a plurality of annular rings. An annular ring is located below each permanent magnet and an annular ring is offset horizontally from at least one of the permanent magnets. The rings are composed of individual high-temperature superconducting elements located circumferentially along the ring. By constructing the horizontally-offset high-temperature superconducting ring so that the c-axis is oriented in a radial direction, a higher levitation force can be achieved. Such an orientation will also provide substantially lower rotational drag losses in the bearing.

The relaxed-polar mechanism of locally optimal Cosserat rotations for an idealized nanoindentation and comparison with 3D-EBSD experiments

NASA Astrophysics Data System (ADS)

Fischle, Andreas; Neff, Patrizio; Raabe, Dierk

2017-08-01

The rotation {{polar}}(F) \\in {{SO}}(3) arises as the unique orthogonal factor of the right polar decomposition F = {{polar}}(F) U of a given invertible matrix F \\in {{GL}}^+(3). In the context of nonlinear elasticity Grioli (Boll Un Math Ital 2:252-255, 1940) discovered a geometric variational characterization of {{polar}}(F) as a unique energy-minimizing rotation. In preceding works, we have analyzed a generalization of Grioli's variational approach with weights (material parameters) μ > 0 and μ _c ≥ 0 (Grioli: μ = μ _c). The energy subject to minimization coincides with the Cosserat shear-stretch contribution arising in any geometrically nonlinear, isotropic and quadratic Cosserat continuum model formulated in the deformation gradient field F :=\

Is the Critical Rotation of Be Stars Really Critical for the Be Phenomenon?

NASA Astrophysics Data System (ADS)

Stee, Ph.; Meilland, A.

We aim to study the effect of the fast rotation, stellar wind and circumstellar disks around active hot stars and their effects on the formation and evolution of these massive stars. For that purpose, we obtained, for the first time, interferometric measurements of three active hot stars, namely α Arae, κ CMa and Achernar, using the VLTI /AMBER and VLTI/MIDI instruments which allow us to study the kinematics of the central star and its surrounding circumstellar matter. These data coupled with our numerical code SIMECA (SIMulation pour Etoiles Chaudes Actives) seem to indicate that the presence of equatorial disks and polar stellar wind around Be stars are not correlated. A polar stellar wind was detected for α Arae and Achernar whereas κ CMa seems to exhibit no stellar wind. On the other hand, these two first Be stars are certainly nearly critical rotators whereas the last one seems to be far from the critical rotation. Thus a polar stellar wind may be due to the nearly critical rotation which induces a local effective temperature change following the von Zeipel theorem, producing a hotter polar region triggering a polar stellar wind. This critical rotation may also explain the formation of a circumstellar disk which is formed by the centrifugal force balancing the equatorial effective gravity of the central star. Following these results we try to investigate if critical rotation may be the clue for the Be phenomenon.

Terahertz broadband polarization converter based on metamaterials

NASA Astrophysics Data System (ADS)

Li, Yonghua; Zhao, Guozhong

2018-01-01

Based on the metamaterial composed of symmetrical split resonant ring, a broadband reflective terahertz polarization converter is proposed. The numerical simulation shows that it can rotate the polarization direction of linear polarized wave 90° in the range of 0.7-1.8THz and the polarization conversion ratio is over 90%. The reflection coefficient of the two electric field components in the diagonal direction is the same and the phase difference is 180° ,which leads to the cross-polarization rotation.In order to further study the physical mechanism of high polarization conversion, we analyze the surface current distribution of the resonant ring. The polarization converter has potential applications in terahertz wave plate and metamaterial antenna design.

Optical field induced rotation of polarization in rubidium atoms with the additional magnetic field

NASA Astrophysics Data System (ADS)

Ummal Momeen, M.; Hu, Jianping

2017-11-01

We present the magnetic and optical field induced rotation of polarization in 87Rb and 85Rb atoms at geophysical magnetic fields. The line shape varies considerably in the presence of a magnetic field of the order of a few mG. Multiple Zeeman sublevel EIT systems involving rubidium atoms are investigated. Theoretical formalism of optical field induced polarization rotation in the presence of a magnetic field is discussed by considering all the Zeeman sublevels. It is noted that the ground state population distribution also plays a major role.

Elliptically polarizing adjustable phase insertion device

DOEpatents

Carr, Roger

1995-01-01

An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets.

Investigation of polarization-selective InGaAs sensor with elliptical two-dimensional holes array structure

NASA Astrophysics Data System (ADS)

Wang, Wenbo; Fu, Dong; Hu, Xiaobin; Xu, Yun; Song, Guofeng; Wei, Xin

2016-10-01

Polarimetric imaging in infrared wavelengths have attracted more and more attention for broad applications in meteorological observations, medicine, remote sensing and many other fields. Metal metamaterial structures are used in nanophotonics in order to localize and enhance the incident electromagnetic field. Here we develop an elliptical gold Two-Dimensional Holes Array (2DHA) in which photons can be manipulated by surface plasmon resonance, and the ellipse introduce the asymmetry to realize a polarization selective function. Strong polarization dependence is observed in the simulated transmission spectra. To further understand the coupling mechanism between gold holes array and InP, the different parameters of the 2DHA are analyzed. It is shown that the polarization axis is perpendicular to the major axis of the ellipse, and the degree of polarization is determined by the aspect ratio of the ellipse. Furthermore, the resonance frequency of the 2DHA shows a linear dependence on the array period, the bandwidth of transmission spectra closely related to duty cycle of the ellipse in each period. This result will establish a basis for the development of innovative polarization selective infrared sensor.

Counter-rotational cell flows drive morphological and cell fate asymmetries in mammalian hair follicles.

PubMed

Cetera, Maureen; Leybova, Liliya; Joyce, Bradley; Devenport, Danelle

2018-05-01

Organ morphogenesis is a complex process coordinated by cell specification, epithelial-mesenchymal interactions and tissue polarity. A striking example is the pattern of regularly spaced, globally aligned mammalian hair follicles, which emerges through epidermal-dermal signaling and planar polarized morphogenesis. Here, using live-imaging, we discover that developing hair follicles polarize through dramatic cell rearrangements organized in a counter-rotational pattern of cell flows. Upon hair placode induction, Shh signaling specifies a radial pattern of progenitor fates that, together with planar cell polarity, induce counter-rotational rearrangements through myosin and ROCK-dependent polarized neighbour exchanges. Importantly, these cell rearrangements also establish cell fate asymmetry by repositioning radial progenitors along the anterior-posterior axis. These movements concurrently displace associated mesenchymal cells, which then signal asymmetrically to maintain polarized cell fates. Our results demonstrate how spatial patterning and tissue polarity generate an unexpected collective cell behaviour that in turn, establishes both morphological and cell fate asymmetry.

The E and B EXperiment: EBEX

NASA Astrophysics Data System (ADS)

Helson, Kyle

2014-03-01

We report on the status of the E and B Experiment (EBEX) a balloon-borne polarimeter designed to measure the polarization of the cosmic microwave background radiation. The instrument employs a 1.5 meter Gregorian Mizuguchi-Dragone telescope providing 8 arc-minute resolution at three bands centered on 150, 250, and 410 GHz. A continuously rotating achromatic half wave plate, mounted on a superconducting magnetic bearing, and a polarizing grid give EBEX polarimetric capabilities. Radiation is detected with a kilo-pixel array of transition edge sensor (TES) bolometers that are cooled to 0.25 K. The detectors are readout using SQUID current amplifiers and a digital frequency-domain multiplexing system in which 16 detectors are readout simultaneously with two wires. EBEX is the first instrument to implement TESs and such readout system on board a balloon-borne platform. EBEX was launched from the Antarctic in December 2012 on an 11-day long-duration balloon flight. This presentation will provide an overview of the instrument and discuss the flight and status of the data analysis.

Constraints on Inner Core Anisotropy Using Array Observations of P'P'

NASA Astrophysics Data System (ADS)

Frost, Daniel A.; Romanowicz, Barbara

2017-11-01

Recent studies of PKPdf travel times suggest strong anisotropy (4% or more) in the quasi-western inner core hemisphere. However, the availability of paths sampling at low angles to the Earth's rotation axis (the fast axis) is limited. To augment this sampling, we collected a travel time data set for the phase P'P'df (PKPPKPdf), for which at least one inner core leg is quasi-polar, at two high latitude seismic arrays. We find that the inferred anisotropy is weak (on the order of 0.5 to 1.5%), confirming previous results based on a much smaller P'P' data set. While previous models of inner core anisotropy required very strong alignment of anisotropic iron grains, our results are more easily explained by current dynamic models of inner core growth. We observe large travel time anomalies when one leg of P'P'df is along the South Sandwich to Alaska path, consistent with PKPdf observations, and warranting further investigation.

Interaction between Faraday rotation and Cotton-Mouton effects in polarimetry modeling for NSTX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J.; Crocker, N. A.; Carter, T. A.

The evolution of electromagnetic wave polarization is modeled for propagation in the major radial direction in the National Spherical Torus Experiment with retroreflection from the center stack of the vacuum vessel. This modeling illustrates that the Cotton-Mouton effect-elliptization due to the magnetic field perpendicular to the propagation direction-is shown to be strongly weighted to the high-field region of the plasma. An interaction between the Faraday rotation and Cotton-Mouton effects is also clearly identified. Elliptization occurs when the wave polarization direction is neither parallel nor perpendicular to the local transverse magnetic field. Since Faraday rotation modifies the polarization direction during propagation,more » it must also affect the resultant elliptization. The Cotton-Mouton effect also intrinsically results in rotation of the polarization direction, but this effect is less significant in the plasma conditions modeled. The interaction increases at longer wavelength and complicates interpretation of polarimetry measurements.« less

A 3D gantry single photon emission tomograph with hemispherical coverage for dedicated breast imaging

NASA Astrophysics Data System (ADS)

Tornai, Martin P.; Bowsher, James E.; Archer, Caryl N.; Peter, Jörg; Jaszczak, Ronald J.; MacDonald, Lawrence R.; Patt, Bradley E.; Iwanczyk, Jan S.

2003-01-01

A novel tomographic gantry was designed, built and initially evaluated for single photon emission imaging of metabolically active lesions in the pendant breast and near chest wall. Initial emission imaging measurements with breast lesions of various uptake ratios are presented. Methods: A prototype tomograph was constructed utilizing a compact gamma camera having a field-of-view of <13×13 cm 2 with arrays of 2×2×6 mm 3 quantized NaI(Tl) scintillators coupled to position sensitive PMTs. The camera was mounted on a radially oriented support with 6 cm variable radius-of-rotation. This unit is further mounted on a goniometric cradle providing polar motion, and in turn mounted on an azimuthal rotation stage capable of indefinite vertical axis-of-rotation about the central rotation axis (RA). Initial measurements with isotopic Tc-99 m (140 keV) to evaluate the system include acquisitions with various polar tilt angles about the RA. Tomographic measurements were made of a frequency and resolution cold-rod phantom filled with aqueous Tc-99 m. Tomographic and planar measurements of 0.6 and 1.0 cm diameter fillable spheres in an available ˜950 ml hemi-ellipsoidal (uncompressed) breast phantom attached to a life-size anthropomorphic torso phantom with lesion:breast-and-body:cardiac-and-liver activity concentration ratios of 11:1:19 were compared. Various photopeak energy windows from 10-30% widths were obtained, along with a 35% scatter window below a 15% photopeak window from the list mode data. Projections with all photopeak window and camera tilt conditions were reconstructed with an ordered subsets expectation maximization (OSEM) algorithm capable of reconstructing arbitrary tomographic orbits. Results: As iteration number increased for the tomographically measured data at all polar angles, contrasts increased while signal-to-noise ratios (SNRs) decreased in the expected way with OSEM reconstruction. The rollover between contrast improvement and SNR degradation of the lesion occurred at two to three iterations. The reconstructed tomographic data yielded SNRs with or without scatter correction that were >9 times better than the planar scans. There was up to a factor of ˜2.5 increase in total primary and scatter contamination in the photopeak window with increasing tilt angle from 15° to 45°, consistent with more direct line-of-sight of myocardial and liver activity with increased camera polar angle. Conclusion: This new, ultra-compact, dedicated tomographic imaging system has the potential of providing valuable, fully 3D functional information about small, otherwise indeterminate breast lesions as an adjunct to diagnostic mammography.

Development of dual-polarization LEKIDs for CMB observations

NASA Astrophysics Data System (ADS)

McCarrick, Heather; Abitbol, Maximilian H.; Ade, Peter A. R.; Barry, Peter; Bryan, Sean; Che, George; Day, Peter; Doyle, Simon; Flanigan, Daniel; Johnson, Bradley R.; Jones, Glenn; LeDuc, Henry G.; Limon, Michele; Mauskopf, Philip; Miller, Amber; Tucker, Carole; Zmuidzinas, Jonas

2016-07-01

We discuss the design considerations and initial measurements from arrays of dual-polarization, lumped-element kinetic inductance detectors (LEKIDs) nominally designed for cosmic microwave background (CMB) studies. The detectors are horn-coupled, and each array element contains two single-polarization LEKIDs, which are made from thin-film aluminum and optimized for a single spectral band centered on 150 GHz. We are developing two array architectures, one based on 160 micron thick silicon wafers and the other based on silicon-on-insulator (SOI) wafers with a 30 micron thick device layer. The 20-element test arrays (40 LEKIDs) are characterized with both a linearly-polarized electronic millimeter wave source and a thermal source. We present initial measurements including the noise spectra, noise-equivalent temperature, and responsivity. We discuss future testing and further design optimizations to be implemented.

Phased-array sources based on nonlinear metamaterial nanocavities

DOE PAGES

Wolf, Omri; Campione, Salvatore; Benz, Alexander; ...

2015-07-01

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization.more » As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.« less

Understanding the rotation of coronal holes

NASA Astrophysics Data System (ADS)

Wang, Y.-M.; Sheeley, N. R., Jr.

1993-09-01

In an earlier study we found that the rotation of coronal holes could be understood on the basis of a nearly current-free coronal field, with the holes representing open magnetic regions. In this paper we illustrate the model by focusing on the case of CH1, the rigidly rotating boot-shaped hole observed by Skylab. We show that the interaction between the polar fields and the flux associated with active regions produces distortions in the coronal field configuration and thus in the polar-hole boundaries; these distortions corotate with the perturbing nonaxisymmetric flux. In the case of CH1, positive-polarity field lines in the northern hemisphere 'collided' with like-polarity field lines fanning out from a decaying active region complex located just below the equator, producing a midlatitude corridor of open field lines rotating at the rate of the active region complex. Sheared coronal holes result when nonaxisymmetric flux is present at high latitudes, or equivalently, when the photospheric neutral line extends to high latitudes. We demonstrate how a small active region, rotating at the local photospheric rate, can drift through a rigidly rotating hole like CH1. Finally, we discuss the role of field-line reconnection in maintaining a quasi-potential coronal configuration.

Climate-Rotation Feedback on Mars

NASA Technical Reports Server (NTRS)

Bills, Bruce G.

1999-01-01

A new model is presented for the coupled evolution of climate and rotation, as applied to Mars. It has long been appreciated that changes in the orbital and rotational geometry of Mars will influence the seasonal and latitudinal pattern of insolation, and this will likely dominate climatic fluctuations on time scales of 10(exp 5) to 10(exp 7) years. Equally important, but less widely appreciated, is the influence climatic change can have on rotational dynamics. The primary means by which climate influences rotation is via its influence on transport of mass (volatiles and dust) into and out of the polar regions. Many important issues remain unresolved: What are the ages of the polar caps? What climatic periods are recorded in the polar layered deposits? What is the long term obliquity history? Additional information is contained in the original extended abstract.

Graphene-based magnetless converter of terahertz wave polarization

NASA Astrophysics Data System (ADS)

Melnikova, Veronica S.; Polischuk, Olga V.; Popov, Vyacheslav V.

2016-04-01

The polarization conversion of terahertz radiation by the periodic array of graphene nanoribbons located at the surface of a high-refractive-index dielectric substrate (terahertz prism) is studied theoretically. Giant polarization conversion at the plasmon resonance frequencies takes place without applying external DC magnetic field. It is shown that the total polarization conversion can be reached at the total internal reflection of THz wave from the periodic array of graphene nanoribbons even at room temperature.

The rotation of Titan and Ganymede

NASA Astrophysics Data System (ADS)

Van Hoolst, Tim; Coyette, Alexis; Baland, Rose-Marie; Trinh, Antony

2016-10-01

The rotation rates of Titan and Ganymede, the largest satellites of Saturn and Jupiter, are on average equal to their orbital mean motion. Here we discuss small deviations from the average rotation for both satellites and evaluate the polar motion of Titan induced by its surface fluid layers. We examine different causes at various time scales and assess possible consequences and the potential of using librations and polar motion as probes of the interior structure of the satellites.The rotation rate of Titan and Ganymede cannot be constant on the orbital time scale as a result of the gravitational torque of the central planet acting on the satellites. Titan is moreover expected to show significant polar motion and additional variations in the rotation rate due to angular momentum exchange with the atmosphere, mainly at seasonal periods. Observational evidence for deviations from the synchronous state has been reported several times for Titan but is unfortunately inconclusive. The measurements of the rotation variations are based on determinations of the shift in position of Cassini radar images taken during different flybys. The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation variations of Ganymede during its orbital phase around the satellite starting in 2032.We report on different theoretical aspects of the librations and polar motion. We consider the influence of the rheology of the ice shell and take into account Cassini measurements of the external gravitational field and of the topography of Titan and similar Galileo data about Ganymede. We also evaluate the librations and polar motion induced by Titan's hydrocarbon seas and use the most recent results of Titan's atmosphere dynamics. We finally evaluate the potential of rotation variations to constrain the satellite's interior structure, in particular its ice shell and ocean.

Emission-angle and polarization-rotation effects in the lensed CMB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Antony; Hall, Alex; Challinor, Anthony, E-mail: antony@cosmologist.info, E-mail: ahall@roe.ac.uk, E-mail: a.d.challinor@ast.cam.ac.uk

Lensing of the CMB is an important effect, and is usually modelled by remapping the unlensed CMB fields by a lensing deflection. However the lensing deflections also change the photon path so that the emission angle is no longer orthogonal to the background last-scattering surface. We give the first calculation of the emission-angle corrections to the standard lensing approximation from dipole (Doppler) sources for temperature and quadrupole sources for temperature and polarization. We show that while the corrections are negligible for the temperature and E-mode polarization, additional large-scale B-modes are produced with a white spectrum that dominates those from post-Bornmore » field rotation (curl lensing). On large scales about one percent of the total lensing-induced B-mode amplitude is expected to be due to this effect. However, the photon emission angle does remain orthogonal to the perturbed last-scattering surface due to time delay, and half of the large-scale emission-angle B modes cancel with B modes from time delay to give a total contribution of about half a percent. While not important for planned observations, the signal could ultimately limit the ability of delensing to reveal low amplitudes of primordial gravitational waves. We also derive the rotation of polarization due to multiple deflections between emission and observation. The rotation angle is of quadratic order in the deflection angle, and hence negligibly small: polarization typically rotates by less than an arcsecond, orders of magnitude less than a small-scale image rotates due to post-Born field rotation (which is quadratic in the shear). The field-rotation B modes dominate the other effects on small scales.« less

Ultrashort polarization-tailored bichromatic fields

NASA Astrophysics Data System (ADS)

Kerbstadt, Stefanie; Englert, Lars; Bayer, Tim; Wollenhaupt, Matthias

2017-06-01

We present a novel concept for the generation of ultrashort polarization-shaped bichromatic laser fields. The scheme utilizes a 4f polarization pulse shaper based on a liquid crystal spatial light modulator for independent amplitude and phase modulation of femtosecond laser pulses. By choice of either a conventional (p) or a composite (p-s) polarizer in the Fourier plane, the shaper setup enables the generation of parallel linearly and orthogonal linearly polarized bichromatic fields. Additional use of a ? wave plate behind the setup yields co-rotating and counter-rotating circularly polarized bichromatic fields. The scheme allows to independently control the spectral amplitude, phase and polarization profile of the output fields, offering an enormous versatility of bichromatic waveforms.

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

PubMed Central

Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

2015-01-01

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation.

PubMed

Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W; Mani, Ramesh G

2015-10-09

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

Generation of continuously rotating polarization by combining cross-polarizations and its application in surface structuring.

PubMed

Lam, Billy; Zhang, Jihua; Guo, Chunlei

2017-08-01

In this study, we develop a simple but highly effective technique that generates a continuously varying polarization within a laser beam. This is achieved by having orthogonal linear polarizations on each side of the beam. By simply focusing such a laser beam, we can attain a gradually and continuously changing polarization within the entire Rayleigh range due to diffraction. To demonstrate this polarization distribution, we apply this laser beam onto a metal surface and create a continuously rotating laser induced periodic surface structure pattern. This technique provides a very effective way to produce complex surface structures that may potentially find applications, such as polarization modulators and metasurfaces.

Magneto-optic current sensor

DOEpatents

Lanagan, Michael T.; Valsko-Vlasov, Vitalii K.; Fisher, Brandon L.; Welp, Ulrich

2003-10-07

An optical current transducer configured to sense current in the conductor is disclosed. The optical current transducer includes a light source and a polarizer that generates linearly polarized light received from a the light source. The light is communicated to a magneto-optic garnet that includes, among other elements, bismuth, iron and oxygen and is coupled to the conductor. The magneto-optic garnet is configured to rotate the polarization of the linearly polarized light received from the polarizer. The optical current transducer also includes an analyzer in optical communication with the magneto-optic garnet. The analyzer detects the rotation of the linearly polarized light caused by the magneto-optic garnet.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Derbenev, Yaroslav S.; Morozov, Vasiliy; Lin, Fanglei

We present a complete scheme for managing the polarization of ion beams in Jefferson Lab's proposed Medium-energy Electron-Ion Collider (MEIC). It provides preservation of the ion polarization during all stages of beam acceleration and polarization control in the collider's experimental straights. We discuss characteristic features of the spin motion in accelerators with Siberian snakes and in accelerators of figure-8 shape. We propose 3D spin rotators for polarization control in the MEIC ion collider ring. We provide polarization calculations in the collider with the 3D rotator for deuteron and proton beams. The main polarization control features of the figure-8 design aremore » summarized.« less

Elliptically polarizing adjustable phase insertion device

DOEpatents

Carr, R.

1995-01-17

An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets. 3 figures.

Absolute plate motions and true polar wander in the absence of hotspot tracks.

PubMed

Steinberger, Bernhard; Torsvik, Trond H

2008-04-03

The motion of continents relative to the Earth's spin axis may be due either to rotation of the entire Earth relative to its spin axis--true polar wander--or to the motion of individual plates. In order to distinguish between these over the past 320 Myr (since the formation of the Pangaea supercontinent), we present here computations of the global average of continental motion and rotation through time in a palaeomagnetic reference frame. Two components are identified: a steady northward motion and, during certain time intervals, clockwise and anticlockwise rotations, interpreted as evidence for true polar wander. We find approximately 18 degrees anticlockwise rotation about 250-220 Myr ago and the same amount of clockwise rotation about 195-145 Myr ago. In both cases the rotation axis is located at about 10-20 degrees W, 0 degrees N, near the site that became the North American-South American-African triple junction at the break-up of Pangaea. This was followed by approximately 10 degrees clockwise rotation about 145-135 Myr ago, followed again by the same amount of anticlockwise rotation about 110-100 Myr ago, with a rotation axis in both cases approximately 25-50 degrees E in the reconstructed area of North Africa and Arabia. These rotation axes mark the maxima of the degree-two non-hydrostatic geoid during those time intervals, and the fact that the overall net rotation since 320 Myr ago is nearly zero is an indication of long-term stability of the degree-two geoid and related mantle structure. We propose a new reference frame, based on palaeomagnetism, but corrected for the true polar wander identified in this study, appropriate for relating surface to deep mantle processes from 320 Myr ago until hotspot tracks can be used (about 130 Myr ago).

Effect of atomic noise on optical squeezing via polarization self-rotation in a thermal vapor cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, M. T. L.; Hetet, G.; Peng, A.

2006-02-15

The traversal of an elliptically polarized optical field through a thermal vapor cell can give rise to a rotation of its polarization axis. This process, known as polarization self-rotation (PSR), has been suggested as a mechanism for producing squeezed light at atomic transition wavelengths. We show results of the characterization of PSR in isotopically enhanced rubidium-87 cells, performed in two independent laboratories. We observed that, contrary to earlier work, the presence of atomic noise in the thermal vapor overwhelms the observation of squeezing. We present a theory that contains atomic noise terms and show that a null result in squeezingmore » is consistent with this theory.« less

Giant Polarization Rotation in BiFeO3/SrTiO3 Thin Films.

NASA Astrophysics Data System (ADS)

Langner, M. C.; Chu, Y. H.; Martin, L. M.; Gajek, M.; Ramesh, R.; Orenstein, J.

2008-03-01

We use optical second harmonic generation to probe dynamics of the ferroelectric polarization in (111) oriented BiFeO3 thin films grown on SrTiO3 substrates. The second harmonic response indicates 3m point group symmetry and is consistent with a spontaneous polarization normal to the surface of the film. We measure large changes in amplitude and lowering of symmetry, consistent with polarization rotation, when modest electric fields are applied in the plane of the film. At room temperature the rotation is an order of magnitude larger than expected from reported values of the dielectric constant and increases further (as 1/T) as temperature is lowered. We propose a substrate interaction model to explain these results.

Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation.

PubMed

Hayama, Kazuhiro; Kuroda, Takami; Nakamura, Ko; Yamada, Shoichi

2016-04-15

We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores just prior to collapse. It has been demonstrated by three dimensional simulations that nonaxisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the postbounce cores. It is not surprising, then, that the gravitational waves emitted by such fluid motions are circularly polarized. We show, in this Letter, that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of the Galaxy as long as the rotation period of the core is shorter than a few seconds prior to collapse.

TOWARD AN EMPIRICAL THEORY OF PULSAR EMISSION. XI. UNDERSTANDING THE ORIENTATIONS OF PULSAR RADIATION AND SUPERNOVA “KICKS”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rankin, Joanna M., E-mail: Joanna.Rankin@uvm.edu

Two entwined problems have remained unresolved since pulsars were discovered nearly 50 yr ago: the orientation of their polarized emission relative to the emitting magnetic field and the direction of putative supernova “kicks” relative to their rotation axes. The rotational orientation of most pulsars can be inferred only from the (“fiducial”) polarization angle of their radiation, when their beam points directly at the Earth and the emitting polar fluxtube field is ∥ to the rotation axis. Earlier studies have been unrevealing owing to the admixture of different types of radiation (core and conal, two polarization modes), producing both ∥ ormore » ⊥ alignments. In this paper we analyze some 50 pulsars having three characteristics: core radiation beams, reliable absolute polarimetry, and accurate proper motions (PMs). The “fiducial” polarization angle of the core emission, we then find, is usually oriented ⊥ to the PM direction on the sky. The primary core emission is polarized ⊥ to the projected magnetic field in Vela and other pulsars where X-ray imaging reveals the orientation. This shows that the PMs usually lie ∥ to the rotation axes on the sky. Two key physical consequences then follow: first, to the extent that supernova “kicks” are responsible for pulsar PMs, they are mostly ∥ to the rotation axis; and, second, most pulsar radiation is heavily processed by the magnetospheric plasma such that the lowest altitude “parent” core emission is polarized ⊥ to the emitting field, propagating as the extraordinary (X) mode.« less

Preliminary investigation of Faraday rotation effects and description of polarization measurements on the AFGL high latitude meteor scatter test bed

NASA Astrophysics Data System (ADS)

Ostergaard, Jens C.

1989-01-01

The background, methodology and preliminary results of an investigation of Faraday rotation effects on the Meteor Scatter High Latitude Test Bed in Greenland are presented. A short review of polarization theory for radio waves, presenting basic properties and changes when reflected from the surface of the earth or propagated through the ionosphere is included. Material published by other workers is presented to give the background for the current interest in Faraday rotation on meteor scatter links. Propagation losses for meteor scatter paths originate from spatial spreading of RF energy, scattering losses at the meteor trail, ionospheric absorption and polarization mismatch at the receiving antenna. That part of the polarization mismatch generated by the ionosphere, the Faraday rotation, is described and evaluated. A method to compute the Faraday rotation is presented and results obtained for the AFGL MSHL Test Bed are given. An experiment, including the measurement of signal strength and polarization throughout the lifetime of the individual meteor scatter return is needed to fully assess the combined affects of absorption and depolarization during both quiet and disturbed ionospheric conditions. The measurement accuracy to be expected from a proposed experiment is evaluated. A few examples of meteor scatter returns obtained with a prototype experiment in Greenland are shown and discussed.

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. I. Imaging BL Lacertae at 21 Microarcsecond Resolution

NASA Astrophysics Data System (ADS)

Gómez, José L.; Lobanov, Andrei P.; Bruni, Gabriele; Kovalev, Yuri Y.; Marscher, Alan P.; Jorstad, Svetlana G.; Mizuno, Yosuke; Bach, Uwe; Sokolovsky, Kirill V.; Anderson, James M.; Galindo, Pablo; Kardashev, Nikolay S.; Lisakov, Mikhail M.

2016-02-01

We present the first polarimetric space very long baseline interferometry (VLBI) imaging observations at 22 GHz. BL Lacertae was observed in 2013 November 10 with the RadioAstron space VLBI mission, including a ground array of 15 radio telescopes. The instrumental polarization of the space radio telescope is found to be less than 9%, demonstrating the polarimetric imaging capabilities of RadioAstron at 22 GHz. Ground-space fringes were obtained up to a projected baseline distance of 7.9 Earth diameters in length, allowing us to image the jet in BL Lacertae with a maximum angular resolution of 21 μas, the highest achieved to date. We find evidence for emission upstream of the radio core, which may correspond to a recollimation shock at about 40 μas from the jet apex, in a pattern that includes other recollimation shocks at approximately 100 and 250 μas from the jet apex. Polarized emission is detected in two components within the innermost 0.5 mas from the core, as well as in some knots 3 mas downstream. Faraday rotation analysis, obtained from combining RadioAstron 22 GHz and ground-based 15 and 43 GHz images, shows a gradient in rotation measure and Faraday-corrected polarization vector as a function of position angle with respect to the core, suggesting that the jet in BL Lacertae is threaded by a helical magnetic field. The intrinsic de-boosted brightness temperature in the unresolved core exceeds 3× {10}12 K, suggesting, at the very least, departure from equipartition of energy between the magnetic field and radiating particles.

Multi-Wavelength, Multi-Beam, and Polarization-Sensitive Laser Transmitter for Surface Mapping

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Ramos-Izquierdo, Luis; Harding, David; Huss, Tim

2011-01-01

A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A second set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A cond set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of

Rotatable spin-polarized electron source for inverse-photoemission experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stolwijk, S. D., E-mail: Sebastian.Stolwijk@wwu.de; Wortelen, H.; Schmidt, A. B.

2014-01-15

We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111)more » highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces.« less

Polarimetric Imaging using Two Photoelastic Modulators

NASA Technical Reports Server (NTRS)

Wang, Yu; Cunningham, Thomas; Diner, David; Davis, Edgar; Sun, Chao; Hancock, Bruce; Gutt, Gary; Zan, Jason; Raouf, Nasrat

2009-01-01

A method of polarimetric imaging, now undergoing development, involves the use of two photoelastic modulators in series, driven at equal amplitude but at different frequencies. The net effect on a beam of light is to cause (1) the direction of its polarization to rotate at the average of two excitation frequencies and (2) the amplitude of its polarization to be modulated at the beat frequency (the difference between the two excitation frequencies). The resulting modulated optical light beam is made to pass through a polarizing filter and is detected at the beat frequency, which can be chosen to equal the frame rate of an electronic camera or the rate of sampling the outputs of photodetectors in an array. The method was conceived to satisfy a need to perform highly accurate polarimetric imaging, without cross-talk between polarization channels, at frame rates of the order of tens of hertz. The use of electro-optical modulators is necessitated by a need to obtain accuracy greater than that attainable by use of static polarizing filters over separate fixed detectors. For imaging, photoelastic modulators are preferable to such other electrio-optical modulators as Kerr cells and Pockels cells in that photoelastic modulators operate at lower voltages, have greater angular acceptances, and are easier to use. Prior to the conception of the present method, polarimetric imaging at frame rates of tens of hertz using photoelastic modulators was not possible because the resonance frequencies of photoelastic modulators usually lie in the range from about 20 to about 100 kHz.

High-efficiency Resonant rf Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, P. -N.; Barron-Palos, L.; Bowman, J. D.

2008-01-01

High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPD Gamma experiment, a search for the small parity-violating {gamma}-ray asymmetry A{sub Y} in polarized cold neutron capture on parahydrogen, is one example. For the NPD Gamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beammore » with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized {sup 3}He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8 {+-} 0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPD Gamma experiment are considered.« less

Polarization Rotation Caused by Cross-Beam Energy Transfer in Direct-Drive Implosions

NASA Astrophysics Data System (ADS)

Edgell, D. H.; Follett, R. K.; Katz, J.; Myatt, J. F.; Shaw, J. G.; Turnbull, D.; Froula, D. H.

2017-10-01

The first evidence of polarization rotation caused by cross-beam energy transfer (CBET) during direct-drive implosions has been provided by a new beamlets diagnostic that was fielded on OMEGA. Beamlet images are, in essence, the end points of beamlets of light originating from different regions of each beam profile and following paths determined by refraction through the coronal plasma. The intensity of each beamlet varies because of absorption and many CBET interactions along that path. The new diagnostic records images in two time windows and includes a Wollaston prism to split each beamlet into two orthogonal polarization images recording the polarization of each beamlet. Only the common polarization components couple during CBET so when each beam is linearly polarized, CBET rotates the polarization of each beam. A 3-D CBET postprocessor for hydrodynamics codes was used to model the beamlet images. The predicted images are compared to the images recorded by the new diagnostic. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Full Field Photoelastic Stress Analysis

NASA Technical Reports Server (NTRS)

Lesniak, Jon R. (Inventor)

2000-01-01

A structural specimen coated with or constructed of photoelastic material, when illuminated with circularly polarized light will, when stressed: reflect or transmit elliptically polarized light, the direction of the axes of the ellipse and variation of the elliptically light from illuminating circular light will correspond to and indicate the direction and magnitude of the shear stresses for each illuminated point on the specimen. The principles of this invention allow for several embodiments of stress analyzing apparatus, ranging from those involving multiple rotating optical elements, to those which require no moving parts at all. A simple polariscope may be constructed having two polarizing filters with a single one-quarter waveplate placed between the polarizing filters. Light is projected through the first polarizing filter and the one-quarter waveplate and is reflected from a sub-fringe birefringent coating on a structure under load. Reflected light from the structure is analyzed with a polarizing filter. The two polarizing filters and the one-quarter waveplate may be rotated together or the analyzer alone may be rotated. Computer analysis of the variation in light intensity yields shear stress magnitude and direction.

ROTATION RATE DIFFERENCES OF POSITIVE AND NEGATIVE SOLAR MAGNETIC FIELDS BETWEEN ±60° LATITUDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, X. J.; Xie, J. L., E-mail: shixiangjun@ynao.ac.cn

2015-04-15

Based on a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotations Nos. 1625 to 2135 (from 1975 February to 2013 March), the sidereal rotation rates of the positive and negative magnetic fields in the latitude range of ±60° are obtained, and the rotation rate differences between them are investigated. The time–latitude distribution of the rate differences is shown, which looks like a butterfly diagram at the low and middle latitudes. For comparison, the time–latitude distribution of the longitudinally averaged photospheric magnetic fields is shown. We conclude that the magnetic fields having the samemore » polarity as the leading sunspots at a given hemisphere rotate faster than those exhibiting the opposite polarity at low and middle latitudes. However, at higher latitudes, the magnetic fields having the same polarity as the leading sunspots at a given hemisphere do not always rotate faster than those with the opposite polarity. Furthermore, the relationship between the rotation rate differences and solar magnetic fields is studied through a correlation analysis. Our result shows that the correlation coefficients between them reach maximum values at 13° (14°) latitude in the northern (southern) hemisphere, and change sign at 28° latitude in both hemispheres, then reach their minimum values at 58° (53°) latitude in the northern (southern) hemisphere.« less

HELICAL MAGNETIC FIELDS IN THE NGC 1333 IRAS 4A PROTOSTELLAR OUTFLOWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ching, Tao-Chung; Lai, Shih-Ping; Zhang, Qizhou

We present Submillimeter Array polarization observations of the CO J = 3–2 line toward NGC 1333 IRAS 4A. The CO Stokes I maps at an angular resolution of ∼1″ reveal two bipolar outflows from the binary sources of NGC 1333 IRAS 4A. The kinematic features of the CO emission can be modeled by wind-driven outflows at ∼20° inclined from the plane of the sky. Close to the protostars the CO polarization, at an angular resolution of ∼2.″3, has a position angle approximately parallel to the magnetic field direction inferred from the dust polarizations. The CO polarization direction appears to vary smoothly frommore » an hourglass field around the core to an arc-like morphology wrapping around the outflow, suggesting a helical structure of magnetic fields that inherits the poloidal fields at the launching point and consists of toroidal fields at a farther distance of outflow. The helical magnetic field is consistent with the theoretical expectations for launching and collimating outflows from a magnetized rotating disk. Considering that the CO polarized emission is mainly contributed from the low-velocity and low-resolution data, the helical magnetic field is likely a product of the wind–envelope interaction in the wind-driven outflows. The CO data reveal a PA of ∼30° deflection in the outflows. The variation in the CO polarization angle seems to correlate with the deflections. We speculate that the helical magnetic field contributes to ∼10° deflection of the outflows by means of Lorentz force.« less

Inclined Pulsar Magnetospheres in General Relativity: Polar Caps for the Dipole, Quadrudipole, and Beyond

NASA Astrophysics Data System (ADS)

Gralla, Samuel E.; Lupsasca, Alexandru; Philippov, Alexander

2017-12-01

In the canonical model of a pulsar, rotational energy is transmitted through the surrounding plasma via two electrical circuits, each connecting to the star over a small region known as a “polar cap.” For a dipole-magnetized star, the polar caps coincide with the magnetic poles (hence the name), but in general, they can occur at any place and take any shape. In light of their crucial importance to most models of pulsar emission (from radio to X-ray to wind), we develop a general technique for determining polar cap properties. We consider a perfectly conducting star surrounded by a force-free magnetosphere and include the effects of general relativity. Using a combined numerical-analytical technique that leverages the rotation rate as a small parameter, we derive a general analytic formula for the polar cap shape and charge-current distribution as a function of the stellar mass, radius, rotation rate, moment of inertia, and magnetic field. We present results for dipole and quadrudipole fields (superposed dipole and quadrupole) inclined relative to the axis of rotation. The inclined dipole polar cap results are the first to include general relativity, and they confirm its essential role in the pulsar problem. The quadrudipole pulsar illustrates the phenomenon of thin annular polar caps. More generally, our method lays a foundation for detailed modeling of pulsar emission with realistic magnetic fields.

Faraday Rotation as a Probe of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Kooi, J. E.; Spangler, S. R.; Kassim, N. E.

2016-12-01

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Although CMEs have been an active field of research since their discovery in the 1970s, there is still much to understand about the plasma structure of CMEs. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We made sensitive Very Large Array (VLA) full-polarization observations in August, 2012, using 1 — 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 — 15 solar radii. Of the nine sources observed, three were occulted by CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the LASCO/C3 instrument to determine the Thomson scattering brightness, BT, providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and FR. The single flux rope model successfully reproduces the observed BT and FR profiles for two sources. The third source (0843+1547) was occulted by two CMEs and, therefore, we modeled observations of this source using two flux ropes embedded in the background corona. The two flux rope model successfully reproduces both BT and FR profiles for 0843+1547 and, in particular, the two flux rope model successfully replicates the appropriate slope in FR before and after occultation by the second CME and predicts the observed change in sign to FR > 0 at the end of the observing session. The plasma densities (6 — 22 × 103 cm-3) and axial magnetic field strengths (2 — 12 mG) inferred from our models are consistent with the modeling work of Liu et al. (2007) and Jensen et al. (2008), as well as previous CME FR observations by Bird et al. (1985). This work was supported at the University of Iowa by grant ATM09-56901.

Garnet film rotator applied in polarizing microscope for domain image modulation (abstract)

NASA Astrophysics Data System (ADS)

Wakabayashi, K.; Numata, T.; Inokuchi, S.

1991-04-01

A garnet film polarization rotator placed before the analyzer in a polarizing microscope was investigated to obtain the difference image of a positive and a negative one of magnetic domain in real time along with an image processor. In the difference image, a nonmagnetic image can be reduced and hence the weak magnetic contrast enhanced. Theoretical calculation of S/N and contrast C of the domain image as a function of the rotation shows they take maxima at the rotation angle of 2.6° and 0.1°, respectively, with the extinction ratio of e=4×10-6 of a polarizing microscope. Thus, since the thickness of the garnet film required is 1 μm or so, the absorption by the garnet rotator does not bring a serious problem even in a visible region for the domain observation. The optimum rotation of the rotator for a high quality observation was obtained by a quantitative study of images obtained experimentally as well as by a visual evaluation. A magnetically unsaturated garnet film with perpendicular magnetization (i.e., multidomain) was employed as a rotator, in which the polarization rotation angle θm of the undeflected beam with respect to the light diffraction could be continuously varied by an applied magnetic field. The dependences of S/N and C on θm were measured, resulting in a well agreement between the measured and the calculated. The visually best image was obtained at θm=0.5° which made the product of S/N and C maximum. The domain image of the Kerr rotation angle of θk=0.22° was observed in S/N=47 dB and C=0.4 when Ar+ laser (λ=515 nm) of tenths of a watt was employed as a light source. Since the domain image with 47 dB S/N does not need an image summation for a noise reduction, a garnet film rotator makes it possible to invert the contrast of a domain image in a real time for an improved domain observation.

The Rotation Period and Magnetic Field of the T Dwarf 2MASSI J1047539+212423 Measured from Periodic Radio Bursts

NASA Astrophysics Data System (ADS)

Williams, P. K. G.; Berger, E.

2015-08-01

Periodic radio bursts from very low mass stars and brown dwarfs simultaneously probe their magnetic and rotational properties. The brown dwarf 2MASSI J1047539+212423 (2M 1047+21) is currently the only T dwarf (T6.5) detected at radio wavelengths. Previous observations of this source with the Arecibo observatory revealed intermittent, 100%-polarized radio pulses similar to those detected from other brown dwarfs, but were unable to constrain a pulse periodicity; previous Very Large Array (VLA) observations detected quiescent emission a factor of ∼100 times fainter than the Arecibo pulses but no additional events. Here we present 14 hr of VLA observations of this object that reveal a series of pulses at ∼6 GHz with highly variable profiles, showing that the pulsing behavior evolves on time scales that are both long and short compared to the rotation period. We measure a periodicity of ∼1.77 hr and identify it with the rotation period. This is just the sixth rotation period measurement in a late T dwarf, and the first obtained in the radio. We detect a pulse at 10 GHz as well, suggesting that the magnetic field strength of 2 M 1047+21 reaches at least 3.6 kG. Although this object is the coolest and most rapidly rotating radio-detected brown dwarf to date, its properties appear continuous with those of other such objects, suggesting that the generation of strong magnetic fields and radio emission may continue to even cooler objects. Further studies of this kind will help to clarify the relationships between mass, age, rotation, and magnetic activity at and beyond the end of the main sequence, where both theories and observational data are currently scarce.

Multiple polarization states of vector soliton in fiber laser

NASA Astrophysics Data System (ADS)

Chen, Weicheng; Xu, Wencheng; Cao, Hui; Han, Dingan

2007-11-01

Vector soliton is obtained in erbium-doped fiber laser via nonlinear polarization rotation techniques. In experiment, we observe the every 4- and 7-pulse sinusoidal peak modulation. Temporal pulse sinusoidal peak modulation owes to evolution behavior of vector solitons in multiple polarization states. The polarizer in the laser modulates the mode-locked pulses with different polarization states into periodical pulse train intensities modulation. Moreover, the increasing pumping power lead to the appearance of the harmonic pulses and change the equivalent beat length to accelerate the polarization rotation. When the laser cavity length is the n-th multiple ratios to the beat length to maintain the mode-locking, the mode-locked vector soliton is in n-th multiple polarization states, exhibiting every n-pulse sinusoidal peak modulation.

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

DOE PAGES

Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; ...

2015-10-09

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

New Combustion Regimes and Kinetic Studies of Plasma Assisted Combustion

DTIC Science & Technology

2012-11-01

IR Faraday Rotational Spectroscopy Method to quantify HO2 29 30 Brian Brumfield, Wenting Sun, Gerard Wysock, and Yinguang Ju, submitted...to JACS, 2012 7.1 μm Mid infra-red Faraday Rotation Spectroscopy (FRS), 1396 cm-1 Quantitative HO2 Measurement (very challenging!): 2L + 1...paramagnetic species Polarization rotation detection Linearly-polarized laser light 610 Hz oscillating magnetic field 125 Gauss rms Sub-ppm level

Measurement of concentration of sugar in solutions with laser speckle decorrelation

NASA Astrophysics Data System (ADS)

Mahajan, Swapnil; Trivedi, Vismay; Chhaniwal, Vani; Prajapati, Mahendra; Zalevsky, Zeev; Javidi, Bahram; Anand, Arun

2015-05-01

Measurement of rotation of plane of polarization of linearly polarized light can provide information about the concentration of the optically active system with which it interacts. For substances containing sugar, accurate measurement of rotation of linearly polarized light can provide quantitative information about concentration of sugar in the material. Measurement of sugar concentration is important in areas ranging from blood sugar level measurement in body fluids to measurement of sugar concentrations in juices and other beverages. But in many of these cases, the changes introduced to the state of polarization considering a sample of practical proportion is low and the measurement of low optical rotations becomes necessary. So methods with higher sensitivity, accuracy and resolution need to be developed for the measurement of low optical rotations. Here we describe the development of a compact, low cost, field portable, device for rotation sensing leading to sugar concentration measurements, using speckle de-correlation technique. The developed device measures rotations by determining the changes occurring to a speckle pattern generated by a laser beam passing through the medium under investigation. The device consists of a sample chamber, a diode laser module, a ground glass diffuser and a digital sensor for recording of laser speckle patterns. The device was found to have high resolution and sensitivity.

CONVECTION IN OBLATE SOLAR-TYPE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Junfeng; Liang, Chunlei; Miesch, Mark S.

2016-10-10

We present the first global 3D simulations of thermal convection in the oblate envelopes of rapidly rotating solar-type stars. This has been achieved by exploiting the capabilities of the new compressible high-order unstructured spectral difference (CHORUS) code. We consider rotation rates up to 85% of the critical (breakup) rotation rate, which yields an equatorial radius that is up to 17% larger than the polar radius. This substantial oblateness enhances the disparity between polar and equatorial modes of convection. We find that the convection redistributes the heat flux emitted from the outer surface, leading to an enhancement of the heat fluxmore » in the polar and equatorial regions. This finding implies that lower-mass stars with convective envelopes may not have darker equators as predicted by classical gravity darkening arguments. The vigorous high-latitude convection also establishes elongated axisymmetric circulation cells and zonal jets in the polar regions. Though the overall amplitude of the surface differential rotation, ΔΩ, is insensitive to the oblateness, the oblateness does limit the fractional kinetic energy contained in the differential rotation to no more than 61%. Furthermore, we argue that this level of differential rotation is not enough to have a significant impact on the oblateness of the star.« less

EFFECT OF CHERENKOV LIGHT POLARIZATION ON TOTAL REFLECTION COUNTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowell, J.D.; Duteil, P.; Leontic, B.

1963-01-01

A rugged total internal reflection counter with a 3- to 5cm thick compact radiator was used at the CERN proton synchrotron for beam analysis. The threshold behavior of this counter was compared when filled with glycerol and with turpentine. Turpentine is optically active and rotates the plane of polarization about 7 un. Concent 85% /cm. Figures illustrate the effect of this polarization rotation. (A.G.W.)

Time-division multiplexing of polarization-insensitive fiber-optic Michelson interferometric sensors

NASA Astrophysics Data System (ADS)

Huang, S. C.; Lin, W. W.; Chen, M. H.

1995-06-01

A system of time-division multiplexing of polarization-insensitive fiber-optic Michelson interferometric sensors that uses Faraday rotator mirror elements is demonstrated. This system is constructed with conventional low-birefringence single-mode fiber and is able to solve the polarization-fading problem by a combination of Faraday rotator mirrors with unbalanced Michelson interferometers. The system is lead-fiber insensitive and has potentials for practical field applications.

Wideband metamaterial array with polarization-independent and wide incident angle for harvesting ambient electromagnetic energy and wireless power transfer

NASA Astrophysics Data System (ADS)

Zhong, Hui-Teng; Yang, Xue-Xia; Song, Xing-Tang; Guo, Zhen-Yue; Yu, Fan

2017-11-01

In this work, we introduced the design, demonstration, and discussion of a wideband metamaterial array with polarization-independent and wide-angle for harvesting ambient electromagnetic (EM) energy and wireless power transfer. The array consists of unit cells with one square ring and four metal bars. In comparison to the published metamaterial arrays for harvesting EM energy or wireless transfer, this design had the wide operation bandwidth with the HPBW (Half Power Band Width) of 110% (6.2 GHz-21.4 GHz), which overcomes the narrow-band operation induced by the resonance characteristic of the metamaterial. On the normal incidence, the simulated maximum harvesting efficiency was 96% and the HPBW was 110% for the random polarization wave. As the incident angle increases to 45°, the maximum efficiency remained higher than 88% and the HPBW remained higher than 83% for the random polarization wave. Furthermore, the experimental verification of the designed metamaterial array was conducted, and the measured results were in reasonable agreement with the simulated ones.

A microstrip array feed for MSAT spacecraft reflector antenna

NASA Technical Reports Server (NTRS)

Huang, John

1988-01-01

An L-band circularly polarized microstrip array antenna with relatively wide bandwidth has been developed. The array has seven subarrays which form a single cluster as part of a large overlapping cluster reflector feed array. Each of the seven subarrays consists of four uniquely arranged linearly polarized microstrip elements. A 7.5 percent impedance (VSWR less than 1.5) as well as axial ratio (less than 1 dB) bandwidths have been achieved by employing a relatively thick honeycomb substrate with special impedance matching feed probes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules

NASA Astrophysics Data System (ADS)

Deng, Y.; You, L.; Yi, S.

2018-05-01

An experimental proposal for realizing spin-orbit (SO) coupling of pseudospin 1 in the ground manifold 1Σ (υ =0 ) of (bosonic) bialkali polar molecules is presented. The three spin components are composed of the ground rotational state and two substates from the first excited rotational level. Using hyperfine resolved Raman processes through two select excited states resonantly coupled by a microwave, an effective coupling between the spin tensor and linear momentum is realized. The properties of Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar interactions are further explored. In addition to the SO-coupling-induced stripe structures, the singly and doubly quantized vortex phases are found to appear, implicating exciting opportunities for exploring novel quantum physics using SO-coupled rotating polar molecules with dipolar interactions.

Report of the Seasat Failure Review Board

NASA Technical Reports Server (NTRS)

1993-01-01

The Seasat spacecraft failed on October 9, 1978, after satisfactory operation in orbit for 105 days, as a result of a loss of electrical power in the Agena bus that was used as a part of the spacecraft. The loss of power was caused by a massive and progressive short in one of the slip ring assemblies that was used to connect the rotating solar arrays into the power subsystem. The most likely cause of this short was the initiation of an arc between adjacent slip ring brush assemblies. The triggering mechanism of this arc could have been either a wire-to-brush assembly contact, a brush-to-brush contact, or a momentary short caused by a contaminant that bridged internal components of opposite electrical polarity.

Granularity in the magnetic field structure of M83

NASA Technical Reports Server (NTRS)

Allen, R. J.; Sukumar, S.

1990-01-01

Researchers recently reported Very Large Array (VLA) 20 cm continuum polarization observations of the bright, nearly face-on southern spiral galaxy M83 (NGC 5236) at a spatial resolution of 2 kpc (Sukumar and Allen 1989). The strongest linearly-polarized emission is found in two giant arcs, with typical lengths of about 30 kpc, which are situated roughly opposite each other in the dark outer regions of the galaxy at a radius of 12 kpc from the center. These regions of high polarized intensity (and hence highly-uniform magnetic field) do not coincide with any prominent spiral-arm tracers, in contrast to the expectations of simple models for the large-scale compression of magnetic field in density-wave shock fronts. From a comparison of the data with previous results at 6 cm, the authors concluded that the low polarization in the central regions of the galaxy is a result of disorder in the interstellar magnetic field. The most likely cause of this disorder is the greater star formation activity observed in the inner parts of the galaxy. The intrinsic direction of the magnetic field in the outer parts of the galaxy has also recently been determined on a length scale of 6.5 kpc from a comparison of the VLA 20 cm results with 6.3 cm observations obtained earlier with the Effelsberg telescope (Sukumar et al. 1989). There is very little Faraday rotation in the regions of the highly-polarized arcs of emission. The magnetic field in these polarized arcs is parallel to the general spiral arm structure seen in the usual optical tracers (dust, HII regions) in the bright inner parts of the galaxy disk. The maximum observed polarization at 2 kpc resolution is about 50 percent.

Propagation of rotational Risley-prism-array-based Gaussian beams in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Chen, Feng; Ma, Haotong; Dong, Li; Ren, Ge; Qi, Bo; Tan, Yufeng

2018-03-01

Limited by the size and weight of prism and optical assembling, Rotational Risley-prism-array system is a simple but effective way to realize high power and superior beam quality of deflecting laser output. In this paper, the propagation of the rotational Risley-prism-array-based Gaussian beam array in atmospheric turbulence is studied in detail. An analytical expression for the average intensity distribution at the receiving plane is derived based on nonparaxial ray tracing method and extended Huygens-Fresnel principle. Power in the diffraction-limited bucket is chosen to evaluate beam quality. The effect of deviation angle, propagation distance and intensity of turbulence on beam quality is studied in detail by quantitative simulation. It reveals that with the propagation distance increasing, the intensity distribution gradually evolves from multiple-petal-like shape into the pattern that contains one main-lobe in the center with multiple side-lobes in weak turbulence. The beam quality of rotational Risley-prism-array-based Gaussian beam array with lower deviation angle is better than its counterpart with higher deviation angle when propagating in weak and medium turbulent (i.e. Cn2 < 10-13m-2/3), the beam quality of higher deviation angle arrays degrades faster as the intensity of turbulence gets stronger. In the case of propagating in strong turbulence, the long propagation distance (i.e. z > 10km ) and deviation angle have no influence on beam quality.

Inversion of ground-motion data from a seismometer array for rotation using a modification of Jaeger's method

USGS Publications Warehouse

Chi, Wu-Cheng; Lee, W.H.K.; Aston, J.A.D.; Lin, C.J.; Liu, C.-C.

2011-01-01

We develop a new way to invert 2D translational waveforms using Jaeger's (1969) formula to derive rotational ground motions about one axis and estimate the errors in them using techniques from statistical multivariate analysis. This procedure can be used to derive rotational ground motions and strains using arrayed translational data, thus providing an efficient way to calibrate the performance of rotational sensors. This approach does not require a priori information about the noise level of the translational data and elastic properties of the media. This new procedure also provides estimates of the standard deviations of the derived rotations and strains. In this study, we validated this code using synthetic translational waveforms from a seismic array. The results after the inversion of the synthetics for rotations were almost identical with the results derived using a well-tested inversion procedure by Spudich and Fletcher (2009). This new 2D procedure can be applied three times to obtain the full, three-component rotations. Additional modifications can be implemented to the code in the future to study different features of the rotational ground motions and strains induced by the passage of seismic waves.

Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data

NASA Astrophysics Data System (ADS)

Kiehlmann, S.; Blinov, D.; Pearson, T. J.; Liodakis, I.

2017-12-01

We identify rotations of the polarization angle in a sample of blazars observed for three seasons with the RoboPol instrument. A simplistic stochastic variability model is tested against this sample of rotation events. The model is capable of producing samples of rotations with parameters similar to the observed ones, but fails to reproduce the polarization fraction at the same time. Even though we can neither accept nor conclusively reject the model, we point out various aspects of the observations that are fully consistent with a random walk process.

Partial polarizer filter

NASA Technical Reports Server (NTRS)

Title, A. M. (Inventor)

1978-01-01

A birefringent filter module comprises, in seriatum. (1) an entrance polarizer, (2) a first birefringent crystal responsive to optical energy exiting the entrance polarizer, (3) a partial polarizer responsive to optical energy exiting the first polarizer, (4) a second birefringent crystal responsive to optical energy exiting the partial polarizer, and (5) an exit polarizer. The first and second birefringent crystals have fast axes disposed + or -45 deg from the high transmitivity direction of the partial polarizer. Preferably, the second crystal has a length 1/2 that of the first crystal and the high transmitivity direction of the partial polarizer is nine times as great as the low transmitivity direction. To provide tuning, the polarizations of the energy entering the first crystal and leaving the second crystal are varied by either rotating the entrance and exit polarizers, or by sandwiching the entrance and exit polarizers between pairs of half wave plates that are rotated relative to the polarizers. A plurality of the filter modules may be cascaded.

Comparison null imaging ellipsometry using polarization rotator

NASA Astrophysics Data System (ADS)

Park, Sungmo; Kim, Eunsung; Kim, Jiwon; An, Ilsin

2018-05-01

In this study, two-reflection imaging ellipsometry is carried out to compare the changes in polarization states between two samples. By using a polarization rotator, the parallel and perpendicular components of polarization are easily switched between the two samples being compared. This leads to an intensity image consisting of null and off-null points depending on the difference in optical characteristics between the two samples. This technique does not require any movement of optical elements for nulling and can be used to detect defects or surface contamination for quality control of samples.

Light polarization management via reflection from arrays of sub-wavelength metallic twisted bands

NASA Astrophysics Data System (ADS)

Nawrot, M.; Haberko, J.; Zinkiewicz, Ł.; Wasylczyk, P.

2017-12-01

With constant progress of nano- and microfabrication technologies, photolithography in particular, a number of sub-wavelength metallic structures have been demonstrated that can be used to manipulate light polarization. Numerical simulations of light propagation hint that helical twisted bands can have interesting polarization properties. We use three-dimensional two-photon photolithography (direct laser writing) to fabricate a few-micrometer-thick arrays of twisted bands and coat them uniformly with metal. We demonstrate that circular polarization can be generated from linear polarization upon reflection from such structures over a broad range of frequencies in the mid infrared.

Feedhorn-Coupled Transition-Edge Superconducting Bolometer Arrays for Cosmic Microwave Background Polarimetry

NASA Technical Reports Server (NTRS)

Hubmayr, J.; Austermann, J.; Beall, J.; Becker, D.; Cho, H.-M.; Datta, R.; Duff, S. M.; Grace, E.; Halverson, N.; Henderson, S. W.;

Three-dimensional imaging through turbid media based on polarization-difference liquid-crystal microlens array

NASA Astrophysics Data System (ADS)

Xin, Zhaowei; Wei, Dong; Li, Dapeng; Xie, Xingwang; Chen, Mingce; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

In this paper, a polarization difference liquid-crystal microlens array (PD-LCMLA) for three dimensional imaging application through turbid media is fabricated and demonstrated. This device is composed of a twisted nematic liquidcrystal cell (TNLCC), a polarizer and a liquid-crystal microlens array. The polarizer is sandwiched between the TNLCC and LCMLA to help the polarization difference system achieving the orthogonal polarization raw images. The prototyped camera for polarization difference imaging has been constructed by integrating the PD-LCMLA with an image sensor. The orthogonally polarized light-field images are recorded by switching the working state of the TNLCC. Here, by using a special microstructure in conjunction with the polarization-difference algorithm, we demonstrate that the three-dimensional information in the scattering media can be retrieved from the polarization-difference imaging system with an electrically tunable PD-LCMLA. We further investigate the system's potential function based on the flexible microstructure. The microstructure provides a wide operation range in the manipulation of incident beams and also emerges multiple operation modes for imaging applications, such as conventional planar imaging, polarization imaging mode, and polarization-difference imaging mode. Since the PD-LCMLA demonstrates a very low power consumption, multiple imaging modes and simple manufacturing, this kind of device presents a potential to be used in many other optical and electro-optical systems.

Polarized-pixel performance model for DoFP polarimeter

NASA Astrophysics Data System (ADS)

Feng, Bin; Shi, Zelin; Liu, Haizheng; Liu, Li; Zhao, Yaohong; Zhang, Junchao

2018-06-01

A division of a focal plane (DoFP) polarimeter is manufactured by placing a micropolarizer array directly onto the focal plane array (FPA) of a detector. Each element of the DoFP polarimeter is a polarized pixel. This paper proposes a performance model for a polarized pixel. The proposed model characterizes the optical and electronic performance of a polarized pixel by three parameters. They are respectively major polarization responsivity, minor polarization responsivity and polarization orientation. Each parameter corresponds to an intuitive physical feature of a polarized pixel. This paper further extends this model to calibrate polarization images from a DoFP (division of focal plane) polarimeter. This calibration work is evaluated quantitatively by a developed DoFP polarimeter under varying illumination intensity and angle of linear polarization. The experiment proves that our model reduces nonuniformity to 6.79% of uncalibrated DoLP (degree of linear polarization) images, and significantly improves the visual effect of DoLP images.

Maximum bandwidth snapshot channeled imaging polarimeter with polarization gratings

NASA Astrophysics Data System (ADS)

LaCasse, Charles F.; Redman, Brian J.; Kudenov, Michael W.; Craven, Julia M.

2016-05-01

Compact snapshot imaging polarimeters have been demonstrated in literature to provide Stokes parameter estimations for spatially varying scenes using polarization gratings. However, the demonstrated system does not employ aggressive modulation frequencies to take full advantage of the bandwidth available to the focal plane array. A snapshot imaging Stokes polarimeter is described and demonstrated through results. The simulation studies the challenges of using a maximum bandwidth configuration for a snapshot polarization grating based polarimeter, such as the fringe contrast attenuation that results from higher modulation frequencies. Similar simulation results are generated and compared for a microgrid polarimeter. Microgrid polarimeters are instruments where pixelated polarizers are superimposed onto a focal plan array, and this is another type of spatially modulated polarimeter, and the most common design uses a 2x2 super pixel of polarizers which maximally uses the available bandwidth of the focal plane array.

Prospects for quantum computing with an array of ultracold polar paramagnetic molecules.

PubMed

Karra, Mallikarjun; Sharma, Ketan; Friedrich, Bretislav; Kais, Sabre; Herschbach, Dudley

2016-03-07

Arrays of trapped ultracold molecules represent a promising platform for implementing a universal quantum computer. DeMille [Phys. Rev. Lett. 88, 067901 (2002)] has detailed a prototype design based on Stark states of polar (1)Σ molecules as qubits. Herein, we consider an array of polar (2)Σ molecules which are, in addition, inherently paramagnetic and whose Hund's case (b) free-rotor pair-eigenstates are Bell states. We show that by subjecting the array to combinations of concurrent homogeneous and inhomogeneous electric and magnetic fields, the entanglement of the array's Stark and Zeeman states can be tuned and the qubit sites addressed. Two schemes for implementing an optically controlled CNOT gate are proposed and their feasibility discussed in the face of the broadening of spectral lines due to dipole-dipole coupling and the inhomogeneity of the electric and magnetic fields.

Field-induced polarization rotation and phase transitions in 0.70 Pb ( M g 1 / 3 N b 2 / 3 ) O 3 – 0.30 PbTi O 3 piezoceramics observed by in situ high-energy x-ray scattering

DOE PAGES

Hou, Dong; Usher, Tedi -Marie; Fulanovic, Lovro; ...

2018-06-12

Changes to the crystal structure of 0.70Pb(Mg 1/3Nb 2/3)O 3–0.30PbTiO 3 (PMN-0.30PT) piezoceramic under application of electric fields at the long-range and local scale are revealed by in situ high-energy x-ray diffraction (XRD) and pair-distribution function (PDF) analyses, respectively. The crystal structure of unpoled samples is identified as monoclinic Cm at both the long-range and local scale. In situ XRD results suggest that field-induced polarization rotation and phase transitions occur at specific field strengths. A polarization rotation pathway is proposed based on the Bragg-peak behaviors and the Le Bail fitting results of the in situ XRD patterns. The PDF resultsmore » show systematic changes to the structures at the local scale, which is in agreement with the changes inferred from the in situ XRD study. More importantly, our results prove that polarization rotation can be detected and determined in a polycrystalline relaxor ferroelectric. Furthermore, this study supports the idea that multiple contributions, specifically ferroelectric-ferroelectric phase transition and polarization rotation, are responsible for the high piezoelectric properties at the morphotropic phase boundary of PMN-xPT piezoceramics.« less

Field-induced polarization rotation and phase transitions in 0.70 Pb ( M g 1 / 3 N b 2 / 3 ) O 3 – 0.30 PbTi O 3 piezoceramics observed by in situ high-energy x-ray scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Dong; Usher, Tedi -Marie; Fulanovic, Lovro

Changes to the crystal structure of 0.70Pb(Mg 1/3Nb 2/3)O 3–0.30PbTiO 3 (PMN-0.30PT) piezoceramic under application of electric fields at the long-range and local scale are revealed by in situ high-energy x-ray diffraction (XRD) and pair-distribution function (PDF) analyses, respectively. The crystal structure of unpoled samples is identified as monoclinic Cm at both the long-range and local scale. In situ XRD results suggest that field-induced polarization rotation and phase transitions occur at specific field strengths. A polarization rotation pathway is proposed based on the Bragg-peak behaviors and the Le Bail fitting results of the in situ XRD patterns. The PDF resultsmore » show systematic changes to the structures at the local scale, which is in agreement with the changes inferred from the in situ XRD study. More importantly, our results prove that polarization rotation can be detected and determined in a polycrystalline relaxor ferroelectric. Furthermore, this study supports the idea that multiple contributions, specifically ferroelectric-ferroelectric phase transition and polarization rotation, are responsible for the high piezoelectric properties at the morphotropic phase boundary of PMN-xPT piezoceramics.« less

Field-induced polarization rotation and phase transitions in 0.70 Pb (M g1 /3N b2 /3 ) O3-0.30 PbTi O3 piezoceramics observed by in situ high-energy x-ray scattering

NASA Astrophysics Data System (ADS)

Hou, Dong; Usher, Tedi-Marie; Fulanovic, Lovro; Vrabelj, Marko; Otonicar, Mojca; Ursic, Hana; Malic, Barbara; Levin, Igor; Jones, Jacob L.

2018-06-01

Changes to the crystal structure of 0.70 Pb (M g1 /3N b2 /3 ) O3-0.30 PbTi O3 (PMN-0.30PT) piezoceramic under application of electric fields at the long-range and local scale are revealed by in situ high-energy x-ray diffraction (XRD) and pair-distribution function (PDF) analyses, respectively. The crystal structure of unpoled samples is identified as monoclinic C m at both the long-range and local scale. In situ XRD results suggest that field-induced polarization rotation and phase transitions occur at specific field strengths. A polarization rotation pathway is proposed based on the Bragg-peak behaviors and the Le Bail fitting results of the in situ XRD patterns. The PDF results show systematic changes to the structures at the local scale, which is in agreement with the changes inferred from the in situ XRD study. More importantly, our results prove that polarization rotation can be detected and determined in a polycrystalline relaxor ferroelectric. This study supports the idea that multiple contributions, specifically ferroelectric-ferroelectric phase transition and polarization rotation, are responsible for the high piezoelectric properties at the morphotropic phase boundary of PMN-x PT piezoceramics.

Kinetic effects on the currents determining the stability of a magnetic island in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poli, E., E-mail: emanuele.poli@ipp.mpg.de; Bergmann, A.; Casson, F. J.

The role of the bootstrap and polarization currents for the stability of neoclassical tearing modes is investigated employing both a drift kinetic and a gyrokinetic approach. The adiabatic response of the ions around the island separatrix implies, for island widths below or around the ion thermal banana width, density flattening for islands rotating at the ion diamagnetic frequency, while for islands rotating at the electron diamagnetic frequency the density is unperturbed and the only contribution to the neoclassical drive arises from electron temperature flattening. As for the polarization current, the full inclusion of finite orbit width effects in the calculationmore » of the potential developing in a rotating island leads to a smoothing of the discontinuous derivatives exhibited by the analytic potential on which the polarization term used in the modeling is based. This leads to a reduction of the polarization-current contribution with respect to the analytic estimate, in line with other studies. Other contributions to the perpendicular ion current, related to the response of the particles around the island separatrix, are found to compete or even dominate the polarization-current term for realistic island rotation frequencies.« less

Controllable rotating behavior of individual dielectric microrod in a rotating electric field.

PubMed

Liu, Weiyu; Ren, Yukun; Tao, Ye; Li, Yanbo; Chen, Xiaoming

2017-06-01

We report herein controllable rotating behavior of an individual dielectric microrod driven by a background rotating electric field. By disposing or removing structured floating microelectrode, the rigid rod suspended in electrolyte solution accordingly exhibits cofield or antifield rotating motion. In the absence of the ideally polarizable metal surface, the dielectric rod rotates opposite to propagation of electric field, with the measured rotating rate much larger than predicted by Maxwell-Wager interfacial polarization theory incorporating surface conduction of fixed bond charge. Surprisingly, with floating electrode embedded, a novel kind of cofield rotation mode occurs in the presence of induced double-layer polarization, due to the action of hydrodynamic torque from rotating induced-charge electroosmosis. This method of achieving switchable spin modes of dielectric particles would direct implications in constructing flexible electrokinetic framework for analyzing 3D profile of on-chip biomicrofluidic samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dual-polarized light-field imaging micro-system via a liquid-crystal microlens array for direct three-dimensional observation.

PubMed

Xin, Zhaowei; Wei, Dong; Xie, Xingwang; Chen, Mingce; Zhang, Xinyu; Liao, Jing; Wang, Haiwei; Xie, Changsheng

2018-02-19

Light-field imaging is a crucial and straightforward way of measuring and analyzing surrounding light worlds. In this paper, a dual-polarized light-field imaging micro-system based on a twisted nematic liquid-crystal microlens array (TN-LCMLA) for direct three-dimensional (3D) observation is fabricated and demonstrated. The prototyped camera has been constructed by integrating a TN-LCMLA with a common CMOS sensor array. By switching the working state of the TN-LCMLA, two orthogonally polarized light-field images can be remapped through the functioned imaging sensors. The imaging micro-system in conjunction with the electric-optical microstructure can be used to perform polarization and light-field imaging, simultaneously. Compared with conventional plenoptic cameras using liquid-crystal microlens array, the polarization-independent light-field images with a high image quality can be obtained in the arbitrary polarization state selected. We experimentally demonstrate characters including a relatively wide operation range in the manipulation of incident beams and the multiple imaging modes, such as conventional two-dimensional imaging, light-field imaging, and polarization imaging. Considering the obvious features of the TN-LCMLA, such as very low power consumption, providing multiple imaging modes mentioned, simple and low-cost manufacturing, the imaging micro-system integrated with this kind of liquid-crystal microstructure driven electrically presents the potential capability of directly observing a 3D object in typical scattering media.

Halbach array generator/motor having an automatically regulated output voltage and mechanical power output

DOEpatents

Post, Richard F.

2005-02-22

A motor/generator having its stationary portion, i.e., the stator, positioned concentrically within its rotatable element, i.e., the rotor, along its axis of rotation. The rotor includes a Halbach array. The stator windings are switched or commutated to provide a DC motor/generator much the same as in a conventional DC motor/generator. The voltage and power are automatically regulated by using centrifugal force to change the diameter of the rotor, and thereby vary the radial gap in between the stator and the rotating Halbach array, as a function of the angular velocity of the rotor.

Simulation and Assessment of a Ku-Band Full-Polarized Radar Scatterometer for Ocean Surface Vector Wind Measurement

NASA Astrophysics Data System (ADS)

Dong, X.; Lin, W.; Zhu, D.; Song, Z.

2011-12-01

Spaceborne radar scatterometry is the most important tool for global ocean surface wind vector (OSVW) measurement. Performances under condition of high-wind speed and accuracy of wind direction retrievals are two very important concerns for the development of OSVW measurement techniques by radar scatterometry. Co-polarized sigma 0 measurements are employed, for all the spaceborne radar scatterometers developed in past, and future planned missions. The main disadvantages of co-polarized only radar scatterometers for OSVW measurement are: firstly, wind vector retrieval performances varies with the position of the wind vector cells (WVC) within the swath, where WVCs with small incident angels with weaker modulation effect between sigma0 and azimuth incident angle, and the WVCs located in the outer part of the swath with lower signal-to-noise ratio and lower radiometric accuracies, have worse retrieval performances; secondly, for co-polarization measurements, Sigma 0 is the even function of the azimuth incident angle with respect to the real wind direction, which can results in directional ambiguity, and more additional information is need for the ambiguity removal. Theoretical and experimental results show that the cross-polarization measurement can provide complementary directional information to the co-polarization measurements, which can provide useful improvement to the wind vector retrieval performances. In this paper, the simulation and performance assessment of a full-polarized Ku-band radar scatterometer are provided. Some important conclusions are obtained: (1) Compared with available dual co-polarized radar scatterometer, the introduction of cross-polarization information can significantly improve the OSVW retrieval accuracies, where a relatively identical performance can be obtained within the whole swath. Simulation show that without significantly power increase, system design based on rotating-pencil beam design has much better performances than rotation fan-beam system due to its higher antenna gain and signal-to-noise ratio; (2) The performances of the full-polarized measurement, where all the 9 element covariant coefficient elements will be measurement, only have a little improvement compared with the "dual-co-polarization+HVVV" design, which is because of the almost identical characteristics of HVVV and VHHH measurement due to reciprocity; (3) The propagation error of rotation pencil-beam system is obviously much smaller than that of the rotation fan-beam system, which is due to the significant difference of antenna gains and signal-to-noise ratios; (4) Introduction of cross-polarized HVVV measurement can lead to almost identical wind direction retrieval performance for both the rotation pencil-beam and rotation fan-beam systems, which show that the cross-polarization information can significantly improve the wind direction retrieval performances by increasing the number of look angles, compared with the available fixed-fan-beam systems.

STELLAR ROTATION EFFECTS IN POLARIMETRIC MICROLENSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sajadian, Sedighe, E-mail: sajadian@ipm.ir

2016-07-10

It is well known that the polarization signal in microlensing events of hot stars is larger than that of main-sequence stars. Most hot stars rotate rapidly around their stellar axes. The stellar rotation creates ellipticity and gravity-darkening effects that break the spherical symmetry of the source's shape and the circular symmetry of the source's surface brightness respectively. Hence, it causes a net polarization signal for the source star. This polarization signal should be considered in polarimetric microlensing of fast rotating stars. For moderately rotating stars, lensing can magnify or even characterize small polarization signals due to the stellar rotation throughmore » polarimetric observations. The gravity-darkening effect due to a rotating source star creates asymmetric perturbations in polarimetric and photometric microlensing curves whose maximum occurs when the lens trajectory crosses the projected position of the rotation pole on the sky plane. The stellar ellipticity creates a time shift (i) in the position of the second peak of the polarimetric curves in transit microlensing events and (ii) in the peak position of the polarimetric curves with respect to the photometric peak position in bypass microlensing events. By measuring this time shift via polarimetric observations of microlensing events, we can evaluate the ellipticity of the projected source surface on the sky plane. Given the characterizations of the FOcal Reducer and low dispersion Spectrograph (FORS2) polarimeter at the Very Large Telescope, the probability of observing this time shift is very small. The more accurate polarimeters of the next generation may well measure these time shifts and evaluate the ellipticity of microlensing source stars.« less

Advanced Antenna-Coupled Superconducting Detector Arrays for CMB Polarimetry

NASA Astrophysics Data System (ADS)

Bock, James

2014-01-01

We are developing high-sensitivity millimeter-wave detector arrays for measuring the polarization of the cosmic microwave background (CMB). This development is directed to advance the technology readiness of the Inflation Probe mission in NASA's Physics of the Cosmos program. The Inflation Probe is a fourth-generation CMB satellite that will measure the polarization of the CMB to astrophysical limits, characterizing the inflationary polarization signal, mapping large-scale structure based on polarization induced by gravitational lensing, and mapping Galactic magnetic fields through measurements of polarized dust emission. The inflationary polarization signal is produced by a background of gravitational waves from the epoch of inflation, an exponential expansion of space-time in the early universe, with an amplitude that depends on the physical mechanism producing inflation. The inflationary polarization signal may be distinguished by its unique 'B-mode' vector properties from polarization from the density variations that predominantly source CMB temperature anisotropy. Mission concepts for the Inflation Probe are being developed in the US, Europe and Japan. The arrays are based on planar antennas that provide integral beam collimation, polarization analysis, and spectral band definition in a compact lithographed format that eliminates discrete fore-optics such as lenses and feedhorns. The antennas are coupled to transition-edge superconducting bolometers, read out with multiplexed SQUID current amplifiers. The superconducting sensors and readouts developed in this program share common technologies with NASA X-ray and FIR detector applications. Our program targets developments required for space observations, and we discuss our technical progress over the past two years and plans for future development. We are incorporating arrays into active sub-orbital and ground-based experiments, which advance technology readiness while producing state of the art CMB polarization measurements.

Einstein-aether theory: dynamics of relativistic particles with spin or polarization in a Gödel-type universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balakin, Alexander B.; Popov, Vladimir A., E-mail: alexander.balakin@kpfu.ru, E-mail: vladipopov@mail.ru

In the framework of the Einstein-aether theory we consider a cosmological model, which describes the evolution of the unit dynamic vector field with activated rotational degree of freedom. We discuss exact solutions of the Einstein-aether theory, for which the space-time is of the Gödel-type, the velocity four-vector of the aether motion is characterized by a non-vanishing vorticity, thus the rotational vectorial modes can be associated with the source of the universe rotation. The main goal of our paper is to study the motion of test relativistic particles with a vectorial internal degree of freedom (spin or polarization), which is coupledmore » to the unit dynamic vector field. The particles are considered as the test ones in the given space-time background of the Gödel-type; the spin (polarization) coupling to the unit dynamic vector field is modeled using exact solutions of three types. The first exact solution describes the aether with arbitrary Jacobson's coupling constants; the second one relates to the case, when the Jacobson's constant responsible for the vorticity is vanishing; the third exact solution is obtained using three constraints for the coupling constants. The analysis of the exact expressions, which are obtained for the particle momentum and for the spin (polarization) four-vector components, shows that the interaction of the spin (polarization) with the unit vector field induces a rotation, which is additional to the geodesic precession of the spin (polarization) associated with the universe rotation as a whole.« less

Polarization dependent color switching by extra-ordinary transmission in H-slit plasmonic metasurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandal, P.; Anantha Ramakrishna, S.; Patil, Raj

2013-12-14

An array of H-shaped subwavelength slits in a plasmonic film has a polarization dependent extra-ordinary transmission due to shape anisotropy. Non-overlapping extra-ordinary transmission bands for the orthogonal linear polarization states of the input light are used to demonstrate a polarization dependent color switch. The fabricated array of submicron sized H-slits on a gold film displayed two transmission bands for the linear x- and y-polarized light at visible (650–850 nm) and near-infra-red (1150–1450 nm) bands, respectively. The relative transmitted light in these two bands can be controlled by changing the linear polarization state of the input radiation from 0° to 90°.

The use of the multiple-gradient array for geoelectrical resistivity and induced polarization imaging

NASA Astrophysics Data System (ADS)

Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.

2014-12-01

The use of most conventional electrode configurations in electrical resistivity survey is often time consuming and labour intensive, especially when using manual data acquisition systems. Often, data acquisition teams tend to reduce data density so as to speed up field operation thereby reducing the survey cost; but this could significantly degrade the quality and resolution of the inverse models. In the present work, the potential of using the multiple-gradient array, a non-conventional electrode configuration, for practical cost effective and rapid subsurface resistivity and induced polarization mapping was evaluated. The array was used to conduct 2D resistivity and time-domain induced polarization imaging along two traverses in a study site at Ota, southwestern Nigeria. The subsurface was characterised and the main aquifer delineated using the inverse resistivity and chargeability images obtained. The performance of the multiple-gradient array was evaluated by correlating the 2D resistivity and chargeability images with those of the conventional Wenner array as well as the result of some soundings conducted along the same traverses using Schlumberger array. The multiple-gradient array has been found to have the advantage of measurement logistics and improved image resolution over the Wenner array.

Characterization of Kilopixel TES detector arrays for PIPER

NASA Astrophysics Data System (ADS)

Datta, Rahul; Ade, Peter; Benford, Dominic; Bennett, Charles; Chuss, David; Costen, Nicholas; Coughlin, Kevin; Dotson, Jessie; Eimer, Joseph; Fixsen, Dale; Gandilo, Natalie; Halpern, Mark; Essinger-Hileman, Thomas; Hilton, Gene; Hinshaw, Gary; Irwin, Kent; Jhabvala, Christine; Kimball, Mark; Kogut, Al; Lazear, Justin; Lowe, Luke; Manos, George; McMahon, Jeff; Miller, Timothy; Mirel, Paul; Moseley, Samuel Harvey; Pawlyk, Samuel; Rodriguez, Samelys; Sharp, Elmer; Shirron, Peter; Staguhn, Johannes G.; Sullivan, Dan; Switzer, Eric; Taraschi, Peter; Tucker, Carole; Walts, Alexander; Wollack, Edward

2018-01-01

The Primordial Inflation Polarization ExploreR (PIPER) is a balloon-borne instrument optimized to measure the polarization of the Cosmic Microwave Background (CMB) at large angular scales. It will map 85% of the sky in four frequency bands centered at 200, 270, 350, and 600 GHz to characterize dust foregrounds and constrain the tensor-to-scalar ratio, r. The sky is imaged on to 32x40 pixel arrays of time-domain multiplexed Transition-Edge Sensor (TES) bolometers operating at a bath temperature of 100 mK to achieve background-limited sensitivity. Each kilopixel array is indium-bump-bonded to a 2D superconducting quantum interference device (SQUID) time-domain multiplexer (MUX) chip and read out by warm electronics. Each pixel measures total incident power over a frequency band defined by bandpass filters in front of the array, while polarization sensitivity is provided by the upstream Variable-delay Polarization Modulators (VPMs) and analyzer grids. We present measurements of the detector parameters from the laboratory characterization of the first kilopixel science array for PIPER including transition temperature, saturation power, thermal conductivity, time constant, and noise performance. We also describe the testing of the 2D MUX chips, optimization of the integrated readout parameters, and the overall pixel yield of the array. The first PIPER science flight is planned for June 2018 from Palestine, Texas.

Holographic arrays for multi-path imaging artifact reduction

DOEpatents

McMakin, Douglas L.; Sheen, David M.; Hall, Thomas E.

2007-11-13

A method and apparatus to remove human features utilizing at least one transmitter transmitting a signal between 200 MHz and 1 THz, the signal having at least one characteristic of elliptical polarization, and at least one receiver receiving the reflection of the signal from the transmitter. A plurality of such receivers and transmitters are arranged together in an array which is in turn mounted to a scanner, allowing the array to be passed adjacent to the surface of the item being imaged while the transmitter is transmitting electromagnetic radiation. The array is passed adjacent to the surface of the item, such as a human being, that is being imaged. The portions of the received signals wherein the polarity of the characteristic has been reversed and those portions of the received signal wherein the polarity of the characteristic has not been reversed are identified. An image of the item from those portions of the received signal wherein the polarity of the characteristic was reversed is then created.

Renormalized vacuum polarization of rotating black holes

NASA Astrophysics Data System (ADS)

Ferreira, Hugo R. C.

2015-04-01

Quantum field theory on rotating black hole spacetimes is plagued with technical difficulties. Here, we describe a general method to renormalize and compute the vacuum polarization of a quantum field in the Hartle-Hawking state on rotating black holes. We exemplify the technique with a massive scalar field on the warped AdS3 black hole solution to topologically massive gravity, a deformation of (2 + 1)-dimensional Einstein gravity. We use a "quasi-Euclidean" technique, which generalizes the Euclidean techniques used for static spacetimes, and we subtract the divergences by matching to a sum over mode solutions on Minkowski spacetime. This allows us, for the first time, to have a general method to compute the renormalized vacuum polarization, for a given quantum state, on a rotating black hole, such as the physically relevant case of the Kerr black hole in four dimensions.

Ultrasensitive biochemical sensing device and method of sensing analytes

DOEpatents

Pinchuk, Anatoliy

2017-06-06

Systems and methods biochemically sense a concentration of a ligand using a sensor having a substrate having a metallic nanoparticle array formed onto a surface of the substrate. A light source is incident on the surface. A matrix is deposited over the nanoparticle array and contains a protein adapted to binding the ligand. A detector detects s-polarized and p-polarized light from the reflective surface. Spacing of nanoparticles in the array and wavelength of light are selected such that plasmon resonance occurs with an isotropic point such that -s and -p polarizations of the incident light result in substantially identical surface Plasmon resonance, wherein binding of the ligand to the protein shifts the resonance such that differences between the -S and -P polarizations give in a signal indicative of presence of the ligand.

Vertically oriented metamaterial broadband linear polariser

DOE PAGES

Campione, Salvatore; Burckel, David Bruce

2018-03-14

Control and manipulation of polarization is an important topic for imaging and light matter interactions. In the infrared regime, the large wavelengths make wire grid polarizers a viable option, as it is possible to create periodic arrays of metallic wires at that scale. The recent advent of metamaterials has spurred an increase in non-traditional polarizer motifs centred around more complicated repeat units, which potentially provide more functionality. In this paper we explore the use of two-dimensional (2D) arrays of single and back-to-back vertically oriented cross dipoles arranged in a cubic in-plane silicon matrix. Here, we show that both single andmore » back-to-back versions have higher rejection ratios and larger bandwidths than either wire grid polarizers or 2D arrays of linear dipoles.« less

Modulation of cosmic microwave background polarization with a warm rapidly rotating half-wave plate on the Atacama B-Mode Search instrument.

PubMed

Kusaka, A; Essinger-Hileman, T; Appel, J W; Gallardo, P; Irwin, K D; Jarosik, N; Nolta, M R; Page, L A; Parker, L P; Raghunathan, S; Sievers, J L; Simon, S M; Staggs, S T; Visnjic, K

2014-02-01

We evaluate the modulation of cosmic microwave background polarization using a rapidly rotating, half-wave plate (HWP) on the Atacama B-Mode Search. After demodulating the time-ordered-data (TOD), we find a significant reduction of atmospheric fluctuations. The demodulated TOD is stable on time scales of 500-1000 s, corresponding to frequencies of 1-2 mHz. This facilitates recovery of cosmological information at large angular scales, which are typically available only from balloon-borne or satellite experiments. This technique also achieves a sensitive measurement of celestial polarization without differencing the TOD of paired detectors sensitive to two orthogonal linear polarizations. This is the first demonstration of the ability to remove atmospheric contamination at these levels from a ground-based platform using a rapidly rotating HWP.

Semiconductor sensor for optically measuring polarization rotation of optical wavefronts using rare earth iron garnets

DOEpatents

Duncan, Paul G.

2002-01-01

Described are the design of a rare earth iron garnet sensor element, optical methods of interrogating the sensor element, methods of coupling the optical sensor element to a waveguide, and an optical and electrical processing system for monitoring the polarization rotation of a linearly polarized wavefront undergoing external modulation due to magnetic field or electrical current fluctuation. The sensor element uses the Faraday effect, an intrinsic property of certain rare-earth iron garnet materials, to rotate the polarization state of light in the presence of a magnetic field. The sensor element may be coated with a thin-film mirror to effectively double the optical path length, providing twice the sensitivity for a given field strength or temperature change. A semiconductor sensor system using a rare earth iron garnet sensor element is described.

Variations in rotation rate and polar motion of a non-hydrostatic Titan

NASA Astrophysics Data System (ADS)

Coyette, Alexis; Baland, Rose-Marie; Van Hoolst, Tim

2018-06-01

Observation of the rotation of synchronously rotating satellites can help to probe their interior. Previous studies mostly assume that these large icy satellites are in hydrostatic equilibrium, although several measurements indicate that they deviate from such a state. Here we investigate the effect of non-hydrostatic equilibrium and of flow in the subsurface ocean on the rotation of Titan. We consider the variations in rotation rate and the polar motion due to (1) the gravitational force exerted by Saturn at orbital period and (2) exchanges of angular momentum between the seasonally varying atmosphere and the solid surface. The deviation of the mass distribution from hydrostaticity can significantly increase the diurnal libration and decrease the amplitude of the seasonal libration. The effect of the non-hydrostatic mass distribution is less important for polar motion, which is more sensitive to flow in the subsurface ocean. By including a large spectrum of atmospheric perturbations, the smaller than synchronous rotation rate measured by Cassini in the 2004-2009 period (Meriggiola et al., 2016) could be explained by the atmospheric forcing. If our interpretation is correct, we predict a larger than synchronous rotation rate in the 2009-2014 period.

Angular-momentum-assisted dissociation of CO in strong optical fields

NASA Astrophysics Data System (ADS)

Mullin, Amy; Ogden, Hannah; Murray, Matthew; Liu, Qingnan; Toro, Carlos

2017-04-01

Filaments are produced in CO gas by intense, chirped laser pulses. Visible emission from C2 is observed as a result of chemical reactions of highly excited CO. At laser intensities greater than 1014 W cm-2, the C2 emission shows a strong dependence on laser polarization. Oppositely chirped pulses of light with ω0 = 800 nm are recombined spatially and temporally to generate angularly accelerating electric fields (up to 30 THz) that either have an instantaneous linear polarization or act as a dynamic polarization grating that oscillates among linear and circular polarizations. The angularly accelerating linear polarization corresponds to an optical centrifuge that concurrently drives molecules into high rotational states (with J 50) and induces strong-field dissociation. Higher order excitation is observed for the time-varying laser polarization configuration that does not induce rotational excitation. The results indicate that the presence of rotational angular momentum lowers the threshold for CO dissociation in strong optical fields by coupling nuclear and electronic degrees of freedom. Support from NSF CHE-1058721 and the University of Maryland.

Switchable thulium-doped fiber laser from polarization rotation vector to scalar soliton

NASA Astrophysics Data System (ADS)

Wu, Zhichao; Fu, Songnian; Jiang, Kai; Song, Jue; Li, Huizi; Tang, Ming; Shum, Ping; Liu, Deming

2016-10-01

We experimentally demonstrate switchable temporal soliton generation from a thulium-doped fiber laser (TDFL), using carbon nanotubes as the mode-locker. With the help of residual polarization dependent loss of a wavelength division multiplexer, a weak nonlinear polarization rotation (NPR) effect can be achieved within the laser cavity, which may provide joint contribution for passive mode-locking operation. By finely adjusting the polarization to alter the strength of NPR-based saturable absorption, the TDFL either approaches the operation regime of scalar soliton with strong NPR effect, or generates polarization rotation locked vector soliton (PRLVS) with weak NPR effect. The scalar solitons and PRLVSs possess 3-dB optical spectrum bandwidth of 2.2 nm and 2 nm, pulse-width of 1.8 ps and 2 ps, respectively. Moreover, the PRLVSs demonstrate a typical energy exchange between two polarized components on optical spectra and a period-doubling feature in time domain. Such operation principle can also be used in 1550 nm band fiber lasers and other nonlinear systems.

Switchable thulium-doped fiber laser from polarization rotation vector to scalar soliton

PubMed Central

Wu, Zhichao; Fu, Songnian; Jiang, Kai; Song, Jue; Li, Huizi; Tang, Ming; Shum, Ping; Liu, Deming

2016-01-01

We experimentally demonstrate switchable temporal soliton generation from a thulium-doped fiber laser (TDFL), using carbon nanotubes as the mode-locker. With the help of residual polarization dependent loss of a wavelength division multiplexer, a weak nonlinear polarization rotation (NPR) effect can be achieved within the laser cavity, which may provide joint contribution for passive mode-locking operation. By finely adjusting the polarization to alter the strength of NPR-based saturable absorption, the TDFL either approaches the operation regime of scalar soliton with strong NPR effect, or generates polarization rotation locked vector soliton (PRLVS) with weak NPR effect. The scalar solitons and PRLVSs possess 3-dB optical spectrum bandwidth of 2.2 nm and 2 nm, pulse-width of 1.8 ps and 2 ps, respectively. Moreover, the PRLVSs demonstrate a typical energy exchange between two polarized components on optical spectra and a period-doubling feature in time domain. Such operation principle can also be used in 1550 nm band fiber lasers and other nonlinear systems. PMID:27708427

Switchable thulium-doped fiber laser from polarization rotation vector to scalar soliton.

PubMed

Wu, Zhichao; Fu, Songnian; Jiang, Kai; Song, Jue; Li, Huizi; Tang, Ming; Shum, Ping; Liu, Deming

2016-10-06

We experimentally demonstrate switchable temporal soliton generation from a thulium-doped fiber laser (TDFL), using carbon nanotubes as the mode-locker. With the help of residual polarization dependent loss of a wavelength division multiplexer, a weak nonlinear polarization rotation (NPR) effect can be achieved within the laser cavity, which may provide joint contribution for passive mode-locking operation. By finely adjusting the polarization to alter the strength of NPR-based saturable absorption, the TDFL either approaches the operation regime of scalar soliton with strong NPR effect, or generates polarization rotation locked vector soliton (PRLVS) with weak NPR effect. The scalar solitons and PRLVSs possess 3-dB optical spectrum bandwidth of 2.2 nm and 2 nm, pulse-width of 1.8 ps and 2 ps, respectively. Moreover, the PRLVSs demonstrate a typical energy exchange between two polarized components on optical spectra and a period-doubling feature in time domain. Such operation principle can also be used in 1550 nm band fiber lasers and other nonlinear systems.

A rotating, expanding disk in the Wolf-Rayet star EZ Canis Majoris?

NASA Technical Reports Server (NTRS)

Schulte-Ladbeck, R. E.; Nordsieck, K. H.; Nook, M. A.; Magalhaes, A. M.; Taylor, M.

1990-01-01

The discovery of linear polarization changes across the extended wings of He II lines, mainly the strong 4-3 transition at 4686 A, in the WN5 star EZ CMa, is reported. When the polarization across the line profiles is plotted in the Stokes parameters plane, it traces loops clockwise from the blue wing through line center to the red, rather than straight lines. Such polarization loops are reminiscent of what is observed in the Balmer lines of Be stars. The continuum polarization in EZ CMa can be understood by an axisymmetric, electron-scattering envelope, with the decrease in polarization in He II being caused by an increase in absorptive opacity in the lines and dilution by unpolarized line emission, while the variations in position angle are due to the Doppler-shifted absorptive opacity and/or scattered line photons. As the sense of rotation in the loops is also independent of phase of this alleged Wolf-Rayet + compact binary, the polarized line profiles are the signature of a rotating, expanding wind geometry around a single star.

The Polarization of Achernar

NASA Astrophysics Data System (ADS)

McDavid, D.

2005-11-01

Recent near-infrared measurements of the angular diameter of Achernar (the bright Be star alpha Eridani) with the ESO VLT interferometer have been interpreted as the detection of an extremely oblate photosphere, with a ratio of equatorial to polar radius of at least 1.56 ± 0.05 and a minor axis orientation of 39° ± 1° (from North to East). The optical linear polarization of this star during an emission phase in 1995 September was 0.12 ± 0.02% at position angle 37° ± 8° (in equatorial coordinates), which is the direction of the projection of the rotation axis on the plane of the sky according to the theory of polarization by electron scattering in an equatorially flattened circumstellar disk. These two independent determinations of the orientation of the rotation axis are therefore in agreement. The observational history of correlations between Hα emission and polarization as found in the literature is that of a typical Be star, with the exception of an interesting question raised by the contrast between Schröder's measurement of a small polarization perpendicular to the projected rotation axis in 1969--70 and Tinbergen's measurement of zero polarization in 1974.5, both at times when emission was reportedly absent.

Polar-interferometry: what can be learnt from the IOTA/IONIC experiment

NASA Astrophysics Data System (ADS)

Le Bouquin, Jean-Baptiste; Rousselet-Perraut, Karine; Berger, Jean-Philippe; Herwats, Emilie; Benisty, Myriam; Absil, Olivier; Defrere, Denis; Monnier, John; Traub, Wesley

2008-07-01

We report the first near-IR polar-interferometric observations, performed at the IOTA array using its integrated optics combiner IONIC. Fringes have been obtained on calibration stars and resolved late-type giants. Optical modeling of the array and dedicated laboratory measures allowed us to confirm the good accuracy obtained on the calibrated polarized visibilities and closure phases. However, no evidences for polarimetric features at high angular resolution have been detected. The simulations and the results presented here open several perspectives for polar-interferometry, especially in the context of fibered, single-mode combiners.

Effects of the Ionosphere on Passive Microwave Remote Sensing of Ocean Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Abaham, Saji; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

Among the remote sensing applications currently being considered from space is the measurement of sea surface salinity. The salinity of the open ocean is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. Passive microwave remote sensors operating near 1.4 GHz (L-band) could provide data needed to fill the gap in current coverage and to complement in situ arrays being planned to provide subsurface profiles in the future. However, the dynamic range of the salinity signal in the open ocean is relatively small and propagation effects along the path from surface to sensor must be taken into account. In particular, Faraday rotation and even attenuation/emission in the ionosphere can be important sources of error. The purpose or this work is to estimate the magnitude of these effects in the context of a future remote sensing system in space to measure salinity in L-band. Data will be presented as a function of time location and solar activity using IRI-95 to model the ionosphere. The ionosphere presents two potential sources of error for the measurement of salinity: Rotation of the polarization vector (Faraday rotation) and attenuation/emission. Estimates of the effect of these two phenomena on passive remote sensing over the oceans at L-band (1.4 GHz) are presented.

Magnetization-induced second- and third-harmonic generation in transparent magnetic films

NASA Astrophysics Data System (ADS)

Ohkoshi, Shin-Ichi; Shimura, Jusuke; Ikeda, Katsuyoshi; Hashimoto, Kazuhito

2005-01-01

We describe the magnetization-induced second-harmonic (SH) generation in (FeIIxCrII1-x)1.5[CrIII(CN)6]. 7.5H2O and the magnetization-induced third-harmonic (TH) generation in Y1.5Bi1.5Fe3.8Al1.2O12 (Bi, Al:YIG). The polarization plane of a SH wave from a (FeIIxCrII1-x)1.5[CrIII(CN)6].7.5H2O film was rotated by an applied external magnetic field. This SH rotation is ascribed to the interaction between the electric polarization along the out-of-plane and spontaneous magnetizations. In particular, the magnetic linear term χijkLmagn(1) contributed to the SH rotation. Applying a longitudinal external magnetic field to a Bi,Al:YIG magnetic film rotated the polarization plane of the TH wave. This TH rotation is understood by the contribution of the magnetic term of χyxxxZmagn(1) in a third-order nonlinear optical susceptibility.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sule, Nishant; Yifat, Yuval; Gray, Stephen K.

We examine the formation and concomitant rotation of electrodynamically bound dimers (EBD) of 150nm diameter Ag nanoparticles trapped in circularly polarized focused Gaussian beams. The rotation frequency of an EBD increases linearly with the incident beam power, reaching high mean values of ~ 4kHz for a relatively low incident power of 14mW. Using a coupled-dipole/effective polarizability model, we reveal that retardation of the scattered fields and electrodynamic interactions can lead to a “negative torque” causing rotation of the EBD in the direction opposite to that of the circular polarization. This intriguing opposite-handed rotation due to negative torque is clearly demonstratedmore » using electrodynamics-Langevin dynamics simulations by changing particle separations and thus varying the retardation effects. Finally, negative torque is also demonstrated in experiments from statistical analysis of the EBD trajectories. These results demonstrate novel rotational dynamics of nanoparticles in optical matter using circular polarization and open a new avenue to control orientational dynamics through coupling to interparticle separation.« less

Polarization-polarization correlation measurement --- Experimental test of the PPCO methods

NASA Astrophysics Data System (ADS)

Droste, Ch.; Starosta, K.; Wierzchucka, A.; Morek, T.; Rohoziński, S. G.; Srebrny, J.; Wesolowski, E.; Bergstrem, M.; Herskind, B.

1998-04-01

A significant fraction of modern multidetector arrays used for "in-beam" gamma-ray spectroscopy consist of a detectors which are sensitive to linear polarization of gamma quanta. This yields the opportunity to carry out correlation measurements between the gamma rays registered in polarimeters to get information concerning spins and parities of excited nuclear states. The aim of the present work was to study the ability of the polarization- polarization correlation method (the PPCO method). The correlation between the linear polarization of one gamma quantum and the polarization of the second quantum emitted in a cascade from an oriented nucleus (due to a heavy ion reaction) was studied in detail. The appropriate formulae and methods of analysis are presented. The experimental test of the method was performed using the EUROGAM II array. The CLOVER detectors are the parts of the array used as polarimeters. The ^164Yb nucleus was produced via the ^138Ba(^30Si, 4n) reaction. It was found that the PPCO method together with the standard DCO analysis and the polarization- direction correlation method (PDCO) can be helpful for spin, parity and multipolarity assignments. The results suggest that the PPCO method can be applied to modern spectrometers in which a large number of detectors (e.g. CLOVER) are sensitive to polarization of gamma rays.

Saturn's North Polar Vortex Revealed by Cassini/VIMS: Zonal Wind Structure and Constraints on Cloud Distributions

NASA Astrophysics Data System (ADS)

Baines, Kevin H.; Momary, T. W.; Fletcher, L. N.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.

2008-09-01

We present the first high-spatial resolution, near-nadir imagery and movies of Saturn's north polar region that reveal the wind structure of a north polar vortex. Obtained by Cassini/VIMS on June 15, 2008 from high over Saturn's polar region (sub-spacecraft latitude of 65 degrees N. lat) at an altitude of 0.42 million km during the long polar night, these 210-per-pixel images of the polar region north of 73 degrees N. latitude show several concentric cloud rings and hundreds of individual cloud features in silhouette against the 5-micron background thermal glow of Saturn's deep atmosphere. In contrast to the clear eye of the south polar vortex, the north polar vortex sports a central cloud feature about 650-km in diameter. Zonal winds reach a maximum of 150 m/s near 88 degrees N. latitude (planetocentric) - comparable to the south polar vortex maximum of 190 m/s near 88 degrees S. latitude - and fall off nearly monotonically to 10 m/s near 80 degrees N. latitude. At slightly greater distance from the pole, inside the north polar hexagon in the 75-77 degree N. latitude region, zonal winds increase dramatically to 130 m/s, as silhouetted clouds are seen speeding aroud the "race track” of the hexagonal feature. VIMS 5-micron thermal observations over a 1.6-year period from October 29, 2006 to June 15, 2008 are consistent with the polar hexagon structure itself remaining fixed in the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) to within an accuracy of 3 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (Icarus 76, 335-356, 1988), but is inconsistent with rotation rates found during the current Cassini era.

Faraday Rotation: Effect of Magnetic Field Reversals

NASA Astrophysics Data System (ADS)

Melrose, D. B.

2010-12-01

The standard formula for the rotation measure (RM), which determines the position angle, ψ = RMλ2, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution Δψ needed to correct this omission. In contrast with a result proposed by Broderick & Blandford, Δψ is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.

Capsize of polarization in dilute photonic crystals.

PubMed

Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

2017-11-29

We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

The First Multichroic Polarimeter Array on the Atacama Cosmology Telescope: Characterization and Performance

NASA Technical Reports Server (NTRS)

Ho, S. P.; Pappas, C. G.; Austermann, J.; Beall, J. A.; Becker, D.; Choi, S. K.; Datta, R.; Duff, S. M.; Gallardo, P. A.; Grace, E.;

The First Multichroic Polarimeter Array on the Atacama Cosmology Telescope: Characterization and Performance

NASA Astrophysics Data System (ADS)

Ho, S. P.; Pappas, C. G.; Austermann, J.; Beall, J. A.; Becker, D.; Choi, S. K.; Datta, R.; Duff, S. M.; Gallardo, P. A.; Grace, E.; Hasselfield, M.; Henderson, S. W.; Hilton, G. C.; Hubmayr, J.; Koopman, B. J.; Lanen, J. V.; Li, D.; McMahon, J.; Nati, F.; Niemack, M. D.; Niraula, P.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Simon, S. M.; Staggs, S. T.; Stevens, J. R.; Ward, J. T.; Wollack, E. J.; Vavagiakis, E. M.

2016-08-01

The Atacama Cosmology Telescope Polarimeter (ACTPol) is a polarization sensitive receiver for the 6-m Atacama Cosmology Telescope (ACT) and measures the small angular scale polarization anisotropies in the cosmic microwave background (CMB). The full focal plane is composed of three detector arrays, containing over 3000 transition edge sensors (TES detectors) in total. The first two detector arrays, observing at 146 GHz, were deployed in 2013 and 2014, respectively. The third and final array is composed of multichroic pixels sensitive to both 90 and 146 GHz and saw first light in February 2015. Fabricated at NIST, this dichroic array consists of 255 pixels, with a total of 1020 polarization sensitive bolometers and is coupled to the telescope with a monolithic array of broad-band silicon feedhorns. The detectors are read out using time-division SQUID multiplexing and cooled by a dilution refrigerator at 110 mK. We present an overview of the assembly and characterization of this multichroic array in the lab, and the initial detector performance in Chile. The detector array has a TES detector electrical yield of 85 %, a total array sensitivity of less than 10 \\upmu K√{ {s}}, and detector time constants and saturation powers suitable for ACT CMB observations.

Magneto-optical polarization rotation in a ladder-type atomic system for tunable offset locking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parniak, Michał, E-mail: michal.parniak@fuw.edu.pl; Leszczyński, Adam; Wasilewski, Wojciech

2016-04-18

We demonstrate an easily tunable locking scheme for stabilizing frequency-sum of two lasers on a two-photon ladder transition based on polarization rotation in warm rubidium vapors induced by magnetic field and circularly polarized drive field. Unprecedented tunability of the two-photon offset frequency is due to strong splitting and shifting of magnetic states in external field. In our experimental setup, we achieve two-photon detuning of up to 700 MHz.

An Update on Phased Array Results Obtained on the GE Counter-Rotating Open Rotor Model

NASA Technical Reports Server (NTRS)

Podboy, Gary; Horvath, Csaba; Envia, Edmane

2013-01-01

Beamform maps have been generated from 1) simulated data generated by the LINPROP code and 2) actual experimental phased array data obtained on the GE Counter-rotating open rotor model. The beamform maps show that many of the tones in the experimental data come from their corresponding Mach radius. If the phased array points to the Mach radius associated with a tone then it is likely that the tone is a result of the loading and thickness noise on the blades. In this case, the phased array correctly points to where the noise is coming from and indicates the axial location of the loudest source in the image but not necessarily the correct vertical location. If the phased array does not point to the Mach radius associated with a tone then some mechanism other than loading and thickness noise may control the amplitude of the tone. In this case, the phased array may or may not point to the actual source. If the source is not rotating it is likely that the phased array points to the source. If the source is rotating it is likely that the phased array indicates the axial location of the loudest source but not necessarily the correct vertical location. These results indicate that you have to be careful in how you interpret phased array data obtained on an open rotor since they may show the tones coming from a location other than the source location. With a subsonic tip speed open rotor the tones can come form locations outboard of the blade tips. This has implications regarding noise shielding.

Broad-Band Analysis of Polar Motion Excitations

NASA Astrophysics Data System (ADS)

Chen, J.

2016-12-01

Earth rotational changes, i.e. polar motion and length-of-day (LOD), are driven by two types of geophysical excitations: 1) mass redistribution within the Earth system, and 2) angular momentum exchange between the solid Earth (more precisely the crust) and other components of the Earth system. Accurate quantification of Earth rotational excitations has been difficult, due to the lack of global-scale observations of mass redistribution and angular momentum exchange. The over 14-years time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) have provided a unique means for quantifying Earth rotational excitations from mass redistribution in different components of the climate system. Comparisons between observed Earth rotational changes and geophysical excitations estimated from GRACE, satellite laser ranging (SLR) and climate models show that GRACE-derived excitations agree remarkably well with polar motion observations over a broad-band of frequencies. GRACE estimates also suggest that accelerated polar region ice melting in recent years and corresponding sea level rise have played an important role in driving long-term polar motion as well. With several estimates of polar motion excitations, it is possible to estimate broad-band noise variance and noise power spectra in each, given reasonable assumptions about noise independence. Results based on GRACE CSR RL05 solutions clearly outperform other estimates with the lowest noise levels over a broad band of frequencies.

Applications of seismic spatial wavefield gradient and rotation data in exploration seismology

NASA Astrophysics Data System (ADS)

Schmelzbach, C.; Van Renterghem, C.; Sollberger, D.; Häusler, M.; Robertsson, J. O. A.

2017-12-01

Seismic spatial wavefield gradient and rotation data have the potential to open up new ways to address long-standing problems in land-seismic exploration such as identifying and separating P-, S-, and surface waves. Gradient-based acquisition and processing techniques could enable replacing large arrays of densely spaced receivers by sparse spatially-compact receiver layouts or even one single multicomponent station with dedicated instruments (e.g., rotational seismometers). Such approaches to maximize the information content of single-station recordings are also of significant interest for seismic measurements at sites with limited access such as boreholes, the sea bottom, and extraterrestrial seismology. Arrays of conventional three-component (3C) geophones enable measuring not only the particle velocity in three dimensions but also estimating their spatial gradients. Because the free-surface condition allows to express vertical derivatives in terms of horizontal derivatives, the full gradient tensor and, hence, curl and divergence of the wavefield can be computed. In total, three particle velocity components, three rotational components, and divergence, result seven-component (7C) seismic data. Combined particle velocity and gradient data can be used to isolate the incident P- or S-waves at the land surface or the sea bottom using filtering techniques based on the elastodynamic representation theorem. Alternatively, as only S-waves exhibit rotational motion, rotational measurements can directly be used to identify S-waves. We discuss the derivations of the gradient-based filters as well as their application to synthetic and field data, demonstrating that rotational data can be of particular interest to S-wave reflection and P-to-S-wave conversion imaging. The concept of array-derived gradient estimation can be extended to source arrays as well. Therefore, source arrays allow us to emulate rotational (curl) and dilatational (divergence) sources. Combined with 7C recordings, a total of 49 components of the seismic wavefield can be excited and recorded. Such data potentially allow to further improve wavefield separation and may find application in directional imaging and coherent noise suppression.

Precise real-time polarization measurement of terahertz electromagnetic waves by a spinning electro-optic sensor.

PubMed

Yasumatsu, Naoya; Watanabe, Shinichi

2012-02-01

We propose and develop a method to quickly and precisely determine the polarization direction of coherent terahertz electromagnetic waves generated by femtosecond laser pulses. The measurement system consists of a conventional terahertz time-domain spectroscopy system with the electro-optic (EO) sampling method, but we add a new functionality in the EO crystal which is continuously rotating with the angular frequency ω. We find a simple yet useful formulation of the EO signal as a function of the crystal orientation, which enables a lock-in-like detection of both the electric-field amplitude and the absolute polarization direction of the terahertz waves with respect to the probe laser pulse polarization direction at the same time. The single measurement finishes around two periods of the crystal rotations (∼21 ms), and we experimentally prove that the accuracy of the polarization measurement does not suffer from the long-term amplitude fluctuation of the terahertz pulses. Distribution of the measured polarization directions by repeating the measurements is excellently fitted by a gaussian distribution function with a standard deviation of σ = 0.56°. The developed technique is useful for the fast direct determination of the polarization state of the terahertz electromagnetic waves for polarization imaging applications as well as the precise terahertz Faraday or Kerr rotation spectroscopy.

Modulus design multiwavelength polarization microscope for transmission Mueller matrix imaging

NASA Astrophysics Data System (ADS)

Zhou, Jialing; He, Honghui; Chen, Zhenhua; Wang, Ye; Ma, Hui

2018-01-01

We have developed a polarization microscope based on a commercial transmission microscope. We replace the halogen light source by a collimated LED light source module of six different colors. We use achromatic polarized optical elements that can cover the six different wavelength ranges in the polarization state generator (PSG) and polarization state analyzer (PSA) modules. The dual-rotating wave plate method is used to measure the Mueller matrix of samples, which requires the simultaneous rotation of the two quarter-wave plates in both PSG and PSA at certain angular steps. A scientific CCD detector is used as the image receiving module. A LabView-based software is developed to control the rotation angels of the wave plates and the exposure time of the detector to allow the system to run fully automatically in preprogrammed schedules. Standard samples, such as air, polarizers, and quarter-wave plates, are used to calibrate the intrinsic Mueller matrix of optical components, such as the objectives, using the eigenvalue calibration method. Errors due to the images walk-off in the PSA are studied. Errors in the Mueller matrices are below 0.01 using air and polarizer as standard samples. Data analysis based on Mueller matrix transformation and Mueller matrix polarization decomposition is used to demonstrate the potential application of this microscope in pathological diagnosis.

Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

NASA Astrophysics Data System (ADS)

Mineo, Hirobumi; Fujimura, Yuichi

2015-06-01

We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

Polarimetric glucose sensing using Brewster reflection applying a rotating retarder analyzer

NASA Astrophysics Data System (ADS)

Boeckle, Stefan; Rovati, Luigi L.; Ansari, Rafat R.

2003-10-01

Previously, we proposed a polarimetric method, that exploits the Brewster-reflection with the final goal of application to the human eye (reflection off the eye lens) for non-invasive glucose sensing. The linearly polarized reflected light of this optical scheme is rotated by the glucose molecules present in the aqueous humor, thus carries the blood glucose concentration information. A proof-of-concept experimental bench-top setup is presented, applying a multi-wavelength true phase measurement approach and a rotating phase retarder as an analyzer to measure the very small rotation angles and the complete polarization state of the measurement light.

Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data

DOEpatents

Ward, Stanley H.

1989-01-01

Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.

Multispectral Stokes polarimetry for dermatoscopic imaging

NASA Astrophysics Data System (ADS)

Castillejos, Y.; Martínez-Ponce, Geminiano; Mora-Nuñez, Azael; Castro-Sanchez, R.

2015-12-01

Most of skin pathologies, including melanoma and basal/squamous cell carcinoma, are related to alterations in external and internal order. Usually, physicians rely on their empirical expertise to diagnose these ills normally assisted with dermatoscopes. When there exists skin cancer suspicion, a cytology or biopsy is made, but both laboratory tests imply an invasive procedure. In this regard, a number of non-invasive optical techniques have been proposed recently to improve the diagnostic certainty and assist in the early detection of cutaneous cancer. Herein, skin optical properties are derived with a multispectral polarimetric dermatoscope using three different illumination wavelength intervals centered at 470, 530 and 635nm. The optical device consist of two polarizing elements, a quarter-wave plate and a linear polarizer, rotating at a different angular velocity and a CCD array as the photoreceiver. The modulated signal provided by a single pixel in the acquired image sequence is analyzed with the aim of computing the Stokes parameters. Changes in polarization state of selected wavelengths provide information about the presence of skin pigments such as melanin and hemoglobin species as well as collagen structure, among other components. These skin attributes determine the local physiology or pathology. From the results, it is concluded that optical polarimetry will provide additional elements to dermatologists in their diagnostic task.

Competing exchange interactions in multiferroic and ferrimagnetic CaBaCo 4 O 7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fishman, Randy Scott; Bordacs, S.; Kocsis, Vilmos

Competing exchange interactions can produce complex magnetic states together with spin-induced electric polarizations. With competing interactions on alternating triangular and kagome layers, the swedenborgite CaBaCo 4O 7 may have one of the largest measured spin-induced polarizations of ~1700 nC/cm 2 below its ferrimagnetic transition temperature at 70 K. Upon rotating our sample about c = [0,0,1] while the magnetic field is fixed along [1,0,0], the threefold splitting of the spin-wave frequencies indicates that our sample is hexagonally twinned. In addition, magnetization measurements then suggest that roughly 20% of the sample is in a domain with the a axis along [1,0,0]more » and that 80% of the sample is in one of two other domains with the a axis along either [-1/2,√3/2, 0] or [-1/2, -√3/2, 0] . Powder neutron-diffraction data, magnetization measurements, and terahertz (THz) absorption spectroscopy reveal that the complex spin order in each domain can be described as a triangular array of bitetrahedral c-axis chains ferrimagnetically coupled to each other in the ab plane. In conclusion, the electric-field dependence of bonds coupling those chains produces the large spin-induced polarization of CaBaCo 4O 7 .« less

Competing exchange interactions in multiferroic and ferrimagnetic CaBaCo 4 O 7

DOE PAGES

Fishman, Randy Scott; Bordacs, S.; Kocsis, Vilmos; ...

2017-01-23

Competing exchange interactions can produce complex magnetic states together with spin-induced electric polarizations. With competing interactions on alternating triangular and kagome layers, the swedenborgite CaBaCo 4O 7 may have one of the largest measured spin-induced polarizations of ~1700 nC/cm 2 below its ferrimagnetic transition temperature at 70 K. Upon rotating our sample about c = [0,0,1] while the magnetic field is fixed along [1,0,0], the threefold splitting of the spin-wave frequencies indicates that our sample is hexagonally twinned. In addition, magnetization measurements then suggest that roughly 20% of the sample is in a domain with the a axis along [1,0,0]more » and that 80% of the sample is in one of two other domains with the a axis along either [-1/2,√3/2, 0] or [-1/2, -√3/2, 0] . Powder neutron-diffraction data, magnetization measurements, and terahertz (THz) absorption spectroscopy reveal that the complex spin order in each domain can be described as a triangular array of bitetrahedral c-axis chains ferrimagnetically coupled to each other in the ab plane. In conclusion, the electric-field dependence of bonds coupling those chains produces the large spin-induced polarization of CaBaCo 4O 7 .« less

Arduino-based experiment demonstrating Malus’s law

NASA Astrophysics Data System (ADS)

Freitas, W. P. S.; Cena, C. R.; Alves, D. C. B.; Goncalves, A. M. B.

2018-05-01

Malus’s law states that the intensity of light after passing through two polarizers is proportional to the square of the cosine of the angle between the polarizers. We present a simple setup demonstrating this law. The novelty of our work is that we use a multi-turn potentiometer mechanically linked to one of the polarizers to measure the polarizer’s rotation angle while keeping the other polarizer fixed. Both the potentiometer and light sensor used to measure the transmitted light intensity are connected to an Arduino board so that the intensity of light is measured as a function of the rotation angle.

Silicon-on-insulator polarization splitting and rotating device for polarization diversity circuits.

PubMed

Liu, Liu; Ding, Yunhong; Yvind, Kresten; Hvam, Jørn M

2011-06-20

A compact and efficient polarization splitting and rotating device built on the silicon-on-insulator platform is introduced, which can be readily used for the interface section of a polarization diversity circuit. The device is compact, with a total length of a few tens of microns. It is also simple, consisting of only two parallel silicon-on-insulator wire waveguides with different widths, and thus requiring no additional and nonstandard fabrication steps. A total insertion loss of -0.6 dB and an extinction ratio of 12 dB have been obtained experimentally in the whole C-band.

Molecular spinning by a chiral train of short laser pulses

NASA Astrophysics Data System (ADS)

Floß, Johannes; Averbukh, Ilya Sh.

2012-12-01

We provide a detailed theoretical analysis of molecular rotational excitation by a chiral pulse train, a sequence of linearly polarized pulses with the polarization direction rotating from pulse to pulse by a controllable angle. Molecular rotation with a preferential rotational sense (clockwise or counterclockwise) can be excited by this scheme. We show that the directionality of the rotation is caused by quantum interference of different excitation pathways. The chiral pulse train is capable of selective excitation of molecular isotopologs and nuclear spin isomers in a mixture. We demonstrate this using 14N2 and 15N2 as examples for isotopologs and para- and ortho-nitrogen as examples for nuclear-spin isomers.

A Si nanocube array polarizer

NASA Astrophysics Data System (ADS)

Chen, Linghua; Jiang, Yingjie; Xing, Li; Yao, Jun

2017-10-01

We have proposed a full dielectric (silicon) nanocube array polarizer based on a silicon dioxide substrate. Each polarization unit column includes a plurality of equal spaced polarization units. By optimizing the length, the width, the height of the polarization units and the center distance of adjacent polarization unit (x direction and y direction), an extinction ratio (ER) of higher than 25dB was obtained theoretically when the incident light wavelength is 1550nm. while for applications of most polarization optical elements, ER above 10dB is enough. With this condition, the polarizer we designed can work in a wide wavelength range from 1509.31nm to 1611.51nm. Compared with the previous polarizer, we have introduced a polarizer which is a full dielectric device, which solves the problems of low efficiency caused by Ohmic loss and weak coupling. Furthermore, compared with the existing optical polarizers, our polarizer has the advantages of thin thickness, small size, light weight, and low processing difficulty, which is in line with the future development trend of optical elements.

Basic principles and recent observations of rotationally sampled wind

NASA Technical Reports Server (NTRS)

Connell, James R.

1995-01-01

The concept of rotationally sampled wind speed is described. The unusual wind characteristics that result from rotationally sampling the wind are shown first for early measurements made using an 8-point ring of anemometers on a vertical plane array of meteorological towers. Quantitative characterization of the rotationally sampled wind is made in terms of the power spectral density function of the wind speed. Verification of the importance of the new concept is demonstrated with spectral analyses of the response of the MOD-OA blade flapwise root bending moment and the corresponding rotational analysis of the wind measured immediately upwind of the MOD-OA using a 12-point ring of anemometers on a 7-tower vertical plane array. The Pacific Northwest Laboratory (PNL) theory of the rotationally sampled wind speed power spectral density function is tested successfully against the wind spectrum measured at the MOD-OA vertical plane array. A single-tower empirical model of the rotationally sampled wind speed is also successfully tested against the measurements from the full vertical plane array. Rotational measurements of the wind velocity with hotfilm anemometers attached to rotating blades are shown to be accurate and practical for research on winds at the blades of wind turbines. Some measurements at the rotor blade of a MOD-2 turbine using the hotfilm technique in a pilot research program are shown. They are compared and contrasted to the expectations based upon application of the PNL theory of rotationally sampled wind to the MOD-2 size and rotation rate but without teeter, blade bending, or rotor induction accounted for. Finally, the importance of temperature layering and of wind modifications due to flow over complex terrain is demonstrated by the use of hotfilm anemometer data, and meteorological tower and acoustic doppler sounder data from the MOD-2 site at Goodnoe Hills, Washington.

Ionospheric Specifications for SAR Interferometry (ISSI)

NASA Technical Reports Server (NTRS)

Pi, Xiaoqing; Chapman, Bruce D; Freeman, Anthony; Szeliga, Walter; Buckley, Sean M.; Rosen, Paul A.; Lavalle, Marco

2013-01-01

The ISSI software package is designed to image the ionosphere from space by calibrating and processing polarimetric synthetic aperture radar (PolSAR) data collected from low Earth orbit satellites. Signals transmitted and received by a PolSAR are subject to the Faraday rotation effect as they traverse the magnetized ionosphere. The ISSI algorithms combine the horizontally and vertically polarized (with respect to the radar system) SAR signals to estimate Faraday rotation and ionospheric total electron content (TEC) with spatial resolutions of sub-kilometers to kilometers, and to derive radar system calibration parameters. The ISSI software package has been designed and developed to integrate the algorithms, process PolSAR data, and image as well as visualize the ionospheric measurements. A number of tests have been conducted using ISSI with PolSAR data collected from various latitude regions using the phase array-type L-band synthetic aperture radar (PALSAR) onboard Japan Aerospace Exploration Agency's Advanced Land Observing Satellite mission, and also with Global Positioning System data. These tests have demonstrated and validated SAR-derived ionospheric images and data correction algorithms.

Measurements of coronal Faraday rotation at 4.6 R {sub ☉}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kooi, Jason E.; Fischer, Patrick D.; Buffo, Jacob J.

2014-03-20

Many competing models for the coronal heating and acceleration mechanisms of the high-speed solar wind depend on the solar magnetic field and plasma structure in the corona within heliocentric distances of 5 R {sub ☉}. We report on sensitive Very Large Array (VLA) full-polarization observations made in 2011 August, at 5.0 and 6.1 GHz (each with a bandwidth of 128 MHz) of the radio galaxy 3C 228 through the solar corona at heliocentric distances of 4.6-5.0 R {sub ☉}. Observations at 5.0 GHz permit measurements deeper in the corona than previous VLA observations at 1.4 and 1.7 GHz. These Faradaymore » rotation observations provide unique information on the magnetic field in this region of the corona. The measured Faraday rotation on this day was lower than our a priori expectations, but we have successfully modeled the measurement in terms of observed properties of the corona on the day of observation. Our data on 3C 228 provide two lines of sight (separated by 46'', 33,000 km in the corona). We detected three periods during which there appeared to be a difference in the Faraday rotation measure between these two closely spaced lines of sight. These measurements (termed differential Faraday rotation) yield an estimate of 2.6-4.1 GA for coronal currents. Our data also allow us to impose upper limits on rotation measure fluctuations caused by coronal waves; the observed upper limits were 3.3 and 6.4 rad m{sup –2} along the two lines of sight. The implications of these results for Joule heating and wave heating are briefly discussed.« less

The E and B EXperiment: EBEX

NASA Astrophysics Data System (ADS)

Helson, Kyle R.

2015-08-01

We report on the status of the E and B Experiment (EBEX) a balloon-borne polarimeter designed to measure the polarization of the cosmic microwave background radiation. The instrument employs a 1.5 meter Gregorian Mizuguchi-Dragone telescope providing 8 arc-minute resolution at three bands centered on 150, 250, and 410 GHz. A continuously rotating achromatic half wave plate, mounted on a superconducting magnetic bearing, and a polarizing grid give EBEX polarimetric capabilities. Radiation is detected with a kilo-pixel array of transition edge sensor (TES) bolometers that are cooled to 0.25 K. The detectors are readout using SQUID current amplifiers and a digital frequency-domain multiplexing system in which 16 detectors are readout simultaneously with two wires. EBEX is the first instrument to implement TESs and such readout system on board a balloon-borne platform. EBEX was launched from the Antarctic in December 2012 on an 11-day long-duration balloon flight. This presentation will provide an overview of the instrument and discuss the flight and status of the data analysis. We also discuss the next generation of EBEX called EBEX10k, currently in development.

Magic angle for barrier-controlled double quantum dots

NASA Astrophysics Data System (ADS)

Yang, Xu-Chen; Wang, Xin

2018-01-01

We show that the exchange interaction of a singlet-triplet spin qubit confined in double quantum dots, when being controlled by the barrier method, is insensitive to a charged impurity lying along certain directions away from the center of the double-dot system. These directions differ from the polar axis of the double dots by the magic angle, equaling arccos(1 /√{3 })≈54 .7∘ , a value previously found in atomic physics and nuclear magnetic resonance. This phenomenon can be understood from an expansion of the additional Coulomb interaction created by the impurity, but also relies on the fact that the exchange interaction solely depends on the tunnel coupling in the barrier-control scheme. Our results suggest that for a scaled-up qubit array, when all pairs of double dots rotate their respective polar axes from the same reference line by the magic angle, crosstalk between qubits can be eliminated, allowing clean single-qubit operations. While our model is a rather simplified version of actual experiments, our results suggest that it is possible to minimize unwanted couplings by judiciously designing the layout of the qubits.

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.

An orthogonal return method for linearly polarized beam based on the Faraday effect and its application in interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Benyong, E-mail: chenby@zstu.edu.cn; Zhang, Enzheng; Yan, Liping

2014-10-15

Correct return of the measuring beam is essential for laser interferometers to carry out measurement. In the actual situation, because the measured object inevitably rotates or laterally moves, not only the measurement accuracy will decrease, or even the measurement will be impossibly performed. To solve this problem, a novel orthogonal return method for linearly polarized beam based on the Faraday effect is presented. The orthogonal return of incident linearly polarized beam is realized by using a Faraday rotator with the rotational angle of 45°. The optical configuration of the method is designed and analyzed in detail. To verify its practicabilitymore » in polarization interferometry, a laser heterodyne interferometer based on this method was constructed and precision displacement measurement experiments were performed. These results show that the advantage of the method is that the correct return of the incident measuring beam is ensured when large lateral displacement or angular rotation of the measured object occurs and then the implementation of interferometric measurement can be ensured.« less

DETECTING EXOMOONS AROUND SELF-LUMINOUS GIANT EXOPLANETS THROUGH POLARIZATION.

PubMed

Sengupta, Sujan; Marley, Mark S

2016-01-01

Many of the directly imaged self-luminous gas giant exoplanets have been found to have cloudy atmospheres. Scattering of the emergent thermal radiation from these planets by the dust grains in their atmospheres should locally give rise to significant linear polarization of the emitted radiation. However, the observable disk averaged polarization should be zero if the planet is spherically symmetric. Rotation-induced oblateness may yield a net non-zero disk averaged polarization if the planets have sufficiently high spin rotation velocity. On the other hand, when a large natural satellite or exomoon transits a planet with cloudy atmosphere along the line of sight, the asymmetry induced during the transit should give rise to a net non-zero, time resolved linear polarization signal. The peak amplitude of such time dependent polarization may be detectable even for slowly rotating exoplanets. Therefore, we suggest that large exomoons around directly imaged self-luminous exoplanets may be detectable through time resolved imaging polarimetry. Adopting detailed atmospheric models for several values of effective temperature and surface gravity which are appropriate for self-luminous exoplanets, we present the polarization profiles of these objects in the infrared during transit phase and estimate the peak amplitude of polarization that occurs during the inner contacts of the transit ingress/egress phase. The peak polarization is predicted to range between 0.1 and 0.3 % in the infrared.

Polar Flagellar Motility of the Vibrionaceae

PubMed Central

McCarter, Linda L.

2001-01-01

Polar flagella of Vibrio species can rotate at speeds as high as 100,000 rpm and effectively propel the bacteria in liquid as fast as 60 μm/s. The sodium motive force powers rotation of the filament, which acts as a propeller. The filament is complex, composed of multiple subunits, and sheathed by an extension of the cell outer membrane. The regulatory circuitry controlling expression of the polar flagellar genes of members of the Vibrionaceae is different from the peritrichous system of enteric bacteria or the polar system of Caulobacter crescentus. The scheme of gene control is also pertinent to other members of the gamma purple bacteria, in particular to Pseudomonas species. This review uses the framework of the polar flagellar system of Vibrio parahaemolyticus to provide a synthesis of what is known about polar motility systems of the Vibrionaceae. In addition to its propulsive role, the single polar flagellum of V. parahaemolyticus is believed to act as a tactile sensor controlling surface-induced gene expression. Under conditions that impede rotation of the polar flagellum, an alternate, lateral flagellar motility system is induced that enables movement through viscous environments and over surfaces. Although the dual flagellar systems possess no shared structural components and although distinct type III secretion systems direct the simultaneous placement and assembly of polar and lateral organelles, movement is coordinated by shared chemotaxis machinery. PMID:11528005

DETECTING EXOMOONS AROUND SELF-LUMINOUS GIANT EXOPLANETS THROUGH POLARIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, Sujan; Marley, Mark S., E-mail: sujan@iiap.res.in, E-mail: Mark.S.Marley@NASA.gov

Many of the directly imaged self-luminous gas-giant exoplanets have been found to have cloudy atmospheres. Scattering of the emergent thermal radiation from these planets by the dust grains in their atmospheres should locally give rise to significant linear polarization of the emitted radiation. However, the observable disk-averaged polarization should be zero if the planet is spherically symmetric. Rotation-induced oblateness may yield a net non-zero disk-averaged polarization if the planets have sufficiently high spin rotation velocity. On the other hand, when a large natural satellite or exomoon transits a planet with a cloudy atmosphere along the line of sight, the asymmetrymore » induced during the transit should give rise to a net non-zero, time-resolved linear polarization signal. The peak amplitude of such time-dependent polarization may be detectable even for slowly rotating exoplanets. Therefore, we suggest that large exomoons around directly imaged self-luminous exoplanets may be detectable through time-resolved imaging polarimetry. Adopting detailed atmospheric models for several values of effective temperature and surface gravity that are appropriate for self-luminous exoplanets, we present the polarization profiles of these objects in the infrared during the transit phase and estimate the peak amplitude of polarization that occurs during the inner contacts of the transit ingress/egress phase. The peak polarization is predicted to range between 0.1% and 0.3% in the infrared.« less

Detecting Exomoons Around Self-Luminous Giant Exoplanets Through Polarization

NASA Technical Reports Server (NTRS)

Sengupta, Sujan; Marley, Mark Scott

2016-01-01

Many of the directly imaged self-luminous gas giant exoplanets have been found to have cloudy atmo- spheres. Scattering of the emergent thermal radiation from these planets by the dust grains in their atmospheres should locally give rise to significant linear polarization of the emitted radiation. However, the observable disk averaged polarization should be zero if the planet is spherically symmetric. Rotation-induced oblateness may yield a net non-zero disk averaged polarization if the planets have sufficiently high spin rotation velocity. On the other hand, when a large natural satellite or exomoon transits a planet with cloudy atmosphere along the line of sight, the asymmetry induced during the transit should give rise to a net non-zero, time resolved linear polarization signal. The peak amplitude of such time dependent polarization may be detectable even for slowly rotating exoplanets. Therefore, we suggest that large exomoons around directly imaged self-luminous exoplanets may be detectable through time resolved imaging polarimetry. Adopting detailed atmospheric models for several values of effective temperature and surface gravity which are appropriate for self-luminous exoplanets, we present the polarization profiles of these objects in the infrared during transit phase and estimate the peak amplitude of polarization that occurs during the the inner contacts of the transit ingress/egress phase. The peak polarization is predicted to range between 0.1 and 0.3 % in the infrared.

DETECTING EXOMOONS AROUND SELF-LUMINOUS GIANT EXOPLANETS THROUGH POLARIZATION

PubMed Central

Sengupta, Sujan; Marley, Mark S.

2017-01-01

Many of the directly imaged self-luminous gas giant exoplanets have been found to have cloudy atmospheres. Scattering of the emergent thermal radiation from these planets by the dust grains in their atmospheres should locally give rise to significant linear polarization of the emitted radiation. However, the observable disk averaged polarization should be zero if the planet is spherically symmetric. Rotation-induced oblateness may yield a net non-zero disk averaged polarization if the planets have sufficiently high spin rotation velocity. On the other hand, when a large natural satellite or exomoon transits a planet with cloudy atmosphere along the line of sight, the asymmetry induced during the transit should give rise to a net non-zero, time resolved linear polarization signal. The peak amplitude of such time dependent polarization may be detectable even for slowly rotating exoplanets. Therefore, we suggest that large exomoons around directly imaged self-luminous exoplanets may be detectable through time resolved imaging polarimetry. Adopting detailed atmospheric models for several values of effective temperature and surface gravity which are appropriate for self-luminous exoplanets, we present the polarization profiles of these objects in the infrared during transit phase and estimate the peak amplitude of polarization that occurs during the inner contacts of the transit ingress/egress phase. The peak polarization is predicted to range between 0.1 and 0.3 % in the infrared. PMID:29430024

Phased array antenna matching: Simulation and optimization of a planar phased array of circular waveguide elements

NASA Technical Reports Server (NTRS)

Dudgeon, J. E.

1972-01-01

A computerized simulation of a planar phased array of circular waveguide elements is reported using mutual coupling and wide angle impedance matching in phased arrays. Special emphasis is given to circular polarization. The aforementioned computer program has as variable inputs: frequency, polarization, grid geometry, element size, dielectric waveguide fill, dielectric plugs in the waveguide for impedance matching, and dielectric sheets covering the array surface for the purpose of wide angle impedance matching. Parameter combinations are found which produce reflection peaks interior to grating lobes, while dielectric cover sheets are successfully employed to extend the usable scan range of a phased array. The most exciting results came from the application of computer aided optimization techniques to the design of this type of array.

An All Silicon Feedhorn-Coupled Focal Plane for Cosmic Microwave Background Polarimetry

NASA Technical Reports Server (NTRS)

Hubmayr, J.; Appel, J. W.; Austermann, J. E.; Beall, J. A.; Becker, D.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.;

Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data

DOEpatents

Ward, S.H.

1989-10-17

Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth. 30 figs.

Angle- and polarization-insensitive, small area, subtractive color filters via a-Si nanopillar arrays (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fountaine, Katherine T.; Ito, Mikinori; Pala, Ragip; Atwater, Harry A.

2016-09-01

Spectrally-selective nanophotonic and plasmonic structures enjoy widespread interest for application as color filters in imaging devices, due to their potential advantages over traditional organic dyes and pigments. Organic dyes are straightforward to implement with predictable optical performance at large pixel size, but suffer from inherent optical cross-talk and stability (UV, thermal, humidity) issues and also exhibit increasingly unpredictable performance as pixel size approaches dye molecule size. Nanophotonic and plasmonic color filters are more robust, but often have polarization- and angle-dependent optical response and/or require large-range periodicity. Herein, we report on design and fabrication of polarization- and angle-insensitive CYM color filters based on a-Si nanopillar arrays as small as 1um2, supported by experiment, simulation, and analytic theory. Analytic waveguide and Mie theories explain the color filtering mechanism- efficient coupling into and interband transition-mediated attenuation of waveguide-like modes—and also guided the FDTD simulation-based optimization of nanopillar array dimensions. The designed a-Si nanopillar arrays were fabricated using e-beam lithography and reactive ion etching; and were subsequently optically characterized, revealing the predicted polarization- and angle-insensitive (±40°) subtractive filter responses. Cyan, yellow, and magenta color filters have each been demonstrated. The effects of nanopillar array size and inter-array spacing were investigated both experimentally and theoretically to probe the issues of ever-shrinking pixel sizes and cross-talk, respectively. Results demonstrate that these nanopillar arrays maintain their performance down to 1um2 pixel sizes with no inter-array spacing. These concepts and results along with color-processed images taken with a fabricated color filter array will be presented and discussed.

Electrically rotating suspended films of polar liquids

NASA Astrophysics Data System (ADS)

Shirsavar, R.; Amjadi, A.; Tonddast-Navaei, A.; Ejtehadi, M. R.

2011-02-01

Controlled rotation of a suspended soap water film, simply generated by applying an electric field, has been reported recently. The film rotates when the applied electric field exceeds a certain threshold. In this study, we investigate the phenomenon in films made of a number of other liquids with various physical and chemical properties. Our measurements show that the intrinsic electrical dipole moments of the liquid molecules seems to be vital for the corresponding film rotation. All the investigated rotating liquids have a molecular electric dipole moment of above 1 Debye, while weakly polar liquids do not rotate. However, the liquids investigated here cover a wide range of physical parameters (e.g. viscosity, density, conductivity, etc.). So far, no significant correlation has been observed between the electric field thresholds and macroscopic properties of the liquids.

Data characteristics and preliminary results from the atacama b-mode search (ABS)

NASA Astrophysics Data System (ADS)

Visnjic, Catherine

The Atacama B-Mode Search (ABS) is a 145 GHz polarimeter located at a high altitude site on Cerro Toco, in the Andes of northern Chile. Having deployed in early 2012, it is currently in its second year of operation, observing the polarization of the Cosmic Microwave Background (CMB). It seeks to probe the as yet undetected odd-parity B-modes of the polarization, which would have been created by the primordial gravitational wave background (GWB) predicted by theories of inflation. The magnitude of the B-mode signal is characterized by the tensor-to-scalar ratio, r. ABS features 60 cm cryogenic reflectors in the crossed-Dragone configuration, and a warm, continuously rotating sapphire half-wave plate to modulate the polarization of incoming radiation. The focal plane consists of 480 antenna-coupled transition edge sensor bolometers, arranged in orthogonal pairs for polarization sensitivity, and coupled to feedhorns in a hexagonal array. In this thesis we describe the ABS instrument in the state in which it is now operating, outline the first season of observations, and characterize the data obtained. Focusing on observations of the primary CMB field during a one month reference period, we detail the algorithms currently used to select the data suitable for making maps. This is the first pass at data cuts and provides a conservative estimate for the sensitivity of ABS to the polarization modes in the sky. We project that with one year total observation time of the primary CMB field, ABS should be able to detect the B-mode signal at roughly the level of r = 0.03.

Polarization-tuned Dynamic Color Filters Incorporating a Dielectric-loaded Aluminum Nanowire Array

PubMed Central

Raj Shrestha, Vivek; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

2015-01-01

Nanostructured spectral filters enabling dynamic color-tuning are saliently attractive for implementing ultra-compact color displays and imaging devices. Realization of polarization-induced dynamic color-tuning via one-dimensional periodic nanostructures is highly challenging due to the absence of plasmonic resonances for transverse-electric polarization. Here we demonstrate highly efficient dynamic subtractive color filters incorporating a dielectric-loaded aluminum nanowire array, providing a continuum of customized color according to the incident polarization. Dynamic color filtering was realized relying on selective suppression in transmission spectra via plasmonic resonance at a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide, each occurring at their characteristic wavelengths for transverse-magnetic and electric polarizations, respectively. A broad palette of colors, including cyan, magenta, and yellow, has been attained with high transmission beyond 80%, by tailoring the period of the nanowire array and the incident polarization. Thanks to low cost, high durability, and mass producibility of the aluminum adopted for the proposed devices, they are anticipated to be diversely applied to color displays, holographic imaging, information encoding, and anti-counterfeiting. PMID:26211625

Progress in Research on Diurnal and Semidiurnal Earth Rotation Change

NASA Astrophysics Data System (ADS)

Xu, Xueqing

2015-08-01

We mainly focus on the progress of research on high frequency changes in the earth rotation. Firstly, we review the development course and main motivating factors of the diurnal and semidiurnal earth rotation change. In recent decades, earth orientation has been monitored with increasing accuracy by advanced space-geodetic techniques, including lunar and satellite laser ranging, very long baseline interferometry and the global positioning system. We are able to obtain the Earth Rotation Parameters (ERP, polar motion and rotation rate changes) by even 1 to 2 hours observation data, form which obvious diurnal and semidiurnal signals can be detected, and compare them with the predicted results by the ocean model. Both the amplitude and phase are in good agreement in the main diurnal and semidiurnal wave frequency, especially for the UT1, whose compliance is 90%, and 60% for polar motion, there are 30% motivating factor of the diurnal and semidiurnal polar motion have not been identified. Then we comprehensively review the different types of global ocean tidal correction models since the last eighties century, as well as the application research on diurnal and semidiurnal polar motion and UT1, the current ocean tidal correction models have 10% to 20% uncertainty, and need for further refinement.

Effect of Faraday rotation on the circular polarization of the Crab Nebula

NASA Technical Reports Server (NTRS)

Gerver, M. J.

1974-01-01

The effect of Faraday rotation on the circular polarization of an electromagnetic wave propagating through a magnetized plasma is calculated for various limits of the plasma and wave parameters appropriate to a 30-Hz wave in the Crab Nebula. It is shown that a static magnetic field of the proper geometry and only a few times stronger than the wave field can reduce the circular polarization of the nonlinear inverse Compton radiation to a value below the observed upper limit.-

First-Principles calculations of Piezoelectricity and Polarization Rotation in Pb(Zr_0.5Ti_0.5)O_3

NASA Astrophysics Data System (ADS)

Wu, Zhigang; Krakauer, Henry

2002-03-01

Recent experimental and theoretical work [1-3] indicates that polarization rotation via a monoclinic phase at the morphotropic phase boundary in PZT [1-3] is responsible for its large piezoelectric response. We investigate this using the first-principles LAPW+LO method within the local density functional approximation. Calculated internal coordinates of monoclinic PZT(50/50) are in good agreement with PZT(52/48) experimental data [4]. Bulk spontaneous polarization and piezoelectric stress tensor elements of chemically ordered PbZr_1/2Ti_1/2O3 (PZT 50/50) are determined from relaxed ground-state Berry's phase calculations while constraining the symmetry to monoclinic Cm. Large piezoelectric response is found as the polarization rotates within the Cm mirror plane. These first-principles results show that polarization rotation can explain the large measured piezoelectric constants in ceramic PZT. * Supported by ONR. [1] H. Fu and Cohen, Nature 403, 281 (2000). [2] B. Noheda, D.E. Cox, G. Shirane, S-E. Park, L.E. Cross and Z. Zhong Phys. Rev. Lett. 86, 3891 (2001). [3] L. Bellaiche, A. Garcia and D. Vanderbilt, Phys. Rev. Lett. 84, 5427 (2000). [4] B. Noheda, J.A. Gonzalo, L.E. Cross, R. Guo, S.-E. Park, D.E. Cox and G. Shirane, Phys. Rev. B 61, 8687 (2000).

Testing New Physics with the Cosmic Microwave Background

NASA Astrophysics Data System (ADS)

Gluscevic, Vera

2013-01-01

In my thesis work, I have developed and applied tests of new fundamental physics that utilize high-precision CMB polarization measurements. I especially focused on a wide class of dark energy models that propose existence of new scalar fields to explain accelerated expansion of the Universe. Such fields naturally exhibit a weak interaction with photons, giving rise to "cosmic birefringence"---a rotation of the polarization plane of light traveling cosmological distances, which alters the statistics of the CMB fluctuations in the sky by inducing a characteristic B-mode polarization. A birefringent rotation of the CMB would be smoking-gun evidence that dark energy is a dynamical component rather than a cosmological constant, while its absence gives clues about the allowed regions of the parameter space for new models. I developed a full-sky formalism to search for cosmic birefringence by cross-correlating CMB temperature and polarization maps, after allowing for the rotation angle to vary across the sky. With my collaborators, I also proposed a cross-correlation of the rotation-angle estimator with the CMB temperature as a novel statistical probe which can boost signal-to-noise in the case of marginal detection and help disentangle the underlying physical models. I then investigated the degeneracy between the rotation signal and the signals from other exotic scenarios that induce a similar B-mode polarization signature, such as chiral primordial gravitational waves, and demonstrated that these effects are completely separable. Finally, I applied this formalism to WMAP-7 data and derived the first CMB constraint on the power spectrum of the birefringent-rotation angle and presented forecasts for future experiments. To demonstrate the value of this analysis method beyond the search for direction-dependent cosmic birefringence, I have also used it to probe patchy screening from the epoch of cosmic reionization with WMAP-7 data.

Successive X-class Flares and Coronal Mass Ejections Driven by Shearing Motion and Sunspot Rotation in Active Region NOAA 12673

NASA Astrophysics Data System (ADS)

Yan, X. L.; Wang, J. C.; Pan, G. M.; Kong, D. F.; Xue, Z. K.; Yang, L. H.; Li, Q. L.; Feng, X. S.

2018-03-01

We present a clear case study on the occurrence of two successive X-class flares, including a decade-class flare (X9.3) and two coronal mass ejections (CMEs) triggered by shearing motion and sunspot rotation in active region NOAA 12673 on 2017 September 6. A shearing motion between the main sunspots with opposite polarities began on September 5 and lasted even after the second X-class flare on September 6. Moreover, the main sunspot with negative polarity rotated around its umbral center, and another main sunspot with positive polarity also exhibited a slow rotation. The sunspot with negative polarity at the northwest of the active region also began to rotate counterclockwise before the onset of the first X-class flare, which is related to the formation of the second S-shaped structure. The successive formation and eruption of two S-shaped structures were closely related to the counterclockwise rotation of the three sunspots. The existence of a flux rope is found prior to the onset of two flares by using nonlinear force-free field extrapolation based on the vector magnetograms observed by Solar Dynamics Observatory/Helioseismic and Magnetic Image. The first flux rope corresponds to the first S-shaped structures mentioned above. The second S-shaped structure was formed after the eruption of the first flux rope. These results suggest that a shearing motion and sunspot rotation play an important role in the buildup of the free energy and the formation of flux ropes in the corona that produces solar flares and CMEs.

Self-Calibration in the Ska: Dealing with Inherently Strong Instrumental Polarization

NASA Astrophysics Data System (ADS)

Hamaker, Johan

The polarization properties of a phased-array SKA will depart radically from those we are familiar with. The E- and H-plane beams of a linear or planar dipole are very different and the primary beam formed by arrays of such dipoles is strongly polarized. The customary quasi-scalar description is inadequate: Polarization must be accounted for in a fundamental way. Once this is done, we must investigate whether or not a phased-array SKA will in principle be capable of achievements comparable to those of conventional synthesis arrays. Selfcal is crucial to these achievements. In this paper I address the vital question of its viability in the presence of arbitrary instrumental polarization. I introduce an interferometer description based on 2x2 matrices. I then propose a matrix-based self-calibration method that is entirely analogous to the scalar one. I show that the standard selfcal assumptions suppress spatial scattering in matrix selfcal like they do in scalar selfcal: Thus the basic condition for obtaining images with a high dynamic range is satisfied. However, matrix selfcal alone cannot guarantee the polarimetric fidelity of the image: It introduces an unknown polrotation of the Stokes (Q,U,V) brightness vector and an unknown polconversion between unpolarized and polarized brightness. Methods similar to those currently applied in quasi-scalar polarimetry must be applied to reduce these poldistorsions to an acceptable level.

Cosmology from CMB Polarization with POLARBEAR and the Simons Array

NASA Astrophysics Data System (ADS)

Barron, Darcy; POLARBEAR Collaboration

2018-01-01

POLARBEAR is a cosmic microwave background (CMB) polarization experiment located in the Atacama desert in Chile. The science goals of the POLARBEAR project are to do a deep search for CMB B-mode polarization created by inflationary gravitational waves, as well as characterize the CMB B-mode signal from gravitational lensing. POLARBEAR-1 started observations in 2012, and the POLARBEAR team has published a series of results from its first season of observations, including the first measurement of a non-zero B-mode polarization angular power spectrum, measured at sub-degree scales where the dominant signal is gravitational lensing of the CMB. Recently, we released an improved measurement of the B-mode polarization power spectrum, improving our band-power uncertainties by a factor of two, by adding new data from our second observing season and re-analyzing the combined data set.To further improve on these measurements, POLARBEAR is expanding to include an additional two telescopes with multi-chroic receivers observing at 95, 150, 220, and 270 GHz, known as the Simons Array. With high sensitivity and large sky coverage, the Simons Array will create a detailed survey of B-mode polarization, and its spectral information will be used to extract the CMB signal from astrophysical foregrounds. We will present the latest POLARBEAR results, as well as the status of development of the Simons Array and its expected capabilities.

Method for attitude determination using GPS carrier phase measurements from nonaligned antennas

NASA Technical Reports Server (NTRS)

Lightsey, Edgar Glenn (Inventor)

1999-01-01

A correction to a differential phase measurement used for vehicle attitude determination on nonaligned antenna arrays is determined by calculating a carrier phase angle of carrier signals received by each antenna, and correcting the measurement for the right-hand circular polarization effect on the nonaligned antennas. Accordingly, circular polarization effects of the carrier signals are removed from a nonaligned antenna array, allowing the nonaligned antenna array to be used for vehicle attitude determination.

Metasurface quantum-cascade laser with electrically switchable polarization

DOE PAGES

Xu, Luyao; Chen, Daguan; Curwen, Christopher A.; ...

2017-04-20

Dynamic control of a laser’s output polarization state is desirable for applications in polarization sensitive imaging, spectroscopy, and ellipsometry. Using external elements to control the polarization state is a common approach. Less common and more challenging is directly switching the polarization state of a laser, which, however, has the potential to provide high switching speeds, compactness, and power efficiency. Here, we demonstrate a new approach to achieve direct and electrically controlled polarization switching of a semiconductor laser. This is enabled by integrating a polarization-sensitive metasurface with a semiconductor gain medium to selectively amplify a cavity mode with the designed polarizationmore » state, therefore leading to an output in the designed polarization. Here, the demonstration is for a terahertz quantum-cascade laser, which exhibits electrically controlled switching between two linear polarizations separated by 80°, while maintaining an excellent beam with a narrow divergence of ~3°×3° and a single-mode operation fixed at ~3.4 THz, combined with a peak power as high as 93 mW at a temperature of 77 K. The polarization-sensitive metasurface is composed of two interleaved arrays of surface-emitting antennas, all of which are loaded with quantum-cascade gain materials. Each array is designed to resonantly interact with one specific polarization; when electrical bias is selectively applied to the gain material in one array, selective amplification of one polarization occurs. The amplifying metasurface is used along with an output coupler reflector to build a vertical-external-cavity surface-emitting laser whose output polarization state can be switched solely electrically. In conclusion, this work demonstrates the potential of exploiting amplifying polarization-sensitive metasurfaces to create lasers with desirable polarization states—a concept which is applicable beyond the terahertz and can potentially be applied to shorter wavelengths.« less

Metasurface quantum-cascade laser with electrically switchable polarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Luyao; Chen, Daguan; Curwen, Christopher A.

Dynamic control of a laser’s output polarization state is desirable for applications in polarization sensitive imaging, spectroscopy, and ellipsometry. Using external elements to control the polarization state is a common approach. Less common and more challenging is directly switching the polarization state of a laser, which, however, has the potential to provide high switching speeds, compactness, and power efficiency. Here, we demonstrate a new approach to achieve direct and electrically controlled polarization switching of a semiconductor laser. This is enabled by integrating a polarization-sensitive metasurface with a semiconductor gain medium to selectively amplify a cavity mode with the designed polarizationmore » state, therefore leading to an output in the designed polarization. Here, the demonstration is for a terahertz quantum-cascade laser, which exhibits electrically controlled switching between two linear polarizations separated by 80°, while maintaining an excellent beam with a narrow divergence of ~3°×3° and a single-mode operation fixed at ~3.4 THz, combined with a peak power as high as 93 mW at a temperature of 77 K. The polarization-sensitive metasurface is composed of two interleaved arrays of surface-emitting antennas, all of which are loaded with quantum-cascade gain materials. Each array is designed to resonantly interact with one specific polarization; when electrical bias is selectively applied to the gain material in one array, selective amplification of one polarization occurs. The amplifying metasurface is used along with an output coupler reflector to build a vertical-external-cavity surface-emitting laser whose output polarization state can be switched solely electrically. In conclusion, this work demonstrates the potential of exploiting amplifying polarization-sensitive metasurfaces to create lasers with desirable polarization states—a concept which is applicable beyond the terahertz and can potentially be applied to shorter wavelengths.« less

Uniform rotating field network structure to efficiently package a magnetic bubble domain memory

NASA Technical Reports Server (NTRS)

Murray, Glen W. (Inventor); Chen, Thomas T. (Inventor); Wolfshagen, Ronald G. (Inventor); Ypma, John E. (Inventor)

1978-01-01

A unique and compact open coil rotating magnetic field network structure to efficiently package an array of bubble domain devices is disclosed. The field network has a configuration which effectively enables selected bubble domain devices from the array to be driven in a vertical magnetic field and in an independent and uniform horizontal rotating magnetic field. The field network is suitably adapted to minimize undesirable inductance effects, improve capabilities of heat dissipation, and facilitate repair or replacement of a bubble device.

Polar exponential sensor arrays unify iconic and Hough space representation

NASA Technical Reports Server (NTRS)

Weiman, Carl F. R.

1990-01-01

The log-polar coordinate system, inherent in both polar exponential sensor arrays and log-polar remapped video imagery, is identical to the coordinate system of its corresponding Hough transform parameter space. The resulting unification of iconic and Hough domains simplifies computation for line recognition and eliminates the slope quantization problems inherent in the classical Cartesian Hough transform. The geometric organization of the algorithm is more amenable to massively parallel architectures than that of the Cartesian version. The neural architecture of the human visual cortex meets the geometric requirements to execute 'in-place' log-Hough algorithms of the kind described here.

Total elimination of sampling errors in polarization imagery obtained with integrated microgrid polarimeters.

PubMed

Tyo, J Scott; LaCasse, Charles F; Ratliff, Bradley M

2009-10-15

Microgrid polarimeters operate by integrating a focal plane array with an array of micropolarizers. The Stokes parameters are estimated by comparing polarization measurements from pixels in a neighborhood around the point of interest. The main drawback is that the measurements used to estimate the Stokes vector are made at different locations, leading to a false polarization signature owing to instantaneous field-of-view (IFOV) errors. We demonstrate for the first time, to our knowledge, that spatially band limited polarization images can be ideally reconstructed with no IFOV error by using a linear system framework.

The Tripole Antenna: An Adaptive Array with Full Polarization Flexibility.

DTIC Science & Technology

1980-12-01

The polarization ellipse 4 3 The Poincare sphere 6 4 SINR vs. Bi. 12 8d=450 , @d=450, ad=1!5, Bd=30 °, SNR=O dB 00i= 45 , INR-4O dB. 5 SINR vs. 01, 13...y and n is most easily visualized by making use of the Poincare Sphere 4 . This tech- nique represents the state of polarization by a point on a...clockwise circular polarization (a = + 450) at the upper pole. Thus, an arbitrary plane wave coming into the array may be character- ized by four

The Design and Characterization of Wideband Spline-profiled Feedhorns for Advanced Actpol

NASA Technical Reports Server (NTRS)

Simon, Sara M.; Austermann, Jason; Beall, James A.; Choi, Steve K.; Coughlin, Kevin P.; Duff, Shannon M.; Gallardo, Patricio A.; Henderson, Shawn W.; Hills, Felicity B.; Ho, Shuay-Pwu Patty;

A novel serrated columnar phased array ultrasonic transducer

NASA Astrophysics Data System (ADS)

Zou, Cheng; Sun, Zhenguo; Cai, Dong; Song, Hongwei; Chen, Qiang

2016-02-01

Traditionally, wedges are required to generate transverse waves in a solid specimen and mechanical rotation device is needed for interrogation of a specimen with a hollow bore, such as high speed railway locomotive axles, turbine rotors, etc. In order to eliminate the mechanical rotation process, a novel array pattern of phased array ultrasonic transducers named as serrated columnar phased array ultrasonic transducer (SCPAUT) is designed. The elementary transducers are planar rectangular, located on the outside surface of a cylinder. This layout is aimed to generate electrically rotating transverse waveforms so as to inspect the longitudinal cracks on the outside surface of a specimen which has a hollow bore at the center, such as the high speed railway locomotive axles. The general geometry of the SCPAUT and the inspection system are illustrated. A FEM model and mockup experiment has been carried out. The experiment results are in good agreement with the FEM simulation results.

Novel Microstrip Patch Antennas with Frequency Agility, Polarization Reconfigurability, Dual Null Steering Capability and Phased Array Antenna with Beam Steering Performance

NASA Astrophysics Data System (ADS)

Babakhani, Behrouz

Nowadays the wireless communication technology is playing an important role in our daily life. People use wireless devices not only as a conventional communication device but also as tracking and navigation tool, web browsing tool, data storage and transfer tool and so for many other reasons. Based on the user demand, wireless communication engineers try to accommodate as many as possible wireless systems and applications in a single device and therefore, creates a multifunctional device. Antenna, as an integral part of any wireless communication systems, should also be evolved and adjusted with development of wireless transceiver systems. Therefore multifunctional antennas have been introduced to support and enhance the functionality on modern wireless systems. The main focus and contribution of this thesis is design of novel multifunctional microstrip antennas with frequency agility, polarization reconfigurablity, dual null steering capability and phased array antenna with beam steering performance. In this thesis, first, a wide bandwidth(1.10 GHz to 1.60 GHz) right-handed circularly polarized (RHCP) directional antenna for global positioning system (GPS) satellite receive application has been introduced which covers all the GPS bands starting from L1 to L5. This design consists of two crossed bow-tie dipole antennas fed with sequentially phase rotated feed network backed with an artificial high impedance surface (HIS) structure to generate high gain directional radiation patterns. This design shows good CP gain and axial ratio (AR) and wide beamwidth performance. Although this design has good radiation quality, the size and the weight can be reduced as future study. In the second design, a frequency agile antenna was developed which also covers the L-band (L1 to L5) satellite communication frequencies. This frequency agile antenna was designed and realized by new implementation of varactor diodes in the geometry of a circular patch antenna. Beside wide frequency agility (1.17 GHz to 1.58 GHz), full polarization reconfiguration was added to the design by controlling ports excitation of circular patch using RF switches (vertical linear, horizontal linear, right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP)). This deign maintains good gain and radiation efficiency over the tunable range as well as acceptable co-polarization and cross-polarization separation for different polarizations. Since many communications applications require beam steering ability, in our third design, we designed and developed a linear phased array antenna using a modified version of our frequency agile polarization reconfigurable antenna for beam steering applications. This design offers wide frequency agility (1.50 GHz to 2.40 GHz), full polarization reconfiguration (vertical linear, horizontal linear, LHCP and RHCP) as well as beam steering of +/-52° and +/-28° at 1.5 GHz and 2.4 GHz, respectively. In this 1x4 array, the excitation magnitude and phase of each element was controlled by an analog beamforming feed network (BFN) for beam steering purposes. The required excitation for each element to steer the beam toward a desired location was calculated using projection matrix method (PMM) which uses measured active element pattern (AEP) as its input. This array antenna performance for frequency agility, radiation quality for each polarization and beam steering capability was obtained in the acceptable range. In the last design, the full spherical dual null steering capability of a triple mode circular microstrip patch antenna was investigated. By combining the radiation patterns of three individual modes of microstrip circular patch antenna, two nulls have been generated. These nulls can be repositioned in the upper hemisphere by controlling excitation ratio of each mode. The modes excitation ratio to steer the nulls toward the desired positions was calculated using a derivative free hybrid optimization method. This optimization method uses particle swarm optimization (PSO) combined with pattern search (PS) to find the optimum modes excitation ratio which minimizes the received power at the null positions. The calculated coefficients were applied to the multimode antenna using an analog BFN. This design shows an independent dual null steering with null depth of around 20 dB. Discussion about the proposed antennas included detailed theoretical analysis, numerical simulation and optimizations, beam forming and null steering algorithms, fabrication of the antennas and its control/beamforming feed networks along with the associated bias networks, microcontroller units, and finally its characterization (impedance matching, gain and 2D and 3D radiation patterns). The research work was performed at the Antenna and Microwave Lab (AML) which has the required resources including full wave analysis tools, PCB milling machine, surface mount component soldering station, vector network analyzers, and far-field/spherical near-field radiation pattern measurement system.

Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

NASA Astrophysics Data System (ADS)

Azzam, R. M. A.; Howlader, M. M. K.; Georgiou, T. Y.

1995-08-01

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectance-versus-angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p -polarized, s -polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented.

Directivity of the radio emission from the K1 dwarf star AB Doradus

NASA Technical Reports Server (NTRS)

Lim, Jeremy; White, Stephen M.; Nelson, Graam J.; Benz, Arnold O.

1994-01-01

We present measurements of the spectrum and polarization of the flaring radio emission from the K1 dwarf star AB Doradus, together with previously reported single frequency measurements (with no polarization information) on 3 other days. On all 4 days spanning a 6 month period, the emission was strong and, when folded with the stellar rotation period, showed similar time variations with two prominant peaks at phase 0.35 and 0.75. These peaks coincide in longitude with two large starspots identified from the stellar optical light curve and have half-powe widths as small as 0.1 rotations and no larger than 0.2 rotations. The modulated emission shows no measurable circular polarization, and its two peaks have different turnover frequencies.

Polarity of the Amphibian Egg

NASA Technical Reports Server (NTRS)

Malacinski, G. M.

1983-01-01

Amphibian egg polarity and the mechanism which generates the polarity is addressed. Of particular concern is the question of whether the activation rotation which responds to gravity is a prerequisite for normal development.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Junjie; Jia, Hongzhi, E-mail: hzjia@usst.edu.cn

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 resultsmore » are consistent and demonstrate the rationality and validity of this method.« less

Direct numerical simulation of moderate-Reynolds-number flow past arrays of rotating spheres

NASA Astrophysics Data System (ADS)

Zhou, Qiang; Fan, Liang-Shih

2015-07-01

Direct numerical simulations with an immersed boundary-lattice Boltzmann method are used to investigate the effects of particle rotation on flows past random arrays of mono-disperse spheres at moderate particle Reynolds numbers. This study is an extension of a previous study of the authors [Q. Zhou and L.-S. Fan, "Direct numerical simulation of low-Reynolds-number flow past arrays of rotating spheres," J. Fluid Mech. 765, 396-423 (2015)] that explored the effects of particle rotation at low particle Reynolds numbers. The results of this study indicate that as the particle Reynolds number increases, the normalized Magnus lift force decreases rapidly when the particle Reynolds number is in the range lower than 50. For the particle Reynolds number greater than 50, the normalized Magnus lift force approaches a constant value that is invariant with solid volume fractions. The proportional dependence of the Magnus lift force on the rotational Reynolds number (based on the angular velocity and the diameter of the spheres) observed at low particle Reynolds numbers does not change in the present study, making the Magnus lift force another possible factor that can significantly affect the overall dynamics of fluid-particle flows other than the drag force. Moreover, it is found that both the normalized drag force and the normalized torque increase with the increase of the particle Reynolds number and the solid volume fraction. Finally, correlations for the drag force, the Magnus lift force, and the torque in random arrays of rotating spheres at arbitrary solids volume fractions, rotational Reynolds numbers, and particle Reynolds numbers are formulated.

A Rotating Source Polarization Measurement Technique Using Two Circularly Polarized Antennas

DTIC Science & Technology

2016-07-15

antenna with high polarization purity. The axial ratio of the polarization ellipse was determined from the ripple in the voltage received by the...is shown in Fig. 6. The linear phase progression has been removed from the phase measurements to show a ripple . The corresponding polarization ratio

Preliminary status of POLICAN: A near-infrared imaging polarimeter

NASA Astrophysics Data System (ADS)

Devaraj, R.; Luna, A.; Carrasco, L.; Mayya, Y. D.

2015-10-01

POLICAN is a near-infrared (J, H, K) imaging polarimeter developed for the Cananea near infrared camera (CANICA) at the 2.1m telescope of the Guillermo Haro Astrophysical Observatory (OAGH) located at Cananea, Sonora, México. The camera has a 1024 x 1024 HgCdTe detector (HAWAII array) with a plate scale of 0.32 arcsec/pixel providing a field of view of 5.5 x 5.5 arcmin. POLICAN is mounted externally to CANICA for narrow-field (f/12) linear polarimetric observations. It consists of a rotating super achromatic (1-2.7μm) half waveplate and a fixed wire-grid polarizer as the analyzer. The light is modulated by setting the half waveplate at different angles (0°, 22.5°, 45°, 67.5°) and linear combinations of the Stokes parameters (I, Q and U) are obtained. Image reduction and removal of instrumental polarization consist of dark noise subtraction, polarimetric flat fielding and background sky subtraction. Polarimetric calibration is performed by observing polarization standards available in the literature. The astrometry correction is performed by matching common stars with the Two Micron All Sky Survey. POLICAN's bright and limiting magnitudes are approximately 6th and 16th magnitude, which correspond to saturation and photon noise, respectively. POLICAN currently achieves a polarimetric accuracy about 3.0% and polarization angle uncertainties within 3°. Preliminary observations of star forming regions are being carried out in order to study their magnetic field properties.

Variations in Rotation Rate and Polar Motion of a Non-hydrostatic Titan

NASA Astrophysics Data System (ADS)

Van Hoolst, T.; Coyette, A.; Baland, R. M.

2017-12-01

Observations of the rotation of large synchronously rotating satellites such as Titan can help to probe their interior. Previous studies (Van Hoolst et al. 2013, Richard et al. 2014, Coyette et al. 2016) mostly assume that Titan is in hydrostatic equilibrium, although several measurements indicate that it deviates from such a state. Here we investigate the effect of non-hydrostatic equilibrium and of flow in the subsurface ocean on the rotation of Titan. We consider (1) the periodic changes in Titan's rotation rate with a period equal to Titan's orbital period (diurnal librations) as a result of the gravitational torque exerted by Saturn, (2) the periodic changes in Titan's rotation rate with a main period equal to half the orbital period of Saturn (seasonal librations) and due to the dynamic variations in the atmosphere of Titan and (3) the periodic changes of the axis of rotation with respect to the figure axis of Titan (polar motion) with a main period equal to the orbital period of Saturn and due to the dynamic variations in the atmosphere of Titan. The non-hydrostatic mass distribution significantly influences the amplitude of the diurnal and seasonal librations. It is less important for polar motion, which is sensitive to flow in the subsurface ocean. The smaller than synchronous rotation rate measured by Cassini (Meriggiola 2016) can be explained by the atmospheric forcing.

Testing CPT Symmetry with Current and Future CMB Measurements

NASA Astrophysics Data System (ADS)

Li, Si-Yu; Xia, Jun-Qing; Li, Mingzhe; Li, Hong; Zhang, Xinmin

2015-02-01

In this paper, we use the current and future cosmic microwave background (CMB) experiments to test the Charge-Parity-Time Reversal (CPT) symmetry. We consider a CPT-violating interaction in the photon sector {L}_cs˜ p_μ A_ν \\tilde{F}μ ν , which gives rise to a rotation of the polarization vectors of the propagating CMB photons. By combining the 9 yr WMAP, BOOMERanG 2003, and BICEP1 observations, we obtain the current constraint on the isotropic rotation angle \\bar{α } = -2.12 +/- 1.14 (1σ), indicating that the significance of the CPT violation is about 2σ. Here, we particularly take the systematic errors of CMB measurements into account. Then, we study the effects of the anisotropies of the rotation angle [Δ {α }({\\hat{n}})] on the CMB polarization power spectra in detail. Due to the small effects, the current CMB polarization data cannot constrain the related parameters very well. We obtain the 95% C.L. upper limit of the variance of the anisotropies of the rotation angle C α(0) < 0.035 from all of the CMB data sets. More interestingly, including the anisotropies of rotation angle could lower the best-fit value of r and relax the tension on the constraints of r between BICEP2 and Planck. Finally, we investigate the capabilities of future Planck polarization measurements on \\bar{α } and Δ {α }({\\hat{n}}). Benefited from the high precision of Planck data, the constraints of the rotation angle can be significantly improved.

Quantum Computation using Arrays of N Polar Molecules in Pendular States.

PubMed

Wei, Qi; Cao, Yudong; Kais, Sabre; Friedrich, Bretislav; Herschbach, Dudley

2016-11-18

We investigate several aspects of realizing quantum computation using entangled polar molecules in pendular states. Quantum algorithms typically start from a product state |00⋯0⟩ and we show that up to a negligible error, the ground states of polar molecule arrays can be considered as the unentangled qubit basis state |00⋯0⟩ . This state can be prepared by simply allowing the system to reach thermal equilibrium at low temperature (<1 mK). We also evaluate entanglement, characterized by concurrence of pendular state qubits in dipole arrays as governed by the external electric field, dipole-dipole coupling and number N of molecules in the array. In the parameter regime that we consider for quantum computing, we find that qubit entanglement is modest, typically no greater than 10 -4 , confirming the negligible entanglement in the ground state. We discuss methods for realizing quantum computation in the gate model, measurement-based model, instantaneous quantum polynomial time circuits and the adiabatic model using polar molecules in pendular states. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection of birefringent microcrystals in bile

DOEpatents

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.

Non-duplicate polarization-diversity 8 × 8 Si-wire PILOSS switch integrated with polarization splitter-rotators.

PubMed

Tanizawa, Ken; Suzuki, Keijiro; Ikeda, Kazuhiro; Namiki, Shu; Kawashima, Hitoshi

2017-05-15

We demonstrate a fully integrated polarization-diversity 8 × 8 thermo-optic Si-wire switch that uses only a single path-independent insertion loss (PILOSS) switch matrix. All input/output ports of the PILOSS switch matrix are uniquely assigned for polarization diversity without switch duplication. To integrate polarization splitter-rotators on a chip, we propose a compact path-length-equalized polarization-diversity switch configuration. Polarization-dependent loss (PDL) and differential group delay (DGD) are minimized. The 8 × 8 switch is fabricated by the CMOS-compatible fabrication process on 300-mm diameter wafer and additional etching of upper cladding after dicing. The chip size is 7 × 10.5 mm 2 . A PDL of 2 dB and a DGD of 1.5 ps are achieved. The crosstalk in the worst-case scenario is -20 dB in the full C-band.

(abstract) Effect of Long Period Ocean Tides on the Earth's Rotation

NASA Technical Reports Server (NTRS)

Gross, R. S.; Chao, B. F.; Desai, S.

1996-01-01

The second-degree zonal tide raising potential, which is responsible for tidal changes in the Earth's rotation rate and length-of-day, is symmetric about the polar axis and hence can excite the Earth's polar motion only through its action upon nonaxisymmetric features of the Earth such as the oceans. Ocean tidal excitation of polar motion in the diurnal and semidiurnal tidal bands has been previously detected and extensively examined. Here, the detection of ocean tidal excitation of polar motion in the long-period tidal band, specifically at the Mf' (13.63-day) and Mf (13.66-day) tidal frequencies, is reported.

Modulus design multiwavelength polarization microscope for transmission Mueller matrix imaging.

PubMed

Zhou, Jialing; He, Honghui; Chen, Zhenhua; Wang, Ye; Ma, Hui

2018-01-01

We have developed a polarization microscope based on a commercial transmission microscope. We replace the halogen light source by a collimated LED light source module of six different colors. We use achromatic polarized optical elements that can cover the six different wavelength ranges in the polarization state generator (PSG) and polarization state analyzer (PSA) modules. The dual-rotating wave plate method is used to measure the Mueller matrix of samples, which requires the simultaneous rotation of the two quarter-wave plates in both PSG and PSA at certain angular steps. A scientific CCD detector is used as the image receiving module. A LabView-based software is developed to control the rotation angels of the wave plates and the exposure time of the detector to allow the system to run fully automatically in preprogrammed schedules. Standard samples, such as air, polarizers, and quarter-wave plates, are used to calibrate the intrinsic Mueller matrix of optical components, such as the objectives, using the eigenvalue calibration method. Errors due to the images walk-off in the PSA are studied. Errors in the Mueller matrices are below 0.01 using air and polarizer as standard samples. Data analysis based on Mueller matrix transformation and Mueller matrix polarization decomposition is used to demonstrate the potential application of this microscope in pathological diagnosis. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Hierarchical scheme for detecting the rotating MIMO transmission of the in-door RGB-LED visible light wireless communications using mobile-phone camera

NASA Astrophysics Data System (ADS)

Chen, Shih-Hao; Chow, Chi-Wai

2015-01-01

Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the light-emitting-diode (LED) based visible light communication (VLC) systems. The MIMO VLC system that uses the mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from the n×n Red-Green-Blue (RGB) LED array is desirable. The key step of decoding this signal is to detect the signal direction. If the LED transmitter (Tx) is rotated, the Rx may not realize the rotation and transmission error can occur. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n×n RGB LED array as the MIMO Tx. In our study, a novel two dimensional Hadamard coding scheme is proposed. Using the different LED color layers to indicate the rotation, a low complexity rotation detection method can be used for improving the quality of received signal. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme.

Spatiotemporal polarization modulation microscopy with a microretarder array

NASA Astrophysics Data System (ADS)

Ding, Changqin; Ulcickas, James R. W.; Simpson, Garth J.

2018-02-01

A patterned microretarder array positioned in the rear conjugate plane of a microscope enables rapid polarizationdependent nonlinear optical microscopy. The pattern introduced to the array results in periodic modulation of the polarization-state of the incident light as a function of position within the field of view with no moving parts or active control. Introduction of a single stationary optical element and a fixed polarizer into the beam of a nonlinear optical microscope enabled nonlinear optical tensor recovery, which informs on local structure and orientation. Excellent agreement was observed between the measured and predicted second harmonic generation (SHG) of z-cut quartz, selected as a test system with well-established nonlinear optical properties. Subsequent studies of spatially varying samples further support the general applicability of this relatively simple strategy for detailed polarization analysis in both conventional and nonlinear optical imaging of structurally diverse samples.

Antenna-coupled TES bolometer arrays for CMB polarimetry

NASA Astrophysics Data System (ADS)

Kuo, C. L.; Bock, J. J.; Bonetti, J. A.; Brevik, J.; Chattopadhyay, G.; Day, P. K.; Golwala, S.; Kenyon, M.; Lange, A. E.; LeDuc, H. G.; Nguyen, H.; Ogburn, R. W.; Orlando, A.; Transgrud, A.; Turner, A.; Wang, G.; Zmuidzinas, J.

2008-07-01

We describe the design and performance of polarization selective antenna-coupled TES arrays that will be used in several upcoming Cosmic Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully lithographic polarimeter arrays utilize planar phased-antennas for collimation (F/4 beam) and microstrip filters for band definition (25% bandwidth). These devices demonstrate high optical efficiency, excellent beam shapes, and well-defined spectral bands. The dual-polarization antennas provide well-matched beams and low cross polarization response, both important for high-fidelity polarization measurements. These devices have so far been developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave atmospheric windows for CMB observations. In the near future, the flexible microstrip-coupled architecture can provide photon noise-limited detection for the entire frequency range of the CMBPOL mission. This paper is a summary of the progress we have made since the 2006 SPIE meeting in Orlando, FL.

Highly accelerated acquisition and homogeneous image reconstruction with rotating RF coil array at 7T-A phantom based study.

PubMed

Li, Mingyan; Zuo, Zhentao; Jin, Jin; Xue, Rong; Trakic, Adnan; Weber, Ewald; Liu, Feng; Crozier, Stuart

2014-03-01

Parallel imaging (PI) is widely used for imaging acceleration by means of coil spatial sensitivities associated with phased array coils (PACs). By employing a time-division multiplexing technique, a single-channel rotating radiofrequency coil (RRFC) provides an alternative method to reduce scan time. Strategically combining these two concepts could provide enhanced acceleration and efficiency. In this work, the imaging acceleration ability and homogeneous image reconstruction strategy of 4-element rotating radiofrequency coil array (RRFCA) was numerically investigated and experimental validated at 7T with a homogeneous phantom. Each coil of RRFCA was capable of acquiring a large number of sensitivity profiles, leading to a better acceleration performance illustrated by the improved geometry-maps that have lower maximum values and more uniform distributions compared to 4- and 8-element stationary arrays. A reconstruction algorithm, rotating SENSitivity Encoding (rotating SENSE), was proposed to provide image reconstruction. Additionally, by optimally choosing the angular sampling positions and transmit profiles under the rotating scheme, phantom images could be faithfully reconstructed. The results indicate that, the proposed technique is able to provide homogeneous reconstructions with overall higher and more uniform signal-to-noise ratio (SNR) distributions at high reduction factors. It is hoped that, by employing the high imaging acceleration and homogeneous imaging reconstruction ability of RRFCA, the proposed method will facilitate human imaging for ultra high field MRI. Copyright © 2013 Elsevier Inc. All rights reserved.

Snakes, rotators, serpents and the octahedral group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fieguth, T.

1986-04-01

Specific configurations of horizontal and vertical bending magnets are given that, when acting on the spin polarization vector of a particle beam, generate a group of 24 operators isomorphic to the group of rotational symmetries of a cube, known as the octahedral group. Some of these configurations have the feature of converting transversely polarized beams to longitudinally polarized beams (or vice versa) at the midpoint of the configuration for, in principle, all beam energies. Since the first order optical transfer matrix for each half of these configurations is nearly that of a drift region, the external geometry remains unchanged andmore » midpoint dispersion is not introduced. Changing field strengths and/or polarities allows a configuration to serve as either a Snake(1/sup st/ or 2/sup nd/ kind) or a Rotator, where in both cases the spin polarization is longitudinal at the midpoint. In this conceptualization, emphasis has been placed on electron beams and, indeed, for these beams some practical applications can be envisioned. However, due to the relatively high integrated field strengths required, application of these concepts to proton beams may be more promising.« less

Ray Scattering by an Arbitrarily Oriented Spheroid: 2. Transmission and Cross-polarization Effects

NASA Technical Reports Server (NTRS)

Lock, James A.

1996-01-01

Transmission of an arbitrarily polarized plane wave by an arbitrarily oriented spheroid in the short-wavelength limit is considered in the context of ray theory. The transmitted electric field is added to the diffracted plus reflected ray-theory electric field that was previously derived to obtain an approximation to the far-zone scattered intensity in the forward hemisphere. Two different types of cross-polarization effects are found. These are: (a) a rotation of the polarization state of the transmitted rays from when they are referenced with respect to their entrance into the spheroid to when they are referenced with respect to their exit from it and (b) a rotation of the polarization state of the transmitted rays when they are referenced with respect to the polarization state of the diffracted plus reflected rays.

Ultracompact and high efficient silicon-based polarization splitter-rotator using a partially-etched subwavelength grating coupler

PubMed Central

Xu, Yin; Xiao, Jinbiao

2016-01-01

On-chip polarization manipulation is pivotal for silicon-on-insulator material platform to realize polarization-transparent circuits and polarization-division-multiplexing transmissions, where polarization splitters and rotators are fundamental components. In this work, we propose an ultracompact and high efficient silicon-based polarization splitter-rotator (PSR) using a partially-etched subwavelength grating (SWG) coupler. The proposed PSR consists of a taper-integrated SWG coupler combined with a partially-etched waveguide between the input and output strip waveguides to make the input transverse-electric (TE) mode couple and convert to the output transverse-magnetic (TM) mode at the cross port while the input TM mode confine well in the strip waveguide during propagation and directly output from the bar port with nearly neglected coupling. Moreover, to better separate input polarizations, an additional tapered waveguide extended from the partially-etched waveguide is also added. From results, an ultracompact PSR of only 8.2 μm in length is achieved, which is so far the reported shortest one. The polarization conversion loss and efficiency are 0.12 dB and 98.52%, respectively, together with the crosstalk and reflection loss of −31.41/−22.43 dB and −34.74/−33.13 dB for input TE/TM mode at wavelength of 1.55 μm. These attributes make the present device suitable for constructing on-chip compact photonic integrated circuits with polarization-independence. PMID:27306112

Excitation of a Parallel Plate Waveguide by an Array of Rectangular Waveguides

NASA Technical Reports Server (NTRS)

Rengarajan, Sembiam

2011-01-01

This work addresses the problem of excitation of a parallel plate waveguide by an array of rectangular waveguides that arises in applications such as the continuous transverse stub (CTS) antenna and dual-polarized parabolic cylindrical reflector antennas excited by a scanning line source. In order to design the junction region between the parallel plate waveguide and the linear array of rectangular waveguides, waveguide sizes have to be chosen so that the input match is adequate for the range of scan angles for both polarizations. Electromagnetic wave scattered by the junction of a parallel plate waveguide by an array of rectangular waveguides is analyzed by formulating coupled integral equations for the aperture electric field at the junction. The integral equations are solved by the method of moments. In order to make the computational process efficient and accurate, the method of weighted averaging was used to evaluate rapidly oscillating integrals encountered in the moment matrix. In addition, the real axis spectral integral is evaluated in a deformed contour for speed and accuracy. The MoM results for a large finite array have been validated by comparing its reflection coefficients with corresponding results for an infinite array generated by the commercial finite element code, HFSS. Once the aperture electric field is determined by MoM, the input reflection coefficients at each waveguide port, and coupling for each polarization over the range of useful scan angles, are easily obtained. Results for the input impedance and coupling characteristics for both the vertical and horizontal polarizations are presented over a range of scan angles. It is shown that the scan range is limited to about 35 for both polarizations and therefore the optimum waveguide is a square of size equal to about 0.62 free space wavelength.

Spin Chirality of Cu3 and V3 Nanomagnets. 1. Rotation Behavior of Vector Chirality, Scalar Chirality, and Magnetization in the Rotating Magnetic Field, Magnetochiral Correlations.

PubMed

Belinsky, Moisey I

2016-05-02

The rotation behavior of the vector chirality κ, scalar chirality χ, and magnetization M in the rotating magnetic field H1 is considered for the V3 and Cu3 nanomagnets, in which the Dzialoshinsky-Moriya coupling is active. The polar rotation of the field H1 of the given strength H1 results in the energy spectrum characterized by different vector and scalar chiralities in the ground and excited states. The magnetochiral correlations between the vector and scalar chiralities, energy, and magnetization in the rotating field were considered. Under the uniform polar rotation of the field H1, the ground-state chirality vector κI performs sawtooth oscillations and the magnetization vector MI performs the sawtooth oscillating rotation that is accompanied by the correlated transformation of the scalar chirality χI. This demonstrates the magnetochiral effect of the joint rotation behavior and simultaneous frustrations of the spin chiralities and magnetization in the rotating field, which are governed by the correlation between the chiralities and magnetization.

Single Molecule and Nanoparticle Imaging in Biophysical, Surface, and Photocatalysis Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ha, Ji Won

2013-01-01

A differential interference contrast (DIC) polarization anisotropy is reported that was successfully used for rotational tracking of gold nanorods attached onto a kinesin-driven microtubule. A dual-wavelength detection of single gold nanorods rotating on a live cell membrane is described. Both transverse and longitudinal surface plasmon resonance (SPR) modes were used for tracking the rotational motions during a fast dynamic process under a DIC microscope. A novel method is presented to determine the full three-dimensional (3D) orientation of single plasmonic gold nanorods rotating on live cell membranes by combining DIC polarization anisotropy with an image pattern recognition technique. Polarization- and wavelength-sensitivemore » DIC microscopy imaging of 2- m long gold nanowires as optical probes in biological studies is reported. A new method is demonstrated to track 3D orientation of single gold nanorods supported on a gold film without angular degeneracy. The idea is to use the interaction (or coupling) of gold nanorods with gold film, yielding characteristic scattering patterns such as a doughnut shape. Imaging of photocatalytic activity, polarity and selectivity on single Au-CdS hybrid nanocatalysts using a high-resolution superlocalization fluorescence imaging technique is described.« less

Torque Induced on Lipid Microtubules with Optical Tweezers

NASA Astrophysics Data System (ADS)

wichean, T. Na; Charrunchon, S.; Pattanaporkratana, A.; Limtrakul, J.; Chattham, N.

2017-09-01

Chiral Phospholipids are found self-assembled into cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We investigate an individual lipid microtubule under a single optical trap of 532 nm linearly polarized laser. Spontaneous rotation of a lipid tubule induced by radiation torque was observed with only one sense of rotation caused by chirality of a lipid tubule. Rotation discontinued once the high refractive index axis of a lipid tubule aligned with a polarization axis of the laser. We further explored a lipid tubule under circularly polarized optical trap. It was found that a lipid tubule was continuously rotated confirming the tubule birefringent property. We modified the shape of optical trap by cylindrical lens obtaining an elliptical profile optical trap. A lipid tubule can be aligned along the elongated length of optical trap. We reported an investigation of competition between polarized light torque on a birefringent lipid tubule versus torque from intensity gradient of an elongated optical trap.

Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials.

PubMed

Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K V; Rödel, Jürgen; Xing, Xianran

2017-07-07

High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic M_{A} structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic M_{B}, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

Stable L-band multi-wavelength SOA fiber laser based on polarization rotation.

PubMed

Liu, Tonghui; Jia, Dongfang; Yang, Tianxin; Wang, Zhaoying; Liu, Ying

2017-04-01

We propose and experimentally demonstrate a stable multi-wavelength fiber ring laser operating in the L-band with wavelength spacing of 25 GHz. The mechanism is induced by a polarization rotation intensity equalizer consisting of a semiconductor optical amplifier and polarization devices. A Fabry-Perot filter is inserted into the cavity to serve as a multi-wavelength selection device. Stable L-band multi-wavelength lasing with 3 dB uniformity of 21.2 nm, and simultaneous oscillation of 101 lines with wavelength spacing of 25 GHz, is obtained.

Tunable multiwavelength SOA fiber laser with ultra-narrow wavelength spacing based on nonlinear polarization rotation.

PubMed

Zhang, Zuxing; Wu, Jian; Xu, Kun; Hong, Xiaobin; Lin, Jintong

2009-09-14

A tunable multiwavelength fiber laser with ultra-narrow wavelength spacing and large wavelength number using a semiconductor optical amplifier (SOA) has been demonstrated. Intensity-dependent transmission induced by nonlinear polarization rotation in the SOA accounts for stable multiwavelength operation with wavelength spacing less than the homogenous broadening linewidth of the SOA. Stable multiwavelength lasing with wavelength spacing as small as 0.08 nm and wavelength number up to 126 is achieved at room temperature. Moreover, wavelength tuning of 20.2 nm is implemented via polarization tuning.

Propagation of Polarized Cosmic Microwave Background Radiation in an Anisotropic Magnetized Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moskaliuk, S. S.

2010-01-01

The polarization plane of the cosmic microwave background radiation (CMBR) can be rotated either in a space-time with metric of anisotropic type and in a magnetized plasma or in the presence of a quintessential background with pseudoscalar coupling to electromagnetism. A unified treatment of these three phenomena is presented for cold anisotropic plasma at the pre-recombination epoch. It is argued that the generalized expressions derived in the present study may be relevant for direct searches of a possible rotation of the cosmic microwave background polarization.

Image acquisition device of inspection robot based on adaptive rotation regulation of polarizer

NASA Astrophysics Data System (ADS)

Dong, Maoqi; Wang, Xingguang; Liang, Tao; Yang, Guoqing; Zhang, Chuangyou; Gao, Faqin

2017-12-01

An image processing device of inspection robot with adaptive polarization adjustment is proposed, that the device includes the inspection robot body, the image collecting mechanism, the polarizer and the polarizer automatic actuating device. Where, the image acquisition mechanism is arranged at the front of the inspection robot body for collecting equipment image data in the substation. Polarizer is fixed on the automatic actuating device of polarizer, and installed in front of the image acquisition mechanism, and that the optical axis of the camera vertically goes through the polarizer and the polarizer rotates with the optical axis of the visible camera as the central axis. The simulation results show that the system solves the fuzzy problems of the equipment that are caused by glare, reflection of light and shadow, and the robot can observe details of the running status of electrical equipment. And the full coverage of the substation equipment inspection robot observation target is achieved, which ensures the safe operation of the substation equipment.

A New Concept in Helicopter Communications Antennas

NASA Technical Reports Server (NTRS)

Pogorzelski, R. J.

1995-01-01

We consider a five blade rotor and envision an array with one element mounted on each rotor blade. These elements may be dipoles or horizontal slots depending upon the desired polarization characteristics. For example, slots would provide vertical polarization on horizontal paths. The array is excited through a novel type of rotary joint located on the rotor shaft.

Interferometric Observations of the SiO High J Transition Maser associated with VY Canis Majoris with the Submillimeter Array

NASA Astrophysics Data System (ADS)

Shinnaga, H.; Moran, J. M.; Young, K. H.; Ho, P. T. P.

2005-12-01

We imaged the SiO maser emission of J=5-4 in the v=1 state associated with the peculiar red supergiant VY Canis Majoris using the partially completed Submillimeter Array. We identified seven maser components and measured the relative positions at sub-arcsecond scale in the high J transition for the first time. We have also measured the polarization of these maser components. The strongest maser feature has a linear polarization of ˜ 60%, and its direction of polarization is approximately aligned with the bipolar axis. Such a high degree of polarization suggests that radiative pumping is probably responsible for the maser inversion. Five of the other maser features have significant linear polarization.

Polar Environmental Monitoring

NASA Technical Reports Server (NTRS)

Nagler, R. G.; Schulteis, A. C.

1979-01-01

The present and projected benefits of the polar regions were reviewed and then translated into information needs in order to support the array of polar activities anticipated. These needs included measurement sensitivities for polar environmental data (ice/snow, atmosphere, and ocean data for integrated support) and the processing and delivery requirements which determine the effectiveness of environmental services. An assessment was made of how well electromagnetic signals can be converted into polar environmental information. The array of sensor developments in process or proposed were also evaluated as to the spectral diversity, aperture sizes, and swathing capabilities available to provide these measurements from spacecraft, aircraft, or in situ platforms. Global coverage and local coverage densification options were studied in terms of alternative spacecraft trajectories and aircraft flight paths.

A new polarimetric active radar calibrator and calibration technique

NASA Astrophysics Data System (ADS)

Tang, Jianguo; Xu, Xiaojian

2015-10-01

Polarimetric active radar calibrator (PARC) is one of the most important calibrators with high radar cross section (RCS) for polarimetry measurement. In this paper, a new double-antenna polarimetric active radar calibrator (DPARC) is proposed, which consists of two rotatable antennas with wideband electromagnetic polarization filters (EMPF) to achieve lower cross-polarization for transmission and reception. With two antennas which are rotatable around the radar line of sight (LOS), the DPARC provides a variety of standard polarimetric scattering matrices (PSM) through the rotation combination of receiving and transmitting polarization, which are useful for polarimatric calibration in different applications. In addition, a technique based on Fourier analysis is proposed for calibration processing. Numerical simulation results are presented to demonstrate the superior performance of the proposed DPARC and processing technique.

Probing the gravitational Faraday rotation using quasar X-ray microlensing.

PubMed

Chen, Bin

2015-11-17

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission.

Chaotic behavior in electro-rotation

NASA Astrophysics Data System (ADS)

Lemaire, E.; Lobry, L.

2002-11-01

We study the dynamics of an insulating cylinder in a weakly conducting liquid when submitted to a DC electric field. The cylinder is free to rotate along its long axis which is perpendicular to the applied field. Above a threshold value of the electric field, the cylinder rotates in either direction with constant angular velocity. This instability is known as Quincke rotation and can be easily understood by considering the polarization induced by the free charges accumulation on the cylinder surface. Here we present preliminary experimental results which exhibit a chaotic dynamics of the cylinder for higher electric fields: the velocity is no longer constant and the rotation direction changes randomly. By taking into account the finite Maxwell-Wagner polarization relaxation time, we show that this chaotic behavior can be described by the Lorenz equations.

The RINGO2 and DIPOL optical polarization catalogue of blazars

NASA Astrophysics Data System (ADS)

Jermak, H.; Steele, I. A.; Lindfors, E.; Hovatta, T.; Nilsson, K.; Lamb, G. P.; Mundell, C.; Barres de Almeida, U.; Berdyugin, A.; Kadenius, V.; Reinthal, R.; Takalo, L.

2016-11-01

We present ˜2000 polarimetric and ˜3000 photometric observations of 15 γ-ray bright blazars over a period of 936 days (2008-10-11 to 2012-10-26) using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT) and Fermi-LAT γ-ray data). In 11 out of 15 sources we identify a total of 19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We group the sources into subclasses based on their broad-band spectral characteristics and compare their observed optical and γ-ray properties. We find that (1) the optical magnitude and γ-ray flux are positively correlated, (2) EVPA rotations can occur in any blazar subclass, four sources show rotations that go in one direction and immediately rotate back, (3) we see no difference in the γ-ray flaring rates in the sample; flares can occur during and outside of rotations with no preference for this behaviour, (4) the average degree of polarization (DoP), optical magnitude and γ-ray flux are lower during an EVPA rotation compared with during non-rotation and the distribution of the DoP during EVPA rotations is not drawn from the same parent sample as the distribution outside rotations, (5) the number of observed flaring events and optical polarization rotations are correlated, however we find no strong evidence for a temporal association between individual flares and rotations and (6) the maximum observed DoP increases from ˜10 per cent to ˜30 per cent to ˜40 per cent for subclasses with synchrotron peaks at high, intermediate and low frequencies, respectively.

Studies of spin-exchange optical pumping

NASA Astrophysics Data System (ADS)

Chann, Bien

Although we still do not understand fully the alkali-alkali relaxation at pressures of an atmosphere or more, an important part of the spin-relaxation comes from the classical dipole-dipole anisotropic spin-axis interaction acting in triplet dimer molecules. The key observation is the existence of magnetic resonances in the magnetic decoupling curves which are predicted from the spin-axis interaction. We identified a new gas-phase, room temperature spin relaxation that is due to the spin-rotation coupling in bound 129Xe-Xe van der Waals molecules. This 129Xe-Xe molecular spin-relaxation is more than an order of magnitude stronger than the well-known 129 Xe-Xe binary spin-relaxation and is the fundamental spin-relaxation process at gas densities below 14 amagat. With external cavity diode laser array bar, we find, based on tests of several cells, that the power required to reach the same polarization is typically three times lower for the spectrally narrowed laser as compared to the unnarrowed diode array bar. This last result indicates that spectrally narrowed lasers are critical to obtaining the highest noble gas polarizations. Furthermore, we find, circularly polarized light propagating at an angle as small as a few degrees to the external magnetic field does not optically pump the atoms to full transparency and causes excess absorption of the pump beam. We measured the Rb-3He spin-exchange rate coefficients using three different methods. We obtained 6.73 +/- 0.12 x 10 -20 cm3/s for the repolarization method. We deduced the spin-exchange rate coefficient to be 6.61 +/- 0.12 x 10 -20 cm3/s for the rate balance method. The third method uses a temperature dependence relaxation of 3He and the deduced value is 8.85 +/- 0.32 x 10-20 cm3/s. This is about 30% higher than the other two methods. This implies a temperature-dependence wall-relaxation or a large value of anisotropic spin-exchange rate coefficient for Rb-3He and would explain the shortfall 3He measured polarization.

The E and B EXperiment: Implementation and Analysis of the 2009 Engineering Flight

NASA Astrophysics Data System (ADS)

Milligan, Michael Bryce

The E and B EXperiment (EBEX) is a balloon-borne telescope designed to map the polarization of the cosmic microwave background (CMB) and emission from galactic dust at millimeter wavelengths from 150 to 410 GHz. The primary science objectives of EBEX are to: detect or constrain the primordial B-mode polarization of the CMB predicted by inflationary cosmology; measure the CMB B-mode signal induced by gravitational lensing; and characterize the polarized thermal emission from interstellar dust. EBEX will observe a 420 square degree patch of the sky at high galactic latitude with a telescope and camera that provide an 8 arcminute beam at three observing bands (150, 250, and 410 GHz) and a 6.2 degree diffraction limited field of view to two large-format bolometer array focal planes. Polarimetry is achieved via a continuously rotating half-wave plate (HWP), and the optical system is designed from the ground up for control of sidelobe response and polarization systematic errors. EBEX is intended to execute fly or more Antarctic long duration balloon campaigns. In June 2009 EBEX completed a North American engineering flight launched from NASA's Columbia Scientific Ballooning Facility (CSBF) in Ft. Sumner, NM and operated in the stratosphere above 30 km altitude for ˜10 hours. During flight EBEX must be largely autonomous as it conducts pointed, scheduled observations; tunes and operates 1432 TES bolometers via 28 embedded Digital frequency-domain multiplexing (DfMux) computers; logs over 3 GiB/hour of science and housekeeping data to onboard redundant disk storage arrays; manages and dispatches jobs over a fault-tolerant onboard Ethernet network; and feeds a complex real-time data processing infrastructure on the ground via satellite and line-of-sight (LOS) downlinks. In this thesis we review the EBEX instrument, present the optical design and the computational architecture for in-flight control and data handling, and the quick-look software stack. Finally we describe the 2009 North American test flight and present analysis of data collected at the end of that flight that characterizes scan-synchronous signals and the expected response to emission from thermal dust in our galaxy.

Effects of translational and rotational motions and display polarity on visual performance.

PubMed

Feng, Wen-Yang; Tseng, Feng-Yi; Chao, Chin-Jung; Lin, Chiuhsiang Joe

2008-10-01

This study investigated effects of both translational and rotational motion and display polarity on a visual identification task. Three different motion types--heave, roll, and pitch--were compared with the static (no motion) condition. The visual task was presented on two display polarities, black-on-white and white-on-black. The experiment was a 4 (motion conditions) x 2 (display polarities) within-subjects design with eight subjects (six men and two women; M age = 25.6 yr., SD = 3.2). The dependent variables used to assess the performance on the visual task were accuracy and reaction time. Motion environments, especially the roll condition, had statistically significant effects on the decrement of accuracy and reaction time. The display polarity was significant only in the static condition.

Optical notch filter with tunable bandwidth based on guided-mode resonant polarization-sensitive spectral feature.

PubMed

Qian, Linyong; Zhang, Dawei; Dai, Bo; Wang, Qi; Huang, Yuanshen; Zhuang, Songlin

2015-07-13

A novel bandwidth-tunable notch filter is proposed based on the guided-mode resonance effect. The notch is created due to the superposition spectra response of two guided-mode resonant filters. The compact, bandwidth tuning capability is realized by taking advantage the effect of spectra-to-polarization sensitivity in one-dimensional classical guided-mode resonance filter, and using a liquid crystal polarization rotator for precise and simple polarization control. The operation principle and the design of the device are presented, and we demonstrate it experimentally. The central wavelength is fixed at 766.4 nm with a relatively symmetric profile. The full width at half maximum bandwidth could be tuned from 8.6 nm to 18.2 nm by controlling the applied voltage in electrically-driving polarization rotator.

Anisotropic Babinet-Invertible Metasurfaces to Realize Transmission-Reflection Switching for Orthogonal Polarizations of Light

NASA Astrophysics Data System (ADS)

Nakata, Yosuke; Urade, Yoshiro; Okimura, Kunio; Nakanishi, Toshihiro; Miyamaru, Fumiaki; Takeda, Mitsuo Wada; Kitano, Masao

2016-10-01

The electromagnetic properties of an extremely thin metallic checkerboard drastically change from resonant reflection (transmission) to resonant transmission (reflection) when the local electrical conductivity at the interconnection points of the checkerboard is switched. To date, such critical transitions of metasurfaces have been applied only when they have fourfold rotational symmetry, and their application to polarization control, which requires anisotropy, has been unexplored. To overcome this applicability limitation and open up alternative pathways for dynamic deep-subwavelength polarization control by utilizing critical transitions of checkerboardlike metasurfaces, we introduce a universal class of anisotropic Babinet-invertible metasurfaces enabling transmission-reflection switching for each orthogonally polarized wave. As an application of anisotropic Babinet-invertible metasurfaces, we experimentally realize a reconfigurable terahertz polarizer whose transmitting axis can be dynamically rotated by 90°.

Coherent Perfect Rotation: The conservative analogue of CPA

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Dawson, Nathan; Andrews, James

2012-06-01

The two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. In analogy with coherent perfect absorption (CPA) resonances, where counter-propagating light fields are completely converted into other degrees of freedom, we show that in a linear conservative medium only time-odd (Faraday) rotation is capable of coherent perfect rotation, by which we mean the complete transfer of any arbitrarily oriented polarization of light into the other orthogonal polarization via the application of phased counter-propagating light fields. This contributes to the understanding of the importance of time reversal symmetry in perfect mode conversion that may be of use in optical device design.

Scalar-vector soliton fiber laser mode-locked by nonlinear polarization rotation.

PubMed

Wu, Zhichao; Liu, Deming; Fu, Songnian; Li, Lei; Tang, Ming; Zhao, Luming

2016-08-08

We report a passively mode-locked fiber laser by nonlinear polarization rotation (NPR), where both vector and scalar soliton can co-exist within the laser cavity. The mode-locked pulse evolves as a vector soliton in the strong birefringent segment and is transformed into a regular scalar soliton after the polarizer within the laser cavity. The existence of solutions in a polarization-dependent cavity comprising a periodic combination of two distinct nonlinear waves is first demonstrated and likely to be applicable to various other nonlinear systems. For very large local birefringence, our laser approaches the operation regime of vector soliton lasers, while it approaches scalar soliton fiber lasers under the condition of very small birefringence.

Neural network approximation of nonlinearity in laser nano-metrology system based on TLMI

NASA Astrophysics Data System (ADS)

Olyaee, Saeed; Hamedi, Samaneh

2011-02-01

In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metrology system using three-longitudinal-mode laser heterodyne interferometer (TLMI) for length and displacement measurements is presented. We model nonlinearity errors that arise from elliptically and non-orthogonally polarized laser beams, rotational error in the alignment of laser head with respect to the polarizing beam splitter, rotational error in the alignment of the mixing polarizer, and unequal transmission coefficients in the polarizing beam splitter. Here we use a neural network algorithm based on the multi-layer perceptron (MLP) network. The simulation results show that multi-layer feed forward perceptron network is successfully applicable to real noisy interferometer signals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai,M.; Ptitsyn, V.; Roser, T.

To keep the spin tune in the spin depolarizing resonance free region is required for accelerating polarized protons to high energy. In RHIC, two snakes are located at the opposite side of each accelerator. They are configured to yield a spin tune of 1/2. Two pairs of spin rotators are located at either side of two detectors in each ring in RHIC to provide longitudinal polarization for the experiments. Since the spin rotation from vertical to longitudinal is localized between the two rotators, the spin rotators do not change the spin tune. However, due to the imperfection of the orbitsmore » around the snakes and rotators, the spin tune can be shifted. This note presents the impact of the horizontal orbital angle between the two snakes on the spin tune, as well as the effect of the vertical orbital angle between two rotators at either side of the collision point on the spin tune.« less

Polarization singularities and orbital angular momentum sidebands from rotational symmetry broken by the Pockels effect

PubMed Central

Lu, Xiancong; Wu, Ziwen; Zhang, Wuhong; Chen, Lixiang

2014-01-01

The law of angular momentum conservation is naturally linked to the rotational symmetry of the involved system. Here we demonstrate theoretically how to break the rotational symmetry of a uniaxial crystal via the electro-optic Pockels effect. By numerical method based on asymptotic expansion, we discover the 3D structure of polarization singularities in terms of C lines and L surfaces embedded in the emerging light. We visualize the controllable dynamics evolution of polarization singularities when undergoing the Pockels effect, which behaves just like the binary fission of a prokaryotic cell, i.e., the splitting of C points and fission of L lines are animated in analogy with the cleavage of nucleus and division of cytoplasm. We reveal the connection of polarization singularity dynamics with the accompanying generation of orbital angular momentum sidebands. It is unexpected that although the total angular momentum of light is not conserved, the total topological index of C points is conserved. PMID:24784778

Polarization singularities and orbital angular momentum sidebands from rotational symmetry broken by the Pockels effect.

PubMed

Lu, Xiancong; Wu, Ziwen; Zhang, Wuhong; Chen, Lixiang

2014-05-02

The law of angular momentum conservation is naturally linked to the rotational symmetry of the involved system. Here we demonstrate theoretically how to break the rotational symmetry of a uniaxial crystal via the electro-optic Pockels effect. By numerical method based on asymptotic expansion, we discover the 3D structure of polarization singularities in terms of C lines and L surfaces embedded in the emerging light. We visualize the controllable dynamics evolution of polarization singularities when undergoing the Pockels effect, which behaves just like the binary fission of a prokaryotic cell, i.e., the splitting of C points and fission of L lines are animated in analogy with the cleavage of nucleus and division of cytoplasm. We reveal the connection of polarization singularity dynamics with the accompanying generation of orbital angular momentum sidebands. It is unexpected that although the total angular momentum of light is not conserved, the total topological index of C points is conserved.

Seismic Excitation of the Polar Motion, 1977-1993

NASA Technical Reports Server (NTRS)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-01-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by CHAO and GROSS (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approximately 140deg E, away from the actual observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by CHAO and GROSS (1987), manifests some geodynamic behavior yet to be explored.

Seismic Excitation of the Polar Motion

NASA Technical Reports Server (NTRS)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-01-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by Chao and Gross (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approx. 140 deg E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by Chao and Gross (1987), manifests some geodynamic behavior yet to be explored.

Shallow water modeling of Jovian polar cyclone and vortices

NASA Astrophysics Data System (ADS)

Li, Cheng; Tabataba-Vakili, Fachreddin; Ingersoll, Andrew P.

2017-10-01

Jupiter’s polar atmosphere was observed for the first time by the Juno visible spectrum camera (JunoCAM) and Juno Infrared Auroral Mapper (JIRAM). Both the visible and infrared images show active vortices and weather systems that are unlike any polar regions previously seen or modeled on any of the planets in our solar system. We developed a global shallow water model on a sphere with poles rotated to the equator to investigate the formation, maintenance and dynamic regimes controlling the morphology of polar cyclones and vortices. Passive Lagrangian particles with finite life time are included to represent the clouds. We verified that a westward barotropically unstable jet can spontaneously break the axial symmetry into a polygon-shaped figure rotating rigidly around the rotation axis as reported by previous laboratory experiments. The number of sides of the polygon depends on the deformation radius and is insensitive to the initial condition. Why Jupiter’s pole is different from Saturn’s is still under investigation.

Polarization singularities and orbital angular momentum sidebands from rotational symmetry broken by the Pockels effect

NASA Astrophysics Data System (ADS)

Lu, Xiancong; Wu, Ziwen; Zhang, Wuhong; Chen, Lixiang

2014-05-01

The law of angular momentum conservation is naturally linked to the rotational symmetry of the involved system. Here we demonstrate theoretically how to break the rotational symmetry of a uniaxial crystal via the electro-optic Pockels effect. By numerical method based on asymptotic expansion, we discover the 3D structure of polarization singularities in terms of C lines and L surfaces embedded in the emerging light. We visualize the controllable dynamics evolution of polarization singularities when undergoing the Pockels effect, which behaves just like the binary fission of a prokaryotic cell, i.e., the splitting of C points and fission of L lines are animated in analogy with the cleavage of nucleus and division of cytoplasm. We reveal the connection of polarization singularity dynamics with the accompanying generation of orbital angular momentum sidebands. It is unexpected that although the total angular momentum of light is not conserved, the total topological index of C points is conserved.

Seismic excitation of the polar motion, 1977 1993

NASA Astrophysics Data System (ADS)

Chao, Benjamin Fong; Gross, Richard S.; Han, Yan-Ben

1996-09-01

The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by Chao and Gross (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0 1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards ˜140°E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by Chao and Gross (1987), manifests some geodynamic behavior yet to be explored.

Dynamically polarized target for the g p 2 and G p E experiments at Jefferson Lab

DOE PAGES

Pierce, J.; Maxwell, J.; Badman, T.; ...

2013-12-16

We describe a dynamically polarized target that has been utilized for two electron scattering experiments in Hall A at Jefferson Lab. The primary components of the target are a new, high cooling power 4 He evaporation refrigerator, and a re-purposed, superconducting split-coil magnet. It has been used to polarize protons in irradiated NH 3 at a temperature of 1 K and at fields of 2.5 and 5.0 Tesla. The performance of the target material in the electron beam under these conditions will be discussed. The maximum polarizations of 28% and 95% were obtained at those fields, respectively. To satisfy themore » requirements of both experiments, the magnet had to be routinely rotated between angles of 0, 6, and 90 degrees with respect to the incident electron beam. This was accomplished using a new rotating vacuum seal which permits rotations to be performed in only a few minutes.« less

Polarization effects associated with thermal processing of HY-80 structural steel using high-power laser diode array

NASA Astrophysics Data System (ADS)

Wu, Sheldon S. Q.; Baker, Bradford W.; Rotter, Mark D.; Rubenchik, Alexander M.; Wiechec, Maxwell E.; Brown, Zachary M.; Beach, Raymond J.; Matthews, Manyalibo J.

2017-12-01

Localized heating of roughened steel surfaces using highly divergent laser light emitted from high-power laser diode arrays was experimentally demonstrated and compared with theoretical predictions. Polarization dependence was analyzed using Fresnel coefficients to understand the laser-induced temperature rise of HY-80 steel plates under 383- to 612-W laser irradiation. Laser-induced, transient temperature distributions were directly measured using bulk thermocouple probes and thermal imaging. Finite-element analysis yielded quantitative assessment of energy deposition and heat transport in HY-80 steel using absorptivity as a tuning parameter. The extracted absorptivity values ranged from 0.62 to 0.75 for S-polarized and 0.63 to 0.85 for P-polarized light, in agreement with partially oxidized iron surfaces. Microstructural analysis using electron backscatter diffraction revealed a heat affected zone for the highest temperature conditions (612 W, P-polarized) as evidence of rapid quenching and an austenite to martensite transformation. The efficient use of diode arrays for laser-assisted advanced manufacturing technologies, such as hybrid friction stir welding, is discussed.

Statistical techniques for detecting the intergalactic magnetic field from large samples of extragalactic Faraday rotation data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akahori, Takuya; Gaensler, B. M.; Ryu, Dongsu, E-mail: akahori@physics.usyd.edu.au, E-mail: bryan.gaensler@sydney.edu.au, E-mail: ryu@sirius.unist.ac.kr

2014-08-01

Rotation measure (RM) grids of extragalactic radio sources have been widely used for studying cosmic magnetism. However, their potential for exploring the intergalactic magnetic field (IGMF) in filaments of galaxies is unclear, since other Faraday-rotation media such as the radio source itself, intervening galaxies, and the interstellar medium of our Galaxy are all significant contributors. We study statistical techniques for discriminating the Faraday rotation of filaments from other sources of Faraday rotation in future large-scale surveys of radio polarization. We consider a 30° × 30° field of view toward the south Galactic pole, while varying the number of sources detectedmore » in both present and future observations. We select sources located at high redshifts and toward which depolarization and optical absorption systems are not observed so as to reduce the RM contributions from the sources and intervening galaxies. It is found that a high-pass filter can satisfactorily reduce the RM contribution from the Galaxy since the angular scale of this component toward high Galactic latitudes would be much larger than that expected for the IGMF. Present observations do not yet provide a sufficient source density to be able to estimate the RM of filaments. However, from the proposed approach with forthcoming surveys, we predict significant residuals of RM that should be ascribable to filaments. The predicted structure of the IGMF down to scales of 0.°1 should be observable with data from the Square Kilometre Array, if we achieve selections of sources toward which sightlines do not contain intervening galaxies and RM errors are less than a few rad m{sup –2}.« less

Dynamic trapping of a polarization rotation vector soliton in a fiber laser.

PubMed

Liu, Meng; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng

2017-01-15

Ultrafast fiber laser, as a dissipative nonlinear optical system, plays an important role in investigating various nonlinear phenomena and soliton dynamics. Vector features of solitons, including polarization locked and polarization rotation vector solitons (PRVSs), are interesting nonlinear dynamics in ultrafast fiber lasers. Herein, we experimentally reveal the trapping characteristics of PRVSs for the first time, to the best of our best knowledge. We show that, for the conventional soliton trapping in the ultrafast fiber laser, the soliton central wavelengths of the two polarization components are constant at the laser output port. However, it is found that the dynamic trapping can be observed for the PRVS. That is, the peak frequencies along the two orthogonal polarization directions are dynamically alternating, depending on the relative intensities of the two polarization components. The obtained results would further unveil the physical mechanism of PRVSs.

An Ultra-wideband and Polarization-independent Metasurface for RCS Reduction

PubMed Central

Su, Pei; Zhao, Yongjiu; Jia, Shengli; Shi, Wenwen; Wang, Hongli

2016-01-01

In this paper, an ultra-wideband and polarization-independent metasurface for radar cross section (RCS) reduction is proposed. The unit cell of the metasurface operates in a linear cross-polarization scheme in a broad band. The phase and amplitude of cross-polarized reflection can be separately controlled by its geometry and rotation angle. Based on the diffuse reflection theory, a 3-bit coding metasurface is designed to reduce the RCS in an ultra-wide band. The wideband property of the metasurface benefits from the wideband cross polarization conversion and flexible phase modulation. In addition, the polarization-independent feature of the metasurface is achieved by tailoring the rotation angle of each element. Both the simulated and measured results demonstrate that the proposed metasurface can reduce the RCS significantly in an ultra-wide frequency band for both normal and oblique incidences, which makes it promising in the applications such as electromagnetic cloaking. PMID:26864084

Polarization control of isolated high-harmonic pulses

NASA Astrophysics Data System (ADS)

Huang, Pei-Chi; Hernández-García, Carlos; Huang, Jen-Ting; Huang, Po-Yao; Lu, Chih-Hsuan; Rego, Laura; Hickstein, Daniel D.; Ellis, Jennifer L.; Jaron-Becker, Agnieszka; Becker, Andreas; Yang, Shang-Da; Durfee, Charles G.; Plaja, Luis; Kapteyn, Henry C.; Murnane, Margaret M.; Kung, A. H.; Chen, Ming-Chang

2018-06-01

High-harmonic generation driven by femtosecond lasers makes it possible to capture the fastest dynamics in molecules and materials. However, thus far, the shortest isolated attosecond pulses have only been produced with linear polarization, which limits the range of physics that can be explored. Here, we demonstrate robust polarization control of isolated extreme-ultraviolet pulses by exploiting non-collinear high-harmonic generation driven by two counter-rotating few-cycle laser beams. The circularly polarized supercontinuum is produced at a central photon energy of 33 eV with a transform limit of 190 as and a predicted linear chirp of 330 as. By adjusting the ellipticity of the two counter-rotating driving pulses simultaneously, we control the polarization state of isolated extreme-ultraviolet pulses—from circular through elliptical to linear polarization—without sacrificing conversion efficiency. Access to the purely circularly polarized supercontinuum, combined with full helicity and ellipticity control, paves the way towards attosecond metrology of circular dichroism.

An Ultra-wideband and Polarization-independent Metasurface for RCS Reduction.

PubMed

Su, Pei; Zhao, Yongjiu; Jia, Shengli; Shi, Wenwen; Wang, Hongli

2016-02-11

In this paper, an ultra-wideband and polarization-independent metasurface for radar cross section (RCS) reduction is proposed. The unit cell of the metasurface operates in a linear cross-polarization scheme in a broad band. The phase and amplitude of cross-polarized reflection can be separately controlled by its geometry and rotation angle. Based on the diffuse reflection theory, a 3-bit coding metasurface is designed to reduce the RCS in an ultra-wide band. The wideband property of the metasurface benefits from the wideband cross polarization conversion and flexible phase modulation. In addition, the polarization-independent feature of the metasurface is achieved by tailoring the rotation angle of each element. Both the simulated and measured results demonstrate that the proposed metasurface can reduce the RCS significantly in an ultra-wide frequency band for both normal and oblique incidences, which makes it promising in the applications such as electromagnetic cloaking.

Comparative study of sub-micrometer polymeric structures: Dot-arrays, linear and crossed gratings generated by UV laser based two-beam interference, as surfaces for SPR and AFM based bio-sensing

NASA Astrophysics Data System (ADS)

Csete, M.; Sipos, Á.; Kőházi-Kis, A.; Szalai, A.; Szekeres, G.; Mathesz, A.; Csákó, T.; Osvay, K.; Bor, Zs.; Penke, B.; Deli, M. A.; Veszelka, Sz.; Schmatulla, A.; Marti, O.

2007-12-01

Two-dimensional gratings are generated on poly-carbonate films spin-coated onto thin gold-silver bimetallic layers by two-beam interference method. Sub-micrometer periodic polymer dots and stripes are produced illuminating the poly-carbonate surface by p- and s-polarized beams of a frequency quadrupled Nd:YAG laser, and crossed gratings are generated by rotating the substrates between two sequential treatments. It is shown by pulsed force mode atomic force microscopy that the mean value of the adhesion is enhanced on the dot-arrays and on the crossed gratings. The grating-coupling on the two-dimensional structures results in double peaks on the angle dependent resonance curves of the surface plasmons excited by frequency doubled Nd:YAG laser. The comparison of the resonance curves proves that a surface profile ensuring minimal undirected scattering is required to optimize the grating-coupling, in addition to the minimal modulation amplitude, and to the optimal azimuthal orientation. The secondary minima are the narrowest in presence of linear gratings on multi-layers having optimized composition, and on crossed structures consisting of appropriately oriented polymer stripes. The large coupling efficiency and adhesion result in high detection sensitivity on the crossed gratings. Bio-sensing is realized by monitoring the rotated-crossed grating-coupled surface plasmon resonance curves, and detecting the chemical heterogeneity by tapping-mode atomic force microscopy. The interaction of Amyloid-β peptide, a pathogenetic factor in Alzheimer disease, with therapeutical molecules is demonstrated.

Optical manipulation of valley pseduospin in 2D semiconductors

NASA Astrophysics Data System (ADS)

Ye, Ziliang

Valley polarization associated with the occupancy in the energy degenerate but quantum mechanically distinct valleys in the momentum space closely resembles spin polarization and has been proposed as a pseudospin carrier for future quantum information technologies. Monolayers of transition metal dichalcogenide (TMDC) crystals, with broken inversion symmetry and large spin-orbital coupling, support robust valley polarization and therefore provide an important platform for studying valley-dependent physics. Besides optical excitation and photoluminescence detection, valley polarization has been electrically measured through the valley Hall effect and created through spin injection from ferromagnetic semiconductor contacts. Moreover, the energy degeneracy of the valley degree of freedom has been lifted by the optical Stark effect. Recently, we have demonstrated optical manipulation of valley coherence, i.e., of the valley pseudospin, by the optical Stark effect in monolayer WSe2. Using below-bandgap circularly polarized light, we rotated the valley pseudospin on the femtosecond time scale. Both the direction and speed of the rotation can be optically controlled by tuning the dynamic phase of excitons in opposite valleys. The pseudospin rotation was identified by changes in the polarization of the photoluminescence. In addition, by varying the time delay between the excitation and control pulses, we directly probed the lifetime of the intervalley coherence. Similar rotation levels have also been observed in static magneto-optic experiments. Our work presents an important step towards the full control of the valley degree of freedom in 2D semiconductors. The work was done in collaboration with Dr. Dezheng Sun and Prof. Tony F. Heinz.

Electrically tunable color filter based on a polarization-tailored nano-photonic dichroic resonator featuring an asymmetric subwavelength grating.

PubMed

Park, Chang-Hyun; Yoon, Yeo-Taek; Shrestha, Vivek Raj; Park, Chul-Soon; Lee, Sang-Shin; Kim, Eun-Soo

2013-11-18

We have demonstrated a highly efficient electrically tunable color filter, which provides precise control of color output, taking advantage of a nano-photonic polarization-tailored dichroic resonator combined with a liquid-crystal based polarization rotator. The visible dichroic resonator based on the guided mode resonance, which incorporates a planar dielectric waveguide in Si3N4 integrated with an asymmetric two-dimensional subwavelength Al grating with unequal pitches along its principal axes, exhibited polarization specific transmission featuring high efficiency up to 75%. The proposed tunable color filters were constructed by combining three types of dichroic resonators, each of which deals with a mixture of two primary colors (i.e. blue/green, blue/red, and green/red) with a polarization rotator exploiting a twisted nematic liquid crystal cell. The output colors could be dynamically and seamlessly customized across the blend of the two corresponding primary colors, by altering the polarization via the voltage applied to the polarization rotator. For the blue/red filter, the center wavelength was particularly adjusted from 460 to 610 nm with an applied voltage variation of 2 V, leading to a tuning range of up to 150 nm. And the spectral tuning was readily confirmed via color mapping. The proposed devices may permit the tuning span to be readily extended by tailoring the grating pitches.

Effects of Long Period Ocean Tides on the Earth's Rotation

NASA Technical Reports Server (NTRS)

Gross, Richard S.; Chao, Ben F.; Desai, Shailen D.

1996-01-01

The spectra of polar motion excitation functions exhibit enhanced power in the fortnightly tidal band. This enhanced power is attributed to ocean tidal excitation. Ocean tide models predict polar motion excitation effects that differ with each other, and with observations, by factors as large as 2-3. There is a need for inproved models for the effect of long-period ocean tides on Earth's rotation.

300 nm bandwidth adiabatic SOI polarization splitter-rotators exploiting continuous symmetry breaking.

PubMed

Socci, Luciano; Sorianello, Vito; Romagnoli, Marco

2015-07-27

Adiabatic polarization splitter-rotators are investigated exploiting continuous symmetry breaking thereby achieving significant device size and losses reduction in a single mask fabrication process for both SOI channel and ridge waveguides. A crosstalk lower than -25 dB is expected over 300nm bandwidth, making the device suitable for full grid CWDM and diplexer/triplexer FTTH applications at 1310, 1490 and 1550nm.

Optical Magnetometry for Detecting Underwater Objects

DTIC Science & Technology

2015-09-21

underwater object. The two mechanisms responsible for the polarization rotation are the Surface Magneto-Optical Kerr Effect (SMOKE) and the Faraday effect...the underwater object itself ( Faraday effect). An analytical expression is obtained for the polarization-rotated field when the incident plane wave...Washington, DC 20375-5320 October 2014 – August 2015 NRL *University of Maryland, College Park, MD 20742-4111 Faraday SMOKE 67-4374-C4 1 Optical

SMMR data set development for GARP. [impact of cross polarization and Faraday rotation on SMMR derived brightness temperatures

NASA Technical Reports Server (NTRS)

Kogut, J.

1981-01-01

The NIMBUS 7 Scanning Multichannel Microwave Radiometer (SMMR) data are analyzed. The impact of cross polarization and Faraday rotation on SMMR derived brightness temperatures is evaluated. The algorithms used to retrieve the geophysical parameters are tested, refined, and compared with values derived by other techniques. The technical approach taken is described and the results presented.

An Almost Complete Radio Survey of Magnetic Cataclysmic Variables

NASA Astrophysics Data System (ADS)

Dieck, Christopher A.; Everett Barrett, Paul; Beasley, Anthony J.; Pal Singh, Kulinder; Boboltz, David A.; Godon, Patrick; Mason, Paul A.

2016-01-01

This poster presents the results of a radio survey using the Jansky Very Large Array (JVLA) of 129 Magnetic Cataclysmic Variables (MCVs) north of declination -35 deg. 103 hours of observations were performed during the JVLA observing sessions 2013B and 2015A, when the array was mostly in its highest spatial-resolution configurations (i.e., A and B). Most targets were observed twice for 2-5 minutes at each of three frequencies (C, X, and K-bands), although a few targets were also observed at a fourth frequency (Q-band). 22 of the 129 MCVS were detected at one or more frequencies. Of these 22 detections, 15 are new. This number nearly triples the number of MCVs that are known radio sources. Most detections are at the C and X-band frequencies, although three sources were detected at the K-band frequency. One of the K-band frequency detections is the known rapidly-rotating radio source AE Aqr, while the other two are the polars, AI Tri and ST LMi. Of the 22 detected sources, two-thirds are polars (15) and all are believed to be nearby (<200 pc). Except for a few stronger sources, most detections are in the range of 100-200 µJy, which at a distance of 150 pc corresponds roughly to a luminosity of 2x1024 erg/s at the X-band frequency. The results of this survey are encouraging in that more MCVs are likely to be detected as the time on-source increases, since the flux from MCVs is highly variable.

The CERTO Beacon on CASSIOPE/e-POP and Experiments Using High-Power HF Ionospheric Heaters

NASA Astrophysics Data System (ADS)

Siefring, Carl L.; Bernhardt, Paul A.; James, H. Gordon; Parris, Richard Todd

2015-06-01

A new Coherent Electromagnetic Radio Tomography (CERTO) beacon is on the CASSIOPE satellite and part of the enhanced-Polar Outflow Probe (e-POP) suite of scientific instruments. CERTO signals can be used to measure ionospheric Total Electron Content (TEC) and radio scintillations along propagation paths between CERTO and receivers. The combination of CERTO and the array of e-POP in-situ diagnostics form a powerful tool for studying ionospheric plasma processes that have not been previously possible. Of note, the combination CERTO and the Radio Receiver Instrument (RRI), a modern digital receiver, which measures between 10 Hz to 18 MHz in selectable bands allows for innovative High Frequency (HF) radio propagation experiments. The use of high-power HF ionospheric heating facilities for such experiments further allows for repeatable studies of a number of important plasma processes. The new CERTO beacon transmits un-modulated, phase-coherent waves at 150, 400, and 1067 MHz with either right-hand-circular or linear polarization and TEC is measured using either differential phase and/or Faraday rotation. With a linear array of CERTO receivers, TEC data can be used for tomographic imaging of the ionosphere yielding two-dimensional maps of the plasma below the satellite orbit. In addition, the three CERTO frequencies cover a wide range for determination of radio scintillation effects caused by diffraction from propagation through ionospheric irregularities. We will describe the CERTO beacon and several potential innovative experiments using HF heating facilities in conjunction with CERTO, the RRI and other e-POP instruments.

Opening and closing of band gaps in magnonic waveguide by rotating the triangular antidots - A micromagnetic study

NASA Astrophysics Data System (ADS)

Vivek, T.; Bhoomeeswaran, H.; Sabareesan, P.

2018-05-01

Spin waves in ID periodic triangular array of antidots are encarved in a permalloy magnonic waveguide is investigated through micromagnetic simulation. The effect of the rotating array of antidots and in-plane rotation of the scattering centers on the band structure are investigated, to indicate new possibilities of fine tuning of spin-wave filter pass and stop bands. The results show that, the opening and closing of band gaps paves a way for band pass and stop filters on waveguide. From the results, the scattering center and strong spatial distribution field plays crucible role for controlling opening and closing bandgap width of ˜12 GHz for 0° rotation. We have obtained a single narrow bandgap of width 1GHz is obtained for 90° rotation of the antidot. Similarly, the tunability is achieved for desired microwave applications done by rotating triangular antidots with different orientation.

Time-resolved fluorescence polarization spectroscopy of visible and near infrared dyes in picosecond dynamics

NASA Astrophysics Data System (ADS)

Pu, Yang; Alfano, Robert R.

2015-03-01

Near-infrared (NIR) dyes absorb and emit light within the range from 700 to 900 nm have several benefits in biological studies for one- and/or two-photon excitation for deeper penetration of tissues. These molecules undergo vibrational and rotational motion in the relaxation of the excited electronic states, Due to the less than ideal anisotropy behavior of NIR dyes stemming from the fluorophores elongated structures and short fluorescence lifetime in picosecond range, no significant efforts have been made to recognize the theory of these dyes in time-resolved polarization dynamics. In this study, the depolarization of the fluorescence due to emission from rotational deactivation in solution will be measured with the excitation of a linearly polarized femtosecond laser pulse and a streak camera. The theory, experiment and application of the ultrafast fluorescence polarization dynamics and anisotropy are illustrated with examples of two of the most important medical based dyes. One is NIR dye, namely Indocyanine Green (ICG) and is compared with Fluorescein which is in visible range with much longer lifetime. A set of first-order linear differential equations was developed to model fluorescence polarization dynamics of NIR dye in picosecond range. Using this model, the important parameters of ultrafast polarization spectroscopy were identified: risetime, initial time, fluorescence lifetime, and rotation times.

Three-dimensional lattice rotation in GaAs nanowire growth on hydrogen-silsesquioxane covered GaAs (001) using molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Tran, Dat Q.; Pham, Huyen T.; Higashimine, Koichi; Oshima, Yoshifumi; Akabori, Masashi

2018-05-01

We report on crystallographic behaviors of inclined GaAs nanowires (NWs) self-crystallized on GaAs (001) substrate. The NWs were grown on hydrogen-silsesquioxane (HSQ) covered substrates using molecular beam epitaxy (MBE). Commonly, the epitaxial growth of GaAs < 111>B (B-polar) NWs is prominently observed on GaAs (001); however, we yielded a remarkable number of epitaxially grown GaAs < 111>A (A-polar) NWs in addition to the majorly obtained B-polar NWs. Such NW orientations are always accompanied by a typical inclined angle of 35° from (001) plane. NWs with another inclined angle of 74° were additionally observed and attributed to be < 111>-oriented, not in direct epitaxial relation with the substrate. Such 74° NWs' existence is related to first-order three-dimensional (3D) lattice rotation taking place at the very beginning of the growth. It turns out that spatially 60° lattice rotation around < 111> directions at GaAs seeds is essentially in charge of A- and B-polar 74° NWs. Transmission electron microscope observations reveal a high density of twinning in the B-polar NWs and twin-free characteristic in the A-polar NWs.

Magnetic Fields in Evolved Stars: Imaging the Polarized Emission of High-frequency SiO Masers

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Humphreys, E. M. L.; Franco-Hernández, R.

2011-02-01

We present Submillimeter Array observations of high-frequency SiO masers around the supergiant VX Sgr and the semi-regular variable star W Hya. The J = 5-4, v = 128SiO and v = 029SiO masers of VX Sgr are shown to be highly linearly polarized with a polarization from ~5% to 60%. Assuming the continuum emission peaks at the stellar position, the masers are found within ~60 mas of the star, corresponding to ~100 AU at a distance of 1.57 kpc. The linear polarization vectors are consistent with a large-scale magnetic field, with position and inclination angles similar to that of the dipole magnetic field inferred in the H2O and OH maser regions at much larger distances from the star. We thus show for the first time that the magnetic field structure in a circumstellar envelope can remain stable from a few stellar radii out to ~1400 AU. This provides further evidence supporting the existence of large-scale and dynamically important magnetic fields around evolved stars. Due to a lack of parallactic angle coverage, the linear polarization of masers around W Hya could not be determined. For both stars, we observed the 28SiO and 29SiO isotopologues and find that they have a markedly different distributions and that they appear to avoid each other. Additionally, emission from the SO 55-44 line was imaged for both sources. Around W Hya, we find a clear offset between the red- and blueshifted SO emission. This indicates that W Hya is likely host to a slow bipolar outflow or a rotating disk-like structure.

ELECTROMAGNETIC SCATTERING AND ANTENNA TECHNOLOGY (EMSAT) Task Order 0003: Design of a Circularly Polarized, 20 60 GHZ Active Phased Array for Wide Angle Scanning

DTIC Science & Technology

2017-08-08

Another area of the design that needs to be experimentally tested is the SMPS connectors used to attach the two beamforming stages together. In...AFRL-RY-WP-TR-2017-0104 ELECTROMAGNETIC SCATTERING AND ANTENNA TECHNOLOGY (EMSAT) Task Order 0003: Design of a Circularly Polarized, 20-60...Order 0003: Design of a Circularly Polarized, 20-60 GHZ Active Phased Array for Wide Angle Scanning 5a. CONTRACT NUMBER FA8650-14-D-1714-0003 5b

Preserving a Unique Archive for Long-Term Solar Variability Studies

NASA Astrophysics Data System (ADS)

Webb, David F.; Hewins, Ian; McFadden, Robert; Emery, Barbara; Gibson, Sarah; Denig, William

2016-05-01

In 1964 (solar cycle 20) Patrick McIntosh began creating hand-drawn synoptic maps of solar activity, based on Hydrogen alpha (Hα) imaging measurements. These synoptic maps were unique because they traced the polarity inversion lines (PILs), connecting widely separated filaments, fibril patterns and plage corridors to reveal the large-scale organization of the solar magnetic field. He and his assistants later included coronal hole (CH) boundaries to the maps, usually from ground-based He-I 10830 images. They continued making these maps until 2010 (the start of solar cycle 24), yielding more than 40 years (~ 540 Carrington rotations) or nearly four complete solar cycles (SCs) of synoptic maps. The McIntosh collection of maps forms a unique and consistent set of global solar magnetic field data, and are unique tools for studying the structure and evolution of the large-scale solar fields and polarity boundaries, because: 1) they have excellent spatial resolution for defining polarity boundaries, 2) the organization of the fields into long-lived, coherent features is clear, and 3) the data are relatively homogeneous over four solar cycles. After digitization and archiving, these maps -- along with computer codes permitting efficient searches of the map arrays -- will be made publicly available at NOAA’s National Centers for Environmental Information (NCEI) in their final, searchable form. This poster is a progress report of the project so far and some suggested scientific applications.

In vivo sensitivity estimation and imaging acceleration with rotating RF coil arrays at 7 Tesla.

PubMed

Li, Mingyan; Jin, Jin; Zuo, Zhentao; Liu, Feng; Trakic, Adnan; Weber, Ewald; Zhuo, Yan; Xue, Rong; Crozier, Stuart

2015-03-01

Using a new rotating SENSitivity Encoding (rotating-SENSE) algorithm, we have successfully demonstrated that the rotating radiofrequency coil array (RRFCA) was capable of achieving a significant reduction in scan time and a uniform image reconstruction for a homogeneous phantom at 7 Tesla. However, at 7 Tesla the in vivo sensitivity profiles (B1(-)) become distinct at various angular positions. Therefore, sensitivity maps at other angular positions cannot be obtained by numerically rotating the acquired ones. In this work, a novel sensitivity estimation method for the RRFCA was developed and validated with human brain imaging. This method employed a library database and registration techniques to estimate coil sensitivity at an arbitrary angular position. The estimated sensitivity maps were then compared to the acquired sensitivity maps. The results indicate that the proposed method is capable of accurately estimating both magnitude and phase of sensitivity at an arbitrary angular position, which enables us to employ the rotating-SENSE algorithm to accelerate acquisition and reconstruct image. Compared to a stationary coil array with the same number of coil elements, the RRFCA was able to reconstruct images with better quality at a high reduction factor. It is hoped that the proposed rotation-dependent sensitivity estimation algorithm and the acceleration ability of the RRFCA will be particularly useful for ultra high field MRI. Copyright © 2014 Elsevier Inc. All rights reserved.

In vivo sensitivity estimation and imaging acceleration with rotating RF coil arrays at 7 Tesla

NASA Astrophysics Data System (ADS)

Li, Mingyan; Jin, Jin; Zuo, Zhentao; Liu, Feng; Trakic, Adnan; Weber, Ewald; Zhuo, Yan; Xue, Rong; Crozier, Stuart

2015-03-01

Using a new rotating SENSitivity Encoding (rotating-SENSE) algorithm, we have successfully demonstrated that the rotating radiofrequency coil array (RRFCA) was capable of achieving a significant reduction in scan time and a uniform image reconstruction for a homogeneous phantom at 7 Tesla. However, at 7 Tesla the in vivo sensitivity profiles (B1-) become distinct at various angular positions. Therefore, sensitivity maps at other angular positions cannot be obtained by numerically rotating the acquired ones. In this work, a novel sensitivity estimation method for the RRFCA was developed and validated with human brain imaging. This method employed a library database and registration techniques to estimate coil sensitivity at an arbitrary angular position. The estimated sensitivity maps were then compared to the acquired sensitivity maps. The results indicate that the proposed method is capable of accurately estimating both magnitude and phase of sensitivity at an arbitrary angular position, which enables us to employ the rotating-SENSE algorithm to accelerate acquisition and reconstruct image. Compared to a stationary coil array with the same number of coil elements, the RRFCA was able to reconstruct images with better quality at a high reduction factor. It is hoped that the proposed rotation-dependent sensitivity estimation algorithm and the acceleration ability of the RRFCA will be particularly useful for ultra high field MRI.

Excitation of high density surface plasmon polariton vortex array

NASA Astrophysics Data System (ADS)

Kuo, Chun-Fu; Chu, Shu-Chun

2018-06-01

This study proposes a method to excite surface plasmon polariton (SPP) vortex array of high spatial density on metal/air interface. A doughnut vector beam was incident at four rectangularly arranged slits to excite SPP vortex array. The doughnut vector beam used in this study has the same field intensity distribution as the regular doughnut laser mode, TEM01* mode, but a different polarization distribution. The SPP vortex array is achieved through the matching of both polarization state and phase state of the incident doughnut vector beam with the four slits. The SPP field distribution excited in this study contains stable array-distributed time-varying optical vortices. Theoretical derivation, analytical calculation and numerical simulation were used to discuss the characteristics of the induced SPP vortex array. The period of the SPP vortex array induced by the proposed method had only half SPPs wavelength. In addition, the vortex number in an excited SPP vortex array can be increased by enlarging the structure.

Advanced Diagnostics for the Study of Linearly Polarized Emission. II. Application to Diffuse Interstellar Radio Synchrotron Emission

NASA Astrophysics Data System (ADS)

Herron, C. A.; Burkhart, Blakesley; Gaensler, B. M.; Lewis, G. F.; McClure-Griffiths, N. M.; Bernardi, G.; Carretti, E.; Haverkorn, M.; Kesteven, M.; Poppi, S.; Staveley-Smith, L.

2018-03-01

Diagnostics of polarized emission provide us with valuable information on the Galactic magnetic field and the state of turbulence in the interstellar medium, which cannot be obtained from synchrotron intensity alone. In Paper I, we derived polarization diagnostics that are rotationally and translationally invariant in the Q–U plane, similar to the polarization gradient. In this paper, we apply these diagnostics to simulations of ideal magnetohydrodynamic turbulence that have a range of sonic and Alfvénic Mach numbers. We generate synthetic images of Stokes Q and U for these simulations for the cases where the turbulence is illuminated from behind by uniform polarized emission and where the polarized emission originates from within the turbulent volume. From these simulated images, we calculate the polarization diagnostics derived in Paper I for different lines of sight relative to the mean magnetic field and for a range of frequencies. For all of our simulations, we find that the polarization gradient is very similar to the generalized polarization gradient and that both trace spatial variations in the magnetoionic medium for the case where emission originates within the turbulent volume, provided that the medium is not supersonic. We propose a method for distinguishing the cases of emission coming from behind or within a turbulent, Faraday rotating medium and a method to partly map the rotation measure of the observed region. We also speculate on statistics of these diagnostics that may allow us to constrain the physical properties of an observed turbulent region.

Valley Topological Phases in Bilayer Sonic Crystals

NASA Astrophysics Data System (ADS)

Lu, Jiuyang; Qiu, Chunyin; Deng, Weiyin; Huang, Xueqin; Li, Feng; Zhang, Fan; Chen, Shuqi; Liu, Zhengyou

2018-03-01

Recently, the topological physics in artificial crystals for classical waves has become an emerging research area. In this Letter, we propose a unique bilayer design of sonic crystals that are constructed by two layers of coupled hexagonal array of triangular scatterers. Assisted by the additional layer degree of freedom, a rich topological phase diagram is achieved by simply rotating scatterers in both layers. Under a unified theoretical framework, two kinds of valley-projected topological acoustic insulators are distinguished analytically, i.e., the layer-mixed and layer-polarized topological valley Hall phases, respectively. The theory is evidently confirmed by our numerical and experimental observations of the nontrivial edge states that propagate along the interfaces separating different topological phases. Various applications such as sound communications in integrated devices can be anticipated by the intriguing acoustic edge states enriched by the layer information.

Scientific Verification of Faraday Rotation Modulators: Detection of Diffuse Polarized Galactic Emission

NASA Technical Reports Server (NTRS)

Moyerman, S.; Bierman, E.; Ade, P. A. R.; Aiken, R.; Barkats, D.; Bischoff, C.; Bock, J. J.; Chiang, H. C.; Dowell, C. D.; Duband, L.;

Selective wave-transmitting electromagnetic absorber through composite metasurface

NASA Astrophysics Data System (ADS)

Sun, Zhiwei; Zhao, Junming; Zhu, Bo; Jiang, Tian; Feng, Yijun

2017-11-01

Selective wave-transmitting absorbers which have one or more narrow transmission bands inside a wide absorption band are often demanded in wireless communication and radome applications for reducing the coupling between different systems, improving anti-jamming capability, and reducing antennas' radar cross section. Here we propose a feasible method that utilizing composite of two metasurfaces with different polarization dependent characteristics, one works as electromagnetic polarization rotator and the other as a wideband polarization dependent electromagnetic wave absorber. The polarization rotator produces a cross polarization output in the wave-transmitting band, while preserves the polarization of the incidence outside the band. The metasurface absorber works for certain linear polarization with a much wider absorption band covering the wave-transmitting frequency. When combining these two metasurfaces properly, the whole structure behaves as a wideband absorber with a certain frequency transmission window. The proposal may be applied in radome designs to reduce the radar cross section of antenna or improving the electromagnetic compatibility in communication devices.

Waveguide modes in sparse III-V nanowire arrays for ultra-broadband tunable perfect absorbers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fountaine, Katherine T.; Cheng, Wen-Hui; Bukowsky, Colton R.; Atwater, Harry A.

2016-09-01

Design of perfect absorbers and emitters has been a primary focus of the metamaterials community owing to their potential to enhance device efficiency and sensitivity in energy harvesting and sensing applications, specifically photovoltaics, thermal emission control, bolometers and photodetectors, to name a few. While reports of perfect absorbers/emitters for a specific frequency, wavevector, and polarization are ubiquitous, a broadband and polarization- and angle-insensitive perfect absorber remains a particular challenge. In this work, we report on directed optical design and fabrication of sparse III-V nanowire arrays as broadband, polarization- and angle-insensitive perfect absorbers and emitters. Specifically, we target response in the UV-Vis-NIR and NIR-SWIR-MWIR via two material systems, InP (Eg=1.34 eV) and InSb (Eg=0.17 eV), respectively. Herein, we present results on InP and InSb nanowire array broadband absorbers, supported by experiment, simulation and analytic theory. Electromagnetic simulations indicate that, with directed optical design, tapered nanowire arrays and multi-radii nanowire arrays with 5% fill fraction can achieve greater than 95% broadband absorption (λInP=400-900nm, λInSb=1.5-5.5µm), due to efficient excitation and interband transition-mediated attenuation of the HE11 waveguide mode. Experimentally-fabricated InP nanowire arrays embedded in PDMS achieved broadband, polarization- and angle-insensitive 90-95% absorption, limited primarily by reflection off the PDMS interface. Addition of a thin, planar VO2 layer above a sparse InSb nanowire array enables active thermal tunability in the infrared, effecting a 50% modulation, from 87% (insulating VO2) to 43% (metallic VO2) average absorption. These concepts and results along with photovoltaic and other optical and optoelectronic device applications will be discussed.

POLARIMETRIC DETECTION OF EXOPLANETS TRANSITING T AND L BROWN DWARFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, Sujan, E-mail: sujan@iiap.res.in

While scattering of light by atoms and molecules yields large amounts of polarization at the B-band of both T and L dwarfs, scattering by dust grains in the cloudy atmosphere of L dwarfs gives rise to significant polarization at the far-optical and infrared wavelengths where these objects are much brighter. However, the observable disk-averaged polarization should be zero if the clouds are uniformly distributed and the object is spherically symmetric. Therefore, in order to explain the observed large polarization of several L dwarfs, rotation-induced oblateness or horizontally inhomogeneous cloud distribution in the atmosphere is invoked. On the other hand, whenmore » an extra-solar planet of Earth-size or larger transits the brown dwarf along the line of sight, the asymmetry induced during the transit gives rise to a net non-zero, time-dependent polarization. Employing atmospheric models for a range of effective temperature and surface gravity appropriate for T and L dwarfs, I derive the time-dependent polarization profiles of these objects during the transit phase and estimate the peak amplitude of polarization that occurs during the inner contact points of the transit ingress/egress phase. It is found that peak polarization in the range of 0.2%–1.0% at I and J band may arise of cloudy L dwarfs occulted by Earth-size or larger exoplanets. Such an amount of polarization is higher than what can be produced by rotation-induced oblateness of even rapidly rotating L dwarfs. Hence, I suggest that time-resolved imaging polarization could be a potential technique for detecting transiting exoplanets around L dwarfs.« less

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition.

PubMed

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D; Renevier, Hubert; Consonni, Vincent

2017-03-03

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 10 7 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

NASA Astrophysics Data System (ADS)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D.; Renevier, Hubert; Consonni, Vincent

2017-03-01

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscaleengineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol–gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on themore » macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscaleengineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.« less

Relaxation of polar order in suspensions with Quincke effect.

PubMed

Belovs, M; Cēbers, A

2014-05-01

The Quincke effect--spontaneous rotation of dielectric particles in a liquid with low conductivity under the action of an electric field--is considered. The distribution functions for the orientation of particle rotation planes are introduced and a set of nonlinear kinetic equations is derived in the mean field approximation considering the dynamics of their orientation in the flow induced by rotating particles. As a result the nonequilibrium phase transition to the polar order, if the concentration of the particles is sufficiently high, is predicted and the condition of the synchronization of particle rotations is established. Two cases are considered: the layer of the Quincke suspension with one free boundary and the ensemble of the particles rolling on the solid wall under the action of a torque in an electric field. It is shown that in both cases the synchronization of particle rotations occurs due to the hydrodynamic interactions. In the limit of small spatial nonhomogeneity a set of nonlinear partial differential equations for the macroscopic variables--the concentration and the director of the polar order--is derived from the kinetic equation. Its properties are analyzed and compared with available recent experimental results.

Relaxation of polar order in suspensions with Quincke effect

NASA Astrophysics Data System (ADS)

Belovs, M.; CÄ`bers, A.

2014-05-01

The Quincke effect—spontaneous rotation of dielectric particles in a liquid with low conductivity under the action of an electric field—is considered. The distribution functions for the orientation of particle rotation planes are introduced and a set of nonlinear kinetic equations is derived in the mean field approximation considering the dynamics of their orientation in the flow induced by rotating particles. As a result the nonequilibrium phase transition to the polar order, if the concentration of the particles is sufficiently high, is predicted and the condition of the synchronization of particle rotations is established. Two cases are considered: the layer of the Quincke suspension with one free boundary and the ensemble of the particles rolling on the solid wall under the action of a torque in an electric field. It is shown that in both cases the synchronization of particle rotations occurs due to the hydrodynamic interactions. In the limit of small spatial nonhomogeneity a set of nonlinear partial differential equations for the macroscopic variables—the concentration and the director of the polar order—is derived from the kinetic equation. Its properties are analyzed and compared with available recent experimental results.

Use of Faraday-rotation data from beacon satellites to determine ionospheric corrections for interplanetary spacecraft navigation

NASA Technical Reports Server (NTRS)

Royden, H. N.; Green, D. W.; Walson, G. R.

1981-01-01

Faraday-rotation data from the linearly polarized 137-MHz beacons of the ATS-1, SIRIO, and Kiku-2 geosynchronous satellites are used to determine the ionospheric corrections to the range and Doppler data for interplanetary spacecraft navigation. The JPL operates the Deep Space Network of tracking stations for NASA; these stations monitor Faraday rotation with dual orthogonal, linearly polarized antennas, Teledyne polarization tracking receivers, analog-to-digital converter/scanners, and other support equipment. Computer software examines the Faraday data, resolves the pi ambiguities, constructs a continuous Faraday-rotation profile and converts the profile to columnar zenith total electron content at the ionospheric reference point; a second program computes the line-of-sight ionospheric correction for each pass of the spacecraft over each tracking complex. Line-of-sight ionospheric electron content using mapped Faraday-rotation data is compared with that using dispersive Doppler data from the Voyager spacecraft; a difference of about 0.4 meters, or 5 x 10 to the 16th electrons/sq m is obtained. The technique of determining the electron content of interplanetary plasma by subtraction of the ionospheric contribution is demonstrated on the plasma torus surrounding the orbit of Io.

Nonlinearity in the rotational dynamics of Haidinger's brushes

NASA Astrophysics Data System (ADS)

Rothmayer, Mark; Dultz, Wolfgang; Frins, Erna; Zhan, Qiwen; Tierney, Dennis; Schmitzer, Heidrun

2007-10-01

Haidinger's brushes are an entoptic effect of the human visual system that enables us to detect polarized light. However, individual perceptions of Haidinger's brushes can vary significantly. We find that the birefringence of the cornea influences the rotational motion and the contrast of Haidinger's brushes and may offer an explanation for individual differences. We have devised an experimental setup to simulate various phase shifts of the cornea and found a switching effect in the rotational dynamics of Haidinger's brushes. In addition, age related macular degeneration reduces the polarization effect of the macula and thus also leads to changes in the brush pattern.

Third-order-harmonic generation in coherently spinning molecules

NASA Astrophysics Data System (ADS)

Prost, E.; Zhang, H.; Hertz, E.; Billard, F.; Lavorel, B.; Bejot, P.; Zyss, Joseph; Averbukh, Ilya Sh.; Faucher, O.

2017-10-01

The rotational Doppler effect occurs when circularly polarized light interacts with a rotating anisotropic material. It is manifested by the appearance of a spectral shift ensuing from the transfer of angular momentum and energy between radiation and matter. Recently, we reported terahertz-range rotational Doppler shifts produced in third-order nonlinear optical conversion [O. Faucher et al., Phys. Rev. A 94, 051402(R) (2016), 10.1103/PhysRevA.94.051402]. The experiment was performed in an ensemble of coherently spinning molecules prepared by a short laser pulse exhibiting a twisted linear polarization. The present work provides an extensive analysis of the rotational Doppler effect in third-order-harmonic generation from spinning linear molecules. The underlying physics is investigated both experimentally and theoretically. The implication of the rotational Doppler effect in higher-order processes like high-order-harmonic generation is discussed.

Faraday rotation of Automatic Dependent Surveillance Broadcast (ADS-B) signals as a method of ionospheric characterization

NASA Astrophysics Data System (ADS)

Cushley, A. C.; Kabin, K.; Noel, J. M. A.

2017-12-01

Radio waves propagating through plasma in the Earth's ambient magnetic field experience Faraday rotation; the plane of the electric field of a linearly polarized wave changes as a function of the distance travelled through a plasma. Linearly polarized radio waves at 1090 MHz frequency are emitted by Automatic Dependent Surveillance Broadcast (ADS-B) devices which are installed on most commercial aircraft. These radio waves can be detected by satellites in low earth orbits, and the change of the polarization angle caused by propagation through the terrestrial ionosphere can be measured. In this work we discuss how these measurements can be used to characterize the ionospheric conditions. In the present study, we compute the amount of Faraday rotation from a prescribed total electron content value and two of the profile parameters of the NeQuick model.

Non-destructive imaging of spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Samson, E.; Vinit, Anshuman; Raman, Chandra

2013-05-01

We present a non-destructive differential imaging technique that enables the observation of the spatial distribution of the magnetization in a spinor Bose-Einstein condensate (BEC) through a Faraday rotation protocol. In our procedure, we utilize a linearly polarized, far-detuned laser beam as our imaging probe, and upon interaction with the condensate, the beam's polarization direction undergoes Faraday rotation. A differential measurement of the orthogonal polarization components of the rotated beam provides a spatial map of the net magnetization density within the BEC. The non-destructive aspect of this method allows for continuous imaging of the condensate. This imaging technique will prove useful in experimental BEC studies, such as spatially resolved magnetometry using ultracold atoms, and non-destructive imaging of non-equilibrium behavior of antiferromagnetic spinor condensates. This work was supported by the DARPA QuASAR program through a grant from ARO.

Probing the gravitational Faraday rotation using quasar X-ray microlensing

PubMed Central

Chen, Bin

2015-01-01

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission. PMID:26574051

Observation of the X-Ray Magneto-Optical Voigt Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mertins, H.-Ch.; Oppeneer, P. M.; Kunes, J.

2001-07-23

The existence of the x-ray magneto-optical Voigt effect is demonstrated. By means of polarization analysis the Voigt rotation and ellipticity of linearly polarized synchrotron radiation are measured at the Co L{sub 3} edge upon transmission through an amorphous Co film. The observed x-ray Voigt rotation is about 7.5{sup o}/{mu}m . On the basis of ab initio calculations it is shown that the x-ray Voigt effect follows sensitively the amount of spin polarization of the 2p core states. Therefore it provides a unique measure of the spin splitting of the core states.

Alignment of the writing beam with the diffractive structure rotation axis in synthesis of diffractive optical elements in a polar coordinate system

NASA Astrophysics Data System (ADS)

Shimanskii, R. V.; Poleshchuk, A. G.; Korolkov, V. P.; Cherkashin, V. V.

2017-03-01

A method is developed to ensure precise alignment of the origin of a polar coordinate system in which the laser beam position is defined in writing diffractive optical elements with the optical workpiece rotation axis. This method is used to improve the accuracy of a circular laser writing system in writing large-scale diffractive optical elements in a polar coordinate system. Results of studying new algorithms of detection and correction of positioning errors of the circular laser writing system in the course of writing are reported.

THE FORMATION AND MAGNETIC STRUCTURES OF ACTIVE-REGION FILAMENTS OBSERVED BY NVST, SDO, AND HINODE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, X. L.; Xue, Z. K.; Wang, J. C.

2015-08-15

To better understand the properties of solar active-region filaments, we present a detailed study on the formation and magnetic structures of two active-region filaments in active region NOAA 11884 during a period of four days. It is found that the shearing motion of the opposite magnetic polarities and the rotation of the small sunspots with negative polarity play an important role in the formation of two active-region filaments. During the formation of these two active-region filaments, one foot of the filaments was rooted in a small sunspot with negative polarity. The small sunspot rotated not only around another small sunspotmore » with negative polarity, but also around the center of its umbra. By analyzing the nonlinear force-free field extrapolation using the vector magnetic fields in the photosphere, twisted structures were found in the two active-region filaments prior to their eruptions. These results imply that the magnetic fields were dragged by the shearing motion between opposite magnetic polarities and became more horizontal. The sunspot rotation twisted the horizontal magnetic fields and finally formed the twisted active-region filaments.« less

The local surface plasmon resonance property and refractive index sensitivity of metal elliptical nano-ring arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Weihua, E-mail: linwh-whu@hotmail.com; Wang, Qian; Dong, Anhua

2014-11-15

In this paper, we systematically investigate the optical property and refractive index sensitivity (RIS) of metal elliptical nano-ring (MENR) arranged in rectangle lattice by finite-difference time-domain method. Eight kinds of considered MENRs are divided into three classes, namely fixed at the same outer size, at the same inner size, and at the same middle size. All MENR arrays show a bonding mode local surface plasmon resonance (LSPR) peak in the near-infrared region under longitudinal and transverse polarizations, and lattice diffraction enhanced LSPR peaks emerge, when the LSPR peak wavelength (LSPRPW) matches the effective lattice constant of the array. The LSPRPWmore » is determined by the charge moving path length, the parallel and cross interactions induced by the stable distributed charges, and the moving charges inter-attraction. High RIS can be achieved by small particle distance arrays composed of MENRs with big inner size and small ring-width. On the other hand, for a MENR array, the comprehensive RIS (including RIS and figure of merit) under transverse polarization is superior to that under longitudinal polarization. Furthermore, on condition that compared arrays are fixed at the same lattice constant, the phenomenon that the RIS of big ring-width MENR arrays may be higher than that of small ring-width MENR arrays only appears in the case of compared arrays with relatively small lattice constant and composed of MENRs fixed at the same inner size simultaneously. Meanwhile, the LSPRPW of the former MENR arrays is also larger than that of the latter MENR arrays. Our systematic results may help experimentalists work with this type of systems.« less

Theory of topological insulator waveguides: polarization control and the enhancement of the magneto-electric effect

NASA Astrophysics Data System (ADS)

Crosse, J. A.

2017-02-01

Topological insulators subject to a time-reversal-symmetry-breaking perturbation are predicted to display a magneto-electric effect that causes the electric and magnetic induction fields to mix at the material’s surface. This effect induces polarization rotations of between ≈1-10 mrad per interface in an incident plane-polarized electromagnetic wave normal to a multilayered structure. Here we show, theoretically and numerically, that by using a waveguide geometry with a topological insulator guide layer and magneto-dielectric cladding it is possible to achieve rotations of ≈100 mrad and generate an elliptical polarization with only a three-layered structure. This geometry is beneficial, not only as a way to enhance the magneto-electric effect, rendering it easier to observe, but also as a method for controlling the polarization of electromagnetic radiation.

Baseline scheme for polarization preservation and control in the MEIC ion complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Derbenev, Yaroslav S.; Lin, Fanglei; Morozov, Vasiliy

2015-09-01

The scheme for preservation and control of the ion polarization in the Medium-energy Electron-Ion Collider (MEIC) has been under active development in recent years. The figure-8 configuration of the ion rings provides a unique capability to control the polarization of any ion species including deuterons by means of "weak" solenoids rotating the particle spins by small angles. Insertion of "weak" solenoids into the magnetic lattices of the booster and collider rings solves the problem of polarization preservation during acceleration of the ion beam. Universal 3D spin rotators designed on the basis of "weak" solenoids allow one to obtain any polarizationmore » orientation at an interaction point of MEIC. This paper presents the baseline scheme for polarization preservation and control in the MEIC ion complex.« less

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas

NASA Astrophysics Data System (ADS)

Wallace, M. S.; Haque, S.; Neill, P.; Pereira, N. R.; Presura, R.

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.