Sense Of Polarization Research Articles

Integrated Polarization-Analyzing CMOS Image Sensor for Detecting the Incoming Light Ray Direction

A complementary metal–oxide–semiconductor (CMOS) image sensor used to detect the incoming light ray direction using polarization information is presented. The chip consists of an array of 128 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 128 pixels, and each pixel is embedded with a metallic wire-grid micropolarizer. It occupies an area of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$5 \times 4\ \hbox{mm}^{2}$</tex> </formula> , and it has been designed and fabricated in a 180-nm CMOS process. Extinction ratios of 6.3 and 7.7 were achieved in two different polarization sense regions. The Stokes parameters, which are needed to evaluate the degree of polarization (DOP) and electric-field vector intensity, are computed from the pixel with the micropolarizer oriented at 0 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> , 45 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{ \circ}$</tex></formula> , and 90 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> . We show that the variations in the DOP and the e-vector pattern with the incoming polarized light ray direction can be used as a directional reference source for autonomous agent navigation. We also show that the measurement results of ellipticity and azimuthal angles for the incoming light ray using the Stokes parameters can allow on-chip position detection based on the angle of the incoming light ray with little complexity. A very high correlation coefficient bigger than 0.94 was obtained between the measured and theoretical incoming light ray angles.

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transmits a single sense of circular polarization, and both senses of circular polarization are received, which allows for the construction of the Stokes polarization vector. From the Stokes vector, daughter products such as the circular polarization ratio, the degree of linear polarization, and linear polarization angle are obtained. Recent polarimetric imaging using Arecibo has included Venus and the Moon. These observations can be compared to radar data for terrestrial surfaces to better understand surface physical properties and regional geologic evolution. For example, polarimetric radar studies of volcanic settings on Venus, the Moon, and Earth display some similarities, but also illustrate a variety of different emplacement and erosion mechanisms. Polarimetric radar data provide important information about surface properties beyond what can be obtained from single-polarization radar. Future observations using polarimetric synthetic aperture radar will provide information on roughness, composition, and stratigraphy that will support a broader interpretation of surface evolution.

Frequency-dependent polarization characteristics of Pc1 geomagnetic pulsations observed by multipoint ground stations at low latitudes

[1] We have investigated Pc1 geomagnetic pulsations observed by induction magnetometers at three low-latitude stations (Paratunka (PTK), Moshiri (MSR), and Sata (STA), L=1.2–2.1). A detailed polarization analysis shows that polarization parameters (angle of polarization ellipse orientation, Ψ, and polarization sense, ɛ) of individual Pc1 bands depend on frequency at all three stations. The dependence of Ψ on frequency was seen in ∼70% of the 93 Pc1 events observed at MSR (L=1.5) from 14 July 2007 to 13 July 2009. The maxima of seasonal and diurnal variations of the occurrence rate were in winter and during the nighttime, as reported previously, indicating that the transmission of observed Pc1 pulsations to lower latitudes is controlled by the density of the F layer plasma. These facts suggest that spatially distributed Pc1 waves with varying frequencies depending on longitude or latitude at high latitudes propagated in the ionospheric duct to cause the frequency dependence of polarization parameters at low latitudes. We also suggest that the Pc1 pearl structure with a repetition period of ∼5–30 s observed at low latitudes is a beat of high-latitude waves with slightly different frequencies.

Ground-based radar observations of Titan: 2000–2008

We have observed Titan with the Arecibo Observatory’s 12.6cm wavelength radar system during the last eight oppositions of the Saturn system with sufficient sensitivity to characterize its scattering properties as a function of sub-Earth longitude. In a few sessions the Green Bank Telescope was used as the receiving instrument in a bistatic configuration to boost sub-radar track length and integration time. Radar echo spectra have been obtained for a total of 92 viewing geometries with sub-Earth locations scattered through all longitudes and at latitudes between 7.6°S and 26.3°S, close to the maximum southern excursion of the sub-Earth track. We find Titan to have globally average radar albedos at this wavelength of 0.161 in the opposite circular polarization sense as that transmitted (OC) and 0.074 in the same sense (SC), giving a polarization ratio SC/OC of 0.46. These values are intermediate between lower reflectivity rocky surfaces and higher reflectivity clean icy surfaces. The variations with longitude in general mirror the surface brightness variations seen through the infrared atmospheric windows. Xanadu Regio’s radar reflectivity and polarization ratio are higher than the global averages, and suggest that its composition is relatively cleaner water ice or, possibly, some other material with low propagation loss at radio wavelengths. For all echo spectra most of the power is in a broad diffuse component but with a specular component whose strength and narrowness is highly variable as a function of surface location. For all data we fit a sum of the standard Hagfors scattering law describing the specular component and an empirical diffuse radar scattering model to extract bulk parameters of the surface. Many areas exhibit very narrow specular reflections implying terrain that are quite flat on centimeter to meter scales over spans of tens to perhaps hundreds of kilometers. The proportion of spectra showing these narrow specular echoes has fallen significantly over the observational time span, indicating either a latitudinal effect related to terrain differences or changing surface conditions over the past several years. A few radar tracks, especially those from the 2008 session, overlap some high resolution Cassini RADAR imagery swaths to allow a direct comparison with terrain.

Time Domain Characterization of Circularly Polarized Ultrawideband Array

The transmitted signal by a circularly polarized ultrawideband (CP-UWB) array is a short pulse of circularly rotating E-field vector in time domain. A mathematical model is derived for a transmitted pulse radiated by a CP-UWB array antenna. To validate the model, an array of four sequentially rotated ridged horns is constructed, and the transmitted pulse is measured in time domain. The measurement is done with a linearly polarized antenna in far-field, for different rotational angles. The E-field vector transmitted by the CP-UWB array is constructed with the measured time-domain pulses. The measured pulse is compared with the derived pulse for validation. Both measured and derived pulses are compared for various parameters such as the CP-UWB array's sense of polarization, axial ratio, gain and phase difference between orthogonal signals.

Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure fluctuations

Several observational studies suggest that solar wind dynamic pressure fluctuations can drive magnetospheric ultralow‐frequency (ULF) waves on the dayside. To investigate this causal relationship, we present results from Lyon‐Fedder‐Mobarry (LFM) global, three‐dimensional magnetohydrodynamic (MHD) simulations of the solar wind–magnetosphere interaction. These simulations are driven with synthetic solar wind input conditions where idealized ULF dynamic pressure fluctuations are embedded in the upstream solar wind. In three of the simulations, a monochromatic, sinusoidal ULF oscillation is introduced into the solar wind dynamic pressure time series. In the fourth simulation, a continuum of ULF fluctuations over the 0–50 mHz frequency band is introduced into the solar wind dynamic pressure time series. In this numerical experiment, the idealized solar wind input conditions allow us to study only the effect of a fluctuating solar wind dynamic pressure, while holding all of the other solar wind driving parameters constant. We show that the monochromatic solar wind dynamic pressure fluctuations drive toroidal mode field line resonances (FLRs) on the dayside at locations where the upstream driving frequency matches a local field line eigenfrequency. In addition, we show that the continuum of upstream solar wind dynamic pressure fluctuations drives a continuous spectrum of toroidal mode FLRs on the dayside. The characteristics of the simulated FLRs agree well with FLR observations, including a phase reversal radially across a peak in wave power, a change in the sense of polarization across the noon meridian, and a net flux of energy into the ionosphere.

Ducting characteristics of Pc 1 waves at high latitudes on the ground and in space

Well‐defined ULF Pc 1 geomagnetic pulsations have been observed simultaneously from a ground array of five search‐coil magnetometers in the morning sector of Antarctica on Mar. 23, 2007. Distributed over a very extensive range of geomagnetic latitudes (−62° to −87°, spanning ∼2920 km geographically) approximately along a magnetic meridian, the array showed poleward propagation of the Pc 1 waves in the ionospheric waveguide. It is observed that attenuation factors are between ∼8 and 20 dB/1000 km and the polarization sense changes from left‐hand to right‐hand as the waves are ducted poleward. However, a complex polarization pattern (i.e., change in ellipticity and major axis angle) was seen on the ground, which might be attributed to the array being close to the wave injection region where the superposed effect of incident waves and ducted waves is dominant. A CHAMP satellite conjunction showed a transverse and nearly linearly polarized Pc 1 ULF wave at the altitude of the ducting layer (∼350 km) over a limited latitudinal extent (−53° to −61° ILAT). The polarization analysis performed using the ground data supports the idea that CHAMP detected the wave activity near the wave injection region. The observations are unique in that the ducted waves, seen over an array with unprecedented geomagnetic latitudinal range and positioning along a magnetic meridian (a condition that provides the most efficient ducting), have rarely been measured before.

Reconfigurable Circularly-Polarized Patch Antenna With Conical Beam

A design method is described for reconfigurable circularly-polarized (CP) microstrip array antennas with conical-beam radiation. The proposed antenna structure consists of four L-shaped patch antennas arranged in a square-ring formation. Each patch antenna is shorted to the ground plane through conducting walls. With a top-loaded monopole feed, two orthogonal resonant modes, loop mode and monopole mode, can be excited simultaneously. The effects of the shorting walls on the resonant frequencies of the two modes are investigated, and it is found that the resonant frequency (fmono) of the monopole mode has a more obvious variation than that (floop) of the loop mode when the width or the number of the shorting walls is changed. In addition, if the two modes are properly coupled, the microstrip array can generate a CP radiation; meanwhile, the polarization sense is left-hand CP if floop > fmono but is right-hand CP if floop <; fmono. A reconfigurable antenna prototype is fabricated, and the experimental results show that the prototype not only has the characteristic of omnidirectional radiation but also possesses the ability of switching between left-hand and right-hand CP. Simulated results carried out by HFSS are also provided and they agree well with the measured results.

The polarization sense in human vision

Unlike humans, numerous animals are differentially sensitive to the vector orientation of linearly polarized light. However as early as 1844 Haidinger noted that weak blue–yellow brushes appear, centered on the fovea, when the sky is observed through a slowly rotating polarizer. Different models have been proposed to try to understand this phenomenon, but the precise mechanism remains unknown and the polarization unexploited. We suggest that when Fresnel’s laws are applied to the unguided oblique rays, that the cylindrical geometry of the blue cones in the fovea along with their distribution induces an extrinsic dichroism and could explain why the human eye is sensitive to polarization. We have constructed an artificial eye model system using the same laws and were able to photograph the appearance of entoptic-like blue-dark brushes, confirming the observations and our mathematical simulations. Moreover, our in vivo and in vitro tests show that in addition to the usual 3 s fading time measured using a stationary stimulus, there exists for this entoptic image a short extra creating and erasing time of about 0.1 s, using a dynamical stimulus. We have also found that, surprisingly, the rotating pattern is more regular and symmetrical with one of our two eyes around a more circular blue cone-free area, the dominant eye. Our results suggest that the polarization sense can provide important information in many areas that remain to be explored.

Probe-Dependent Microenvironments within Biodegradable Films Formed from Poly(L-Lactic Acid) and Pluronic 104

We report on the local microenvironment surrounding three small fluorescent probe molecules (pyrene, [6-propionyl-2-(N,N-dimethylamino) naphthalene] (PRODAN), and [4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran] (DCM)) when they are sequestered at low concentration within thin biodegradable films formed from poly( L-lactic acid) (PLLA) and Pluronic P104 blends. Despite each probe molecule being neutral, they sense and report from much different microenvironments in comparison to each other. Specifically, the non-polar pyrene probe senses a slightly more polar microenvironment as the PLLA content in the polymer blend increases. In contrast, the polar PRODAN and DCM probes sense less polar microenvironments as the PLLA content within the polymer blend increases. Time-resolved fluorescence intensity decay experiments on pure PLLA films reveal that each probe molecule encounters significant heterogeneity. Pyrene emits simultaneously from three discrete microenvironments. This is consistent with pyrene molecules reporting from crystalline, amorphous-crystalline intermediate, and amorphous regions. PRODAN and DCM appear to emit from a continuum of microenvironments. These results have ramifications on the performance of biodegradable drug delivery platforms loaded with small drug molecules.

비대칭 U자형 슬롯 접지면을 이용한 편파변환 마이크로스트립 안테나

본 논문에서는 원형편파 변환에 적합한 정사각형 마이크로스트립 안테나를 제안하였다. 제안한 안테나는 접지면의 비대칭 U자형 슬롯의 구조적 특징으로 인하여, 90도의 위상 차이를 갖는 직교전계가 형성되어 원형편파 특성을 형성한다. 또한 비대칭 U자형 슬롯의 대칭축에 따라 원형편파의 방향을 쉽게 조절할 수 있는 장점을 가지고 있다. 비대칭 U자형 슬롯의 대칭축은 두 개의 스위칭 다이오드를 이용하여, 전압조건의 상태에 따라 좌회전편파와 우회전 편파를 각각 실험적으로 구현하였다. 측정된 원형편파의 축비는 2.46 GHz 동작주파수에서 편파방향에 상관없이 약 1.5 dB의 높은 축비특성을 보여주며, 29 MHz (약 1.2 %) 축비 대역폭을 가짐을 실험적으로 확인하였다. In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

A Reconfigurable Circularly Polarized Microstrip Antenna With a Slotted Ground Plane

This letter describes a square patch antenna with a switchable circular polarization (CP) sense. The proposed antenna has four L-shaped slots on the ground plane, and the CP radiation can be generated by current perturbation due to the slotted ground plane. Because the CP sense of the proposed antenna is altered by the current path that is redirected with switched p-i-n diodes on the slots, the CP direction of the proposed antenna can be simply switched between the right-handed and left-handed CPs. As the slot and bias circuits are not placed on the patch side, the proposed antenna has a simple structure and can radiate a CP wave without altering the main beam direction. The experimental results show that antennas have excellent switchable radiation performance at 2.4 GHz.

Low-frequency (0.7-7.4 mHz) geomagnetic field fluctuations at high latitude: frequency dependence of the polarization pattern

A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.7-7.4 mHz) covering the entire 24-h interval was performed at the Antarctic station Terra Nova Bay (80.0°S geomagnetic latitude) throughout 1997 and 1998. The results show that the polarization pattern exhibits a frequency dependence, as can be expected from the frequency dependence of the latitude where the coupling between the magnetospheric compressional mode and the field line resonance takes place. The polarization analysis of single pulsation events shows that wave packets with different polarization sense, depending on frequency, can be simultaneously observed.

Evaluation of magnetic helicity density in the wave number domain using multi-point measurements in space

Abstract. We develop an estimator for the magnetic helicity density, a measure of the spiral geometry of magnetic field lines, in the wave number domain as a wave diagnostic tool based on multi-point measurements in space. The estimator is numerically tested with a synthetic data set and then applied to an observation of magnetic field fluctuations in the Earth foreshock region provided by the four-point measurements of the Cluster spacecraft. The energy and the magnetic helicity density are determined in the frequency and the wave number domain, which allows us to identify the wave properties in the plasma rest frame correcting for the Doppler shift. In the analyzed time interval, dominant wave components have parallel propagation to the mean magnetic field, away from the shock at about Alfvén speed and a left-hand spatial rotation sense of helicity with respect to the propagation direction, which means a right-hand temporal rotation sense of polarization. These wave properties are well explained by the right-hand resonant beam instability as the driving mechanism in the foreshock. Cluster observations allow therefore detailed comparisons with various theories of waves and instabilities.

The OD interpretation of the crystal structure of kettnerite CaBiOFCO3

The mineral kettnerite, CaBi(OFCO(3)), is a rare example of an order-disorder (OD) structure with a quadratic net. The lattice parameters of the simplest possible 1O polytype are a = 5.3641 (1), b = 5.3641 (1), c = 13.5771 (2) A, and the space group is Pbaa. There are three kinds of OD layers, identical to structure-building layers. Two of them are non-polar: the Bi-O and Ca-F at z = 0 and z = 1/2, respectively, with the layer-group symmetry C2/m2/m(4/a,b)2(1)/m2(1)/m. The third kind of OD layer of CO(3) groups (located between the Bi-O and Ca-F layers) is polar, with alternating sense of polarity. The layer group is Pba(4)mm. Triangular CO(3) groups are parallel to (110) or (110) planes with one O atom oriented towards the Bi-O layer and the remaining two O atoms oriented towards the Ca-F layer. The orientations of CO(3) groups alternate along the [110] and [110] directions. As a result, each group parallel to (110) is surrounded by four nearest neighbors parallel to (110) and vice versa. These positions can be interchanged by an (a + b)/2 shift or by pi/2 rotation; thus stacking of the layer onto adjacent ones is ambiguous. Instead of OD layers, the polytypes are generated by stacking of OD packets, comprising the whole CO(3) layers and adjacent halves of the Bi-O and Ca-F layers. They are polar, with alternating sense of polarity; the layer group is Pba(4)mm. Stacking sequences are expressed by ball-and-stick models, with the aid of symbolic figures, and by sequences of orientational characters. There are two maximum-degree-of-order (MDO) polytypes, 1O (really found and described, see lattice parameters and space group above) and 2O, with doubled c parameter and space group Ibca (not yet found). The derivation of the MDO generating operations of both polytypes is presented in this paper. The stacking rule also allows another, non-MDO, polytype with doubled c, i.e. the 2Q polytype, space group P4(2)bc (tetragonal, not yet found). Various kinds of domains can exist: (i) out-of-step domains shifted by (a + b)/2, (ii) twin domains rotated by pi/2 around local tetrads of odd or even packets, and (iii) upside-down domains in the polar 2Q polytype. Stacking sequences of 16 possible domains of the polytypes mentioned above are listed. Also 60 domains of four distinct six-packet polytypes are theoretically possible.

Transverse Photovoltage Induced by Circularly Polarized Light

We discovered that when circularly polarized light is obliquely incident on a two-dimensional metallic photonic crystal slab, electrical voltage is induced perpendicular to the incident plane. The sign of the signal is reversed by changing the sense of polarization or incident angle. The origin of this transverse photoinduced voltage is explained in terms of the force proportional to the light intensity induced by the asymmetry, which is brought about by the angular momentum of the incident light, along with the modification of local near-surface electromagnetic fields in the slab and field enhancement due to surface plasmon resonance.

Coupled Magnetic and Ferroelectric Domains in MultiferroicNi3V2O8

Electric control of multiferroic domains is demonstrated through polarized magnetic neutron diffraction. Cooling to the cycloidal multiferroic phase of Ni3V2O8 in an electric field E causes the incommensurate Bragg reflections to become neutron spin polarizing, the sense of neutron polarization reversing with E. Quantitative analysis indicates the E-treated sample has a handedness that can be reversed by E. We further show a close association between cycloidal and ferroelectric domains through E-driven spin and electric polarization hysteresis. We suggest that a definite cycloidal handedness is achieved through magnetoelastically induced Dzyaloshinskii-Moriya interactions.

Comment on “Limits on Fluorescence Detected Circular Dichroism of Single Helicene Molecules”

Comment on “Limits on Fluorescence Detected Circular Dichroism of Single Helicene Molecules”

STATISTICAL ANALYSIS OF FLARING LOOPS OBSERVED BY NOBEYAMA RADIOHELIOGRAPH. I. COMPARISON OF LOOPTOP AND FOOTPOINTS

Twenty-four events with looplike structures at 17 and 34 GHz are selected from the flare list of Nobeyama Radioheliograph. We obtained the brightness temperatures at 17 and 34 GHz, the polarization degrees at 17 GHz, and the power-law spectral indices at the radio peak time for one looptop (LT) and two footpoints (FPs) of each event. We also calculated the magnetic field strengths and the column depths of nonthermal electrons in the LT and FPs of each event, using the equations modified from the gyrosynchrotron equations by Dulk. The main statistical results from those data are summarized as follows. (1) The spectral indices, the brightness temperatures at 17 and 34 GHz, the polarization degrees at 17 GHz, the calculated magnetic field strengths, and the calculated column densities of nonthermal electrons are always positively correlated between the LT and the two FPs of the selected events. (2) About one-half of the events have the brightest LT at 17 and 34 GHz. (3) The spectral indices in the two FPs are larger (softer) than those in the corresponding LT in most events. (4) The calculated magnetic field strengths in the two FPs are always larger than those in the corresponding LT. (5) Most of the events have the same positive or negative polarization sense in the LT and the two FPs. (6) The brightness temperatures at 17 and 34 GHz in each of the LT and the two FPs statistically decrease with their spectral indices and the calculated magnetic field strengths, but increase with their calculated column densities of nonthermal electrons. Moreover, we try to discuss the possible causes of the present statistical results.

An Analysis of Ionospheric Variations Before the Wenchuan Earthquake with DEMETER Data

AbstractThe French micro‐satellite DEMETER was launched on June 29, 2004 in a polar and circular orbit with an altitude of about 665 km. The main objective of the satellite is to research ionospheric disturbance related to seismic activities. This paper reports the ionospheric anomalies observed by DEMETER within one week before the Ms8.0 Wenchuan Earthquake (31.02°N, 103.37°E) which occurred at 06:28 UT on May 12, 2008. The observation results include: (1) Electron density, electron temperature and oxygen ion density changed sharply (greater than 20%) near the epicenter four and five days prior to the shock. (2) Increased electromagnetic emissions were registered when the satellite passed the epicenter three and seven days before the shock. A further analysis (calculations of electric and magnetic power spectra, the wave vector direction and polarization sense) of the increased EM emissions is carried out based on the three‐component electric and magnetic ELF (extremely low frequency, 0~1250 Hz) data. In addition, the geophysical conditions are also investigated and it can be inferred that the observed anomalies are not likely due to geomagnetic activity. Finally, a possible mechanism which could account for these pre‐earthquake ionospheric perturbations is discussed.