Polarization Detector Research Articles

Atmospheric Effects of >30‐keV Energetic Electron Precipitation in the Southern Hemisphere Winter During 2003

AbstractThe atmospheric effects of precipitating electrons are not fully understood, and uncertainties are large for electrons with energies greater than ~30 keV. These electrons are underrepresented in modeling studies today, primarily because valid measurements of their precipitating spectral energy fluxes are lacking. This paper compares simulations from the Whole Atmosphere Community Climate Model (WACCM) that incorporated two different estimates of precipitating electron fluxes for electrons with energies greater than 30 keV. The estimates are both based on data from the Polar Orbiting Environmental Satellite Medium Energy Proton and Electron Detector (MEPED) instruments but differ in several significant ways. Most importantly, only one of the estimates includes both the 0° and 90° telescopes from the MEPED instrument. Comparisons are presented between the WACCM results and satellite observations poleward of 30°S during the austral winter of 2003, a period of significant energetic electron precipitation. Both of the model simulations forced with precipitating electrons with energies >30 keV match the observed descent of reactive odd nitrogen better than a baseline simulation that included auroral electrons, but no higher energy electrons. However, the simulation that included both telescopes shows substantially better agreement with observations, particularly at midlatitudes. The results indicate that including energies >30 keV and the full range of pitch angles to calculate precipitating electron fluxes is necessary for improving simulations of the atmospheric effects of energetic electron precipitation.

Polarization Vision: Targets of Polarization-Sensitive Photoreceptors in the Drosophila Visual System.

Insects can perceive the polarization pattern in the sky and use the information to navigate: a new study has delineated neural circuitry immediately downstream of the polarization detectors in the dorsal rim area of the Drosophila retina, which is devoted to the task of polarization vision.

Improving polarization detection for optoelectronic devices

Researchers improve on a polarization detector by integrating a plasmonic cavity with a graphene phototransistor to enhance high-performance optoelectronic applications.

Photoelectric properties of monolayer black phosphorus in visible regime at room temperature

In the present study, we theoretically study the photoelectric properties in visible regime of monolayer black phosphorus at room temperature. The low energy k·p method is applied to study the anisotropic band structure of monolayer black phosphorus. The energy-balance equation deduced from Boltzmann equation is used to calculate the energy transfer rate for the photon polarization at armchair and zigzag direction coupling with electrons. Then the optical conductivity and transmission coefficient as a function of wavelength are calculated for various electron densities. It is found that the optical responses of monolayer black phosphorus to the radiation field with two kinds of polarizations are anisotropic obviously. Specifically, the optical conductivity (transmission coefficient) for photon polarization at armchair direction is much larger (smaller) than that zigzag direction. We believe that the results obtained from this study can provide a guidance for novel photoelectric device applications suck like polarization detector.

Polarization-selective dual-band infrared plasmonic absorber based on sub-wavelength gaps

A dual-band (mid- and long-wave infrared) polarization-selective plasmonic absorber was designed and numerically investigated. This absorber traps definite polarization light and reflects light that is perpendicular to the polarization direction. It is extremely sensitive to polarization angle and can keep robustness to oblique incidence. The extinction rate does not reduce when the incident angle is even near 80°and rate value keeps above 130 for both resonance peaks. The absorber can respond to mid- and long-wave infrared atmospheric windows simultaneously and achieve near-unity absorption at 3.3 μm and 9.8 μm for specific polarization under normal radiation. The resonance condition is tuned by altering the geometric design. Owing to its high absorptivity and fine polarization properties, the absorber combines the advantages of a light absorber and a polarizer, and can be utilized in an uncooled infrared polarization detector, which simplify the optical system design and avoid the polarization information reconstruction error caused by the misplacement between the polarizer and the pixel.

An electronic electroscope for determining polarity of charge

In this study, we made a simple electronic electroscope called a ‘polarity detector’ which can determine the type of electric charge on any objects. We used the polarity detector in some student experiments in the physics laboratory. For example, when we applied a plastic rod to a piece of fabric made of wool, we could easily determine that the plastic rod was electrified with a negative electrical charge using the polarity detector. Similarly, we could show that a glass rod applied to a piece of silk fabric was electrified with a positive type of charge. However, when we carried out the same experiments with a metal leaf electroscope instead of the polarity detector, in both cases, the leaves of the electroscope were opened and gave the same response for plastic and glass rods. Thus, the electroscope with a metal leaf does not provide an idea of the type of electric charge on plastic or glass rods. Although this tool is made of cheap materials and is very simple, we have seen that it works quite well in the laboratory and contributes to the easy learning of static electricity. Therefore, we think it would be useful to use this simple instrument in the physics laboratory as an aid to metal–leaf electroscopy.

A dual-port THz Time Domain Spectroscopy System optimized for recovery of a sample\u2019s Jones matrix

We describe the design, build and characterization of a novel two-output port configuration for a THz-Time Domain Spectroscopy (TDS) system. By introducing a tilted THz ultra-broadband polarizer, we split the THz beam in two orthogonal polarization detector branches. The probe laser is similarly split (with an optical polarizer) replicating the detection chain to obtain two independent orthogonal polarization detection units. We describe the system’s performance highlighting some of the advantages of this system in one of its two modes of operation: optimized polarimetry for Jones matrix measurements. A bi-refringent sapphire standard was measured to confirm its capabilities and assess the performance of the system showing good agreement with existing literature data.

TurkiS: A Turkish Sentiment Analyzer Using Domain-specific Automatic Labelled Dataset

A preliminary task of sentiment analysis aims to detect polarities of a text either positive or negative. These texts vary from movie reviews to customer comments on electronic devices. The polarity detector trained in one domain may not achieve remarkable results in another domain. In this study, we provide a training and test dataset generator for domain-specific sentiment analysis in which machine learning methods can be trained without any human labor. To do it, we extract comments and polarity scores from a popular e-commerce website for electronic devices in Turkey. Also, we translate a well-known sentiment lexicon into Turkish and use this lexicon in a lexicon-based polarity detection. We compare well-known machine learning methods trained by automatically labeled dataset and lexicon-based method for Turkish texts in the electronics domain. The experimental setup is conducted by the generated evaluation dataset for the e-commerce domain. The test set contains 30% randomly selected from the generated dataset. Our lexicon-based method has achieved 0.62 F1 score and other three supervised learning methods achieved the best results. Further, logistic regression gets the highest score when it uses count vectorizer as a feature extraction mechanism.

Monopolatic motion vision in the butterfly Papilio xuthus.

The swallowtail butterfly Papilio xuthus can perceive the linear polarization of light. Using a novel polarization projection system, we recently demonstrated that P. xuthus can detect visual motion based on polarization contrast. In the present study, we attempt to infer via behavioural experiments the mechanism underlying this polarization-based motion vision. Papilio xuthus do not perceive contrast between unpolarized and diagonally polarized light, implying that they cannot unambiguously estimate angle and degree of polarization, at least as far as motion detection is concerned. Furthermore, they conflate brightness and polarization cues, such that bright vertically polarized light resembles dim unpolarized light. These observations are consistent with a one-channel 'monopolatic' detector mechanism. We extend our existing model of motion vision in P. xuthus to incorporate these polarization findings, and conclude that the photoreceptors likely to form the basis for the putative monopolatic polarization detector are R3 and R4, which respond maximally to horizontally polarized green light. R5-R8, we propose, form a polarization-insensitive secondary channel tuned to longer wavelengths of light. Consistent with this account, we see greater sensitivity to polarization for green-light stimuli than for subjectively equiluminant red ones. Somewhat counter-intuitively, our model predicts greatest sensitivity to vertically polarized light; owing to the non-linearity of photoreceptor responses, light polarized to an angle orthogonal to a monopolatic detector's orientation offers the greatest contrast with unpolarized light.

Polarization-Controlled and Flexible Single-/Penta-Band Metamaterial Absorber.

In this paper, a polarization-controlled and flexible metamaterial absorber made of a set of wires etched on ultrathin teflon dielectric substrate is proposed. The simulation results showed that the proposed absorber achieved single-band absorptivity of 99.8% at 6.64 GHz for the TM (transverse magnetic) polarization wave and penta-band absorptivity of more than 99% at 11.68 GHz, 13.58 GHz, 15.48 GHz, 17.38 GHz, and 19.28 GHz for the TE (transverse electric) polarization waves. Moreover, each absorption peak had very narrow relative bandwidth and the position of penta-band absorption peaks could be adjusted by changing the length of the corresponding wire or selecting suitable substrate material according to actual requirements, because each wire can independently respond to electromagnetic (EM) waves. Furthermore, the surface current distributions corresponding to each absorption peak were studied to demonstrate the absorption mechanism. The absorption properties of the proposed structure with different bending radii and under different incident angles of the EM waves were investigated, showing good flexibility and incident angle-insensitive properties. In addition, the simulation results were confirmed by measuring a fabricated prototype. The proposed absorber may have useful applications in polarizers, sensors, bolometers, polarization detectors, etc.

Polarization-sensitive tunable absorber in visible and near-infrared regimes

A broadband tunable absorber is designed and fabricated. The tunable absorber is comprised of a dielectric-metal-dielectric multilayer and plasmonic grating. A large size of tunable absorber device is fabricated by nano-imprinting method. The experimental results show that over 90% absorption can be achieved within visible and near-infrared regimes. Moreover, the high absorption can be controlled by changing the polarization of incident light. This polarization-sensitive tunable absorber can have practical applications such as high-efficiency polarization detectors and transmissive polarizer.

Design techniques of all‐digital arithmetic units for time‐mode signal processing

This study provides a comprehensive treatment of the design techniques of all-digital arithmetic units for time-mode signal processing. The arithmetic units investigated include time polarity detectors, time absolute-value generators, time adders, time baluns, time amplifiers, time quantisers, time registers, and time integrators. The principle, circuit implementation, constraints and limitations of these units are investigated in detail. An emphasis is given to time adders and time integrators. An in-depth study of time adders constructed from switched delay units, dual discharge paths, and unidirectional gated delay lines is provided. It is followed with the presentation of three time registered evolved from these time adders. Three time integrators developed from the preceding time adders and time registers are studied and their characteristics are compared. Finally, the design of a first-order time-to-digital converter utilising these arithmetic units is presented.

Generating Aspect-based Extractive Opinion Summary: Drawing Inferences from Social Media Texts

This paper presents an integrated framework to generate extractive aspect-based opinion summary from a large volume of free-form text reviews. The framework has three major components: (a) aspect identifier to determine the aspects in a given domain; (b) sentiment polarity detector for computing the sentiment polarity of opinion about an aspect; and (c) summary generator to generate opinion summary. The framework is evaluated on SemEval-2014 dataset and obtains better results than several other approaches.

Design and construction of the POLAR detector

The POLAR detector is a space based Gamma Ray Burst (GRB) polarimeter with a wide field of view, which covers almost half the sky. The instrument uses Compton scattering of gamma rays on a plastic scintillator hodoscope to measure the polarization of the incoming photons. The instrument has been successfully launched on board of the Chinese space laboratory Tiangong 2 on September 15, 2016. The construction of the instrument components is described in this article. Details are provided on problems encountered during the construction phase and their solutions. Initial performance of the instrument in orbit is as expected from ground tests and Monte Carlo simulation.

Instrument performance and simulation verification of the POLAR detector

POLAR is a new satellite-born detector aiming to measure the polarization of an unprecedented number of Gamma-Ray Bursts in the 50–500 keV energy range. The instrument, launched on-board the Tiangong-2 Chinese Space lab on the 15th of September 2016, is designed to measure the polarization of the hard X-ray flux by measuring the distribution of the azimuthal scattering angles of the incoming photons. A detailed understanding of the polarimeter and specifically of the systematic effects induced by the instrument’s non-uniformity are required for this purpose. In order to study the instrument’s response to polarization, POLAR underwent a beam test at the European Synchrotron Radiation Facility in France. In this paper both the beam test and the instrument performance will be described. This is followed by an overview of the Monte Carlo simulation tools developed for the instrument. Finally a comparison of the measured and simulated instrument performance will be provided and the instrument response to polarization will be presented.

A Study on Text-Score Disagreement in Online Reviews

In this paper, we focus on online reviews and employ artificial intelligence tools, taken from the cognitive computing field, to help understand the relationships between the textual part of the review and the assigned numerical score. We move from the intuitions that (1) a set of textual reviews expressing different sentiments may feature the same score (and vice-versa), and (2) detecting and analyzing the mismatches between the review content and the actual score may benefit both service providers and consumers, by highlighting specific factors of satisfaction (and dissatisfaction) in texts. To prove the intuitions, we adopt sentiment analysis techniques and we concentrate on hotel reviews, to find polarity mismatches therein. In particular, we first train a text classifier with a set of annotated hotel reviews, taken from the Booking website. Then, we analyze a large dataset, with around 160k hotel reviews collected from TripAdvisor, with the aim of detecting a polarity mismatch, indicating if the textual content of the review is in line, or not, with the associated score. Using well-established artificial intelligence techniques and analyzing in depth the reviews featuring a mismatch between the text polarity and the score, we find that—on a scale of five stars—those reviews ranked with middle scores include a mixture of positive and negative aspects. The approach proposed here, beside acting as a polarity detector, provides an effective selection of reviews—on an initial very large dataset—that may allow both consumers and providers to focus directly on the review subset featuring a text/score disagreement,which conveniently convey to the user a summary of positive and negative features of the review target.

Controlled Pinning of Conjugated Polymer Spherulites and Its Application in Detectors

The nucleation of single macroscopic spherulites at desired positions, as well as ordered arrays of multiple spherulites, is demonstrated by combining the use of crystallizable solvents with local control of solvent evaporation during solution deposition. Moreover, the temperature assisted localized frustration of molecular orientation is shown, enabling the fabrication of samples containing both isotropic areas and spherulites. These macroscopic circular polycrystalline structures are characterized using a range of polarized spectroscopic techniques that allow quantifying their large degree of chain orientation. In order to show the potential of these large conjugated polymer spherulites centered at desired locations, graded bilayer organic photovoltaic devices were fabricated to be used as polarimeters, solid state light polarization detectors with no moving parts, and position sensitive photodetectors.

A Polarization-Dependent Frequency-Selective Metamaterial Absorber with Multiple Absorption Peaks

A polarization-dependent, frequency-selective metamaterial (MM) absorber based on a single-layer patterned resonant structure intended for F frequency band is proposed. The design, fabrication, and measurement for the proposed absorber are presented. The absorber’s absorption properties at resonant frequencies have unique characteristics of a single-band, dual-band, or triple-band absorption for different polarization of the incident wave. The calculated surface current distributions and power loss distribution provide further understanding of physical mechanism of resonance absorption. Moreover, a high absorption for a wide range of TE-polarized oblique incidence was achieved. Hence, the MM structure realized on a highly flexible polyimide film, makingthe absorber suitable for conformal geometry applications. The proposed absorber has great potential in the development of polarization detectors and polarizers.

Real-time observational evidence of changing Asian dust morphology with the mixing of heavy anthropogenic pollution

Natural mineral dust and heavy anthropogenic pollution and its complex interactions cause significant environmental problems in East Asia. Due to restrictions of observing technique, real-time morphological change in Asian dust particles owing to coating process of anthropogenic pollutants is still statistically unclear. Here, we first used a newly developed, single-particle polarization detector and quantitatively investigate the evolution of the polarization property of backscattering light reflected from dust particle as they were mixing with anthropogenic pollutants in North China. The decrease in observed depolarization ratio is mainly attributed to the decrease of aspect ratio of the dust particles as a result of continuous coating processes. Hygroscopic growth of Calcium nitrate (Ca(NO3)2) on the surface of the dust particles played a vital role, particularly when they are stagnant in the polluted region with high RH conditions. Reliable statistics highlight the significant importance of internally mixed, ‘quasi-spherical’ Asian dust particles, which markedly act as cloud condensation nuclei and exert regional climate change.

Circularly polarized light detection in stomatopod crustaceans: a comparison of photoreceptors and possible function in six species.

A combination of behavioural and electrophysiological experiments have previously shown that two species of stomatopod, Odontodactylus scyllarus and Gonodactylaceus falcatus, can differentiate between left- and right-handed circularly polarized light (CPL), and between CPL and linearly polarized light (LPL). It remains unknown if these visual abilities are common across all stomatopod species, and if so, how circular polarization sensitivity may vary between and within species. A subsection of the midband, a specialized region of stomatopod eyes, contains distally placed photoreceptor cells, termed R8 (retinular cell number 8). These cells are specifically built with unidirectional microvilli and appear to be angled precisely to convert CPL into LPL. They are mostly quarter-wave retarders for human visible light (400-700 nm), as well as being ultraviolet-sensitive linear polarization detectors. The effectiveness of the R8 cells in this role is determined by their geometric and optical properties. In particular, the length and birefringence of the R8 cells are crucial for retardation efficiency. Here, our comparative studies show that most species investigated have the theoretical ability to convert CPL into LPL, such that the handedness of an incoming circular reflection or signal could be discriminated. One species, Haptosquilla trispinosa, shows less than quarter-wave retardance. Whilst some species are known to produce circularly polarized reflections (some Odontodactylus species and G. falcatus, for example), others do not, so a variety of functions for this ability are worth considering.