Showing papers on "Polarimetry published in 2019"
university of lille1, Chinese Academy of Sciences2, Goddard Institute for Space Studies3, EUMETSAT4, California Institute of Technology5, University of Maryland, Baltimore County6, Goddard Space Flight Center7, Netherlands Institute for Space Research8, NASA Headquarters9, European Space Agency10, Taras Shevchenko National University of Kyiv11, Kyoto College of Graduate Studies for Informatics12, Kindai University13, Royal Netherlands Meteorological Institute14, Langley Research Center15
TL;DR: Polarimetry is one of the most promising types of remote sensing for improved characterization of atmospheric aerosol, and several new-generation retrieval approaches have recently been proposed to address these challenges.
Abstract: Polarimetry is one of the most promising types of remote sensing for improved characterization of atmospheric aerosol. Indeed, aerosol particles constitute a highly variable atmospheric component characterized by a large number of parameters describing particle sizes, morphologies (including shape and internal structure), absorption and scattering properties, amounts, horizontal and vertical distribution, etc. Reliable monitoring of all these parameters is very challenging, and therefore the aerosol effects on climate and environment are considered to be among the most uncertain factors in climate and environmental research. In this regard, observations that provide both the angular distribution of the scattered atmospheric radiation as well as its polarization state at multiple wavelengths covering the UV–SWIR spectral range carry substantial implicit information on the atmospheric composition. Therefore, high expectations in improving aerosol characterization are associated with detailed passive photopolarimetric observations. The critical need to use space-borne polarimetry for global accurate monitoring of detailed aerosol properties was first articulated in the late 1980s and early 1990s. By now, several orbital instruments have already provided polarization observations from space, and a number of advanced missions are scheduled for launch in the coming years by international and national space agencies. The first and most extensive record of polarimetric imagery was provided by POLDER-I, POLDER-II, and POLDER/PARASOL multi-angle multi-spectral polarization sensors. Polarimetric observations with the POLDER-like design intended for collecting extensive multi-angular multi-spectral measurements will be provided by several instruments, such as the MAI/TG-2, CAPI/TanSat, and DPC/GF-5 sensors recently launched by the Chinese Space Agency. Instruments such as the 3MI/MetOp-SG, MAIA, SpexOne and HARP2 on PACE, POSP, SMAC, PCF, DPC–Lidar, ScanPol and MSIP/Aerosol-UA, MAP/Copernicus CO2 Monitoring, etc. are planned to be launched by different space agencies in the coming decade. The concepts of these future instruments, their technical designs, and the accompanying algorithm development have been tested intensively and analyzed using diverse airborne prototypes. Certain polarimetric capabilities have also been implemented in such satellite sensors as GOME-2/MetOp and SGLI/GCOM-C. A number of aerosol retrieval products have been developed based on the available measurements and successfully used for different scientific applications. However, the completeness and accuracy of aerosol data operationally derived from polarimetry do not yet appear to have reached the accuracy levels implied by theoretical sensitivity studies that analyzed the potential information content of satellite polarimetry. As a result, the dataset provided by MODIS is still most frequently used by the scientific community, yet this sensor has neither polarimetric nor multi-angular capabilities. Admittedly polarimetric multi-angular observations are highly complex and have extra sensitivities to aerosol particle morphology, vertical variability of aerosol properties, polarization of surface reflectance, etc. As such, they necessitate state-of-the-art forward modeling based on first-principles physics which remains rare, and conventional retrieval approaches based on look-up tables turn out to be unsuitable to fully exploit the information implicit in the measurements. Several new-generation retrieval approaches have recently been proposed to address these challenges. These methods use improved forward modeling of atmospheric (polarized) radiances and implement a search in the continuous space of solutions using rigorous statistically optimized inversions. Such techniques provide more accurate retrievals of the main aerosol parameters such as aerosol optical thickness and yield additional parameters such as aerosol absorption. However, the operational implementation of advanced retrieval approaches generally requires a significant extra effort, and the forward-modeling part of such retrievals still needs to be substantially improved. Ground-based passive polarimetric measurements have also been evolving over the past decade. Although polarimetry helps improve aerosol characterization, especially of the fine aerosol mode, the operators of major observational networks such as AERONET remain reluctant to include polarimetric measurements as part of routine retrievals owing to their high complexity and notable increase in effort required to acquire and interpret polarization data. In addition to remote-sensing observations, polarimetric characteristics of aerosol scattering have been measured in situ as well as in the laboratory using polar nephelometers. Such measurements constitute direct observations of single scattering with no contributions from multiple scattering effects and therefore provide unique data for the validation of aerosol optical models and retrieval concepts. This article overviews the above-mentioned polarimetric observations, their history and expected developments, and the state of resulting aerosol products. It also discusses the main achievements and challenges in the exploitation of polarimetry for the improved characterization of atmospheric aerosols.
211 citations
TL;DR: Bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss are reported with great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing, circular dichroism spectroscopy, biomedical diagnosis, and remote sensing applications.
Abstract: The manipulation and characterization of light polarization states are essential for many applications in quantum communication and computing, spectroscopy, bioinspired navigation, and imaging. Chiral metamaterials and metasurfaces facilitate ultracompact devices for circularly polarized light generation, manipulation, and detection. Herein, we report bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss. We experimentally demonstrated submicron-thick circularly polarized light filters with peak extinction ratios up to 35 and maximum transmission efficiencies close to 80% at near-infrared wavelengths (the best operational wavelengths can be engineered in the range of 1.3–1.6 µm). We also monolithically integrated the microscale circular polarization filters with linear polarization filters to perform full-Stokes polarimetric measurements of light with arbitrary polarization states. With the advantages of easy on-chip integration, ultracompact footprints, scalability, and broad wavelength coverage, our designs hold great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing, circular dichroism spectroscopy, biomedical diagnosis, and remote sensing applications. Inspired by the polarization-sensitive vision of the compound eyes in a marine crustacean called the Mantis Shrimp, researchers from Arizona State University, US have designed a chiral metasurface for manipulating the polarization of light. The metasurface design consists of a thin nanostructured silicon layer, a dielectric spacer layer and a gold nanowire polarizer, and has a total thickness of less than 1 micrometer. This thin planar surface offers low optical loss with a transmission as high as 80% in the near-infrared wavelength range, and acts as a circular polarization filter with an extinction ratio as high as 35. The circular polarization filters, in combination with linear polarization filters, can enable chip-scale polarimeters for sensing the polarization state of light. This on-chip integrated approach could prove useful in ultra-compact devices for advanced imaging and sensing applications.
143 citations
TL;DR: The Stokes-Mueller matrix polarimetry (SMMP) as discussed by the authors has been used extensively in biomedical applications, such as biomedical studies and clinical diagnosis, to characterize the anisotropic optical properties of complex biomedical specimens.
Abstract: Recently, with the emergence of new light sources, polarization devices, and detectors, together with a prominent increase in data processing capability, polarization techniques find more and more applications in various areas, one of which is biomedicine. For probing the characteristic features of complex biomedical specimen, Mueller matrix polarimetry has demonstrated distinctive advantages. Mueller matrix polarimetry can be achieved on other optical techniques by adding the polarization state generator and analyzer to their existing optical paths appropriately. Common biomedical optical equipment, such as microscopes and endoscopes, can be upgraded to fulfill Mueller matrix imaging and measurement abilities. Compared with traditional non-polarization optical methods, Mueller matrix polarimetry can provide far more information to characterize the samples, including the anisotropic optical properties, such as birefringence and diattenuation, as well as the distinctive features of various scattering particles and microstructures. Also, Mueller matrix polarimetry is more sensitive to scattering by sub-wavelength microstructures. As a label-free and non-invasive tool, Mueller matrix polarimetry has broad application prospects in biomedical studies and clinical diagnosis. In this review, we provide an introduction to the Mueller matrix methodology, including the Stokes–Mueller formalism, and also the decomposition and transformation methods to derive new parameters. We also summarize the status of the Mueller matrix polarimetric field, including recent improvements, both in instrumentation and data analysis. The current and future applications of Mueller matrix polarimetry in biomedicine are provided and discussed.
110 citations
20 Sep 2019
TL;DR: In this article, a multiplexed Pancharatnam-berry phase metasurface was used to generate orthogonally polarized holograms that partially overlap with a spatially varying phase difference.
Abstract: Polarization, which represents the vector nature of electromagnetic waves, plays a fundamental role in optics. Fast, simple, and broadband polarization state characterization is required by applications such as polarization communication, polarimetry, and remote sensing. However, conventional polarization detection methods face great difficulty in determining the phase difference between orthogonal polarization states and often require a series of measurements. Here, we demonstrate how polarization-dependent holography enables direct polarization detection in a single measurement. Using a multiplexed Pancharatnam–Berry phase metasurface, we generate orthogonally polarized holograms that partially overlap with a spatially varying phase difference. Both amplitude and phase difference can be read from the holographic image in the circular polarization basis, facilitating the extraction of all Stokes parameters for polarized light. The metahologram detects polarization reliably at several near-infrared to visible wavelengths, and simulations predict broadband operation in the 580–940 nm spectral range. This method enables fast and compact polarization analyzing devices, e.g., for spectroscopy, sensing, and communications.
90 citations
TL;DR: In this paper, the authors construct and calibrate a full-Stokes imaging polarimeter system by combining the video data from two separate polarization cameras with a nonpolarizing beamsplitter and a waveplate.
Abstract: We show how to construct and calibrate a full-Stokes imaging polarimeter system by combining the video data from two separate polarization cameras with a nonpolarizing beamsplitter and a waveplate. As a result, this system can capture the full Stokes vector at each pixel for 3 megapixel images at up to 60 Hz. To demonstrate some of the advantages of measuring the s 3 Stokes vector component that is normally not measured in polarization cameras, we show three experiments: viewing three-dimensional glasses, detecting a scarab beetle in a natural environment via the circular dichroism of its shell, and mixing an optically active liquid with a neutral liquid.
83 citations
European Atomic Energy Community1, Laval University2, Oregon State University3, University of Maine4, Goddard Institute for Space Studies5, National Oceanic and Atmospheric Administration6, Columbia University7, California Institute of Technology8, university of lille9, Scripps Institution of Oceanography10, United States Naval Research Laboratory11, Netherlands Institute for Space Research12, State Oceanic Administration13, University of Baltimore14, Stevens Institute of Technology15, Langley Research Center16
TL;DR: Lidar and polarimetry can provide depth-resolved values of attenuation and scattering parameters and additional information about particle morphology and chemical composition in the ocean surface layer as discussed by the authors.
Abstract: Passive ocean color images have provided a sustained synoptic view of the distribution of ocean optical properties and color and biogeochemical parameters for the past 20-plus years. These images have revolutionized our view of the ocean. Remote sensing of ocean color has relied on measurements of the radiance emerging at the top of the atmosphere, thus neglecting the polarization and the vertical components. Ocean color remote sensing utilizes the intensity and spectral variation of visible light scattered upward from beneath the ocean surface to derive concentrations of biogeochemical constituents and inherent optical properties within the ocean surface layer. However, these measurements have some limitations. Specifically, the measured property is a weighted-integrated value over a relatively shallow depth, it provides no information during the night and retrievals are compromised by clouds, absorbing aerosols, and low Sun zenithal angles. In addition, ocean color data provide limited information on the morphology and size distribution of marine particles. Major advances in our understanding of global ocean ecosystems will require measurements from new technologies, specifically lidar and polarimetry. These new techniques have been widely used for atmospheric applications but have not had as much as interest from the ocean color community. This is due to many factors including limited access to in-situ instruments and/or space-borne sensors and lack of attention in university courses and ocean science summer schools curricula. However, lidar and polarimetry technology will complement standard ocean color products by providing depth-resolved values of attenuation and scattering parameters and additional information about particle morphology and chemical composition. This review aims at presenting the basics of these techniques, examples of applications and at advocating for the development of in-situ and space-borne sensors. Recommendations are provided on actions that would foster the embrace of lidar and polarimetry as powerful remote sensing tools by the ocean science community.
66 citations
TL;DR: X-ray and gamma-ray polarization measurements of the prompt emission of Gamma-ray bursts (GRBs) are believed to be extremely important for testing various models of GRBs as mentioned in this paper.
Abstract: X-ray and gamma-ray polarization measurements of the prompt emission of gamma-ray bursts (GRBs) are believed to be extremely important for testing various models of GRBs. So far, the available meas ...
61 citations
TL;DR: In this article, a detailed Mueller matrix model was developed to correct the instrumental polarization effects of the complete optical system, i.e., the telescope and IRDIS, and applied to observations of the circumstellar disk of T Cha.
Abstract: Context. Circumstellar disks and self-luminous giant exoplanets or companion brown dwarfs can be characterized through direct-imaging polarimetry at near-infrared wavelengths. SPHERE/IRDIS at the Very Large Telescope has the capabilities to perform such measurements, but uncalibrated instrumental polarization effects limit the attainable polarimetric accuracy. Aims. We aim to characterize and correct the instrumental polarization effects of the complete optical system, i.e. the telescope and SPHERE/IRDIS. Methods. We create a detailed Mueller matrix model in the broadband filters Y-, J-, H- and Ks, and calibrate it using measurements with SPHERE's internal light source and observations of two unpolarized stars. We develop a data-reduction method that uses the model to correct for the instrumental polarization effects, and apply it to observations of the circumstellar disk of T Cha. Results. The instrumental polarization is almost exclusively produced by the telescope and SPHERE's first mirror and varies with telescope altitude angle. The crosstalk primarily originates from the image derotator (K-mirror). At some orientations, the derotator causes severe loss of signal (>90% loss in H- and Ks-band) and strongly offsets the angle of linear polarization. With our correction method we reach in all filters a total polarimetric accuracy of <0.1% in the degree of linear polarization and an accuracy of a few degrees in angle of linear polarization. Conclusions. The correction method enables us to accurately measure the polarized intensity and angle of linear polarization of circumstellar disks, and is a vital tool for detecting unresolved (inner) disks and measuring the polarization of substellar companions. We have incorporated the correction method in a highly-automatic end-to-end data-reduction pipeline called IRDAP which is publicly available at this https URL.
55 citations
University of Baltimore1, Goddard Space Flight Center2, University of Maryland, Baltimore County3, California Institute of Technology4, Columbia University5, Netherlands Institute for Space Research6, Lille University of Science and Technology7, University of Maine8, Goddard Institute for Space Studies9, University of Colorado Boulder10, University of Connecticut11, Scripps Institution of Oceanography12, United States Naval Research Laboratory13, Langley Research Center14
TL;DR: The Plankton, Aerosol, Clouds, ocean ecosystem (PACE) mission presents new opportunities and new challenges in applying observations of two complementary multi-angle polarimeters for the space-based retrieval of global aerosol properties as discussed by the authors.
Abstract: The Plankton, Aerosol, Clouds, ocean Ecosystem (PACE) mission presents new opportunities and new challenges in applying observations of two complementary multi-angle polarimeters for the space-based retrieval of global aerosol properties.Aerosol remote sensing from multi-angle radiometric-only observations enables aerosol characterization to a greater degree than single-view radiometers, as demonstrated by nearly two decades of heritage instruments. Adding polarimetry to the multi-angle observations allows for the retrieval of aerosol optical depth, Angstrom exponent,parameters of size distribution, measures of aerosol absorption, complex refractive index and degree of non-sphericity of the particles, as demonstrated by two independent retrieval algorithms applied to the heritage POLarization and Directionality of the Earth's Reflectance (POLDER) instrument. The reason why this detailed particle characterization is possible is because a multi-angle polarimeter measurement contains twice the number of Degrees of Freedom of Signal (DFS) compared to an observation from a single-view radiometer. The challenges of making use of this information content involve separating surface signal from atmospheric signal, especially when the surface is optically complex and especially in the ultraviolet portion of the spectrum where we show the necessity of polarization in making that separation. The path forward is likely to involve joint retrievalsthat will simultaneously retrieve aerosol and surface properties, although advances will berequired in radiative transfer modeling and in representing optically complex constituents in those models. Another challenge is in having the processing capability that can keep pace with the output of these instruments in an operational environment. Yet, preliminaryalgorithms applied to airborne multi-angle polarimeter observations offer encouraging results that demonstrate the advantages of these instruments to retrieve aerosol layer height, particle single scattering albedo, size distribution and spectral optical depth, and also show the necessity of polarization measurements, not just multi-angle radiometricmeasurements, to achieve these results.
50 citations
Posted Content•
Université Paris-Saclay1, PSL Research University2, University of Oxford3, New York University4, Cardiff University5, University of California, Berkeley6, Lawrence Berkeley National Laboratory7, California Institute of Technology8, Netherlands Institute for Space Research9, Delft University of Technology10, University of Bonn11, Cornell University12, INAF13, University of Barcelona14, Centre national de la recherche scientifique15, University of Manchester16, University of Paris17, University of Toronto18, Chinese Academy of Sciences19, University of Science and Technology of China20, Max Planck Society21, Sapienza University of Rome22, University of New South Wales23, Kavli Institute of Nanoscience24, University of Maryland, College Park25, Imperial College London26, Harvard University27, Goddard Space Flight Center28, Ben-Gurion University of the Negev29, RWTH Aachen University30, Perimeter Institute for Theoretical Physics31, University of Ferrara32, University of Porto33, University of Geneva34, European Southern Observatory35, Yale University36, University of California, Los Angeles37, University of La Laguna38, University of British Columbia39, Johns Hopkins University40, University of Oslo41, Indian Institute of Science Education and Research, Pune42, National Institutes of Natural Sciences, Japan43, University of Cambridge44
TL;DR: In this article, the authors proposed a spectro-polarimetric survey of the microwave sky using a broadband polarised imager and a moderate resolution spectroimager at the focus of a 3.5m aperture telescope actively cooled to about 8K.
Abstract: This paper discusses the science case for a sensitive spectro-polarimetric survey of the microwave sky. Such a survey would provide a tomographic and dynamic census of the three-dimensional distribution of hot gas, velocity flows, early metals, dust, and mass distribution in the entire Hubble volume, exploit CMB temperature and polarisation anisotropies down to fundamental limits, and track energy injection and absorption into the radiation background across cosmic times by measuring spectral distortions of the CMB blackbody emission. In addition to its exceptional capability for cosmology and fundamental physics, such a survey would provide an unprecedented view of microwave emissions at sub-arcminute to few-arcminute angular resolution in hundreds of frequency channels, a data set that would be of immense legacy value for many branches of astrophysics. We propose that this survey be carried-out with a large space mission featuring a broad-band polarised imager and a moderate resolution spectro-imager at the focus of a 3.5m aperture telescope actively cooled to about 8K, complemented with absolutely-calibrated Fourier Transform Spectrometer modules observing at degree-scale angular resolution in the 10-2000 GHz frequency range. We propose two observing modes: a survey mode to map the entire sky as well as a few selected wide fields, and an observatory mode for deeper observations of regions of specific interest.
TL;DR: In this article, chip-integrated metasurface devices for polarization detection of mid-infrared light with arbitrary polarization states are presented. But they are not suitable for on-chip mid-IR polarimeters and polarimetric imaging systems.
Abstract: Flat optics presents a new path to control the phase, amplitude, and polarization state of light with ultracompact devices. Here we demonstrate chip-integrated metasurface devices for polarization detection of mid-infrared light with arbitrary polarization states. Six high-performance microscale linear and circular polarization filters based on vertically stacked plasmonic metasurfaces (with total thickness <600 nm) are integrated on the same chip to obtain all four Stokes parameters of light with high accuracy. The device designs can be tailored to operate at any wavelength in the mid-infrared spectral region and are feasible for on-chip integration with mid-infrared (mid-IR) photodetectors and imager arrays. Our work will enable on-chip mid-IR polarimeters and polarimetric imaging systems, which are highly desirable for many applications, such as clinical diagnosis, target detection, and space exploration.
TL;DR: Combining optical and polarimetric synthetic aperture radar (PolSAR) earth observations offers a complementary data set with a significant number of spectral, textural, and polar-imetric features as mentioned in this paper.
Abstract: Combining optical and polarimetric synthetic aperture radar (PolSAR) earth observations offers a complementary data set with a significant number of spectral, textural, and polarimetric features fo...
TL;DR: PolarLight as mentioned in this paper is a CubeSat mission Polarimeter light (Polarlight) to demonstrate and test the gas pixel detector (GPD) directly in space, which is designed and developed for high-sensitivity astronomical X-ray polarimetry.
Abstract: The gas pixel detector (GPD) is designed and developed for high-sensitivity astronomical X-ray polarimetry, which is a new window about to open in a few years. Due to the small mass, low power, and compact geometry of the GPD, we propose a CubeSat mission Polarimeter Light (PolarLight) to demonstrate and test the technology directly in space. There is no optics but a collimator to constrain the field of view to 2.3 degrees. Filled with pure dimethyl ether (DME) at 0.8 atm and sealed by a beryllium window of 100 μm thick, with a sensitive area of about 1.4 mm by 1.4 mm, PolarLight allows us to observe the brightest X-ray sources on the sky, with a count rate of, e.g., ∼0.2 counts s− 1 from the Crab nebula. The PolarLight is 1U in size and mounted in a 6U CubeSat, which was launched into a low Earth Sun-synchronous orbit on October 29, 2018, and is currently under test. More launches with improved designs are planned in 2019. These tests will help increase the technology readiness for future missions such as the enhanced X-ray Timing and Polarimetry (eXTP), better understand the orbital background, and may help constrain the physics with observations of the brightest objects.
TL;DR: In this article, a simple setup, including a FPB as input light, has been designed and implemented to measure the Mueller matrix of a homogeneous sample, and the polarization states of the input and output fields are measured using a commercial polarimeter.
Inter-University Centre for Astronomy and Astrophysics1, California Institute of Technology2, Saint Petersburg State University3, University of Crete4, Foundation for Research & Technology – Hellas5, Max Planck Society6, Aalto University7, University of Turku8, Nicolaus Copernicus University in Toruń9, Stanford University10
TL;DR: In this paper, the authors present RoboPol, a four-channel optical polarimeter operating at the Skinakas Observatory in Crete, Greece, which is capable of measuring both relative linear Stokes parameters $q$ and $u$ in one sky exposure.
Abstract: We present the design and performance of RoboPol, a four-channel optical polarimeter operating at the Skinakas Observatory in Crete, Greece. RoboPol is capable of measuring both relative linear Stokes parameters $q$ and $u$ (and the total intensity $I$) in one sky exposure. Though primarily used to measure the polarization of point sources in the R-band, the instrument features additional filters (B, V and I), enabling multi-wavelength imaging polarimetry over a large field of view (13.6' $\times$ 13.6'). We demonstrate the accuracy and stability of the instrument throughout its five years of operation. Best performance is achieved within the central region of the field of view and in the R band. For such measurements the systematic uncertainty is below 0.1% in fractional linear polarization, $p$ (0.05% maximum likelihood). Throughout all observing seasons the instrumental polarization varies within 0.1% in $p$ and within 1$^\circ$ in polarization angle.
TL;DR: This review article explains the development of Stokes-Mueller formalism in context of linear optics and shows how application of Mueller matrix decomposition (MMD) method to derive sample properties is demonstrated in several bio-medical studies.
Abstract: Polarization microscopy, a powerful optical tool to study anisotropic properties of biomolecules, provides better microstructural information of a sample as compared with conventional optical microscopic techniques. The measurement and analysis of polarization states of light can be performed using both Jones matrix as well as Stokes algebra. Further, the details of optical properties of specimen are characterized by Mueller matrix. However, the application of Jones calculus is limited to perfectly polarized light, but Stokes-Mueller polarimetry is emerging as a promising tool for tissue imaging due to its application irrespective of polarization state of the light. In this review article, we explain the development of Stokes-Mueller formalism in context of linear optics. Furthermore, application of Mueller matrix decomposition (MMD) method to derive sample properties is demonstrated in several bio-medical studies.
TL;DR: In this article, a pixelated polarization camera and Stokes parameters are used to extract the polarization information of linearly polarized incident light for optical rotation measurement, which can be used for identification, purity test and content detection of chiral materials.
Abstract: Chirality is an essential consideration in the field of life sciences and pharmaceutical industry because most biomolecules and pharmaceuticals are chiral, and optical rotation measurement is a simple and efficient means for identification, purity test and content detection of chiral materials. However, there are some drawbacks in existing methods, such as small measurement range, non-real-time performance, low measurement accuracy and resolution. This paper presents a novel system to implement optical rotation measurement, and pixelated polarization cameras and Stokes parameters are employed in the system. The polarization information of linearly polarized incident light can be recorded and extracted by a pixelated polarization camera and Stokes parameters respectively. Experiments demonstrate that the proposed system has the necessary advantages for optical rotation measurement, such as real time, wide range ( − 90 ° to + 90 °), high accuracy ( 1 × 1 0 − 4 °) and high resolution ( ± 6 × 1 0 − 6 °). Thus, this measurement system has great practical prospects in the hospital clinical diagnosis, chemical research, sugar production and pharmaceutical industry.
TL;DR: This work relies on the superposition principle, which enables the splitting of the input beam into identical copies, allowing the simultaneous measurement of all intensities, to reliably reconstruct the SoP with high fidelity and at speeds of up to 27 Hz, paving the way for real-time polarimetry of structured light.
Abstract: Stokes polarimetry (SP) is a powerful technique that enables spatial reconstruction of the state of polarization (SoP) of a light beam using only intensity measurements. A given SoP is reconstructed from a set of four Stokes parameters, which are computed through four intensity measurements. Since all intensities must be performed on the same beam, it is common to record each intensity individually, one after the other, limiting its performance to light beams with static SoP. Here, we put forward a novel technique to extend SP to a broader set of light beams with dynamic SoP. This technique relies on the superposition principle, which enables the splitting of the input beam into identical copies, allowing the simultaneous measurement of all intensities. For this, the input beam is passed through a multiplexed digital hologram displayed on a polarization-insensitive Digital Micromirror Device (DMD) that grants independent and rapid (20 kHz) manipulation of each beam. We are able to reliably reconstruct the SoP with high fidelity and at speeds of up to 27 Hz, paving the way for real-time polarimetry of structured light.
21 Aug 2019-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Imaging X-ray Polarimetry Explorer (IXPE) as mentioned in this paper was selected by NASA as the next SMall EXplorer (SMEX) mission for a launch in 2021.
Abstract: Recently selected by NASA as the next SMall EXplorer (SMEX) mission for a launch in 2021, the Imaging X-ray Polarimetry Explorer (IXPE) marks the renaissance of X-ray polarimetry, with the prospect of measuring linear polarization from tens of astronomical X-ray sources . IXPE will expand the X-ray view of the Universe by providing new and unique insight into our understanding of some of the most violent celestial objects, such as stellar and supermassive black holes and neutron stars . In this contribution we shall discuss the scientific prospects of the mission, as well as the status of the program, with particular emphasis on the development of the focal plane detectors sensitive to polarization.
TL;DR: The results verify that the performance accuracy of the HCP architecture is comparable to the accuracy delivered by a quadrature-polarized SAR, and an alternative and recommended group of methodologies yields reliable results, illustrated by polarimetrically classified images.
Abstract: Compact polarimetry for a synthetic aperture radar (SAR) system is reviewed. Compact polarimetry (CP) is intended to provide useful polarimetric image classifications while avoiding the disadvantages of space-based quadrature-polarimetric (quad-pol) SARs. Two CP approaches are briefly described, π/4 and circular. A third form, hybrid compact polarimetry (HCP) has emerged as the preferred embodiment of compact polarimetry. HCP transmits circular polarization and receives on two orthogonal linear polarizations. When seen through its associated data processing and image classification algorithms, HPC’s heritage dates back to the Stokes parameters (1852), which are summarized and explained in plain language. Hybrid dual-polarimetric imaging radars were in the payloads of two lunar-orbiting satellites, India’s Earth-observing RISAT-1, and Japan’s ALOS-2. In lunar or planetary orbit, a satellite equipped with an HCP imaging radar delivers the same class of polarimetric information as Earth-based radar astronomy. In stark contrast to quad-pol, compact polarimetry is compatible with wide swath modes of a SAR, including ScanSAR. All operational modes of the SARs aboard Canada’s three-satellite Radarsat Constellation Mission (RCM) are hybrid dual-polarimetric. Image classification methodologies for HCP data are reviewed, two of which introduce errors for reasons explained. Their use is discouraged. An alternative and recommended group of methodologies yields reliable results, illustrated by polarimetrically classified images. A survey over numerous quantitative studies demonstrates HCP polarimetric classification effectiveness. The results verify that the performance accuracy of the HCP architecture is comparable to the accuracy delivered by a quadrature-polarized SAR. Four appendices are included covering related topics, including comments on inflight calibration of an HCP radar.
TL;DR: In this article, the problem of Synthetic Aperture Radar (SAR) polarimetric decomposition, where oriented urban areas and vegetation signatures are decomposed into the same volume scattering mechanism is discussed.
Abstract: One of the problems of Synthetic Aperture Radar (SAR) polarimetric decomposition, is that oriented urban areas and vegetation signatures are decomposed into the same volume scattering mechanism. Su...
TL;DR: A new PolPSI algorithm, named CMD-PolPSI, is proposed to achieve a compromise between phase optimization and computational cost, utilizing the polarimetric synthetic aperture radar (PolSAR) coherency matrix decomposition to determine the optimal polarization channel for each pixel.
Abstract: The rationale of polarimetric optimization techniques is to enhance the phase quality of the interferograms by combining adequately the different polarization channels available to produce an improved one. Different approaches have been proposed for polarimetric persistent scatterer interferometry (PolPSI). They range from the simple and computationally efficient BEST, where, for each pixel, the polarimetric channel with the best response in terms of phase quality is selected, to those with high-computational burden like the equal scattering mechanism (ESM) and the suboptimum scattering mechanism (SOM). BEST is fast and simple, but it does not fully exploit the potentials of polarimetry. On the other side, ESM explores all the space of solutions and finds the optimal one but with a very high-computational burden. A new PolPSI algorithm, named coherency matrix decomposition-based PolPSI (CMD-PolPSI), is proposed to achieve a compromise between phase optimization and computational cost. Its core idea is utilizing the polarimetric synthetic aperture radar (PolSAR) coherency matrix decomposition to determine the optimal polarization channel for each pixel. Three different PolSAR image sets of both full- (Barcelona) and dual-polarization (Murcia and Mexico City) are used to evaluate the performance of CMD-PolPSI. The results show that CMD-PolPSI presents better optimization results than the BEST method by using either $D_{\mathrm{ A}}$ or temporal mean coherence as phase quality metrics. Compared with the ESM algorithm, CMD-PolPSI is 255 times faster but its performance is not optimal. The influence of the number of available polarization channels and pixel’s resolutions on the CMD-PolPSI performance is also discussed.
TL;DR: In this paper, the authors developed a theory of polarimetry based on nonlinear Compton scattering, which can determine the polarization of spin-polarized electron beams via single-shot interaction with a strong laser pulse, by detecting the asymmetry in high-energy-photon spectra.
Abstract: Precise measurement of the polarization of relativistic spin-polarized electron beams is crucial for experiments in nuclear physics and high-energy physics. However, the usual methods are not applicable for low-repetition-rate, dense ultrarelativistic electron beams, such as those produced by strong laser pulses. The authors develop a theory of polarimetry based on nonlinear Compton scattering, which can determine the polarization of such a beam via single-shot interaction with a strong laser pulse, by detecting the asymmetry in high-energy-photon spectra. Statistical precision better than 0.3% can be achieved within femtoseconds.
TL;DR: An achromatic snapshot full-Stokes imaging polarimeter that enables the acquisition of 2D-spatial full Stokes parameters from a single exposure is presented and an extended eigenvalue calibration method (ECM) is proposed to calibrate the system, which considers the imperfectness of retarder and polarizer samples and the intensity attenuation of polarizer sample.
Abstract: An achromatic snapshot full-Stokes imaging polarimeter (ASSIP) that enables the acquisition of 2D-spatial full Stokes parameters from a single exposure is presented. It is based on the division-of-aperture polarimetry using an array of four-quadrant achromatic elliptical analyzers as polarization state analyzer (PSA). The optimization of PSA is addressed for achieving immunity of Gaussian and Poisson noises. An extended eigenvalue calibration method (ECM) is proposed to calibrate the system, which considers the imperfectness of retarder and polarizer samples and the intensity attenuation of polarizer sample. A compact prototype of ASSIP operating over the waveband of 450-650 nm and an optimized calibration setup are developed. The achromatic performance is evaluated at three bandwidths of 10, 25, and 200 nm, respectively. The results show that the prototype with an uncooled CMOS camera works well at each bandwidth. The instrument matrix determined at the narrower bandwidth is more applicable to the wider one. The uncertainties of the calibrated instrument matrices and reconstructed Stokes parameters are improved by using the extended EMC at each bandwidth. To speed up the acquisition of high-contrast images, wide bandwidth along with short exposure time is preferable. The snapshot capability was verified via capturing dynamic scenes.
TL;DR: WIRC+Pol as discussed by the authors is a low-resolution near-infrared spectropolarimetry mode of the WIRC on the 200-inch Hale Telescope at Palomar Observatory, which utilizes a novel polarimeter design based on a quarter-wave plate and a polarization grating.
Abstract: WIRC+Pol is a newly commissioned low-resolution (R 100), near-infrared (J and H bands) spectropolarimetry mode of the Wide-field InfraRed Camera (WIRC) on the 200-inch Hale Telescope at Palomar Observatory. The instrument utilizes a novel polarimeter design based on a quarter-wave plate and a polarization grating (PG), which provides full linear polarization measurements (Stokes I, Q, and U ) in one exposure with no need for a polarimetric modulator. The PG also has high transmission across the J and H bands. The instrument is situated at the prime focus of an equatorially mounted telescope. As a result, the system only has one reflection in the light path and the instrument does not rotate with respect to the sky, which provides minimal and stable telescope induced polarization. A data reduction pipeline has been developed for WIRC+Pol to produce linear polarization measurements from observations, allowing, e.g., real-time monitoring of the signal-to-noise ratio of ongoing observations. WIRC+Pol has been on-sky since February 2017. Results from the first year commissioning data show that the instrument has a high dispersion efficiency as expected from the polarization grating. We discuss instrumental systematics we have uncovered in the data, their potential causes, along with calibrations that are necessary to eliminate them. We demonstrate the polarimetric stability of the instrument with RMS variation at 0.2% level over 30 minutes for a bright standard star (J = 8.7). While the spectral extraction is photon noise limited, polarization calibration between sources remain limited by systematics.
TL;DR: In this paper, a pilot program with an automated system of small telescopes that can simultaneously conduct high cadence optical photometry and polarimetry of active galactic nuclei (AGN) in multiple passbands is described.
Abstract: Various quantum gravity approaches that extend beyond the Standard Model predict Lorentz invariance and charge-parity-time violation at energies approaching the Planck scale. These models frequently predict a wavelength-dependent speed of light, which would result in time delays between promptly emitted photons at different energies, as well as a wavelength-dependent rotation of the plane of linear polarization for photons resulting from vacuum birefringence. Here, we describe a pilot program with an automated system of small telescopes that can simultaneously conduct high cadence optical photometry and polarimetry of active galactic nuclei (AGN) in multiple passbands. We use these observations as a proof of principle to demonstrate how such data can be used to test various Lorentz violation models, including special cases of the Standard Model extension (SME). In our initial campaign with this system, the Array Photo Polarimeter, we observed two AGN sources, including BL Lacertae at redshift $z=0.069$, and S5 $\mathrm{B}0716+714$ at $z=0.31$. We demonstrate that optical polarimetry with a broadband Luminance filter combined with simultaneous ${I}_{c}$-band observations yields SME parameter constraints that are up to $\ensuremath{\sim}10$ and $\ensuremath{\sim}30$ times more sensitive than with a standard ${I}_{c}$-band filter, for SME models with mass dimension $d=5$ and $d=6$, respectively. Using only a small system of telescopes with an effective 0.45-m aperture, we further demonstrate $d=5$ constraints for individual lines of sight that are within a factor of $\ensuremath{\sim}1--10$ in sensitivity to comparable constraints from optical polarimetry with a 3.6-m telescope. Such an approach could significantly improve existing SME constraints via a polarimetric all-sky survey of AGN with multiple 1-meter class telescopes.
27 Oct 2019
TL;DR: Polarimetry has been a standard tool to probe the active galactic nucleus (AGN) jet magnetic field, and several optical polarization monitoring programs have been carried out, bringing in many exciting new results and insights into jet dynamics and emission as mentioned in this paper.
Abstract: Polarimetry has been a standard tool to probe the active galactic nucleus (AGN) jet magnetic field. In recent years, several optical polarization monitoring programs have been carried out, bringing in many exciting new results and insights into jet dynamics and emission. This article discusses current progress in blazar optical polarimetry. The main focus is the variability of polarization signatures, which has spurred a lot of theoretical studies. These novel developments have provided unique constraints on the blazar flares and emphasized the role of the magnetic field in jet evolution. Optical polarimetry will continue to act as an essential component in the multi-messenger study of AGN jets, in particular with the upcoming high-energy polarimetry. Comparing to first-principle numerical simulations, future multi-wavelength polarimetry can shed light on jet dynamics, particle acceleration, and radiation processes.
TL;DR: In this paper, the authors investigate the possibility that multi-epoch broadband polarimetry could act as a complement or limited proxy for VLBI observations of blazars, in that the number of polarised emission components in the jet, and some of their properties and those of the foreground environment, might be inferred from the object's time-varying 1D Faraday depth spectrum (FDS) alone.
Abstract: We investigate the previously proposed possibility that multi-epoch broadband polarimetry could act as a complement or limited proxy for VLBI observations of blazars, in that the number of polarised emission components in the jet, and some of their properties and those of the foreground environment, might be inferred from the object's time-varying 1D Faraday depth spectrum (FDS) alone. We report on a pilot-scale experiment designed to establish the basic plausibility and utility of this idea. We analyse temporal changes in the complex polarisation spectra of nine spatially unresolved (at arcsecond scales) blazars in two epochs separated by $\sim$5 years, using data taken with the Australia Telescope Compact Array. The data allow for precise modelling, and we demonstrate that all objects in our sample show changes in their polarisation spectrum that cannot be accounted for by uncertainties in calibration or observational effects. By associating polarised emission components across epochs, we infer changes in their number, intrinsic fractional polarisation, intrinsic polarisation angle, rotation measure, and depolarisation characteristics. We attribute these changes to evolution in the structure of the blazar jets, most likely located at distances of up to tens of parsecs from the central active galactic nuclei. Our results suggest that continued work in this area is warranted; in particular, it will be important to determine the frequency ranges and temporal cadence most useful for scientifically exploiting the effects.