Dissertations / Theses on the topic 'Polarimetry'

Soil conditions under vegetation cover and their spatial and temporal variations from point to catchment scale are crucial for understanding hydrological processes within the vadose zone, for managing irrigation and consequently maximizing yield by precision farming. Soil moisture and soil roughness are the key parameters that characterize the soil status. In order to monitor their spatial and temporal variability on large scales, remote sensing techniques are required. Therefore the determination of soil parameters under vegetation cover was approached in this thesis by means of (multi-angular) polarimetric SAR acquisitions at a longer wavelength (L-band, lambda=23cm). In this thesis, the penetration capabilities of L-band are combined with newly developed (multi-angular) polarimetric decomposition techniques to separate the different scattering contributions, which are occurring in vegetation and on ground. Subsequently the ground components are inverted to estimate the soil characteristics. The novel (multi-angular) polarimetric decomposition techniques for soil parameter retrieval are physically-based, computationally inexpensive and can be solved analytically without any a priori knowledge. Therefore they can be applied without test site calibration directly to agricultural areas. The developed algorithms are validated with fully polarimetric SAR data acquired by the airborne E-SAR sensor of the German Aerospace Center (DLR) for three different study areas in Germany. The achieved results reveal inversion rates up to 99% for the soil moisture and soil roughness retrieval in agricultural areas. However, in forested areas the inversion rate drops significantly for most of the algorithms, because the inversion in forests is invalid for the applied scattering models at L-band. The validation against simultaneously acquired field measurements indicates an estimation accuracy (root mean square error) of 5-10vol.% for the soil moisture (range of in situ values: 1-46vol.%) and of 0.37-0.45cm for the soil roughness (range of in situ values: 0.5-4.0cm) within the catchment. Hence, a continuous monitoring of soil parameters with the obtained precision, excluding frozen and snow covered conditions, is possible. Especially future, fully polarimetric, space-borne, long wavelength SAR missions can profit distinctively from the developed polarimetric decomposition techniques for separation of ground and volume contributions as well as for soil parameter retrieval on large spatial scales.
Zur Verbesserung der hydrologischen Abflussmodellierung, der Flutvorhersage, der gezielten Bewässerung von landwirtschaftlichen Nutzflächen und zum Schutz vor Ernteausfällen ist die Bestimmung der Bodenfeuchte und der Bodenrauhigkeit von grosser Bedeutung. Aufgrund der hohen zeitlichen sowie räumlichen Dynamik dieser Bodenparameter ist eine flächenhafte Erfassung mit hoher Auflösung und in kurzen zeitlichen Abständen notwendig. In situ Messtechniken stellen eine sehr zeit- und personalaufwändige Alternative dar, deshalb werden innovative Fernerkundungsverfahren mit aktivem Radar erprobt. Diese Aufnahmetechniken sind von Wetter- und Beleuchtungsverhältnissen unabhängig und besitzen zudem die Möglichkeit, abhängig von der Wellenlänge, in Medien einzudringen. Mit dem in dieser Arbeit verwendeten polarimetrischen Radar mit synthetischer Apertur (PolSAR) werden die Veränderungen der Polarisationen ausgewertet, da diese aufgrund der physikalischen Eigenschaften der reflektierenden Medien objektspezifisch verändert und gestreut werden. Es kann dadurch ein Bezug zwischen der empfangenen Radarwelle und den dielektrischen Eigenschaften (Feuchtegehalt) sowie der Oberflächengeometrie (Rauhigkeit) des Bodens hergestellt werden. Da vor allem in den gemässigten Klimazonen die landwirtschaftlichen Nutzflächen die meiste Zeit des Jahres mit Vegetation bestanden sind, wurden in dieser Dissertation Verfahren entwickelt, um die Bodenfeuchte und die Bodenrauhigkeit unter der Vegetation erfassen zu können. Um die einzelnen Rückstreubeiträge der Vegetation und des Bodens voneinander zu trennen, wurde die Eindringfähigkeit von längeren Wellenlängen (L-band, lambda=23cm) mit neu entwickelten (multi-angularen) polarimetrischen Dekompositionstechniken kombiniert, um die Komponente des Bodens zu extrahieren und auszuwerten. Für die Auswertung wurden polarimetrische Streumodelle benutzt, um die Bodenkomponente zu modellieren und dann mit der extrahierten Bodenkomponente der aufgenommenen Daten zu vergleichen. Die beste Übereinstimmung von Modell und Daten wurde als die gegebene Bodencharakteristik gewertet und dementsprechend invertiert. Die neu entwickelten, polarimetrischen Dekompositionstechniken für langwelliges polarimetrisches SAR basieren auf physikalischen Prinzipien, benötigen wenig Rechenzeit, erfordern keine Kalibrierung und sind ohne Verwendung von a priori Wissen analytisch lösbar. Um die entwickelten Algorithmen zu testen, wurden in drei verschiedenen Untersuchungsgebieten in Deutschland mit dem flugzeuggetragenen E-SAR Sensor des Deutschen Zentrums für Luft- und Raumfahrt (DLR) polarimetrische SAR Daten aufgenommen. Die Auswertungen der PolSAR Daten haben bestätigt, dass die besten Invertierungsergebnisse mit langen Wellenlängen erzielt werden können (L-Band). Des Weiteren konnten bei der Bestimmung der Bodenfeuchte und der Bodenrauhigkeit hohe Inversionsraten erreicht werden (bis zu 99% der Untersuchungsfläche). Es hat sich gezeigt, dass die polarimetrischen Streumodelle bei der gegebenen Wellenlänge nicht für bewaldete Gebiete geeignet sind, was die Anwendbarkeit des Verfahrens auf landwirtschaftliche Nutzflächen einschränkt. Die Validierung mit Bodenmessungen in den Untersuchungsgebieten, die zeitgleich zu den PolSAR Aufnahmen durchgeführt wurden, hat ergeben, dass eine kontinuierliche Beobachtung des Bodenzustandes (ausgenommen in Zeiten mit gefrorenem oder Schnee bedecktem Boden) mit einer Genauigkeit (Wurzel des mittleren quadratischen Fehlers) von 5-10vol.% für die Bodenfeuchte (in situ Messbereich: 1-46vol.%) und von 0.37-0.45cm für die Bodenrauhigkeit (in situ Messbereich: 0.5-4.0cm) möglich ist. Besonders künftige Fernerkundungsmissionen mit langwelligem, voll polarimetrischem SAR können von den entwickelten Dekompositionstechniken profitieren, um die Vegetationskomponente von der Bodenkomponente zu trennen und die Charakteristik des Oberbodens flächenhaft zu bestimmen.

Polarization specific measurements are advancing the capabilities of scientific instruments looking for ever smaller effects and material parameters. For example, the magneto-optical nonlinear Faraday effect can be used to characterize various electric and magnetic polarizability parameters of an individual molecule. Another major application is detection of desired particles in a highly scattering environment, the physical effect of which has been extensively researched, and is being overcome by using time-gated and polarization techniques. The polarimeter sensitivity is limited by the extinction-ratio obtained from polarizers. Of available polarizer materials, naturally occurring Calcite crystals provide the best extinction ratios because of their good optical homogeneity and high birefringence. However, there is a need for polarization determination with higher sensitivities, and thus a necessity to find better polarizing materials and methods. I developed a next-generation polarimeter in an attempt to sensitively detect the second-order Faraday effect, along with a substance s chirality and Verdet constant. Also, I developed a device uniquely able to sensitively detect chiral signatures in the presence of massive depolarizing scattering. In addition, I begun developing a novel type of polarimeter based on the highly-polarization-sensitive nonlinear-optical process of harmonic generation, whose required crystals can be grown with extremely high quality.

Many animals perceive changes in the polarization of light in addition to, or instead of, changes in intensity and wavelength, allowing them to more effectively perform tasks. Although humans lack this ability, recent work allows humans to exploit polarization using imaging polarimeters, and many applications which use this technology have been developed. A major challenge of polarimetry is image degradation due to noise, which has led to incorrect conclusions in the literature and reduces the effectiveness of computer vision algorithms. Local feature extraction is a technique for extracting information from images which is a common intermediate step in many computer vision applications. No work has yet been done assessing the performance of existing local feature extraction algorithms with polarimetry, or how they can be most effectively used. In this thesis degradation caused by noise in polarimetry is investigated, and mitigating steps are proposed. Denoising algorithms are then investigated which are shown to improve the peak signal-to-noise ratio of polarization images by 4.5dB over existing algorithms. This is done by adapting an existing denoising algorithm, Block-Matching 3D, to create a method specifically for polarimetry, Polarization-BM3D (PBM3D). PBM3D will be shown to provide superior visual quality to existing algorithms. This thesis also investigates the use of common local feature extraction algorithms with polarimetry, and compares their effectiveness with colour imagery. It will be demonstrated that using local features with polarimetry can yield better results than using colour imagery (by 7.5%), specifically when the Stokes representation is used. It will also be shown that Hessian-affine is the most effective detection algorithm and SIFT is the most effective description algorithm for use with polarimetry. Finally the effects of noise on features extraction with polarimetry will be presented, and it will be shown that PBM3D improves detector and descriptor performance by 35% and 5% respectively.

In this work, image processing algorithms are presented for an advanced sensor classification known collectively as imaging modulated polarimetry. The image processing algorithms presented are novel in that they use frequency domain based approaches, in comparison to the data domain based approaches that all previous algorithms have employed. Under the conditions on the data and imaging device derived in this work, the frequency domain based demodulation algorithms will optimally reduced reconstruction artifacts in a least squared sense. This work provides a framework for objectively comparing polarimeters that modulate in different domains (i.e. time vs. space), referred to as the spectral density response function. The spectral density response function is created as an analog to the modulation transfer function (or the more general transfer function for temporal devices) employed in the design of conventional imaging devices. The framework considers the total bandwidth of the object to be measured, and then can consider estimation artifacts that arise in both time and space due to the measurement modality that has been chosen. Using the framework for objectively comparing different modulated polarimeters (known as the spectral density response function), a method of developing a Wiener filter for multi-signal demodulation is developed, referred to as the polarimetric Wiener filter. This filter is then shown to be optimal for one extensive test case. This document provides one extensive example of implementing the algorithms and spectral density response calculations on a real system, known as the MSPI polarimeter. The MSPI polarimeter has been published extensively elsewhere, so only a basic system description here is used as necessary to describe how the methods presented here can be implemented on this system.

The magnetic field is a major contributor to the physics of many types of astronomical objects. Polarimetry is a powerful tool for probing directly into the magnetic field to estimate its degree of ordering and orientation. This knowledge is often essential in order to constrain theoretical models in astrophysics. The advent of submillimetre polarimetry has opened a new window through which polarised emission produced by dust grains or the synchrotron mechanism can be investigated. This has immediate applications to the study of star forming regions and radio-loud extragalactic sources. The work presented in this thesis covers several aspects of doing polarimetry in the submillimetre with the James Clerk Maxwell Telescope (JCMT), and its application to an on-going observing programme dedicated to monitor the polarisation of highly variable extragalactic sources, which include BL Lac Objects and a subset of Quasars, often referred to collectively as Blazars. The more instrumental parts of this project are concerned with the development of data reduction algorithms and their implementation in a new common user software package for the analysis of JCMT polarimetry data, the optimisation of data acquisition techniques in the currently available observing mode and the development of a new (potentially more efficient) observing mode, including numerical simulations, extensive laboratory experiments and telescope tests. The Blazar monitoring programme consists of a series of observing runs during which polarimetry and multi-frequency photometry have been done on a sample of sources. The observations allow two different types of study to be carried out: one in terms of the variability of individual sources and the other in terms of the overall properties derived for the two classes of object. While variability observations are used to discern between and place constrains on theoretical models that deal with the energy production and transport mechanisms, the comparison between BL Lac Objects and Quasars investigates whether they are likely to have different parent populations, or if their properties can be accounted for within a single unifying theory.

On temporal, spatial and spectral scales which are small enough, all fields are fully polarized. In the optical regime, however, instantaneous fields can rarely be examined, and, instead, only average quantities are accessible. The study of polarimetry is concerned with both the description of electromagnetic fields and the characterization of media a field has interacted with. The polarimetric information is conventionally presented in terms of second order field correlations which are averaged over the ensemble of field realizations. Motivated by the deficiencies of classical polarimetry in dealing with specific practical situations, this dissertation expands the traditional polarimetric approaches to include higher order field correlations and the description of fields fluctuating in three dimensions. In relation to characterization of depolarizing media, a number of fourth-order correlations are introduced in this dissertation. Measurements of full polarization distributions, and the subsequent evaluation of Stokes vector element correlations and Complex Degree of Mutual Polarization demonstrate the use of these quantities for material discrimination and characterization. Recent advancements in detection capabilities allow access to fields near their sources and close to material boundaries, where a unique direction of propagation is not evident. Similarly, there exist classical situations such as overlapping beams, focusing, or diffusive scattering in which there is no unique transverse direction. In this dissertation, the correlation matrix formalism is expanded to describe three dimensional electromagnetic fields, providing a definition for the degree of polarization of such a field. It is also shown that, because of the dimensionality of the problem, a second parameter is necessary to fully describe the polarimetric properties of three dimensional fields. Measurements of second-order correlations of a three dimensional field are demonstrated, allowing the determination of both the degree of polarization and the state of polarization. These new theoretical concepts and innovative experimental approaches introduced in thiss dissertation are expected to impact scientific areas as diverse as near field optics, remote sensing, high energy laser physics, fluorescence microscopy, and imaging.
Ph.D.
Optics and Photonics
Optics

Light reflected by planetary atmospheres and/or surfaces is polarised, and the degree and direction of polarisation can yield information that cannot always be gleaned from flux measurements alone. Polarimetric studies of solar system planets can reveal more details about the seasonal variations in their atmospheres, and the variation with orbital geometry can place constraints on the properties of cloud particles. With the advent of extremely large telescopes, and potentially the most accurate instruments ever realised thus far, polarimetry has great potential for both detecting and characterising exoplanets. A key difference when observing exoplanets with respect to the planets of our solar system is that despite the much lower signal-to-noise than solar system planets, we can access them at wider phase angle ranges, thus enabling us to probe their scattering properties more extensively, especially at geometries where the degree of polarisation is highest. This can result in an easier interpretation of the atmospheric characteristics through theoretical modelling. My original contribution to the field that is presented in this thesis is the observation, data reduction and analysis of polarimetric data along with model interpretation of the six most outer solar system planets and Titan. In addition, model results for exoplanets of varying types are shown and discussed. The overall goal is to show that polarimetry is necessary for giving a full description of light reflected by planetary atmospheres and surfaces, and to demonstrate its worth as a diagnostic tool for atmospheric characterisation, from both ground-based observations of solar system and exoplanets, and from in-situ missions to the outer planets, such as a potential atmospheric probe into any of the outer planets.

The motivation of this thesis was the study of radio-loud, active galaxies. These galaxies house relativistic jets at their centres, powered by accretion onto a super massive black hole. The focus was on the optical flux and polarised emission produced by these powerful jets. An automated pipeline was developed to reduce data from the Liverpool Telescope Ringo2 and Ringo3 polarimeters. As part of this work, the Ringo3 instrumental polarisation and depolarisation were characterised by repeated observations of standard stars. The Ringo2 and Ringo3 optical polarimetry and photometry of a sample of 20 gamma-ray bright blazars were combined with Fermi gamma-ray space telescope data and were used to explore possible correlations and thus probe the emission sites in the jet. We found that optical and gamma-ray fluxes had strong, positive correlations. This suggests that the dominant source of optical and gamma-ray emission is from shared emission regions. If the Inverse Compton model is adopted to explain the gamma-ray emission (i.e. upscattering of photons by relativistic electrons), this correlation suggests that synchrotron self-Compton emission processes are occurring in the jet, along with inverse Compton upscattering from nearby electrons (rather than those outside the jet). The gamma-ray flux and optical degree of polarisation were not significantly correlated. The optical flux and degree of polarisation were weakly positively correlated (with correlations that did not improve with an introduced lag). Both of these results imply that there is no large scale highly ordered magnetic field in the region where the gamma-ray emission originates. We found that the maximum degree of polarisation differs depending on the location of the source's synchrotron-peak. This may be a result of the viewing angle of the observer with respect to the jet. This suggests that the majority of optical polarisation is produced in shocked regions within the jet, downstream of the main emission region. We found that the degree of polarisation was lower during a period of polarisation angle rotation compared with a period of non-rotation. This implies that the downstream magnetic field structure is either helical or compressed in a direction transverse to that of the jet. Consistent with other work, our Ringo3 colour analysis showed that, with the exception of one source, flat spectrum radio quasars had a `redder' when brighter property. This suggests that when the source is more luminous, the jet (i.e. non-thermal) emission dominates over the thermal emission from the accretion disk (which is powerful in FSRQs). We found that BL~Lacs had a `bluer' when brighter behaviour, suggesting that the brighter emission may come from more energetic photons within the jet. We presented data from our long-term, multi-colour, blazar monitoring campaign. We found that all but one source had a `redder' polarisation when the polarisation was higher. This implies that the highest polarisation is associated with higher densities of lower energy particles in the jet. Well-sampled, regular cadence data is very important for the effective study and interpretation of blazars. This is particularly crucial for the interpretation of the position angle rotations, which can afford information about the electric vector angle (and hence the magnetic field angle). In this work, we presented the design of a new multicolour polarimeter, MOPTOP. The optical components in MOPTOP allow as much of the light from the source to be exploited as possible by replacing the rotating Polaroid (from the Ringo polarimeter design) with a rotating half-wave plate and beam splitter. MOPTOP's design minimises exposure times, allowing more frequent observations and a better sampling of data. A densely sampled monitoring program that is not interrupted by periods of sunlight would be highly desirable for the study of blazar jets.

Physics
Ph.D.
Jefferson Lab's cutting-edge parity-violating electron scattering program has increasingly stringent requirements for systematic errors. Beam polarimetry is often one of the dominant systematic errors in these experiments. A new Moeller Polarimeter in Hall A of Jefferson Lab (JLab) was installed in 2015 and has taken first measurements for a polarized scattering experiment. Upcoming parity violation experiments in Hall A include CREX, PREX-II, MOLLER and SOLID with the latter two requiring < 0.5% precision on beam polarization measurements, a precision which has not been achieved to date. The polarimeter measures the Moeller scattering rates of the polarized electron beam incident upon an iron target placed in a saturating magnetic field. The spectrometer consists of four quadrupoles and one momentum selection dipole. The detector is designed to measure the scattered and knock out target electrons in coincidence. Beam polarization is extracted by constructing an asymmetry from the scattering rates when the incident electron spin is parallel and anti-parallel to the target electron spin. The largest systematic errors associated with Moeller polarimetry comes from the precision that the target polarization and the detector acceptance is known will be discussed. Other errors including the Levchuk effect, beam stability, and target heating will be addressed.
Temple University--Theses

Els oceans mantenen una fràgil i complexa cadena que enllaça un alt nombre de factors biològics, sociològics i econòmics. Actualment, aquest ecosistema està amenaçat per l'activitat humana i uns dels punts més crítics és la sobreexplotació pesquera. Això ha despertat la consciencia de les autoritats d'arreu per a protegir l'entorn marí i assegurar, així, la seguretat i supervivència dels éssers humans. Tal objectiu demana el desenvolupament de polítiques de control que monitorin l'activitat dels vaixells.

Fins l'actualitat, diferents propostes s'han estudiat per monitorar vaixells, com per exemple transpondedors, teledetecció òptica i sensors acústics passius. L'experiència en entorns reals ha demostrat que cap d'aquestes solucions és eficient. Una alternativa poden ser els Radars d'Obertura Sintètica (SAR). Aquests sistemes utilitzen les propietats de reflectivitat i dispersió dels vaixells per identificar-los amb independència de qualsevol fenomen atmosfèric i del cicle dia/nit. El sensors SAR sintetitzen una obertura més gran que la real permetent l'obtenció d'imatges de reflectivitat d'uns quants kilòmetres d'amplada amb una resolució de pocs metres.

En la monitorització de vaixells, la tecnologia SAR ha demostrat unes bones prestacions per la detecció. Treu profit del fet que els vaixells dispersen més energia que el mar i, així, apareixen en les imatges com punts molt brillants. Però, la seva utilitat en la identificació de vaixells encara no està clara. Hi ha dues limitacions importants: 1) les resolucions dels sistemes actuals no semblen suficients per aïllar característiques geomètriques a partir de la informació de reflectivitat i 2) les distorsions que les signatures dels vaixells experimenten en entorns marins. Aquests problemes es poden resoldre parcialment si s'utilitzen dades SAR multidimensional. Aquest concepte es refereix al fet d'adquirir imatges SAR modificant un o més paràmetres del sistema. En la classificació de vaixells, hi ha dues opcions clares: 1) Polarimetria SAR (PolSAR) que utilitza les dues components polarimètriques de l'ona EM i 2) la Interferometria SAR que s'obté per la combinació de dues imatges SAR adquirides des de posicions molt properes. Per a una banda, la polarització de l'ona EM és una propietat intrínseca de l'ona que ajuda a aïllar estructures geomètriques particulars per mitjà de la teoria de descomposició de blancs (TD). Per l'altra, la interferometria treu profit de la diferencia de fase entre les dues imatges SAR per obtenir la tercera dimensió de l'escena.

PolSAR and InSAR presenten grans possibilitats per la monitorització de vaixells ja que poden solucionar algunes de les limitacions dels mètodes clàssics. Desafortunadament, encara no han estat profundament estudiades a causa de les dificultats en obtenir dades reals validades. Això ha limitat el nombre d'estudis en aquesta temàtica. En aquest entorn, la tesi està orientada a avaluar fins a quin punt les tècniques PolSAR i InSAR poden ser útils per la monitorització de vaixells. Per a tal propòsit, s'han fixat quatre objectius importants:
1. El desenvolupament d'un simulador SAR eficient que doni imatges realistes de vaixells i que solucioni el dèficit de dades reals en entorns marins.
2. L'estudi de la dispersió dels vaixells que fixi els principals mecanismes de dispersió observats en imatges SAR i com es relacionen amb la geometria dels vaixells.
3. Un estudi de les prestacions de les tècniques actuals d'anàlisis de dades PolSAR en la classificació de vaixells.
4. El desenvolupament d'un mètode nou i eficient per la identificació de vaixells.

Al llarg de la tesis, els diferents punts seran estudiats i resolts. El desenvolupament de GRECOSAR, un simulador SAR de blancs complexes que dóna imatges de vaixells similars a les adquirides en entorns reals, ha estat essencial per estudiar les propietats de dispersió dels vaixells. Ha permès demostrar que els vaixells es poden distingir a partir del seu patró dispersiu, el qual és senzill i dominat per alguns dispersors guia que presenten una marcada estabilitat i potència de dispersió. Amb aquests resultats ha estat possible desenvolupar un nou mètode que pot identificar vaixells sota condicions d'observació adverses. Combina característiques polarimètriques i interferomètriques SAR (PolInSAR) per inferir estimacions 3D de la geometria dels vaixells. Diferents tests han demostrat que aquest mètode dóna una millor fiabilitat en la identificació que altres mètodes actualment disponibles. Malgrat tot, fixa uns requeriments tecnològics més elevats, sobretot en la resolució de les imatges i en les característiques PolInSAR. La nova generació de sensors SAR els poden cobrir.
Oceans support a complex and fragile chain that links a high number of biological, sociological and economical factors. In these days, this ecosystem is endangered by human activity and one of the main hot spots is overfishing. As a result, authorities worldwide have become aware about the necessity to law-protect the marine environment in order to assure the safety and sustenance of human beings. This demands the development of fisheries policy to monitor the activities of ships.

Up to now, different vessel monitoring proposals have been considered, for instance transponders, optical remote sensing or passive acoustic sensors. The lessons learnt in real scenarios have shown that none of these solutions is efficient. A feasible option may be the so-called active Synthetic Aperture Radar (SAR) technology. It uses the reflectivity/scattering properties of vessels for basing the identification process with independence of any atmospheric phenomena and day/night cycle. SAR sensors synthesize an antenna aperture larger than the real one and this allows to acquire reflectivity images of some tens of kilometers wide with a resolution of few meters.

In vessel monitoring, SAR imagery has proven good performance for vessel detection. They take profit of the fact that vessels normally backscatter more power than the sea and, hence, they appear in the images as bright spots. But their usefulness in vessel identification has not been established yet. There are two main limitations, namely: 1) the resolution of current systems that appears to be not enough for isolating geometrical features from the reflectivity information of SAR images and 2) the distortions that vessel' signatures experiment within sea scenarios. Such problems can be solved up to certain extend if multidimensional SAR data is used. This concept refers to the possibility to acquire different SAR images by modifying one or more imaging parameters. In the scope of vessel classification, there are two main options, namely: 1) SAR polarimetry (PolSAR) that refers to the usage of the two polarimetric components of the EM wave and 2) SAR interferometry (InSAR) derived by combining two SAR images acquired from slightly different positions. On the one hand, the polarization of an EM wave is an intrinsic wave property that helps on identifying specific geometrical structures via Target Decomposition (TD) theory. On the other hand, Interferometry takes profit of the phase difference between the two SAR images to retrieve the third dimension of the scene.

PolSAR and InSAR have great potentialities for supporting vessel monitoring as they can overcome some of the limitations of classical methods. Unfortunately, they have not been exploited yet due to the difficulties on having at one's disposal real data with reliable ground-truth. This has limited the number of works tackling such issue. In this framework, the current thesis is focused to evaluate up to which extend PolSAR and InSAR imagery are reliable for vessel monitoring. For such purpose, four main goals are proposed, namely:
1. The development of an efficient SAR simulation environment that provides realistic vessel SAR images and overcomes the current data deficiency related to marine scenarios.
2. The study of vessel scattering to fix the main polarimetric scattering mechanisms observed in vessel SAR images and how they are related with the geometries of vessels.
3. A performance study of current analysis tools of PolSAR data in vessel classification.
4. The development of a novel and efficient methodology for vessel identification.

Along the thesis, the different points are studied and solved. The development of GRECOSAR, a SAR simulator of complex targets able to provide vessel images similar to those obtained in real scenarios, has been essential for studying the scattering properties of vessels. It has allowed to show that vessels can be distinguished by means of their scattering pattern, which appear to be not so complex and dominated by some guide scatters that present a marked reflectivity stability and scattered power. With these results, a new approach able to identify vessels even under adverse observation conditions has been developed. It combines polarimetric and interferometric SAR (PolInSAR) capabilities to retrieve 3D estimates of the geometry of ships. Different tests have shown that the proposed method provides better identification confidence than other available methods. However, it demands higher technological requirements in terms of image resolution and PolInSAR features. The new generation of SAR sensors may fulfill them.

In this work a review of many of the current theories of star formation as it is understood today is presented. New polarimetric observations of three cometary nebulae, RMon/NGC2261, RCr A/NGC6729 and the Chamaeleon Infrared Nebula are presented and discussed. It is shown how previous polarimetric measurements of the illuminating source of Hubble's variable nebula (NGC2261) have often produced results which increase in error with increasing wavelength. The reason for this is that previous authors have used an aperture size for measurements of R Mon which includes effects of a highly polarized feature ~ 5" north of RMon. Though this phenomenon has been seen before by other observers, its effect on polarimetric measurements of R Mon has not been recognised before despite tests to check for this. The data presented here agree with the interpretation that this feature is the northern-lobe of a mini-bipolar nebula, and it is further suggested that this is a manifestation of episodic mass outflow from R Mon. Previous explanations for the polarization of R Mon and RCr A cannot explain the rapid change in polarization and position angle that these young stellar objects are seen to undergo. Models of these objects which assume that they appear as polarized sources are used to explain the polarizations and are discussed. These models are not only able to produce the level of polarization seen at the source, but they are also currently the best models for explaining the rapid changes in polarization that are observed. A jet-like feature is seen to the south-west of the main nebulosity in the Chamaeleon IRN for the first time in observations presented in this thesis. A similar jet seen emerging from RCr A has been explained as being an emission feature collimated by an inner-circumstellar disc by previous authors. Evidence presented in this work for the jets seen emanating from both RCr A and the Chamaeleon IRN, suggests that these features are merely the preferentially illuminated rims of one of the outflow cavities, seen mainly by reflection of light from the source. Further evidence is provided to show that NGC2261 and NGC6729 are illuminated by RMon and RCr A respectively. In the case of the Chamaeleon IRN new evidence is provided to show that the nebula is illuminated by a heavily obscured infrared source located midway between the two outflow cavities.

Bibliography: pages 136-138.
The design and construction of an astronomical polarimeter is described and an evaluation made of its performance. Extensive observations of cataclysmic variables with emphasis on the AM Her and DQ Her classes are then presented. After consideration of the basic principles involved in the development of an efficient and accurate polarimeter, a design using two super-achromatic retarders (a 1/4 wave and a 1/2 wave) rotating above a fixed analyser was adopted. This permitted simultaneous linear and circular polarisation measurements, or, by rearranging the order of the retarders in the beam, linear polarisation measurements alone, or circular polarisation measurements alone, with enhanced efficiency. The polarimeter was found to have extremely low instrumental polarisations and, because of the superachromatic retarders used, the efficiency correction factors were very close to 1 at all wavelengths. The polarisations are calculated at the telescope and the light curve at a higher time resolution may also be recorded if this is required. Extensive sets of observations using the polarimeter were obtained for six of the ten AM Her variables (or "polars"). EF Eri and El405-451 were observed most. Evidence was found in El405-451 for movement of the apparent location of the accretion region on the primary star and the inclination and magnetic dipole off set from the rotation axis was determined. This allowed a comparison to be made between the competing models for the cyclotron emission, showing that those which take into account the temperature structure of the accretion region provide the best results. Observations and an analysis of the polarisation data from H0139-68, E2003+225, VV Puppis and PG1550+191 are also presented in some detail. A final chapter presents results from observations made to detect a modulation in the polarisation at the rotation period of the primary in the DQ Her variables. Upper limits are set for 4 members of the class and the implications of the results are discussed.

In this work, three methods of measuring the polarization state of light in the thermal infrared (3-12 microns) are modeled, simulated, calibrated and experimentally verified in the laboratory. The first utilizes the method of channeled spectropolarimetry (CP) to encode the Stokes polarization parameters onto the optical power spectrum. This channeled spectral technique is implemented with the use of two Yttrium Vanadate (YVO4) crystal retarders. A basic mathematical model for the system is presented, showing that all the Stokes parameters are directly present in the interferogram. Theoretical results are compared with real data from the system, an improved model is provided to simulate the effects of absorption within the crystal, and a modified calibration technique is introduced to account for this absorption. Lastly, effects due to interferometer instabilities on the reconstructions, including nonuniform sampling and interferogram translations, are investigated and techniques are employed to mitigate them.Second is the method of prismatic imaging polarimetry (PIP), which can be envisioned as the monochromatic application of channeled spectropolarimetry. Unlike CP, PIP encodes the 2-dimensional Stokes parameters in a scene onto spatial carrier frequencies. However, the calibration techniques derived in the infrared for CP are extremely similar to that of the PIP. Consequently, the PIP technique is implemented with a set of four YVO4 crystal prisms. A mathematical model for the polarimeter is presented in which diattenuation due to Fresnel effects and dichroism in the crystal are included. An improved polarimetric calibration technique is introduced to remove the diattenuation effects, along with the relative radiometric calibration required for the BPIP operating with a thermal background and large detector offsets. Data demonstrating emission polarization are presented from various blackbodies, which are compared to data from our Fourier transform infrared spectropolarimeter. Additionally, limitations in the PIP technique with regards to the spectral bandwidth and F/# of the imaging system are analyzed. A model able to predict the carrier frequency's fringe visibility is produced and experimentally verified, further reinforcing the PIP's limitations.The last technique is significantly different from CP or PIP and involves the simulation and calibration of a thermal infrared division of amplitude imaging Stokes polarimeter. For the first time, application of microbolometer focal plane array (FPA) technology to polarimetry is demonstrated. The sensor utilizes a wire-grid beamsplitter with imaging systems positioned at each output to analyze two orthogonal linear polarization states simultaneously. Combined with a form birefringent wave plate, the system is capable of snapshot imaging polarimetry in any one Stokes vector (S1, S2 or S3). Radiometric and polarimetric calibration procedures for the instrument are provided and the reduction matrices from the calibration are compared to rigorous coupled wave analysis (RCWA) and raytracing simulations. The design and optimization of the sensor's wire-grid beam splitter and wave plate are presented, along with their corresponding prescriptions. Polarimetric calibration error due to the spectrally broadband nature of the instrument is also overviewed. Image registration techniques for the sensor are discussed and data from the instrument are presented, demonstrating a microbolometer's ability to measure the small intensity variations corresponding to polarized emission in natural environments.

La polarimetria proporciona informació crucial en nombroses aplicacions en diferents camps, com en la medicina, la biologia, la teledetecció, la caracterització de materials, l’astronomia, etc. Els polarímetres són els instruments bàsics per a la metrologia de polarització. Nombroses arquitectures de polarímetres han estat analitzades en la literatura, cada una d’elles presenta les seves desavantatges i avantatges. En general, els paràmetres del muntatge del polarímetre són optimitzats per tal de reduir l’amplificació del soroll present en les mesures radiomètriques fins a la mesura final de polarització. D'altra banda, els errors experimentals, com una desalineació o un calibratge erroni, ocasionen una reducció de la precisió del polarímetre en la mesura del contingut polarimètric. Recentment, els dispositius de cristall líquid s'han introduït en les arquitectures de polarímetres, aprofitant les seves atractives característiques de canviar les seves propietats òptiques de manera dinàmica i ràpida. Degut a que les arquitectures basades en cristalls líquids no tenen parts mòbils, s'eviten errors experimentals relacionats amb moviments mecànics, i aquells errors deguts a desalineaments poden ser significativament reduïts després d'un calibratge del sistema complet. Aquesta tesi s'emmarca en el camp de la polarimetria, centrant-se en el disseny òptic, optimització, anàlisi i comparativa de polarímetres basats en materials que presenten anisotropia d’índex de refracció. En concret, es revisen algunes arquitectures de polarímetres conegudes basades en cristalls líquids existents en la literatura, s’introdueixen algunes variants als dissenys d’aquests polarímetres per tal de millorar alguns aspectes del seu funcionament, com ara la minimització de soroll, i es presenten nous dissenys de polarímetres basats en cristalls líquids. Concretament, s'utilitzen tres tipus diferents de làmines de cristall líquid: amb estructura paral·lela, amb estructura helicoïdal i ferroelèctriques. A més, es presenta un nou polarímetre estàtic capaç de mesurar qualsevol estat de polarització. Aquesta última arquitectura es basa en el fenomen de la refracció cònica que es produeix quan la llum es propaga al llarg d'un dels eixos òptics d'un cristall biàxic. Per a cada prototip de polarímetre es duu a terme una anàlisi completa del seu disseny, que inclou una optimització de soroll, estudi de robustesa, anàlisi de tolerància, així com també es detalla la implementació del polarímetre, incloent el seu calibratge i mesures experimentals. Es realitza una comparativa entre els diferents prototips implementats, donant una revisió molt valuosa de les principals característiques dels polarímetres basats en cristalls líquids, així com el polarímetre basat en la refracció cònica. A partir d'aquesta comparativa, es selecciona el millor candidat per a la polarimetria d'imatge. Finalment, en aquesta tesi es proposa un nou muntatge experimental que combina un polarímetre d'imatge i un mòdul utilitzat per a aconseguir imatges amb una resolució sub-píxel en un sistema en què la resolució està limitada per la grandària del píxel del detector. Es proporcionen resultats experimentals crucials, validant la millora de la resolució espaial aconseguida en les imatges de polarització.
Polarimetry provides crucial information in many applications in diverse fields, including medicine, biology, remote sensing, material characterization, astronomy, etc. Polarimeters are the basic instruments for polarization metrology. Several polarimeters architectures have been analyzed in the literature, each one presenting its own drawbacks and strengths. In general, the parameters of the polarimeter set-up are optimized in order to reduce the amplification of noise present at the radiometric measurements to the final polarization measurement. Moreover, experimental errors, as misalignment or miscalibration, lead to a polarimeter accuracy reduction to the measure of such polarization content. Recently, liquid crystal (LC) devices have been introduced in polarimeters architectures, taking advantage of their appealing features of changing their optical properties dynamically and at high rates. Because architectures based on LC have no moving parts, experimental errors related to mechanical movements are avoided, and those due to misalignments may be significantly reduced after a calibration of the whole system. This thesis is framed in the field of polarimetry, focusing on the optical design, optimization, analysis and comparative of polarimeters based on materials presenting index anisotropy. In particular, it reviews some existing LC based polarimeter architectures popular in the literature, introduces some variants to those polarimeter layouts in order to improve some aspects in their performance such as noise minimization, and presents new designs of LC based polarimeters. In particular, we use three different types of LC cells: parallel aligned nematic, twisted nematic and ferroelectric. Moreover, it presents a new static polarimeter able to measure any state of polarization. This last architecture is based on the conical refraction (CR) phenomenon occurring when light propagates along one of the optical axes of a biaxial crystal. For each polarimeter prototype we conduct a comprehensive analysis of its design, including a noise optimization, robustness study, tolerance analysis, as well as we detail the implementation of the polarimeter, including its experimental calibration and measurements. A comparative between the different implemented prototypes is conducted, giving a very valuable review of the main features of LC based polarimeters as well as the CR based polarimeter. From this comparative, the best candidate for imaging polarimetry is selected. Finally, in this thesis it is proposed a new experimental configuration which combines an imaging polarimeter and a module used to achieve sub-pixel-resolution imaging in a system where the resolution is limited by detector pixel size. Crucial experimental results are provided, validating the resolution enhancement achieved in polarization images.

Ever since automobiles became affordable for the average American, with the introduction of the Ford Model T in 1908, making driving safer has been a priority. While driver intoxication and distraction are the leading causes of automotive fatalities, poor road conditions increase the frequency and deadliness of these incidents. Monitoring road conditions for thousands of miles of road is a huge undertaking, one too large for human surveillance. Automated systems capable of detecting and reacting to dangerous road conditions would be life-saving. These systems could be mounted to the sides of road and notify an operator of conditions in real-time. Drivers could be warned, action taken, and many lives saved. This thesis investigated the science behind polarimetric road ice detection systems. Laboratory Mueller matrix measurements of a simulated road under differing surface conditions were collected searching for a discriminatory polarization property. These Mueller matrices were decomposed into depolarization, diattenuation, and retardance. Individual sample surface polarization properties were then calculated from these three unique matrices and compared. Simulated road samples were measured under many wavelengths and angles, which gave us a larger data library from which to observe trends. Specular and off-specular reflection responses of each sample were also collected. Four polarization properties stood out for having high separation between dry and iced measurements: Depolarization Index, Linear Diattenuation, Linear Polarizance, and Linear Retardance. Through our investigation polarimetric ice detection is possible. Continued research of the polarization properties of road ice can result in the development of a road ice detection system. Proposed deployment methods of such a system have been outlined following the analysis of the data collected in this experiment. Not only is polarimetric ice detection an exciting and novel use of polarization, it has the potential to improve road safety through real-time ice response measures.

Optical imaging polarimetry has been carried out for a number of starburst galaxies under various morphological classifications. In several cases, kpc-scale reflection nebulae are detected which arise from dust grains scattering starburst radiation towards the observer. In general, the scattering medium is displaced up to several kpc from the current star- forming environment and in one case, the dust distribution extends above and below the galactic disk in a manner reminiscent of M82. It is now well established that galactic-scale outflows (superwinds) are prevalent in starburst galaxies and it is tempting to attribute the anomalous dust distributions detected in this thesis with these powerful processes. Furthermore, there is increasing evidence that tidal encounters initiate starburst activity and in some cases a dynamic event of this kind may also be responsible for the observed distribution of scattering material. Mie scattering models were constructed for two of the objects observed in this work. An optically-thin approximation was used which, for many plausible distributions of the dust along the line-of-sight, can be shown to be roughly valid. Although the estimates derived from this technique have a range of values, in all cases the dust component detected in scattered light appears to be at least an order of magnitude more massive than the amount of FIR-emitting dust derived from IRAS data. This is not too surprising - the material detected via polarimetry is probably too cold for IRAS which is sensitive to dust warmer than about 30-50 K.

Optical imaging polarimetry has been performed on seven nearby Seyfert galaxies, three with face-on and four with edge-on host galaxies of various morphological classifications. Observations in V, R, B and H(_a) wavebands are presented as maps of total intensity and of polarized intensity, overlaid with polarization vectors. Independent determinations of the interstellar polarization (ISP) contribution from our own galaxy are made where possible, and are used to produce ISP corrected maps. The polarization patterns seen in the maps show evidence of either dichroic extinction, which indicates the presence of non-spherical dust grains in large-scale galactic magnetic fields, or scattering, which is due to the illumination of regions of dust grains or electrons. The polarization features, which are observed at the different wavebands, are then compared to recent models of polarization in external galaxies. Estimates of the intrinsic Seyfert nuclear polarization are made where possible by correcting for ISP and for an approximation of the dilution due to the host galaxy flux by using values from previous studies. Both the measured and the corrected nuclear polarizations are compared with previously published values, and are discussed in the context of the standard models of Seyfert galaxies. Most of the observed galaxies show evidence of polarization, both from the host galaxy and from the intrinsic Seyfert nucleus. In particular, distinct polarization features: bands of polarization consistent with extended dusty disks aligned with the dusty tori proposed in Seyferts, and regions of polarization corresponding to scattering of the nuclear continuum along the biconical extended Seyfert emission-line regions, have been identified in several of the observed galaxies.

Cette thèse a été consacrée au développement et à la mise en oeuvre d’un imageur polarimétrique de Müller installé sur un colposcope standard dans le but de diagnostiquer invivo des lésions précancéreuses du col utérin.Ce travail s’est appuyé sur le développement réalisé durant les dix dernières années au LPICM à l'École polytechnique d’une nouvelle technologie d'imagerie médicale non invasive et a priori adaptée à la détection précoce du cancer : l’imagerie polarimétrique
This thesis was devoted to the development and the implementation of a polarimetric imager of Müller installed on a standard colposcope in order to diagnose invivo precancerous lesions of the cervix.This work was based on the development carried out during the last ten years at the LPICM at the Ecole polytechnique of a new non-invasive medical imaging technology and a priori adapted to the early detection of cancer: polarimetric imaging

El índice de refracción (RI) es un parámetro físico que proporciona información sobre la propagación de la luz a través de una muestra y está relacionado con algunas propiedades ópticas y eléctricas del medio. El RI es una propiedad intrínseca de los materiales, pero en muchos casos, cambios en la materia producidos por interacciones físicas o químicas, pueden producir una modificación de su valor, como, por ejemplo, debido a variaciones de temperatura, estrés mecánico o cambios en su composición química. Otros materiales pueden presentar diferentes valores de RI dependiendo de la dirección de propagación de la luz, como es el caso de los materiales anisótropos. Existen múltiples aplicaciones en diferentes campos, como biología, farmacología, mineralogía o caracterización de materiales, donde el valor de RI puede proporcionar información de gran utilidad. En esta tesis, hemos desarrollado un método óptico para caracterizar los índices de refracción de muestras dieléctricas isótropas y cristales anisótropos uniáxicos. Una ventaja de nuestro método es que es capaz de medir el RI en materiales en fase sólida o líquida y superficies planas o no-planas, iluminando la muestra en reflexión. Esto nos permitiría caracterizar elementos ópticos ya integrados en sistemas ópticos. La caracterización del índice de refracción in situ es hoy en día un problema por resolver, de gran interés para la industria y la investigación. La principal motivación de este trabajo es caracterizar las lentes integradas en sistemas ópticos, para las que no existe un método estándar. Hemos diseñado e implementado por primera vez, un microscopio conoscópico de Mueller que trabaja en reflexión para medir los RIs de varias muestras, independientemente de su superficie. En particular, medimos la matriz de Mueller de cualquier muestra dieléctrica mediante un polarímetro de Mueller completo y un objetivo de gran apertura numérica (HNAO). Como consecuencia, se obtiene un haz de luz polarizado y altamente focalizado que incide sobre la muestra, siendo el tamaño del punto focal más pequeño que la curvatura de la superficie de la muestra, lo que nos permite medir superficies no planas. Gracias al HNAO, el microscopio conoscópico propuesto mide simultáneamente la matriz de Mueller para un gran número de ángulos de incidencia (aquellos dentro del cono iluminando la muestra), sin ningún movimiento mecánico del sistema y obteniendo una gran redundancia de datos. Con una cámara de alta resolución se pueden registrar los diferentes patrones de intensidad correspondientes a distintas configuraciones polarimétricas, y utilizarlos para calcular la imagen de la matriz de Mueller. Hemos desarrollado el modelo matemático que nos permite determinar la matriz de Mueller teórica de la muestra. Éste se basa en los coeficientes de Fresnel, que describen la relación entre los campos eléctricos reflejado y transmitido con el haz incidente, en una interfaz entre diferentes medios. Estos coeficientes dependen, por un lado, del ángulo de incidencia, la polarización y la frecuencia del haz incidente y, por otro lado, de los índices de refracción de ambos medios. El modelo desarrollado se probó realizando una serie de simulaciones y se validó midiendo las características ópticas de matrices de Mueller simulando materiales reales e incluyendo efectos experimentales (ruido, desalineamiento, etc.). Finalmente, se ha utilizado el instrumento para medir la matriz de Mueller de materiales reales. Los diferentes parámetros ópticos del modelo pueden ser ajustados para que la matriz de Mueller teórica coincida con la experimental. Para tal fin, se ha desarrollado un programa de optimización para hallar el mejor ajuste entre simulación y datos experimentales, mediante la minimización de una función de mérito basada en el error cuadrático medio (MSE). El microscopio conoscópico de Mueller ha mostrado su potencial para caracterizar muestras dieléctricas independientemente de su superficie.
Refractive index (RI) provides information about the propagation of light through a specimen and it is related with some optical and electrical properties of materials. In many cases, certain changes in matter can produce a modification of the refractive index, such as, for example, temperature variations, mechanical stress or changes in the chemical composition of the material. Other materials may present different RI values depending on light propagation direction, as is the case of anisotropic materials. Hence, there are multiple applications in different fields such as biology, pharmacology, mineralogy or material characterization, where the RI value can give interesting information. In this thesis, we have developed an optical method to characterize the RIs of dielectric isotropic samples and uniaxial anisotropic crystals. The particularity of our method is to measure, in a reflection configuration, solid or liquid phases and planar or non-planar surfaces, allowing to characterize optical elements already integrated in optical systems. In-situ characterization of the refractive index is nowadays an unsolved problem of interest for industry and research. Particularly, lenses integrated in optical systems are the major motivation of this work, because they may modify their RI value when inserted into devices. Our proposal was to design, implement and use, for the first time, a conoscopic Mueller microscope working in reflection to measure the RIs of several samples with arbitrary surfaces. The working principle of our microscope is based on measuring the angle-resolved Mueller matrix of any dielectric specimen by using a complete Mueller matrix polarimeter and a high numerical aperture objective (HNAO). Under this scenario, a polarized incident light beam is highly focused over the studied sample, being the spot size smaller than the curvature of the sample surface, this allowing us to measure non-planar surfaces. The reflected cone of light passes through the same HNAO, being collimated and then, it is polarimetrically analyzed. Note that the incident and reflected light cones are formed by light rays with different angles of incidence and polarizations. As a consequence, the proposed conoscopic microscope is able to measure the angle-resolved Mueller matrix in reflection at numerous incident angles simultaneously, obtaining data redundancy without any mechanical motion of the set-up. A camera with high-resolution records the different intensity patterns that ultimately are used to calculate the Mueller matrix image. Data redundancy is function of the maximum angle of incidence of the HNAO and the number of pixels of the camera. A mathematical model was developed to theoretically determine the Mueller matrix image. It is based on the Fresnel coefficients that describe the ratio of the reflected and transmitted electric fields to that of the incident beam on an interface between different optical media. These coefficients depend, on the one hand, on the angle of incidence, the polarization and the frequency (or wavelength) of the incident beam and, on the other hand, on the RIs of the media. The model was tested by performing a collection of simulations and we analyzed the validity of the method by measuring the characteristics of different artificial samples. The model parameters, such as the refractive indices can be calculated by fitting them with the experimental data measured with the conoscopic Mueller microscope. An iterative optimization routine was developed in order to find the best-fit parameters that minimize a merit function based on the Mean Squared Error (MSE) between both experimental and simulated Mueller matrix images. The conoscopic Mueller microscope was finally tested by measuring well-known polarimetric samples with different surface forms.

A linha de instabilidade (LI) pré-frontal que atingiu a Região Metropolitana de São Paulo em 26 de abril de 2007 foi monitorada e analisada por meio de medições de superfície, altitude, radar e satélite. As análises indicam que havia ambiente sinótico favorável para a formação e manutenção da LI. Na região de formação da LI havia ar relativamente quente e úmido em baixos níveis e ar relativamente frio e seco em níveis médios com convergência de massa em baixos níveis e divergência em altos níveis, além de gradiente de temperatura produzido pela aproximação do sistema frontal. A LI foi monitorada pelo radar meteorológico MXPOL e permitiu a avaliação dinâmica e microfísica do sistema. Esta última realizada por meio da classificação de hidrometeororos com as variáveis polarimétricas medidas com o MXPOL. Preliminarmente, os dados de refletividade diferencial (ZDR) e refletividade efetiva (Z) foram consistidos por meio do método da autoconsistência (Vivekanadan et al., 2003), entre essas duas variáveis e a fase diferencial específica (KDP). Removido os viéses de ZDR (-0,36 dB) e da refletividade efetiva (-0,46 dBZ), a classificação de hidrometeoros, em dezessete categorias (gotículas a granizo, insetos, ecos de terreno e de segunda viagem), foi realizada pelo método de lógica fuzzy (Vivekanadan et al., 2003). A classificação de hidrometeoros foi realizada em planos de elevação constante (PPI). Os tipos e estratificação de hidrometeoros são compatíveis com estudos anteriores. Por exemplo, a banda brilhante foi classificada com uma região de mistura de gelo e gotas líquidas com predominância de gotas abaixo e cristais de gelo acima desta. A dinâmica interna da LI foi avaliada por meio da velocidade radial e evidenciou um jato de baixos níveis, convergência ciclônica na dianteira do sistema, e divergência em altos níveis, entre outras características. O rápido deslocamento da LI resultou em precipitação de 7 mm e rajadas de vento de 18 m s-1. Assim, o impacto mais significativo desse sistema na RMSP foi produzido pelo vento.
A prefrontal squal line (LI) that reached tne metropolitan area of São Paulo on April 26 2007 was monitored and analyzed by means of of surface and upper air measurements, weather radar and satellite data. Analyses indicate a favorable synoptic environment to form and sustain the LI. In its genesis region there was relatively warm and moiture air near the surface and relatively cold and dry air aloft with mass convergence below and divergence aloft, as well as temperature gradient along its path induced by the associated cold front. This LI was measured with the MXPOL weather radar and allowed a mesoscale dynamic analysis as well as a microphysics of this weather system. The later was performed by means of a hydrometeor classification with the polarimetric data sets of MXPOL. Initially, the differential reflectivity (ZDR) and the efective reflectivity (Z) were corrected by the selfconsistency method (Vivekanandan et al., 2003) together with the specific diferrential phase (KDP). Ounce removed the ZDR (-0,36 dB) and Z (-0,46 dBZ) biases, the hydrometeoro classification (small drops to hail, insects, ground clutter and second trip echoes) was carrie out by the fuzzy logic method (Vivekanadan et al., 2003). The hydrometeor classification was made at constant elevation angles (PPI) across the LI. The hydrometeoro types are compatible to similar studies. For instance, the bright band was classified as a region mixed phase with drops below and ice crystals aboce it. The LI internal dynamics was analyzed with the help of the radial velocity and indicated a low level jet, cyclonic convergence at the leading edge and divergence aloft at the convective band, among other features. This fast moving LI produced 7 mm of rainfall and wind gust of 18 m s-1. Its most significant impact over RMSP was caused by the wind intensity.

Diese (Doktor)arbeit beschäftigt sich mit Radar-Polarimetrie, insbesondere mit der Untersuchung der Eigenschaften von polarimetrischen Variablen, die potenziellen Nutzen für die Radar-Meteorologie haben. Für den Einsatz in Dual-Polarisations-Radargeräten wird der Polarisationsgrad analysiert. Diese Variable wird in künftigen operationellen Radargeräten verfügbar sein. Der Polarisationsgrad hängt vom transmittierten Polarisationszustand und in weiterer Folge auch vom Betriebsmodus des Radargeräts ab. Der Hauptbetriebsmodus von operationellen Radargeräten sendet und empfängt gleichzeitig sowohl die horizontale als auch die vertikale Komponente. Der sekundäre Betriebsmodus sendet und empfängt simultan die horizontal polarisierte Komponente. In dieser Arbeit werden beide Polarisationsgrade untersucht. Da operationelle Systeme derzeit auf den Dual-Polarisationsmodus aufgerüstet werden, sollte künftig die Anwendungsmöglichkeiten von vollpolarimetrischen Wetterradarsystemen untersucht werden. Aus allen Variablen, die in diesem Betriebsmodus zur Verfügung stehen, wurde die Entropie (des gemessen Objektes) ausgewählt und wegen seiner engen Beziehung zum Polarisationsgrad näher untersucht
The present doctoral thesis deals with radar polarimetry, namely with the investigation of properties of polarimetric variables potentially useful in radar meteorology. For use with dual-polarization radars, the degree of polarization is analyzed. This variable is available to planned operational radars. The degree of polarization is dependent on transmit polarization state and, consequently, it is dependent on the radar system operating mode. The primary operating mode of operational radars consists in simultaneous transmission and simultaneous receive of both horizontal and vertical components. The secondary operating mode consists of horizontal transmission and simultaneous receive. Both degrees of polarization are investigated in this thesis. Also, as operational systems are being updated to dual-polarization, research should start investigating the capabilities of fully polarimetric weather radar systems. Among the numerous variables available from this operating mode, the target entropy was chosen for investigation, also because of its close relation to the degree of polarization

The Mini-RF radar, launched on the Lunar Reconnaissance Orbiter, imaged the lunar surface using hybrid-polarimetric, transmitting one circular polarization and receiving linear H and V polarizations. Earth-based radar operating at the same frequency has acquired data of the same terrains using circular-polarized transmit waves and sampling circular polarizations. For lunar targets where the viewing geometry is nearly the same, the polarimetry derived from Mini-RF and the earth-based data should be very similar. However, we have discovered that there is a considerable difference in circular polarization ratio (CPR) values between the two data sets. We investigate possible causes for this discrepancy, including cross-talk between channels, sampling, and the ellipticity of the Mini-RF transmit wave. We find that none of these can reproduce the observed CPR differences, though a nonlinear block adaptive quantization function used to compress the data will significantly distort some other polarimetry products. A comparison between earth-based data sets acquired using two different sampling modes (sampling received linear polarizations and sampling circular polarizations) suggests that the CPR differences may be partially due to sampling the data in a different receive polarimetry bases.

Des de la invenció del microscopi al segle XVII, l’ús de tecnologies d’imatge ha estat fonamental per a l’estudi de teixits biològics. Al llarg dels segles, s’han anat desenvolupant i implementant noves tecnologies d’imatge per tal de millorar la visualització del teixits biològics i facilitar la comprensió de la seva estructura a partir de la mesura d’algunes de les seves propietats físiques. En aquest context, la polarimetria és una interessant tècnica òptica no invasiva que s’ha utilitzat per a la millora d’imatges en diversos camps com l’astronomia, la teledetecció i la caracterització de materials. A més, la polarimetria es pot combinar amb altres tècniques òptiques per millorar, encara més, la visualització de mostres. La polarimetria compren un conjunt de mètodes òptics basats en mesurar la polarització de la llum i com aquesta varia a l’interactuar amb les mostres. En aquesta tesi, s’estudien, s’implementen experimentalment i s’apliquen per primera vegada en l’anàlisi de teixits biològics alguns mètodes polarimètrics recentment proposats en la literatura (així com de nous) per tal de millorar la visualització de teixits animals i vegetals. En l’àmbit de la biomedicina, el potencial d’utilitzar la polarització està demostrat en una gran varietat d’estudis. Aquests estudis solen basar-se en dos grups de tècniques polarimètriques: tècniques anomenades Portes de Polarització (de l’anglès “Polarization Gating”) i tècniques basades en la matriu de Mueller. En aquesta tesi, s’investiga la relació que hi ha entre aquests dos grups de tècniques polarimètriques i proposem un nou mètode polarimètric més general que permet analitzar diferents configuracions de “Polarization Gating” a partir de la mesura experimental d’una sola matriu de Mueller. Respecte els estudis biomèdics basats en la matriu de Mueller, diferents propietats polarimètriques (diatenuació, retard i despolarització) són analitzades en base a observables per tal d’obtenir informació física relacionada amb l’estructura dels teixits biològics i també per incrementar la seva visualització. En aquests estudis, el retard és analitzat en profunditat mitjançant la descomposició de Lu-Chipman i el càlcul del retard lineal, el retard circular, i l’orientació de l’eix ràpid, entre d’altres. En canvi, l’anàlisi de la despolarització es restringeix al càlcul d’observables que quantifiquen la despolarització global de les mostres i no permeten l’estudi d’informació més específica, com poden ser possibles anisotropies en aquest procés de despolarització. Per aquest motiu, en aquesta tesi s’estudien diferents observables que descriuen amb més detall les propietats de despolarització de la mostra per, posteriorment, ser aplicats per millorar la visualització dels teixits animals mesurats. En aquest sentit, uns observables anomenats Índexs de Puresa Polarimètrica (de l’anglès “Indices of Polarimetric Purity”) són aplicats en l’estudi de teixits d’origen animal. Aquests observables són utilitzats per millorar la visualització dels teixits, revelant certes estructures ocultes en els canals de despolarització estàndard, i també per classificar diferents teixits d’origen animal amb una millor eficiència. Finalment, també estudiem l’ús de la polarització per a l’anàlisi de teixits d’origen vegetal. A diferència dels teixits d’origen animal, la polarimetria és molt menys utilitzada en l’anàlisi de plantes, sent els mètodes basats en la matriu de Mueller molt poc usats. Per aquesta raó, en aquesta tesi s’estudia el potencial de la polarimetria de Mueller per a l’anàlisi de teixits d’origen vegetal i es comparen els resultats amb els obtinguts amb algunes tècniques polarimètriques i no polarimètriques comunament utilitzades. Com a resultat, la polarimetria de Mueller és un mètode polarimètric òptim per a l’obtenció d’imatges de teixits d’origen vegetal que, a més a més, es pot utilitzar com una eina complementària a les altres tècniques òptiques no polarimètriques.
Desde la invención del microscopio en el siglo XVII, el uso de tecnologías de imagen ha sido fundamental para el estudio de tejidos biológicos. A lo largo de los siglos, se han desarrollado e implementado nuevas tecnologías de imágenes para mejorar la visualización de los tejidos biológicos y facilitar la comprensión de su estructura a partir de la medición de algunas de sus propiedades físicas. En este contexto, la polarimetría es una interesante técnica óptica no invasiva que se ha utilizado para la mejora de imágenes en diversos campos como la astronomía, la teledetección y la caracterización de materiales. Además, la polarimetría se puede combinar con otras técnicas ópticas para mejorar aún más la visualización de muestras. La polarimetría comprende un grupo de métodos ópticos que se basan en medir la polarización de la luz y cómo esta varía al interactuar con las muestras. En esta tesis, se estudian, se implementan experimentalmente y se aplican por primera vez en el análisis de tejidos biológicos algunos métodos polarimétricos propuestos recientemente en la literatura (así como nuevos) para mejorar la visualización de tejidos animales y vegetales. En el campo de la biomedicina, el potencial de la polarimetría se demuestra en una amplia variedad de estudios. Estos estudios se basan generalmente en dos grupos de técnicas polarimétricas: técnicas denominadas Puertas de Polarización (del inglés “Polarización Gating”) y técnicas basadas en matrices de Mueller. En esta tesis, investigamos la relación entre estos dos grupos de técnicas polarimétricas y proponemos un nuevo método polarimétrico más general que permite el análisis de diferentes configuraciones de “Polarization Gating” a partir de la medida experimental de una única matriz de Mueller. Respecto a los estudios biomédicos basados en la matriz de Mueller, diferentes propiedades polarimétricas (diatenuación, retardo y despolarización) son analizadas a partir de un grupo de observables para obtener información física relacionada con la estructura de los tejidos biológicos y también para mejorar su visualización. En estos estudios, el retardo es analizado en profundidad mediante la descomposición de Lu-Chipman y el cálculo del retardo lineal, el retardo circular y la orientación del eje rápido, entre otros. Por el contrario, el análisis de la despolarización se restringe al cálculo de observables que cuantifican la despolarización global de las muestras y no permiten el estudio de información más específica, como pueden ser posibles anisotropías en ese proceso de despolarización. Por ello, en esta tesis se estudian diferentes observables que describen con más detalle las propiedades de despolarización de la muestra para, posteriormente, ser aplicados para mejorar la visualización de los tejidos animales medidos. En ese sentido, los parámetros denominados Índices de Pureza Polarimétrica (del inglés “Indices of Polarimetric Purity”) se aplican para inspeccionar los tejidos de origen animal. Estos observables de despolarización se utilizan para mejorar la visualización de tejidos, revelando ciertas estructuras ocultas en canales de despolarización estándar, y también para clasificar con mayor eficiencia diferentes tejidos de origen animal. Finalmente, también estudiamos el uso de la polarimetría para el análisis de tejidos de origen vegetal. A diferencia de los tejidos de origen animal, la polarimetría se utiliza mucho menos en el ámbito del análisis de plantas, siendo las técnicas basadas en Mueller muy poco utilizadas. Por este motivo, esta tesis estudia el potencial de la polarimetría de Mueller para el análisis de tejidos de origen vegetal y compara los resultados obtenidos con los obtenidos con algunas técnicas polarimétricas y no polarimétricas de uso común. Como resultado, la polarimetría de Mueller es un método polarimétrico óptimo para la obtención de imágenes no invasivas de tejidos de origen vegetal que, además, puede utilizarse como herramienta complementaria a otras técnicas ópticas no polarimétricas.
Since the invention of the microscope in the 17th century, the use of imaging technologies has been fundamental in the study of biological tissues. Over the centuries, new imaging technologies have been developed and implemented to enhance the visualization of tissues and ease the understanding of their structure from the measurement of some of their physical properties. In that context, polarimetry is an interesting non-contact and non-invasive optical technique that has been used for image enhancement in a wide range of fields such as astronomy, remote sensing, and characterization of materials. Moreover, polarimetry can be combined with other optical techniques to further improve the visualization of samples. Polarimetry comprises a group of optical methods that are based on measuring the polarization of light and how it varies when interacting with samples. In this thesis, some polarimetric methods recently proposed in the literature (as well as new ones) are studied, experimentally implemented, and applied for the first time in the analysis of biological tissues to improve the visualization of animal and plant tissues. In the field of biomedicine, the potential of polarimetry is demonstrated in a wide variety of studies. These studies are usually based on two groups of polarimetric techniques: Polarization Gating techniques and Mueller matrix-based techniques. In this thesis, we investigate the relationship between these two groups of polarimetric techniques and we propose a new generalized polarimetric method that allows the analysis of different Polarization Gating configurations from a single Mueller matrix measurement. Concerning to the biomedical studies based on the Mueller matrix, different polarimetric properties (diattenuation, retardance, and depolarization) are analyzed from a group of observables to obtaining physical information related to the structure of biological tissues and also to enhance their visualization. In these studies, retardance is completely studied through the Lu-Chipman decomposition and the calculation of the linear retardance, the circular retardance, and the orientation of the fast axis, among others. By contrast, the analysis of depolarization content is restricted to the calculation of observables that quantify the overall depolarization of samples and do not allow the study of more specific information, as can be possible anisotropies in that depolarization process. For that reason, in this thesis, different observables that further describe the depolarization properties of the sample are studied to, afterwards, be applied for visualization enhancement of the measured animal tissues. In that sense, the parameters called Indices of Polarimetric Purity are applied to inspect animal tissues. These depolarizing observables are used to improve tissue visualization, revealing certain structures hidden in standard depolarization channels, and also to classify, with improved efficiency, different animal tissues. Finally, we also study the use of polarimetry for the analysis of plant tissues. Unlike animal tissues, polarimetry is much less used in the plant analysis framework, being Mueller-based techniques scarcely used. For this reason, this thesis studies the potential of Mueller polarimetry for plant tissue analysis and compares the obtained results with those obtained with some commonly used polarimetric and non-polarimetric techniques. As a result, Mueller polarimetry is an optimal polarimetric method for obtaining non-invasive images of plant tissues that, in addition, can be used as a complementary tool to other non-polarimetric optical techniques.
Universitat Autònoma de Barcelona. Programa de Doctorat en Física

Since the late 1970's, various synthetic aperture radar (SAR) satellite missions have provided a valuable source of information about the earth's surface. Providing their own illumination, these sensors generate imagery of our planet 24 hours a day, regardless of cloud cover. Until recently, except for the short term space shuttle SIR-C system, these SAR missions carried single-polarized sensors, meaning that the information extracted from the imagery, and the resulting quality of interpretation, was limited. In 2006 the first of a series of planned satellites carrying fully polarimetric SAR sensors was launched. In polarimetric SAR systems, images can be acquired with horizontal (H) and vertical (V) polarizations of the electric field on both transmission and reception. The resulting multipolarized imagery makes available a higher level of information content for a number of applications, including man made target detection. The potential of polarimetric SAR for man made target detection is investigated in this thesis. In the man made target detection field, the purpose is to differentiate the signature of the targets from those of adjacent natural areas. The most operationally successful application in this field is ship detection, as the sea surface usually forms a quite homogeneous and easily distinguishable clutter. Vegetated surfaces, however, usually constitute a more challenging clutter, as the backscatter levels can be very high and the signatures diverse, often being confused with those of man made targets. A few algorithms have been developed with the purpose of separating the targets from clutter. A methodology that employs the following three algorithms was recently tested in order to discriminate crashed aircraft from the surrounding terrain: Polarimetric Whitening Filter (PWF), Even Bounce Analysis and Cameron Decomposition. In these tests, successful results were achieved when the terrain was composed of a homogeneous field of grass and the targets were crashed airplanes. In this work the same methodology is tested with different man made targets and with different clutters. Also, methodologies involving the use of two other algorithms are tested in order to reduce the false alarm rates. These algorithms are Coherence Test of the Symmetric Scattering Characterization Method (SSCM) and Freeman-Durden Decomposition. The methodologies are applied to three different data sets acquired over different Canadian locations - Ottawa (ON), Gagetown (NB) and Vancouver (BC) - with the CV-580 polarimetric SAR system and the false alarm rates are assessed. Results show that the Coherence Test can lower false alarm rates on high vegetation clutter when applied in combination with other algorithms, while Freeman-Durden Decomposition does not perform effectively in the same experiments.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

Optical imaging polarimetry has been performed on a small sample of objects which are associated with that stage of stellar evolution occurring between the Asymptotic Giant Branch and full Planetary Nebula. Three such systems are considered, specifically, the young planetary nebulae M 1-16 and Mz3, and the protoplanetary nebula, IRAS 09371+1212 (the 'Frosty Leo' nebula). The work is based upon CCD polarimetry obtained with the Durham Imaging Polarimeter. Planetary nebulae are believed to form as a low to intermediate mass star evolves from the main sequence, through the mass-loss stages of the Red Giant Branch and Asymptotic Giant Branch, towards its final destiny as a White Dwarf. A brief review of the relevant aspects of post-main sequence stellar evolution is given as a basis for understanding the transitionary planetary nebula phase in relation to the character of the central star and its role in the creation of a nebula. The theory of light scattering from both homogeneous and core-mantle spherical dust grains (Mie theory) is discussed. The results of a series of scattering calculations, using the theory, for dust grains composed of those materials believed to be abundant in the atmospheres of late-type stars and planetary nebulae are presented. The levels of polarization and scattered intensities predicted in the scattering analysis have been applied in the interpretation of the polarimetric data for the three planetary nebulae. Constraints upon the nature of the dust component, the size distribution of the dust and the nebula geometry are suggested for each of the nebulae. The inferred character of the dust material is in good agreement with the classification of the nebulae using the two-colour diagram for the IRAS fluxes.

A high resolution linear polarization map is presented of the peculiar elliptical galaxy NGC5128 (= Centaurus A) and is used to investigate the polarizing mechanism at work in the dust lane. The spatial distribution and orientation of the polarization, together with a possible correlation between the degree of polarization and the extinction through the dust, suggest scattering from aligned non-spherical grains as the probable cause of the polarization. A computer model of the passage of light from an extended source, through a dust cloud of arbitrary shape, has been developed, using a backward Monte-Carlo method. This model has been applied to an NGC5128-like system and it is found that in order to obtain the structure and degree of polarization observed in NGC5128, the dust needs to be aligned by a toroidal magnetic field of about the same strength as that in our Galaxy. It is suggested that the magnetic field could have originally belonged to a spiral galaxy which subsequently collided with NGC5128.

The work in this thesis uses neutron polarimetry and representational analysis to illuminate complex magnetic structures. The combination of these techniques is particularly suited to examining magnetic materials that have frustrated magnetic order and domain structures. The materials that are investigated in depth are Er2Ti2O7 and MnWO4. Er2Ti2O7 is a member of the pyrochlore family of materials and exhibits the classic signs of geometric frustration. The material has been proposed as an XY antiferromagnet that selects a specic basis vector ground state due to an order-by-disorder transition. The previous experimental work could not fully determine the precise details of the ground state and hence was not able to fully conrm the proposed theory. The structure was examined using neutron polarimetry and representational analysis to try and determine the magnetic order at low temperature. MnWO4 is an example of a magnetic material with complex order and frustration that arises due to competing exchange interactions. The material has a cycloidal magnetic structure that breaks the inversion symmetry and gives rise to dierent k-domains. The population of these dierent domains is intrinsically linked to the electronic polarization of the material, such that when one domain is populated MnWO4 has a spontaneous electric polarization and is belongs to the multiferroic family of materials. By using representation analysis the number of parameters that is required to describe the magnetic structure is greatly reduced and the link between inversion symmetry breaking and multiferroicity may be better understood. This thesis aims to identify the structures of both Er2Ti2O7 and MnWO4 as well as develop the interpretation of the polarimetry techniques.

Light has provided the means to learn and gather information about the physical world throughout history. In a world where science moves to smaller scales and more specialised problems however, the boundaries of current technology are continually challenged, motivating the search for more sophisticated systems providing greater information content, sensitivity and increased dimensionality. Utilising the vectorial nature of light presents a promising avenue by which to meet these growing requirements. Polarisation can, for example, be used to transmit information, or alternatively, changes in polarisation induced by an object allow study of previously neglected material properties, such as birefringence and diattenuation. Central to this thesis is thus the characterisation and exploitation of the opportunities afforded by the electromagnetic (i.e. vectorial) nature of light. To this end the work follows three running themes: quantification of polarisation information; formulation of simple propagation tools for electromagnetic waves; and development of specific polarisation based optical systems. Characterising the informational limits inherent to polarisation based systems reduces to considering the uncertainty present in any observations. Uncertainty can, for example, arise from stochastic variation in the polarisation state being measured, or from random noise perturbations upon detection. Both factors are considered and quantified here. Development of vectorial optical systems does, however, pose significant difficulties in modelling, due to mathematical complexity and computational requirements. A number of new tools are hence developed, as prove applicable to a wide variety of applications. Examples are naturally given. To illustrate the potential of polarisation based systems, specific current topics are discussed; namely the growing demand for data storage, and single molecule studies. It will be shown that polarisation, can not only be used to multiplex information in data pits on optical media, but also to allow full 3D study of single molecules. Factors pertinent to such studies are studied in detail.

The assumption of a linear relationship between enantiomeric composition of catalyst and enantiomeric composition of the product of an asymmetric reaction is not always valid. The first part of this thesis describes work directed towards understanding and predicting the phenomenon of nonlinear effects (NLEs) in the addition of diethylzinc to benzaldehyde promoted by chiral ligands. This work includes the synthesis of amino alcohol and amino thiol ligands from readily available amino acid derivatives as well as measuring the nonlinear effects in the reaction of diethylzinc and benzaldehyde promoted by these ligands. The nonlinear effect exhibited for amino alcohol ligands are the subject of computational investigation according to the reservoir model demonstrated by Noyori, aiming towards the prediction of sense and magnitude of the nonlinear effects observed. I show that nonlinear effects operate in many of the ligands studied, and the magnitude of these effects is larger for the amino alcohol ligands than their amino thiol counterparts. NLEs are also shown temperature and solvent dependant. I show that extensive modelling of the dimers responsible for the occurrence of the nonlinear effects is unable to account for the experiment results. The second part of this thesis describes efforts towards developing a new method of screening asymmetric reactions in real time, based on polarimetry. The optical rotation of a chiral molecule in the solution depends on the nature of the molecule as well as its concentration. I show that monitoring changes of the optical rotation in real time provides a qualitative and sometimes quantitative profile of an asymmetric reaction. This thesis describes the use of polarimetry to monitor asymmetric organocatalytic reactions where one and two stereocentres are generated. A simple optimization of various conditions of the reaction, such as temperature and solvent, is shown using this method as well as efficient screening for a (known) catalyst in the reactions investigated.

Cette thèse examine une nouvelle méthode de diagnostic, appelée Polarimètrie de Mueller, pour l’étude des interactions plasma-surface. Cette technique d’imagerie permet la caractérisation optique résolue en temps des cibles exposées au plasma. Les matrices de Mueller mesurées sont analysées en utilisant la décomposition logarithmique donnant des informations polarimétriques sur la diattenuation, la dépolarisation et la biréfringence. Cette dernière est exploitée en examinant des matériaux optiquement actifs afin d’identifier des aspects spécifiques de l’interaction avec le plasma, tels que les champs électriques ou la température de surface.Ce travail se concentre sur les cibles électro-optiques, qui permettent principalement la détection de champs électriques induits par la charge de surface déposée lors de l’interaction. La biréfringence est couplée analytiquement au champ électrique, en rapportant le retard de phase du faisceau sonde de lumière polarisée, à l’ellipsoïde d’index perturbé suivant l’effet Pockels. Grâce à cette approche analytique, les matériaux ayant des propriétés électrooptiques spécifiques peuvent être choisis de telle manière que toutes les composantes individuelles de champ électrique (axiales et radiales) induites à l’intérieur de l’échantillon soient imagées séparément. Pour la première fois les composantes du champ électriques peuvent être découplées permettant de mieux comprendre la dynamique du plasma proche d’une surface diélectrique.Cette technique est utilisée pour étudier l’impact d’ondes d’ionisation sur des surfaces. Ces décharges, générées par un jet de plasma à pression atmosphérique dans la gamme kHz, sont des plasmas froids filamentaires généralement utilisés pour des applications diverses telles que la fonctionnalisation de surface de polymères ou des traitements biomédicaux, mais les méthodes de diagnostic disponibles pour étudier les effets induits sur les surfaces sont limités. L’imagerie de polarimètrie Mueller appliquée aux cibles électro-optiques permet d’examiner les champs axiaux et radiaux en termes d’amplitude (3-6 kV/cm), d’échelles spatiales (<1mm axiales and <1cm radiales) et d’échelles temporelles (< 1μs pulsée and < 10μs CA) pour divers paramètres de fonctionnement du jet, e.g. amplitude de tension et gaz environnant.Simultanément à la biréfringence transitoire induite par le champ électrique, un signal de fond constant est également observé. Il est induit par la contrainte résultante du gradient de température induit à l’intérieur du matériau ciblé. Une relation analytique est obtenue en utilisant l’effet photo-élastique, permettant de développer une procédure de fitting pour retrouver la distribution de température. Cette procédure est utilisée, après calibration, pour montrer que la température de l’échantillon peut varier jusqu’`a 25 degrés par rapport aux conditions ambiantes – tandis que les changements dans le champ électrique sont également mesurés – et dépend de la fréquence de la tension d’alimentation AC du jet de plasma. La détermination précise de la température induite dans les cibles est importante car la plupart des applications visent des échantillons thermosensibles.Enfin, ce travail montre comment des échantillons complexes (aussi bien en terme d’état de surface que de composition chimique) peuvent être examinés lors d’une interaction plasma-surface, en les combinant avec une cible électrooptique. En raison de l’ajout d’un échantillon complexe, une composante de dépolarisation est ajoutée due à la diffusion du faisceau lumineux polarisé. Les changements de dépolarisation sont liés à l’évolution de l’échantillon complexe au cours du traitement par plasma. Ceux-ci, couplés aux champs électriques mesurés simultanément, fournissent un outil de diagnostic unique pour examiner les interactions plasma-surface. Cela a été appliqué à un cas test où une seule couche de cellules d’oignon est exposée aux ondes d’ionisation générées par le jet de plasma froid
In this thesis, a new diagnostic method called Mueller Polarimetry is examined for the investigation of plasma-surface interactions. This imaging technique allows the time-resolved optical characterization of targets under plasma exposure. The measured Mueller matrices are analyzed by using the logarithmic decomposition providing polarimetric data on diattenuation, depolarization, and birefringence. The latter is used by examining materials that possess optically active behavior to identify specific aspects of the plasma interaction, e.g. electric fields or temperature.This work focusses on electro-optic targets, which primarily enables the detection of electric fields induced by surface charge deposited during the interaction. The birefringence is coupled to the externally induced electric field by analytically relating the phase retardance for the probing polarized light beam to the perturbed index ellipsoid, according to the Pockels effect. Through this analytical approach, materials with specific electro-optic properties can be chosen in such a way – together with the orientation of the Mueller polarimeter itself – that all the individual electric field components (axial and radial) induced inside the sample are imaged separately. This has never been done before and allows to better understand the plasma dynamics in the vicinity of a dielectric surface.It is used to investigate the surface impact by guided ionization waves generated by a kHz-driven atmospheric pressure plasma jet. These non-thermal filamentary discharges are generally applied to various samples for e.g. surface functionalization of polymers or biomedical treatment of organic tissues. However, available diagnostic tools are limited to study these interactions. Imaging Mueller polarimetry applied to electro-optic targets examines the axial and radial field patterns in terms of amplitude (3-6 kV/cm), spatial scales (< 1mm axial and <1cm radial), and timescales (<1μs pulsed and <10μs AC) for various operating parameters of the jet, for example voltage amplitude and surrounding gas.Simultaneous with the transient birefringence induced by the electric field, a constant background pattern is also observed. This results from strain induced by temperature gradients inside the targeted material. An analytical relation is obtained following the photo-elastic effect, which allowed a fitting procedure to be designed to retrieve the temperature pattern. This procedure is used after calibration to show that the temperature of the sample can vary up to 25 degrees relative to room conditions – while changes in the electric field are seen as well – depending on the operating frequency of the AC driven plasma jet. The accurate determination of the temperature is important since most applications involve temperature sensitive samples.Lastly, this work shows how complex samples (in terms of surface geometry and/or chemical composition) can be examined during a plasma-surface interaction. This is done by combining them with the electro-optic targets. Due to the addition of a (thin) complex sample, depolarization is added to the system through scattering of the polarized light beam. In-situ observed changes of depolarization relate to the evolution of the complex sample during the plasma treatment. This, coupled with the simultaneously monitored electric field patterns, provides a unique diagnostic tool to examine the plasma-surface interactions. This has been applied for a test case where a single layer of onion cells is exposed to the ionization waves generated by the non-thermal plasma jet

La polarimetria è l'ultima branca dell'Astronomia nella banda dei raggi X ancora inesplorata. Nonostante un vasto interesse testimoniato da un'estesa letteratura, il suo sviluppo è stato impedito dalla mancanza di dispositivi la cui sensibilità giustificasse l'inserimento di polarimetri X a bordo delle missioni spaziali moderne. Ciononostante nuovi strumenti basati sull'effetto fotoelettrico, capaci di risolvere le tracce dei fotoelettroni in un gas, offrono oggi la possibilità di colmare il divario tra aspettative teoriche e gli scarsi risultati ad oggi raggiunti: in questo ambito, uno dei progetti più avanzati è il Gas Pixel Detector (GPD), sviluppato in Italia dall'INFN di Pisa e dall'INAF/IASF di Roma. Questa tesi ha contribuito dell'inserimento del GPD a bordo delle prossime missioni in differenti aspetti. Innanzitutto è stata misurata la risposta dello strumento a radiazione polarizzata di alcuni keV, ovvero nell'intervallo energetico di massima sensibilità, grazie ad una sorgente di calibrazione basata sulla diffrazione di Bragg a circa 45 gradi. Quest'ultima, insieme a sorgenti radioattive e a tubi a raggi X, è stata montata su un sistema meccanico, progettato e costruito in modo tale che lo strumento in esame potesse essere spostato, inclinato e ruotato rispetto al fascio incidente. Questo rende disponibile una struttura per la completa caratterizzazione del GPD (e di altri strumenti): prime e preliminari misure di calibrazione sono state effettuate grazie ad essa e sono di seguito presentate. Infine ho calcolato la sensibilità del GPD nel caso in cui esso sia posto nel piano focale di telescopi progettati per le prossime missioni spaziali, come PolariX e IXO, e ho discusso ulteriori applicazioni del GPD e dei polarimetri fotoelettrici in generale. In particolare, sono presentati il possibile utilizzo di questi dispositivi come strumenti a grande campo di vista o e quello come rivelatori sensibili fino ad energie di decine di keV.
Polarimetry is the last unexplored branch of X-ray Astronomy. Despite a wide interest proved by an extended literature, its development has suffered the lack of instruments which could assure a sufficient sensitivity to justify the inclusion of X-ray polarimeters on-board modern missions. Nevertheless new devices based on photoelectric absorption, which are able to image the track of photoelectrons in a gas mixture, offer today the possibility to fill the gap between theoretical expectations and the current meagre results: in this regard, one of the most advanced project is the GPD (Gas Pixel Detector), developed in Italy by INFN of Pisa and INAF/IASF of Rome. This work of thesis contributed to the use of the GPD on-board future space missions from different points of view. The response of the instrument to polarized radiation at a few keV, namely in the energy range of maximum sensitivity, was measured thanks to a calibration source based on Bragg diffraction at nearly 45 degrees. This source, together with radioactive unpolarized sources and X-ray tubes, were also interfaced with a mechanical assembly which was designed and built allowing for the movement, the inclination and the rotation of the instrument with respect to the incident beam. This makes available a facility for the complete characterization of the GPD (and other instruments) and the first and preliminary systematic measurements of calibration are presented. I also derive the scientific performances of the GPD when the instrument is placed in the focal plane of realistic X-ray telescopes planned for future missions, such as PolariX or IXO, and discuss some further applications of the GPD and of the photoelectric polarimeters in general. In particular the possible use of these devices as large field of view instruments or at energies up to tens of keV are presented.

Avec la diminution constante de la taille des transistors dans la microélectronique, les outils de caractérisation doivent être de plus en plus précis et doivent fournir un débit de plus en plus élevé. La fabrication de semi-conducteurs étant un processus couche par couche, le positionnement précis de la pile est crucial. Le mauvais alignement de la pile est appelé overlay, et nous proposons ici un nouvel instrument et une nouvelle méthode pour caractériser avec précision l'overlay en mesurant une cible unique construite dans les lignes de découpe. La méthode utilise les propriétés fondamentales de symétrie de la matrice de Mueller mesurée dans le plan focal arrière d'un objectif de microscope à grande ouverture numérique et permet une caractérisation de l'overlay avec une incertitude de mesure totale de 2nm. Après une brève introduction à la polarisation et la matrice de Mueller, nous décrivons la nouvelle conception de l'instrument et son étalonnage complet. Le corps principal de ce manuscrit est dédié à la caractérisation de l'overlay, mais les applications de cet instrument sont très diverses aussi détaillerons nous comment notre instrument peut apporter des pistes pour la caractérisation et la compréhension de l'auto-organisation de l'exosquelette des scarabées. Ces coléoptères présentent un très fort dichroïsme circulaire et de nombreux groupes de recherche dans le monde entier essaient d'imiter leur exosquelette. Nous concluons ce manuscrit par un bref aperçu des principales perspectives pour notre instrument
With the constant decrease of the size of the transistors in microelectronics, the characterization tools have to be more and more accurate and have to provide higher and higher throughput. Semiconductor manufacturing being a layer-by-layer process, the fine positioning of the stack is crucial. The misalignment of the stack is called overlay and we here propose a new tool and method to accurately characterize overlay by measuring a single target built in the scribe lines. The method uses the fundamental symmetry properties of the Mueller matrix acquired in the back focal plane of a high-aperture microscope objective and enables a characterization of the overlay with a total measurement uncertainty of 2nm. After a brief introduction to polarization and the Mueller matrix, we describe the new design of the instrument and its complete calibration. The main body of this manuscript is dedicated to the overlay characterization but the applications of this instrument are very diverse so we also detail how our instrument can shed some light on the characterization and the understanding of the auto-organization of some scarab beetles' exoskeleton. These beetles exhibit a very strong circular dichroism and many research groups around theworld try to mimic their exoskeleton. We conclude this manuscript with a brief overview of the main perspectives from our instrument

This thesis presents the first measurement of the d*(2380) (hexaquark) electromagnetic coupling, extracted from the deuteron photodisintegration (~γd → d* → ~np) reaction. The experiment was carried out at the Mainzer Microtron (MAMI) facility in the Institut für Kernphysik in Mainz, Germany. A racetrack microtron at the MAMI facility provided a 1557 MeV longitudinally polarised electron beam. This electron beam was directed onto a thin radiator to produce a bremsstrahlung photon beam. Diamond and amorphous (metallic) radiators were used to produce linearly and circularly polarised photons respectively. The produced bremsstrahlung photon beam was energy 'tagged' with a resolution of ~4 MeV over the photon-energy range of 150-1400 MeV using the Glasgow Photon Tagger. The tagged photons were incident on a 10 cm long liquid deuterium target. This target was surrounded by a new nucleon recoil polarimeter apparatus and placed within the Crystal Ball calorimeter at MAMI. An array of PbWO4 and BaF2 detectors (TAPS) was used to provide calorimetry at forward angles. The newly constructed large acceptance recoil polarimeter measures the polarisation of the nucleons in the final state. The combination of this new apparatus with the polarised photon beam facility gives access to a number of single and double polarisation observables. The photon beam asymmetry, Σ, and the double polarisation observable, Cx', were examined in measurements of the reaction d(→γ,→n→p) over a large range of energies with a close to full angular coverage. The observable Cx' is determined for the neutron produced in deuteron photodisintegration for the first time. The new data constrains mechanisms of deuteron photodisintegration and assesses the existence and contribution of the d*(2380) resonance.

This thesis includes work on both microchannel plate X-ray detectors and X-ray polarimetry, which although essentially distinct, have a common link through X-ray photocathodes. The source(s) of the background noise count rate in microchannel plates are investigated. Various noise mechanisms assessed include outgassing, cosmic rays, field emission, internal radioactivity, ion feedback and thermal emission. Experimental measurements are compared with calculations from a Monte Carlo model based on the assumption that radioactive decay (by beta emission) of elements within the microchannel plate glass is the major source of dark noise. The performance of Caesium Bromide as an X-ray photocathode for enhancing the quantum detection efficiency of microchannel plates is reported and compared with that of Caesium Iodide. A new type of microchannel plate configuration, a Sandwich Plate, consisting of three standard microchannel plates bonded in permanent contact is examined for use as an X-ray photon counting detector. This investigation includes a study of the correlation between gain reduction with increased count rate and the size of the illuminated area. An evaluation is made of Galileo Long Life (L2) Microchannel plates operated in pulse counting mode with special emphasis on the stability of the gain as a function of abstracted charge. Further evidence for radioactivity as the major source of background noise is obtained; L2 plates contain different radioactive isotopes compared to the 'standard' (Mullard) microchannel plate glass. The design and performance of a new type of polarimeter, a Photoemission Polarimeter, for use in soft X-ray astronomy is presented. The polarimeter utilises the linear polarisation sensitivity in the photoemission from a CsI photocathode. Possible sources of instrumental modulation are evaluated by comparing experimental measurements with calculations from a Monte Carlo model. The sensitivity of the photoemission polarimeter is compared with X-ray polarimeters presently used in X-ray astronomy.

In the first part of this thesis an automated polarimeter is described, and details are given of a dedicated CCD camera system based on a personal computer. The quality of the data produced by these instruments is demonstrated by the results presented in the succeeding chapters. Polarimetric observations of nebulae associated with two pre-MS objects, HH83/Rel7 and GL2591, and two post-MS objects, IRAS 07131-0147 and OH 231.8+4.2, are presented and discussed with reference to previous observations. In each case the location of the exciting source is determined and a simple model is described which explains the observed characteristics of the system. Both HH83/Rel7 and GL2591 are shown to be illuminated by nearby IRAS sources which have no optical counterparts. The nebula associated with HH83/Rel7 is caused by the reflection of radiation off the insides of the walls of a cavity excavated in the dark cloud by outflows from the IRS, and is crossed by a narrow unpolarised jet seen in emission-line radiation. The nebula associated with GL2591 is illuminated at optical wavelengths by both the IRS and a second, visible, source, and is composed of material ejected by the IRS in a discrete period of mass loss. IRAS 07131-0147 and OH 231.8+4.2 are shown to be stars which have evolved off the AGB and which will soon become the central stars of planetary nebulae. The protoplanetary nebulae which have formed as a result of the action of the fast stellar wind on the extended RGE around each star are bipolar and axially symmetric. The fast wind is shown to have ceased in the case of IRAS 07131-0147, but that related to OH 231.8+4.2 is still carrying material away from the star in a highly collimated fashion, producing narrow dusty filaments along the axes of the cavities. High levels of polarisation are measured in both nebulae, which indicates that the scattering particles are much smaller than those in the ISM.A brief comparison of the pre- and post-MS nebulae shows that the two phases of stellar evolution are linked by a number of observationally similar characteristics, and it is thought that similar processes may occur at opposite ends of the evolutionary track. Most notably, circumstellar discs appear to be common at various stages in the stellar life-cycle.

This thesis is concerned with the development of a general theory for the characterisation of polarimetric scattering problems. Traditionally, two main approaches have been used in the literature: the first based on measurement of the coherent scattering matrix (Jones calculus) and the second on measurement of the wave Stokes parameters (Mueller calculus). This thesis contains three main developments which extend and complement the published work in this area: 1) The representation of nonsymmetric scattering matrices on the Poincaré sphere, using an extension of the fork analysis first introduced by Kennaugh. 2) The construction of a geometry based on the Lorentz , transformation for analysing, on the Poincaré sphere. The interaction of partially polarised waves with single targets. 3) The reformulation of polarisation scattering problems in terms of a target spinor and associated coherency matrix. This leads to the construction of a target sphere in 6 dimensions analogous to the Poincaré sphere in 3 dimensions. This new formulation also leads to the development of a decomposition theorem for dynamic targets based on the eigenvectors of the coherency matrix. This decomposition is more fundamental than that used by Huynen and the two are compared and contrasted. In order to demonstrate main features of the new theory and to highlight its importance to experimental polarimetry, a laser based optical polarimeter was constructed. Results for the measured coherency Matrix obtained for transmission through quarter and half wave plates are presented and analysed using the target spinor theory.