SCExAO is the premier high-contrast imaging platform for the Subaru Telescope. It offers high Strehl ratios at near-IR wavelengths (y-K band) with stable pointing and coronagraphs with extremely small inner working angles, optimized for imaging faint companions very close to the host. In the visible, it has several interferometric imagers which offer polarimetric and spectroscopic capabilities. A recent addition is the RHEA spectrograph enabling spatially resolved high resolution spectroscopy of the surfaces of giant stars, for example. New capabilities on the horizon include post-coronagraphic spectroscopy, spectral differential imaging, nulling interferometry as well as an integral field spectrograph and an MKID array. Here we present the new modules of SCExAO, give an overview of the current commissioning status of each of the modules and present preliminary results.

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The dispersion quality of nanoinclusions within a matrix material is often overlooked when relating the effect of nanoscale structures on functional performance and processing/property relationships for nanocomposite materials. This is due in part to the difficulty in visualizing the nanoinclusion and ambiguity in the description of dispersion. Understanding the relationships between the composition of the nanofiller, matrix chemistry, processing procedures and resulting dispersion is a necessary step to tailor the physical properties. A method is presented that incorporates high-contrast imaging, an emerging scanning electron microscopy technique to visualize conductive nanofillers deep within insulating materials, with various image processing procedures to allow for the quantification and validation of dispersion parameters. This method makes it possible to quantify the dispersion of various single wall carbon nanotube (SWCNT)-polymer composites as a function of processing conditions, composition of SWCNT and polymer matrix chemistry. Furthermore, the methodology is utilized to show that SWCNT dispersion exhibits fractal-like behavior thus allowing for simplified quantitative dispersion analysis. The dispersion analysis methodology will be corroborated through comparison to results from small angle neutron scattering dispersion analysis. Additionally, the material property improvement of SWCNT nanocomposites are linked to the dispersion state of the nanostructure allowing for correlation between dispersion techniques, quantified dispersion of SWCNT at the microscopic scale and the material properties measured at the macroscopic scale. / Ph. D.

Cette thèse s'inscrit dans la thématique de l'étude de la formation et de l'évolution des systèmes planétaire grâce à la méthode de l'imagerie à haut contraste, aussi appelée imagerie directe, par comparaison aux méthodes de détection dites "indirectes". Le travail que je présente dans ce manuscrit s'articule en deux parties bien distinctes. La première partie concerne la composante observationnel de ma thèse, à l'aide de l'instrument SPHERE installé au Very Large Telescope, au sein du consortium du même nom. L'instrument SPHERE a pour objectif la détection et la caractérisation de jeunes et massives exoplanètes mais également de disques circumstellaires allant des très jeune disques protoplanétaires aux disques de débris, plus âgés. Ainsi, je présente dans ce manuscrit ma contribution au programme SHINE, un grand relevé de 200 nuits dont le but est la détection de nouvelles exoplanètes ainsi que la caractérisation spectrale et orbitale des quelques compagnons déjà connus. J'y présente également les deux études de disques circumstellaires que j'ai réalisées, autour des étoiles HD 141569 et HIP 86598. La première étude ayant permis la découverte d'anneaux concentriques à quelques dizaine d'UA de l'étoile ainsi que de asymétrie dans le flux du disque inhabituelle. La seconde étude porte sur la découverte d'un disque de débris présentant également une asymétrie en flux inhabituelle. La deuxième partie concerne la composante instrumentale de mon travail de thèse, au sein du consortium MICADO, en charge de la conception de la caméra du même nom qui sera l'un des instruments de première lumière de l'Extremely Large Telescope Européen (ELT). Dans ce manuscrit, je présente l'étude que j'ai menée afin de définir le design de certain composant du mode coronographique de MICADO tout en tenant compte des contraintes de l'instrument qui n'est pas dédié à l'imagerie haut contraste, contrairement à SPHERE. / This thesis is performed in the context of the study of the formation and evolution of planetary systems using high contrast imaging, also known as direct imaging in contrast to so-called "indirect" detection methods. The work I present in this manuscript is divided into two distinct parts.The first part concerns the observational component of my thesis, using the SPHERE instrument installed at Very LargeTelescope. This work was done as part of the consortium of the same name. The purpose of the SPHERE instrument is to detect and characterize young and massive exoplanets, but also circumstellar disks ranging from very young protoplanetary disks to older debris disks. In this manuscript, I present my contribution to the program SHINE, a large survey with an integration time of 200 nights' worth of observation, the goal of which is the detection of new exoplanets and the spectral and orbital characterization of some previously-known companions. I also present the two studies of circumstellar disks that I made, around the stars HD 141569 and HIP 86598. The first study allowed the discovery of concentric rings at about ten AU of the star along with an unusual flux asymmetry in the disk. The second study is about the discovery of a debris disk that also has an unusual flux asymmetry. The second part concerns the instrumental component of my thesis work done within the MICADO consortium, in charge of the design of the camera of the same name which will be one of the first light instruments of the European Extremely Large Telescope (ELT). In this manuscript, I present the study in which I define the design of some components of the coronagraphic mode of MICADO while taking into account the constraints of the instrument - which is not dedicated to high contrast imaging, unlike SPHERE.

The viability of using a slicer based integral field spectrograph (IFS) for high contrast observations has been under scrutiny due to the belief that the one dimensional coherence that persists along the slice to the point of sampling at the detector will cause the creation of secondary speckles that will not have the same characteristics as normal speckles, thus stopping us from calibrating them out. It has also been previously assumed that a suitably low differential wavefront error when moving slice to slice was not guaranteed by design. It was for these reasons that slicer based IFSs were not selected for the current generation of planet finding instruments. As part of the EPICS (Exo Planet Imaging Camera and Spectrograph for the E-ELT) design study it was decided that slicers should be re-investigated due to results from on sky observations suggesting these limitations did not exist. The purpose of this thesis was to determine whether there was validity to the concerns mentioned above and therefore to answer the question; Would implementing a slicer based integral field spectrograph limit the achievable contrast of an instrument designed for the direct detection of exoplanets? Chapter 1 gives a brief introduction into the field of exoplanet research. Charpter 2 describes the noise limiting direct detection of exoplanets and the ways to get around it. Chapter 3 gives an overview of the two types of IFS under investigation by the EPICS consortium. Chapter 4 looks into details of the EPICS instrument and the IFS design study that came about. Chapter 5 shows simulations performed for the aim of achieving better contrasts via post processing methods and accurate data reduction as well as simulations of slicer based integral field spectrographs. Experimental tests using a slicer and a preoptics setup designed to simulate the limiting noise are described in Chapter 6. Chapter 7 looks at using SINFONI for high contrast observations and Chapter 8 details the conclusions drawn from the work presented in this thesis, as well as possible extensions to it. The work performed in this thesis dispels the concerns about the continued one dimensional coherence up to the detecter and suggests that slicer based integral field spectrographs do not inherently limit the contrast achievable; Results from experiments fit well with the requirements for EPICS to achieve its goals. Simulations also supported the idea that secondary speckle noise should not be an issue for the slicer based IFS. This means that a slicer based IFS is a viable option for the EPICS instrument.

Cette thèse a été réalisée entre 2014 et 2017 en vue de la préparation d'une mission probatoire du projet Imageur de Fresnel permettant de réaliser des observations astronomiques dans le domaine ultraviolet (UV). Il s'agit d'un modèle de télescope spatial diffractif imaginé et développé principalement par Laurent Koechlin depuis 2004. Son optique primaire est une grille de Fresnel, optique très légère (de l'ordre du kilogramme) parfaitement adaptée pour servir à une mission d'observation spatiale de très grande envergure, utilisant le principe des réseaux zonés de Fresnel. Afin de prouver la faisabilité d'une mission probatoire sur la Station Spatiale Internationale (ISS) fonctionnant dans l'ultraviolet, l'instrument doit d'abord faire la preuve de ses performances au sol. Le premier objectif a donc été de concevoir un nouveau prototype sol adapté à l'observation dans l'ultraviolet. Cela a nécessité la définition d'une nouvelle configuration de l'ensemble du système imageur, ainsi que la réalisation de nouvelles optiques, et en particulier celle du correcteur du chromatisme induit par la grille d'un nouveau genre. Il s'agit d'un miroir de Fresnel blazé concave, qui a été réalisé pour la première fois avec succès. Le second a été de perfectionner le modèle de grille de Fresnel, afin d'en améliorer ses qualités de haut contraste en conservant sa résolution maximale. Cela s'est fait par la modification des barreaux de maintien des anneaux, ainsi que par l'application d'une apodisation adaptée à cette optique particulière. La nouvelle grille du prototype d'une largeur de 65 mm seulement, permet théoriquement d'atteindre une dynamique de 10^6 à 15 resels (éléments de résolution), probablement meilleure avec la grille qui sera utilisée pour la mission probatoire, et bien supérieure encore avec les grilles de grandes dimensions si un jour elles sont utilisées pour l'astrophysique UV. / This Ph.D. thesis work was made between 2014 and 2017, in order to prepare a probatory mission of the Fresnel Imager for astronomical observations in the ultraviolet (UV) domain. The Fresnel Imager is a concept of diffractive telescope created and developed mainly by Laurent Koechlin since 2004. Its primary optics is a Fresnel grid: a very light weight optics (in the range of kilograms) using the principle of Fresnel zone plates. Fresnel arrays are adapted to large apertures in space. In order to prove the feasibility of a probatory mission on the International Space Station (ISS), the instrument has first to prove its performances on the ground. The initial goal of my thesis was to conceive a new prototype adapted to UV. This required a new configuration of the entire imaging system, as well as the realization of new optics, particularly those correcting the chromatism induced by that new kind of diffractive imaging. This chromatic corrector is a concave blazed Fresnel mirror, which has been successfully realized for the first time. The second goal was to improve the design of the Fresnel grid, in order to enhance its high contrast performances while preserving its diffraction-limited resolution. This was obtained by modifying the setup which holds the rings in place, as well as by the application of an apodization adapted to this particular optics. The new Fresnel grid in the prototype is 65 mm x 65 mm only, but its point spread function reaches a dynamic range of 10^6 at 15 resels (resolution element) from center. This will be further improved when a slightly larger array planned for the probatory mission on the ISS. Later, space missions could feature Fresnel grids several meters in size, yielding diffraction-limited images in the UV.

Imager une exo-terre à proximité d’une étoile est une tâche complexe : le signal de la planète est noyé dans le flux immense de l’étoile, très proche. Doivent donc être combinés :- de grands télescopes spatiaux segmentés. La segmentation du miroir primaire facilite le transport mais crée des erreurs liées à l’alignement.- un coronographe, permettant d’éteindre la lumière stellaire. - enfin, toute aberration optique crée un résidu lumineux nuisible dans l’image. La mesure et le contrôle des aberrations d’un système coronographique, notamment celles liées à la segmentation du télescope, sont donc primordiaux et constituent le sujet de ma thèse.Tout d’abord, j’ai développé PASTIS, un modèle simplifié du contraste d’un coronographe en présence d’une pupille segmentée, permettant d’analyser facilement les performances pour contraindre les aberrations optiques lors du design de l’instrument. PASTIS prend en compte les spécificités des instruments : structure de la pupille, aberrations optiques dues à la segmentation, coronographe. Je l’ai appliqué au télescope LUVOIR afin d’analyser les modes limitant le contraste et ainsi mieux répartir les contraintes sur les segments. Par la suite, j’ai travaillé sur l’analyse de front d’onde coronographique en présence d’un télescope segmenté sur le banc expérimental HiCAT avec une première démonstration de l’analyseur COFFEE permettant de reconstruire les erreurs de phasage avec une grande précision. Enfin, j’ai mené une analyse comparative des multiples méthodes de contrôle de front d’onde existantes et validé l’une d’elles (Dark Hole Non Linéaire) expérimentalement dans un cadre simplifié sur le banc MITHIC du LAM / Direct imaging of exo-Earths is extremely complex: the star is by far brighter and very close to the planet. Several tools have to be combined:- a giant primary mirror. For manufacturing and transportation reasons, we tend to use segmented mirrors, ie. mirrors made of smaller mirrors but that have to be well-aligned and stabilised.- a coronagraph, enabling to remove the starlight.- the smallest residual wavefront aberration into residual light that decreases the image quality. The measurement and control of the aberrations, including the ones due to the telescope segmentation, are crucial and consist in the topic of my thesis.First, I developed PASTIS, a model of the contrast of a coronagraphic system in presence of a segmented pupil, enabling to analyze the performance to set up constraints on the optical aberrations during the instrument design. PASTIS takes into account the specificities of high-contrast instruments: pupil structure, optical aberrations due to the segmentation, coronagraph. I applied it to the LUVOIR telescope to analyze the main modes limiting the contrast and therefore optimizing the repartition of the constraints on the segments. In parallel, I worked on the analysis of the coronagraphic wavefront in presence of a segmented telescope on the experimental testbed called HiCAT, with a first demonstration of the COFFEE sensor enabling to reconstruct phasing errors with a high precision.Eventually, I ran a comparative analysis of existing methods of wavefront control and experimentally validated one of them (Non Linear Dark Hole) in a simplified case on the MITHIC testbed at LAM

Cette thèse vise à investiguer des moyens d'optimiser les performances de l'imagerie à haut contraste dans l'optique et le proche infrarouge pour la détection d'exo-planètes. L'étude principale a été menée sur le contraste à faible séparation permettant l'imagerie d'exo-planètes dans leur zone habitable. Cette détection directe est rendue possible par le développement des futurs grands télescopes et de coronographes de plus en plus performants à faible séparation. L'approche retenue permet de créer une zone sombre à haut contraste grâce à la coronographie et au « wavefront shaping » (contrôle de l'amplitude et de la phase avec 2 miroirs déformables), mais qui est limité par les effets de propagation de Fresnel. Les résultats obtenus ont déterminé les limitations de configuration optique pour le « wavefront shaping ». Grâce à une approche semi-analytique soutenue par des simulations numériques et une approche Monte-Carlo, ces limitations ont été analysées et quantifiées pour extraire les configurations optimales. Les résultats ont été appliqués au banc SPEED dont l'objectif est d'optimiser et de tester le haut contraste à faible séparation. Une deuxième étude a été une contribution à une étude générale de stabilité, en traitant la stabilité temporelle comme un paramètre indispensable dans la conception en amont d'instrument haut contraste. Un travail préliminaire a été initié sur la stabilité des instruments de mesure eux-mêmes à travers l'étude thermique d'un système de métrologie. Enfin, un dernier volet a été une étude de simulation de performances d'un nouveau concept d'imagerie différentielle basé sur l'acquisition d'images réalisées avec différentes tailles de pupilles. / This thesis aims to optimize high-contrast imaging performance in visible and near infrared for exoplanet detection. The main study focuses on high-contrast at small separation, to image exoplanets in their habitable zone. This direct detection is achievable with the next Extremely Large Telescopes and with the development of coronagraph providing high performance at small separation. The approach adopted for this study creates a high-contrast region (a dark hole) with the combination of coronagraphy and wavefront shaping (wavefront control of both phase and amplitude with 2 deformable mirrors) but is limited by the Fresnel propagation of phase aberrations. The goal of this work is to define the wavefront shaping limitation in optical configuration (deformable mirrors location, component optical quality, beam diameter). A semi-analytic approach followed by a Monte-Carlo analysis of numerical end-to-end simulations is studied, resulting in the definition of the optimal configuration. Results are then applied to SPEED, a test bench to optimize and test high-contrast imaging at small separation with a segmented pupil. Another aspect of this thesis is a contribution to a stability study to treat the temporal stability as a crucial parameter in high-contrast imaging instrumentation, at the conception level. A preliminary work is initiated during the thesis to analyse the stability of the measuring instrument itself. A metrology tool and its thermal behaviour are thus studied. Finally, the last part of this thesis is a performance analysis of a new differential imaging technique, developed to improve high contrast with observations with different diaphragm sizes.

<p>Digital fringe projection (DFP) methods are commonly used to obtain high-accuracy shape measurements of opaque, diffusely-reflective objects. While some objects may have constant texture across its surface, this is not true for all; many measured objects may have high-contrast texture caused by edges of dark- and light-colored sections of the object. In these high-contrast areas, a phase artifact has been consistently observed, which in turn creates a specific measurement error that is sometimes referred to as ``discontinuity-induced measurement artifacts" (DMA). Our study indicated that this error is most likely caused by camera defocusing, which produces a Gaussian point spread function (PSF) that is convoluted across every captured image, thus creating an phase artifact shaped like a Gaussian function. Based on this finding, this thesis outlines a method for removing this error via Gaussian curve fitting on the affected regions. These regions can be found by locating large spikes in the image intensity gradient, which directly correspond to the edge of the phase artifact, and then using a weighted least squared method to fit a Gaussian function to the affected area. We propose to use this error removal method in two ways: first, to remove errors on a checkerboard calibration target in order to increase calibration accuracy; and second, to directly remove errors in high-contrast areas in order to decrease shape measurement error. Experimental results demonstrate that the proposed method succeeds in decreasing calibration error for a checkerboard calibration target by as much as 12\%. Shape measurement experiments were not only conducted across simple, flat boards, but also more complex surfaces, such as that of a coffee mug. This thesis will show that this measurement error can be significantly decreased for both simple and complex surfaces.</p>

In this dissertation, novel phase compensation technologies are applied to the designs of wide viewing angle and high transmittance liquid crystal displays. First, a design of wide viewing angle liquid crystal displays utilizing crossed linear polarizers is proposed. The designed multi-domain vertical-alignment liquid crystal display predicts superb contrast ratio over wide viewing angles. Next, to increase the bright state transmittance while maintain the high contrast. Finally, to reduce the cost and improve the applicability of the broadband and wide-view circular polarizer, the device configuration of the broadband and wide-view circular polarizer is significantly simplified by the application of biaxial compensation films. The produced states of polarization remain close to the ideal circular polarization over a wide range of incident angles within the visual spectrum. With this circular polarizer, the presented wide-view liquid crystal display predicts high contrast ratio as well as high and uniform transmittance over wide viewing angles within the visual spectrum. ratio, wide viewing angle circular polarizers are developed. The produced states of polarization are very close to the ideal circular state of polarization over a wide range of incident angles within the visual spectrum. This guarantees not only high contrast ratio but also high and uniform transmittance.