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No description available.

In this thesis, we investigate the propagation of some coherent and partially coherent laser beams, including a dark hollow beam (DHB), an elliptical Gaussian beam (EGB), a flat-topped beam and a twisted anisotropic Gaussian Schell-model (TAGSM) beam, through a paraxial optical system or a turbulent atmosphere. Several theoretical models are proposed to describe a DHB of circular or non-circular symmetry. Approximate analytical formulas for a DHB and a partially coherent TAGSM beam propagating through an apertured paraxial optical system are derived based on the generalized Collins formula. Analytical formulas for a DHB, an EGB, a flat-topped beam and a partially coherent TAGSM beam propagating in a turbulent atmosphere are derived in a tensor form based on the extended Huygens-Fresnel integral formula. It is found that after a long propagation distance these beams become circular Gaussian beams in a turbulent atmosphere, and this is quite different from their propagation properties in free space. The conversion of any of these beams to a circular Gaussian beam becomes quicker and the beam spot in the far field spreads more rapidly for a larger structure constant of the turbulent atmosphere, a shorter wavelength and a smaller waist size of the initial beam. Lower coherence and larger twist have a stronger effect of anti-circularization of the beam spot. Our analytical formulas provide a convenient way for studying the propagation of various laser beams through a paraxial optical system or a turbulent atmosphere. The concept of coincidence fractional Fourier transform (FRT) with an incoherent or partially coherent beam is introduced, and the optical system for its implementation is designed. The coincidence FRT is demonstrated experimentally with a partially coherent beam, and the experimental results are consistent with the theoretical results. / QC 20100831

Ziele wie eine hohe Auflösung und ein hoher Durchsatz sind bisher in der Elektronenstrahllithografie nicht gleichzeitig erreichbar; es existieren daher die Belichtungskonzepte Gaussian-Beam und Variable-Shaped-Beam (VSB), die auf Hochauflösung respektive Durchsatz optimiert sind. In dieser Arbeit wird der experimentelle Kreuzvergleich beider Belichtungskonzepte mit Hilfe chemisch verstärkter und nicht verstärkter Lacksysteme präsentiert. Als quantitativer Parameter wurde die Gesamtunschärfe eingeführt, die sich durch quadratische Addition der auflösungslimitierenden Fehlerquellen, also Coulomb-Wechselwirkungen (Strahlunschärfe), Lackprozess (Prozessunschärfe) und Proximity-Effekt (Streuunschärfe), ergibt. Für den Vergleich wurden wohldefinierte Prozesse auf 300 mm Wafern entwickelt und umfassend charakterisiert. Weitere Grundlage ist die Anpassung oder Neuentwicklung spezieller Methoden wie Kontrast- und Basedosebestimmung, Doughnut-Test, Isofokal-Dosis-Methode für Linienbreiten und Linienrauheit sowie die Bestimmung der Gesamtunschärfe unter Variation des Fokus. Es wird demonstriert, dass sich mit einer kleineren Gesamtunschärfe die Auflösung dichter Linien verbessert. Der direkte Vergleich der Gesamtunschärfen beider Belichtungskonzepte wird durch die variable Strahlunschärfe bei VSB-Schreibern erschwert. Da für die Bestimmung der Gesamtunschärfe keine Hochauflösung nötig ist, wird das Testpattern mit größeren Shots belichtet und induziert somit eine größere Gesamtunschärfe. Es wird gezeigt, dass die Prozessunschärfe den größten Anteil der Gesamtunschärfe stellt. Außerdem spielt die Streuunschärfe bei Lackdicken kleiner 100 nm und Beschleunigungsspannungen von 50 kV oder größer keine Rolle. / Up to now, targets like high resolution and high throughput can not be achieved at the same time in electron beam lithography; therefore, the exposure concepts Gaussian-Beam and Variable-Shaped-Beam (VSB) exist, which are optimized for high resolution and throughput, respectively. In this work, the experimental cross-comparison of both exposure concepts is presented using chemically amplified and non-chemically amplified resist systems. For quantification the total blur parameter has been introduced, which is the result of the quadratic addition of the resolution limiting error sources, like Coulomb interactions (beam blur), resist process (process blur) and proximity-effect (scatter blur). For the comparison, well-defined processes have been developed on 300 mm wafers and were fully characterized. Further basis is the adaption or the new development of special methods like the determination of contrast and basedose, the doughnut-test, the isofocal-dose-method for line widths and line roughness as well as the determination of the total blur with variation of the focus. It is demonstrated, that the resolution of dense lines is improved with a smaller total blur. The direct comparison of the total blur values of both exposure concepts is complicated by the variable beam blur of VSB writers. Since high resolution is not needed for the determination of the total blur, the test pattern is exposed with larger shots on the VSB writer, which induces a larger total blur. It is shown that the process blur makes the largest fraction of the total blur. The scatter blur is irrelevant using resist thicknesses smaller than 100 nm and acceleration voltages of 50 kV or larger.

This master´s thesis provides basic properties and measurement of optical beams. In the first chapter is shown division of light on ray, wave and beam optics. Atmospheric optics and properties associated with propagation of light through the earth's atmosphere is presented in the second chapter. In the third part are shown basic techniques for Gaussian beam shaping. The last chapter deals with measurement of optical beam after propagating through a turbulent medium. In this section is shown distribution of relative variance of optical intensity in Gaussian and Top-Hat beam. There is also measured spatial coherence of laser beam in the turbulent atmospheric transmission media. Finally effect of the beam wander is investigated.

This work is focused on the study of the intensity profile of optical beams. In the first part problematics of optical beams from theoretical point of view is discussed, Model of realistically circular symmetric beam in an ideal lossless, stationary, homogeneous and isotropic medium is formed in Matlab®. The next part of the thesis deals with implementation of automatic workplace for measuring intensity profile of optical beams. Within the thesis - PCB desing of photodetector in Eagle®, is discussed. Custom application for controlling the motorized linear stage M – IMS 400 and communication with photodetector in the Microsoft Visual Studio 2010® was created.

Dans certains contextes, les méthodes classiques utilisées pour le calcul de champs rayonnés ou diffractés en présence d'obstacles de grande taille par rapport à la longueur d'onde, comme l'Optique Physique ou les méthodes de rayons, ne sont pas valides ou deviennent très lourdes en temps de calcul. La théorie des frames de Gabor fournit un cadre rigoureux permettant de décomposer une distribution de sources électromagnétiques, définie dans une ouverture équivalente plane, en une somme plus ou moins redondante de fenêtres gaussiennes. Cette décomposition peut servir de base à des algorithme de lancer de faisceaux gaussiens.Jusqu'à présent cette théorie était limitée à des décompositions dans un plan (rayonnement dans un demi-espace). L'objet de cette thèse est d'utiliser cette théorie pour décomposer des champs rayonnés ou diffractés dans toutes les directions de l'espace. Ce travail de thèse commence par une étude approfondie de l'influence des paramètres utilisés pour le calcul des coefficients de frame. La mise en oeuvre numérique permet de tester l'efficacité de techniques de troncation et de compression en termes de compromis précision/temps de calcul. Le coeur de la thèse consiste en une méthode originale de partitionnement spectral, utilisant des fonctions de partition de l'unité, qui permet d'utiliser le lancer de faisceaux gaussiens à partir de frames définis dans six plans, pour un rayonnement dans tout l'espace tridimensionnel. La formulation de la méthode est présentée. Elle est appliquée à la décomposition en faisceaux gaussiens du champ rayonné par des antennes théoriques omnidirectionnelles (réseau de dipôles et dipôle demi-onde). Une antenne réaliste sert enfin de cas test pour la mise en œuvre de la décomposition à partir de données expérimentales discrètes / In some contexts, conventional methods used for large problems involving radiated or diffracted field computations in the presence of obstacles, such as Physical Optics and ray based methods, become really inaccurate or prohibitively time-consuming. Gabor frame theory provides a rigorous framework for the initial decomposition of equivalent source distributions into a redundant set of Gaussian windows. Frame decomposition has been introduced as a first discretization step into Gaussian Beam Shooting (GBS) algorithms. Until now, frame decomposition has essentially been restricted to planar source distributions, radiating into one half space. The main goal of this thesis is to extend the application range of this theory to radiated or diffracted field decomposition into Gaussian beams propagating into the whole space. The thesis begins with a thorough study of influence of the parameters used for frame coefficient calculation. Numerical implementation is used to test the efficiency of truncation and compression techniques in terms of accuracy / computation time balance optimization. The core of the thesis consists of an original spectral domain partitioning method involving partition of unity functions, which allows to use Gaussian beam shooting from frames defined in six planes, for radiation into the whole three-dimensional space. The formulation of the method is presented and applied to the decomposition of fields radiated by theoretical omnidirectional antennas (dipole array and half-wave dipole) into Gaussian beams. A realistic antenna is used as a test case for the implementation of decompositions based on experimental discrete initial data

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Akustiska kanaler för undervattenskommunikation är flervägskanaler där ljudet reflekteras från havets yta och botten och bryts vid ljudhastighetsförändringar. I grunt vatten är impulssvaret långt jämfört med symbolernas tidslängd i ett utskickat meddelande. Detta orsakar intersymbolinterferens, vilket gör det svårt att återskapa meddelandet. Denna avhandling behandlar fysikalisk modellering av kommunikationskanalen. Sådan modellering kan öka insikten om de svårigheter som finns vid design av kommunikationssystem och kan vara till hjälp vid utveckling av lämpliga modulationstekniker och avkodningsalgoritmer. Ljudutbredningen simuleras med en strålgångsmetod med reflektionskoefficienter beräknade för plana vågor. I artikel 4 och 5 utvidgas modellen till en algoritm för gaussisk strålsummation. De viktigaste vetenskapliga bidragen är följande. Artikel 1: Aktuell kunskap om impulssvaret hos kommunikationskanalen gör det betydligt lättare att tolka det mottagna meddelandet. I denna artikel studeras tidsvariabiliteten hos impulssvaret i termer av bitfelssannolikhet när ett gammalt impulssvar används för kanalutjämning. Tidsvariabiliteten visar sig variera avsevärt med mottagarpositionen, inte bara när det gäller avståndet till sändaren, utan även när det gäller placeringen i djupled. Artikel 2: En hybridmetod presenteras, där strålgång i ett avståndsberoende medium kombineras med lokal fullfältsmodellering av interaktionen med havsbottnen. Metoden används för simuleringar av akustisk kommunikation i grunt vatten. Artikel 3: För att kunna göra tillförlitliga simuleringar av ljudutbredning behöver man god kunskap om mediets ljudhastighetsprofil --- information som inte alltid är tillgänglig. I denna artikel används den hybrida strålgångsmetoden från artikel 2 för att skatta ljudhastighetsprofilen från kommunikationsdata. Miljöparametrarna som beräknats genom inversionen minskar avvikelsen mellan simulerade och observerade skattningar av impulssvaret jämfört med avvikelsen då en uppmätt, två dagar gammal ljudhastighetsprofil används vid simuleringen. Miljömodellen används också för en genomgång av alternativa käll- och mottagarpositioner. Artikel 4: Gaussisk strålsummation är en vågutbredningsmodell som liknar strålgång men kan ge korrekta resultat i strålgångens singulära områden, som skuggzoner och kaustikor. I denna artikel diskuteras hur några olika val av den komplexa strålparametern $\epsilon$ fungerar i grunda vågledare. Bäst resultat erhålls om man väljer $\epsilon$ så att strålen blir smal i punkten närmast mottagaren och får en plan vågfront där. Artikel 5: En adaptiv metod för gaussisk strålsummation i grunda vågledare presenteras. Algoritmen ger en noggrannhet som är bättre än eller minst lika bra som strålgångens, även i grunda vågledare med en starkt djupberoende ljudhastighet. / Acoustic underwater communication channels are multipath channels where sound is reflected from the surface and the bottom of the sea and refracted by sound speed variations. In shallow water, the impulse response is typically long compared to the time length of the symbols in a transmitted message. This causes inter-symbol interference, which makes the message difficult to decode. This thesis deals with physical modelling of the communication channel. Such modelling can provide insight into the difficulties of communication system design and may serve as an aid in the development of appropriate modulation techniques and decoding algorithms. The sound propagation is simulated by a ray tracing method with plane-wave reflection coefficients, in papers 4 and 5 expanded to a Gaussian beam summation algorithm. The main scientific contributions are the following. Paper 1: Up-to-date knowledge of the impulse response of the communication channel considerably simplifies the extraction of information from a detected signal. In this paper the time variability of the impulse response is studied in terms of the bit-error rate, when an old impulse response is used for channel equalisation. The time variability is found to vary significantly with the receiver position, not only in range, but also in depth. Paper 2: A hybrid raytrace method is presented, combining ray tracing in a range-dependent water column with local full-field modelling of the seabed interaction. The method is applied to simulations of acoustic communication in shallow water. Paper 3: To be able to make reliable simulations of sound propagation, one needs to know, quite accurately, the sound speed profile of the medium --- information which is not always available. In this paper the hybrid raytrace method from paper 2 is used to estimate the sound speed profile from communication data. The environmental model obtained by the inversion reduces the mismatch between the modelled and the observed impulse response estimates, compared to the mismatch with a two-days-old sound speed profile. The model is also used to investigate alternative source-receiver configurations. Paper 4: Gaussian beam summation is a wave propagation model similar to ray tracing, which can yield correct results in singular regions like shadow zones and caustic points. In this paper some different choices of the complex beam parameter $\epsilon$ are discussed for shallow waveguides. Best results are observed when $\epsilon$ is chosen so that each beam is narrow at the point where it is closest to the receiver and has a plane wavefront there. Paper 5: An adaptive method for Gaussian beam summation in shallow waveguides is presented. The algorithm yields better or at least as good accuracy as ray tracing, even in shallow waveguides with a strongly depth-dependent sound speed profile. / QC 20100819

Dans le cadre des recherches menées sur les SFR (Sodium cooled Fast Reactor), le CEA souhaite développer une instrumentation innovante et spécifique à ces réacteurs. Le travail présenté concerne la mesure par ultrasons, de la température du sodium à la sortie des têtes des assemblages du coeur du réacteur. Cette instrumentation implique la propagation d'ultrasons dans du sodium liquide, thermiquement inhomogène et turbulent. Le milieu provoque des déviations du faisceau acoustique qu'il faut prévoir et quantifier pour envisager d'employer les ultrasons comme moyen de mesure dans un coeur de réacteur SFR.Pour cela un code nommé AcRaLiS (Acoustic Ray in Liquid Sodium) a été implémenté. Une étude thermo-hydraulique précise du sodium a tout d'abord été menée afin de proposer une description adaptée du milieu et de choisir le modèle de propagation acoustique adéquat. Puis une implémentation a été réalisée afin de permettre la simulation rapide de la propagation d'ondes de plusieurs mégahertz dans ce milieu particulier. Ce code prévoit les déviations et l'évolution de l'intensité du faisceau acoustique. Deux expériences ont ensuite été conçues et réalisées pour vérifier ce code. La première, nommée UPSilon, innove en remplaçant le sodium par de l'huile de silicone afin d'avoir une inhomogénéité thermique stable pendant l'expérience. Elle permet de déterminer la validité du code AcRaLiS dans des inhomogénéités thermiques. La seconde, nommée IKHAR, permet d'étudier en eau l'influence de la turbulence sur la propagation d'ondes, en exploitant les instabilités de Kelvin-Helmholtz. Les conclusions et les perspectives sont présentées en élargissant à d'autres domaines d'application. / In the frame of research on Sodium cooled Fast nuclear Reactor (SFR), CEA aims to develop an innovative instrumentation, specific to these reactors. The present work relates to the measurement of the sodium temperature at the outlet of the assemblies of the reactor's core by an ultrasonic method. This instrumentation involves the propagation of ultrasonic waves in liquid sodium, thermally inhomogeneous and turbulent. Environment causes deviations of the acoustic beam that must be understood to predict and quantify to consider ultrasound as a measure means in a core of SFR reactor. To determine the magnitude of these influences, a code named AcRaLiS (Acoustic Ray in Liquid Sodium) has been implemented. In a first step, a thermal-hydraulic study specific to the medium, was conducted to provide an adequate description of the environment and choose a suitable acoustic propagation model. Then an implementation has been performed to allow rapid simulations of the wave propagation at several megahertz in this particular environment. This code provides ultrasounds deviations and changes in beam intensity.Two experiments were designed and conducted to verify the code. The first, named UPSilon innovates by replacing sodium by silicone oil in order to have a stable thermal inhomogeneity during the experiment. It allows to determine the validity of the code AcRaLiS with thermal inhomogeneities. The second, called IKHAR allows to study the influence of water turbulence on the propagation of waves, using the Kelvin-Helmholtz instabilities. Conclusions and perspectives are presented, including perspectives for other application domains.