L’étude des rendements de fission a un impact majeur sur la caractérisation du processus de fission mais également sur le fonctionnement des réacteurs nucléaires. Bien que les rendements de fission thermiques des actinides majeurs (U-235, Pu-239) soient bien connus, ce n’est pas le cas de ceux de l’Am-242, ce que confirment les désaccords observés entre les principales bases de données évaluées. L’utilisation grandissante du combustible MOX dans les réacteurs nucléaires et la réduction de la radiotoxicité des déchets nucléaires nous poussent à étudier l’Am-241 et l’Am-242. Ainsi, les rendements issus de la fission de la réaction Am-241(2n,f) ont été mesurés auprès du spectromètre de masse Lohengrin situé à l’Institut Laue Langevin de Grenoble (France). Ces mesures ont permis la détermination de 41 rendements en masse. De plus, 20 rendements isotopiques ont pu être mesurés par spectrométrie gamma. Les expériences menées dans le cadre de cette thèse avaient également pour but de déterminer si les rendements de fission sont influencés par l’état de spin de l’Am-242. Afin de répondre à cette question, la mesure répétitive de rendements en masse pour différents rapports de taux de fission (Am-242m/Am-242g) a été réalisée. Nos résultats montrent que le spin du noyau cible n’a que peu d’influence sur les rendements en masse. De nouvelles expériences sont proposées afin de déterminer son influence sur les rapports isomériques. Les modèles théoriques actuels sont dans l’incapacité de prédire avec une précision suffisante les rendements de fission. Ainsi, l’industrie nucléaire a recours aux bases de données évaluées et aux modèles phénoménologiques. Néanmoins, les prédictions issues de modèles semi-empiriques implémentés dans le code GEF ont atteint un niveau suffisant pour faire de ce code un outil d’évaluation performant. Le contenu physique, les développements, les validations et l’extension du code seront également présentés dans cette thèse. / The study of fission yields has a major impact on the characterization and understanding of the fission process and is mandatory for reactor applications. While the yields are known for the major actinides (U-235, Pu-239) in the thermal neutron-induced fission, only few measurements were performed on Am-242. Moreover, the two main data libraries do not agree among each other on the light peak. Am-241 and Am-242 are nuclei of interest for the MOX-fuel reactors and for the reduction of nuclear waste radiotoxicity using transmutation reactions. Thus, a campaign of precise measurement of the fission mass yields from the reaction Am-241(2n,f) was performed at the Lohengrin mass spectrometer (ILL, France) for both the light and the heavy peak. Forty-one masses were measured. Moreover, the measurement of the isotopic fission yields on the heavy peak by gamma-ray spectrometry led to the extraction of 20 independent isotopic yields. Our measurement was also meant to determine whether there is a difference in fission yields between the Am-242 isomeric state and its ground state as it exists in fission cross sections. The experimental method used to answer this question is based on the measurement a set of fission mass yields as a function of the ratio of Am-242gs to Am-242m fission rate. Results show that the mass yields are independent of the fission rate ratio. A future experimental campaign is proposed to observe a possible influence on the isomeric yields. The theoretical models are nowadays unable to predict the fission yields with enough accuracy and therefore we have to rely on experimental data and phenomenological models. The accuracy of the predictions of the semi empirical GEF fission model predictions makes it a useful tool for evaluation. This thesis also presents the physical content and part of the development of this model. Validation of the kinetic energy distributions, isomeric yields and fission yields predictions was performed. The extension of the GEF model at high energy is also presented.

Magneto-optical materials such as permalloy can be used to create artificial spin- ice (ASI) lattices with antiferromagnetic ordering. Magneto-optical materials used to create diffraction lattices are known to exhibit magnetic scattering at the half- order Bragg peak while in the ground state. The significant drawbacks of studying the magneto-optical generation of OAM using x-rays are cost, time, and access to proper equipment. In this work, it is shown that the possibility of studying OAM and magneto-optical materials in the spectrum of visible light at or around 2 eV is viable. Using spectroscopic ellipsometry it is possible to detect a change in the magnetization of thin permalloy films with thicknesses between 5 and 20 nm. Patterns consistent with OAM were found at 1.95 eV using a square lattice with a 4𝜋 radial phase shift in the antiferromagnetic ground state. Evidence of magnetic scattering at the half-order Bragg peak using 1.95 eV was also found.

Exploiter le degré de liberté angulaire de la lumière pour contrôler les forces optiques ouvre une nouvelle voie pour la manipulation optique de systèmes matériels. Dans ce contexte, notre travail porte sur l’interaction lumière-matière en présence de chiralité, qu’elle soit matérielle ou ondulatoire. Expérimentalement, nous avons utilisé des gouttes de cristaux liquides cholestériques interagissant avec un ou plusieurs champs lumineux polarisés circulairement et nous avons apporté une description quantitative de nos observations. Notre principal résultat correspond à la démonstration que la pression de radiation optique peut être contrôlée par l’hélicité du photon. Ce phénomène est ensuite utilisé, d’une part pour faire une démonstration de principe du tri de la chiralité matérielle via une approche optofluidique et d’autre part pour réaliser un piège optique tridimensionnel sensible à la chiralité de l’objet piégé. / Exploiting the angular momentum degree of freedom of light to control the mechanical effects that result from light-matter exchanges of linear momentum is an intriguing challenge that may open new routes towards enhanced optical manipulation of material systems. In this context, our work addresses the interplay between the chirality of matter and the chirality of optical fields. Experimentally, this is done by using cholesteric liquid crystal droplets interacting with circularly polarized light and we provide with theoretical developments to quantitatively support our observations. Our main result is the demonstration of optical radiation force controlled by the photon helicity. This phenomenon is then used to demonstrate the optofluidic sorting of material chirality and the helicity-dependent three-dimensional optical trapping of chiral liquid crystal microspheres.

We shall present a theoretical description of paraxial beams, showing the propagation modes that arise from the solution of the paraxial equation in free space. We then discuss the angular momentum carried by light beams, with its decomposition in spin and orbital angular momentum and its quantization. We present the polarization and transverse modes of a beam as potential degrees of freedom to encode information. We define the Spin-Orbit modes and explain the experimental methods to produce such modes. We then apply the Spin-Orbit modes to perform a BB84 quantum key distribution protocol without a shared reference frame.We propose a Bell-like inequality criterion as a sufficient condition for the spin-orbit non-separability of a classical laser beam. We show that the notion of separable and non-separable spin-orbit modes in classical optics builds a useful analogy with entangled quantum states, allowing for the study of some of their important mathematical properties. We present a detailed quantum optical description of the experiment in which a comprehensive range of quantum states are considered.Following the study of Bell's inequalities we consider bipartite quantum systems characterized by a continuous angular variable θ. We show how to reveal non-locality on this type of system using inequalities similar to CHSH ones, originally derived for bipartite spin 1/2 like systems. Such inequalities involve correlated measurement of continuous angular functions and are equivalent to the continuous superposition of CHSH inequalities acting on two-dimensional subspaces of the infinite dimensional Hilbert space. As an example, we discuss in detail one application of our results, which consists in measuring orientation correlations on the transverse profile of entangled photons.

In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i.e., the increased plasma response observed in the direction of Earth's magnetic field. Using ray tracing, we study the propagation of ordinary (O) mode HF radio waves in an ionosphere modified by density depletions, with special attention to transmission through the radio window (RW), where O mode waves convert into the extraordinary (X, or Z) mode. The depletions are shown to shift the position of the RW, or to introduce RWs at new locations. In a simplified model neglecting absorption, we estimate the wave electric field strength perpendicular to the magnetic field at altitudes normally inaccessible. This field could excite upper hybrid waves on small scale density perturbations. We also show how transmission and focussing combine to give stronger fields in some directions, notably at angles close to the MZ, with possible implications for the MZ effect. In a separate study, we consider electromagnetic (e-m) beams with helical wavefronts (i.e., twisted beams), which are associated with orbital angular momentum (OAM). By applying geometrical optics to each plane wave component of a twisted nonparaxial e-m Bessel beam, we calculate analytically the shift of the beam's centre of gravity during propagation perpendicularly and obliquely to a weak refractive index gradient in an isotropic medium. In addition to the so-called Hall shifts expected from paraxial theory, the nonparaxial treatment reveals new shifts in both the transverse and lateral directions. In some situations, the new shifts should be significant also for nearly paraxial beams.

We present the theory of orbital angular momentum of light (MAO), based on the basic concepts of electromagnetism, as well as some techniques from generation and characterization of light beams possessing MAO. We also present non-linear optical processes of parametric conversion spontaneous descendant (CPD) and stimulated (CPDE). We reviewed the problem of conservation of MAO in CPD in the scheme does not collinear, describing States of using Laguerre-Gauss beams MAO. We extend this study to the case in which Bessel beams are used to describe the States of MAO. Our results show that rape occurs on conservation law of MAO, which is attributed to deformation of the angular spectrum of beam pumping (pump) transferred to the twin photons. However, this violation can be advantageous because through breach of MAO have access to entangled States of dimension greater than those generated with collinear geometry. As an alternative to the note of the violation of the law of conservation in parametric down conversion process we proposed an experiment based on CPDE, where the experimental implementation is simpler. Using MAO as target and polarization qubit as qubit control, we experimentally a alternative to optical circuit proposal for Li-Ping et al. [16] for the implementation of the logic gate C-NOT. Also we present an application of logic gate C-NOT for the generation of entangled States of a single photon, which can be implemented with our optical circuit. The generation of entangled States, multidimensional, and the implementation quantum logic gates are important for the areas of information and quantum computation. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Apresentamos a teoria do momento angular orbital da luz (MAO), baseada nos conceitos básicos do eletromagnetismo, bem como algumas técnicas de geração e caracterização de feixes de luz possuindo MAO. Apresentamos também os processos ópticos não lineares de conversão paramétrica descendente espontânea (CPD) e estimulada (CPDE). Revisamos o problema da conservação do MAO na CPD no regime não colinear, descrevendo os estados de MAO utilizando feixes Laguerre-Gauss. Extendemos este estudo para o caso em que feixes Bessel são usados para descrever os estados de MAO. Nossos resultados mostram que ocorre violação na lei de conservação do MAO, que é atribuída a deformação do espectro angular do feixe de bombeamento (pump) transferido para os fótons gêmeos. Entretanto, esta violação pode ser vantajosa, pois através da violação do MAO conseguimos ter acesso a estados emaranhados de dimensão maior do que aqueles gerados com geometria colinear. Como alternativa para a observação da violação da lei de conservação no processo de conversão paramétrica descendente, propusemos um experimento baseado na CPDE, onde a realização experimental é mais simples. Utilizando o MAO como qubit alvo e a polarização como qubit controle, realizamos experimentalmente um circuito ótico alternativo à proposta de Li-Ping e colaboradores [16] para a implementação da porta lógica C-NOT. Também apresentamos uma aplicação da porta lógica C-NOT para a geração de estados emaranhados de um único fóton, que pode ser implementada com nosso circuito ótico. A geração de estados emaranhados multidimensionais e a implementaçãode portas lógicas quânticas são importantes para as áreas de informação e computação quântica.

In this work, we develop a new technique to determine the topological charge of a light beam with orbital angular momentum. Our technique is based on the diffraction by a triangular aperture. By performing numerical simulations, for Laguerre-Gaus beams and Bessel beams with different values of l, we found tha the diffraction pattern contains the signature of the topological charge of the beam. Our theoretical predictions for a triangular aperture were experimentally verifiel, demonstrating the the diffraction pattern reveals the topological charge of the light beam. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Neste trabalho, desenvolvemos uma nova técnica para determinar a carga topológica de um feixe de luz com momento angular orbital. Nossa técnica é baseada na difração por uma abertura triangular. Através da realização de simulações numérica, para feixes Laguerre-Gauss e feixes Bessel com diferentes valores de l, descobrimos que o padrão de difração contém a assinatura da carga topológica do feixe. Nossas previsões teóricas para uma abertura triangular foram verificadas experimentalmente, demonstrando que o padrão de difração revela a carga topológica do feixe de luz. Esta técnica torna possível a determinação do módulo e do sinal da carga topológica de um feixe de luz de uma maneira simples e direta.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-04-26T16:56:47Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Anderson_Amaral.pdf: 6016426 bytes, checksum: d9633b708d004572ce2495387f757089 (MD5) / Made available in DSpace on 2017-04-26T16:56:47Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Anderson_Amaral.pdf: 6016426 bytes, checksum: d9633b708d004572ce2495387f757089 (MD5) Previous issue date: 2016-02-29 / CNPQ / In this thesis are presented various results regarding the transverse structure of light beams in the paraxial propagation regime, with a special concern with singularities in the transverse profile and in nonlinear optics applications. Theoretical and experimental tools were developed for the study of Optical Vortices (OV) and its most important characteristics, as the Orbital Angular Momentum (OAM) and the Topological Charge (TC). In a first step, we theoretically described and experimentally demonstrated that it is possible to shape the intensity profile of a beam containing OV by distributing TC over the plane transverse to the propagation direction [1]. The TC is associated with a phase singularity that implies in points of zero intensity. By distributing the TC on the transverse plane, it is possible to shape the beam dark region and also the OAM profile with the goal of optimizing the light beam for a given application. However, a problem identified in [1] was that most of the current available techniques to characterize OAM light implicitly assume that the beam has cylindrical symmetry, thus being inadequate to characterize fields resulting from more general TC distributions. These problems were approached in a second work [2], where it was shown that by measuring the field transverse amplitude and phase profiles it is possible to measure the OAM and the TC in TC distributions with arbitrary geometries. By combination of the results [1] and [2] it is possible to optimize and characterize the TC distributions for given applications, as for example by designing the transverse forces in an optical tweezer for microparticle manipulation. An important theoretical unfold during these works was the identification of an analogous relation between the field transverse phase in a TC distribution with the Coulomb potential in two-dimensional electrostatics. We then introduced in [3] the Topological Potential (TP) concept which allows the design of structured optical beams with complex spatial profiles inspired by two-dimensional electrostatics analogies. The TP can be used to describe a broad class of TC distributions, as those from [1,2] or the more sophisticate examples in [3]. In another set of results, it is discussed the possibility of using concepts and the formalism of quantum mechanics to solve light propagation problems in the classical approximation. Among the results obtained, it should be remarked that the formalism obtained has a simple and direct relation with ABCD matrices and ray optics [4]. These results were used to understand light propagation in systems containing nonlinear materials, as in SLIM [5] and D4σ [6] techniques. In [5, 6] the theoretical results were compared with experimental data obtained from standard samples, as carbon dissulfide (CS2), acetone and fused silica. It was obtained a very good agreement between the measured optical nonlinearities and the results established in literature for these materials. / Nesta tese são apresentados resultados relacionados com a estrutura transversal de feixes de luz no regime paraxial de propagação, com uma atenção especial em singularidades no perfil transversal e em aplicações para óptica não linear. Foram desenvolvidas ferramentas teóricas e experimentais para o estudo de vórtices ópticos (Optical Vortices - OVs), e suas características mais importantes, como o momento angular orbital (Orbital Angular Momentum - OAM) e a carga topológica (Topological Charge - TC). Inicialmente, foi teoricamente descrito e experimentalmente demonstrado como é possível moldar o perfil de intensidade de um feixe contendo OVs usando uma distribuição de TC sobre o plano transversal à direção de propagação [1]. A TC está associada a uma singularidade na fase, o que implica em um zero de intensidade. Ao se distribuir a TC sobre o plano transversal, é possível moldar o formato da região de intensidade nula e também o perfil de OAM no intuito de otimizar o feixe para uma dada aplicação. No entanto, um problema identificado neste trabalho é que a maior parte das técnicas de caracterização disponíveis para luz com OAM implicitamente supunham que o feixe possui simetria cilíndrica, e portanto não eram adequadas para caracterizar campos obtidos a partir de distribuições de TC com geometrias mais gerais. Tais problemas foram abordados em um segundo trabalho [2], onde foi mostrado que por meio de medições dos perfis transversais de amplitude e fase do campo elétrico é possível medir o OAM e a TC em distribuições de TC com formas geométricas arbitrárias. A união dos trabalhos [1] e [2] permite então que as distribuições de TC possam ser adequadamente otimizadas e caracterizadas para aplicações específicas, como por exemplo ao moldar as forças transversais numa pinça óptica para a manipulação de micropartículas. Um desdobramento teórico importante obtido foi identificar uma relação análoga entre o perfil de fase em uma distribuição de TC com o potencial de Coulomb em eletrostática bidimensional. Foi então introduzido em [3] o conceito de potencial topológico (Topological Potential - TP) que possibilita a construção de feixes ópticos estruturados com perfis espaciais complexos inspirados em analogias com eletrostática bidimensional. O TP pode ser usado na descrição de uma grande variedade de distribuições de TC, como nos feixes em [1, 2] ou nos exemplos mais sofisticados em [3]. Posteriormente, é discutida a possibilidade de se utilizar conceitos e o formalismo da mecânica quântica na solução de problemas de propagação da luz descrita na aproximação clássica. Dentre os resultados obtidos, destaca-se que o formalismo possui uma relação simples e direta com as matrizes ABCD e a óptica de raios [4]. Estes resultados foram utilizados na compreensão da propagação da luz em sistemas contendo materiais não lineares, como nas técnicas SLIM [5] e D4σ[6]. Nos trabalhos [5,6] os resultados teóricos foram comparados com dados experimentais obtidos em amostras padrão, como dissulfeto de carbono (CS2), acetona e sílica fundida. Foi obtida uma concordância muito boa entre os valores medidos para as não linearidades ópticas nestes materiais e os valores estabelecidos na literatura.

Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-03-27T20:46:23Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação.pdf: 3142879 bytes, checksum: 86acc16510c6eb3acd7d645922238d47 (MD5) / Made available in DSpace on 2017-03-27T20:46:23Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação.pdf: 3142879 bytes, checksum: 86acc16510c6eb3acd7d645922238d47 (MD5) / Trabalhos anteriores já mostraram o dobramento do momento angular orbital de feixes após a geração de segundo harmônico em meios não lineares. Nesse trabalho pretendemos usar a polarização como parâmetro auxiliar para poder incidir em um cristal não linear dois feixes colineares com momentos angulares orbitais diferentes e obter na geração de seu segundo harmônico a soma de seus momentos angulares orbitais e veri car este resultado experimentalmente. / Previous work have already shown the orbital angular momentum doubling after second harmonic generation in non-linear media. In this work we intend to use the polarization as an auxiliary parameter to focus in a non-linear crystal two colinear beams with different orbital angular momentum and obtain in its second harmonic generation the sum of their orbital angular momentum and to verify it exeperimentally.

Cette thèse porte sur la manipulation du moment angulaire de la lumière à l'échelle sub-micronique. Le moment angulaire total de la lumière est composé d'une partie de spin, relié au degré de liberté de polarisation circulaire de la lumière, et d'une partie orbitale, relié au degré de libertés spatiaux de la lumière que sont sa direction de propagation (locale et globale) et sa distribution spatiale d'intensité. Le couplage spin-orbite existant entre ces deux contributions permet alors de manipuler les degrés de libertés spatiaux de la lumière par un simple contrôle de son état de polarisation circulaire. Dans cette thèse, nous avons étudié et exploité ce couplage à l'échelle sub-micronique dans deux nouveaux phénomènes que nous avons mis en évidence. Le premier met à profit ce couplage pour permettre d'exciter de manière unidirectionnelle des modes plasmoniques guidés. Une étude complète (numérique, expérimentale et analytique) de ce phénomène nouveau, basé sur un couplage entre le moment de spin du photon incident et le moment orbital extrinsèque des modes plasmoniques guidés dans la courbure d'un guide, est présentée. La deuxième étude présente une voie pour tirer parti du transfert de moment orbital de la lumière à un gaz d'électrons libres dans un métal afin de générer et contrôler le sens et la géométries de boucles de courants sub-microniques dans des structures métalliques. Ce contrôle permettrait la génération d'optomaimants nanométriques, entièrement contrôlés par la lumière, pouvant être modulés aux fréquences optiques. Ce travail a été soutenu par le LABEX Action. / This thesis focuses on the manipulation of the angular momentum of light at the nanoscale.The total angular momentum of light is composed of a spin component, connected to the polarization degree of freedom of light, and an orbital component, related to the spatial degrees of freedom of the light which are its propagation direction (local and global) and its intensity distribution. The spin-orbit coupling between these two contributions allows the control of the spatial degrees of freedom of light by a simple manipulation of its circular polarization state. In this thesis, we have studied and applied this coupling at the nanoscale anbd we have highlighted two new phenomenas. The first one takes part of this coupling to allows unidirectional excitation of plasmonic guided modes. A complete study (numerical, experimental and analytical) of this new phenomenon, based on a coupling between the spin of the incident photon and the extrinsic orbital momentum of the plasmonic guided modes within the curvature of a waveguide, is presented. The second study propose a way to benefit from the transfer of the angular momentum of light to the free electrons gas in a metal to generate and control the direction and the geometry of nanoscale current loops in metallic structures. this control would at optical frequencies. This work was supported by the LABEX Action.