Investigating the behavior of an atom in response to the applied electric field when the latter frequency is in resonance with the natural frequency of the atom is an interesting subject. Near resonance, some of the most interesting optical phenomena such as dispersion, and absorption are more pronounced. Moreover, considering resonant and near resonant interaction of light with two-level atoms, uncovers fascinating physical phenomena such as area theorem and self-induced transparency describing stable pulse propagation regimes in which the pulses maintain their identity. Existence of these optical structures in on-resonance optical media has not been investigated in detail. In this thesis, the on-resonance interaction of optical field with atoms is considered and the formation of several novel self-similar and kink waves in linear and nonlinear resonant media is discovered and theoretically explored. First, self-similar pulse formation in homogeneous broadened linear amplifiers in a vicinity of an optical resonance is analyzed. It is demonstrated that the self-similar pulses serve as universal asymptotics of any near resonance short pulses propagating in coherent linear amplifiers. Second, ultrashort self-similar pulse propagation in coherent linear absorbers near optical resonance is investigated. Third, existence of self-similar optical waves with kink structure in resonant optical systems is discovered. Fourth, it is found that self-induced transparency quadratic solitons are realizable in the media with quadratic optical nonlinearities, doped with resonant impurities. Finally, stable spatial similaritons supported by homogeneous conservative optical media with quintic nonlinearities are explored. To experimentally realize the presented results, physical models are presented for all systems under consideration. The stability of the proposed near resonance optical systems is demonstrated through a series of numerical case studies.

<div>Aperiodic structures offer new functionalities for control, manipulation, and sensing that can benefit applications in all frequency ranges. We present a study of the influence of the degrees of freedom from a binary aperiodic nanostructure in free space, where each pixel is either the scatterer or the background, that uses a multivariate statistical analysis to examine the covariance matrix of the output field distributions. The total variance of the output fields and the rank can be evaluated to provide quantitative measurements of control. In addition, the field statistics provide an improved understanding of the scattering properties of aperiodic structures.</div><div><br></div><div><br></div><div><div>It has been proposed that structuring a metal surface can substantially increase the optical pressure over that possible with a planar interface. Based upon the forces on the mirrors of a one-dimensional asymmetric Fabry-Perot cavity, we show that the sum of the pressures on both mirrors increases through asymmetry and with quality factor. Using cavity quality factor as a measure, we present the physical basis of the enhanced pressure on a nanostructured metallic surface as being due to an array of asymmetric resonant cavities.</div></div><div><br></div><div><div>With use of optimized, aperiodic structures, more control and higher pressure should be possible. We present a design method by which the electromagnetic pressure on a nanostructured binary material can be controlled in terms of both the enhancement and the direction. This analysis offers new avenues for optomechanics.</div></div>

Made available in DSpace on 2015-05-14T12:14:17Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3305943 bytes, checksum: 4db7e993b605a6945a324ace5ef053e4 (MD5) Previous issue date: 2006-08-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis, the electromagnetism in material media is considered. It starts from the Macroscopic Maxwell Equations assuming that the fields have a temporal dependence that can be expressed by a Fourier transform. The conservation of the energy, linear momentum and angular momentum are studied from a general point of view. By taking the temporal average of the angular momentum, the orbital and spin contributions were derived without appealing to gauge fields. Following, the central issue is considered: the electromagnetic field propagation in bounded media. It is demonstrated the equivalence in the field propagation from both, ondulatory and energetic, points of view. A plane-parallel-faces medium geometry was considered and the field propagation from the energetic point of view is here established. The resulting set of equations allows to deal with the electromagnetic field propagation in general bounded media. Thus, this equation set, that we called S Formalism, is viewed as a method to solve this kind of problems. This approach emphasizes the possible nonequivalence between the squared field amplitude and the temporal-averaged Poynting vector modulus. This fact motivated the study of such nonequivalence and leaves open the possibility to introduce a new kind of medium, so-called Poynting medium. Since the S-Formalism allows to study media whose response is a function of the temporal-averaged Poynting vector, the light-induced charge carrier media and finally, saturable media are considered / Nesta tese é abordado o eletromagnetismo nos meios materiais. Parte-se das Equações de Maxwell Macroscópicas e supõe-se que os campos possuem uma dependência temporal que pode ser expressa em termos de uma transformada de Fourier. A conservação da energia, do momento linear e do momento angular são estudados nos meios materiais em geral. Calculando a média temporal do momento angular, as contribuições orbital e de spin são expressas sem a necessidade de apelar aos campos de gauge. Seguidamente é considerado o assunto central da pesquisa: a propagação de campos eletromagnéticos em meios materiais finitos. Demonstra-se a equivalência entre estudar a propagação dos campos desde o ponto de vista ondulatório ou desde o ponto de vista energético. A geometria considerada é a de meios com faces planas e paralelas e nela a propagação dos campos desde o ponto de vista energético é estabelecida. O conjunto de equações resultante serve para tratar a propagação de campos eletromagnéticos em meios finitos em geral. Portanto, este conjunto de equações, nomeado de Formalismo S, é visto como um método de resolução deste tipo de problemas. O Formalismo S deixa entrever uma possível não equivalência entre o módulo ao quadrado do campo e a média temporal do vetor de Poynting fato que motiva o estudo dessa não equivalência e a introdução de um novo tipo de meio chamado meio Poynting. Dado que o Formalismo S permite estudar meios cuja resposta é função da média temporal do vetor de Poynting, são considerados os meios com portadores de carga foto-induzidos. Finalmente, os meios não lineares saturáveis são analisados

In the Thesis, two important theoretical problems arising in the theory of one-dimensional defocusing nonlinear Schrödinger (NLS) flows are investigated analytically and numerically: (i) the resonant generation of dispersive shock waves (DSWs) in one-dimensional NLS flow past a broad repulsive penetrable barrier; and (ii) the interaction of counter-propagating DSW and a simple rarefaction wave (RW), which is referred to as the DSW refraction problem. The first problem is motivated by the recent experimental observations of dark soliton radiation in a cigar-shaped BEC by sweeping through it a localised repulsive potential; the second problem represents a dispersive-hydrodynamic counterpart of the classical gas-dynamics problem of the shock wave refraction on a RW, and, apart from its theoretical significance could also find applications in superfluid dynamics. Both problems also naturally arise in nonlinear optics, where the NLS equation is a standard mathematical model and the `superfluid dynamics of light' can be used for an all-optical modelling of BEC flows. The main results of the Thesis are as follows: (i) In the problem of the transcritical flow of a BEC through a wide repulsive penetrable barrier an asymptotic analytical description of the arising wave pattern is developed using the combination of the localised ``hydraulic'' solution of the 1D Gross-Pitaevskii (GP) equation with repulsion (the defocusing NLS equation with an added external potential) and the appropriate exact solutions of the Whitham-NLS modulation equations describing the resolution of the upstream and downstream discontinuities through DSWs. We show that the downstream DSW effectively represents the train of dark solitons, which can be associated with the excitations observed experimentally by Engels and Atherton (2008). (ii) The refraction of a DSW due to its head-on collision with the centred RW is considered in the frameworks of two one-dimensional defocusing NLS models: the standard cubic NLS equation and the NLS equation with saturable nonlinearity, the latter being a standard model for the light propagation through photorefractive optical crystals. For the cubic nonlinearity case we present a full asymptotic description of the DSW refraction by constructing appropriate exact solutions of the Whitham modulation equations in Riemann invariants. For the NLS equation with saturable nonlinearity, whose modulation system does not possess Riemann invariants, we take advantage of the recently developed method for the DSW description in non-integrable dispersive systems to obtain key parameters of the DSW refraction. In both problems, we undertake a detailed analysis of the flow structure for different parametric regimes and calculate physical quantities characterising the output flows in terms of relevant input parameters. Our modulation theory analytical results are supported by direct numerical simulations of the corresponding full dispersive initial value problems (IVP).

Cette thèse s’inscrit dans le mouvement des études interdisciplinaires portant sur la presse. Son objet est double : la presse de vulgarisation scientifique et les dispositifs optiques. Notre étude débute en 1851, moment de la fondation des premiers titres représentatifs, et s’achève en 1903, période de crise où ces périodiques entament une redéfinition de leurs lignes éditoriales. L’objectif de ce travail est d’étudier la façon dont la presse de vulgarisation scientifique s’empare des dispositifs optiques. Nous montrons que ces dispositifs, mieux que tout autre objet, permettent de comprendre efficacement l’évolution générale de la presse de vulgarisation scientifique dans ses pratiques d’écriture, dans le choix de ses rédacteurs et dans l’évolution des lignes éditoriales. L’étude conjointe de la presse photographique, laquelle se rattache explicitement au mouvement de vulgarisation scientifique, et des périodiques de vulgarisation scientifique généraliste, montre que, si ces deux types de presse cohabitent initialement en s’ignorant largement, ils finissent par se rencontrer et s’influencer mutuellement. Cette thèse visant à offrir une cartographie détaillée des périodiques et du personnel qui y officie, elle s’accompagne d’annexes incluant un répertoire des périodiques traités, ainsi qu’un premier répertoire des personnalités de la vulgarisation scientifique et une chronologie. / This dissertation is part of interdisciplinary studies dealing with the press. Its subject-matter is twofold: french popular science newspapers and optical devices. Our study begins in 1851 with the founding of the first popular science magazines, and ends in 1903, year of crisis during which this periodical press begins to redefine its editorial lines.The purpose of this work is to study how the popular science press got hold of optical devices. We show that these devices, better than any other object, allow effectively to understand the general development of the popular science press in its writing practices, in the choice of its writers, and in the evolution of its editorial lines. The joint study of photographic newspapers, which are explicitly linked to the popular science movement, and general popular scientific journals, shows that both types of press initially ignore each other, but eventually meet and influence each other.This dissertation aims at providing a detailed description of this periodical press and its staff: it is accompanied by appendices including a detailed index of those newspapers, and another detailed index of popular science writers. It also includes a chronology.