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Organic materials exhibiting second-order non-linear optical (NLO) properties are a key to the development of advanced electro-optic (EO) modulators used in fiber-optic communications system. This work addresses the fabrication and characterization of organic materials with NLO properties using a self-assembly approach by alternately dipping a charged substrate into positively and negatively charged polymers to build up layer-by-layer (LbL) films. The effect of solution pH on the formation of LbL films fabricated using the polycation poly(allylamine hydrochloride) (PAH) and the polyanion poly{1-[p-(3–-carboxy-4–-hydroxyphenylazo)benzenesulfonamido]-1,2-ethandiyl} (PCBS) was studied using a quartz crystal microbalance with dissipation (QCM-D) monitoring, ellipsometry, absorbance, and second harmonic generation (SHG) measurements. PCBS has an azo-benzene chromophore side group that, when sufficiently oriented, results in measurable SHG. Films of PAH/PCBS fabricated at neutral pH where both PAH and PCBS are highly charged led to thin bilayers, ~1 nm, with a 1:1 molar ratio of PCBS:PAH. This molar ratio was found to be important for long-range polar ordering of PCBS in these films. Increasing the rate of convection was found to reduce the time required for complete adsorption of the polyion. This can have a significant impact on fabrication of films with high bilayer numbers. A variation of the above technique, which involves adsorbing one of the constituents electrostatically and another covalently, was studied using PAH and a reactive dye, Procion Brown (PB), which has a significantly higher hyperpolarizability than PCBS. It was found that a high pH, ~10.5, was important for achieving covalent attachment of the PB to the underlying PAH films. This resulted in much higher SHG intensities compared to when PB was deposited pH at 8.5-9.5 where the attachment of PB was due to a combination of electrostatic and covalent interactions. QCM-D results for PAH/PB films revealed the presence of a high percentage of unreacted amine groups in the underlying PAH film. A rate constant value for PB attachment step to the underlying PAH was also calculated. To enhance the SHG intensity of these films, silver nanoprisms were synthesized and deposited onto films using physisorption. An enhancement in the SHG intensity was observed for both PAH/PCBS and PAH/PB films. / Ph. D.

This dissertation demonstrates the feasibility of using novel electrostatic self-assembly (ESA) methods to fabricate linear and nonlinear optical thin films and components. The ESA process involves the layer-by-layer alternate adsorption of anionic and cationic complexes from aqueous solutions. Selection of the molecules in each layer, their orientation at the molecular level, and the order in which the layers are assembled determine the film's bulk optical, electronic, magnetic, thermal, mechanical and other properties. In this work, the capability of nanoscale control over film optical properties allowed the fabrication of complicated refractive index profiles required for linear optical interference filters. The inherent ordered nature of ESA films yielded extremely stable noncentrosymmetric thin films for second-order nonlinear optical applications. The ESA technique offers numerous advantages over conventional thin film fabrication methods and offers great potential in commercial applications such as reflectance and AR filters, EO waveguides and modulators and other optoelectronic devices. The structure of each monolayer in ESA films is dependent on the processing parameters, producing subsequent variations in bulk film properties both intentionally and incidentally. As this method is still in its infancy, variations in ESA processing methods, including process automation, are considered first in this document. These results allowed carefully controlled refractive index experiments and the synthesis of both step and graded index structures, several microns thick. Dielectric stack, Rugate, and antireflection optical interference filters were designed, synthesized and demonstrated. c(2) films of both commercially available polymer dyes and novel polymers designed specifically for the ESA process were demonstrated using second harmonic generation. UV/vis spectroscopy, ellipsometry and atomic force microscopy analysis are presented. / Ph. D.

Les calculs de précision dans les théories de jauge jouent un rôle très important pour l'étude de la physique du Modèle Standard et au-delà dans les super-collisionneurs de particules comme le LHC, TeVatron et ILC. Par conséquent, il est extrêmement important de fournir des outils du calcul d'amplitudes à une boucle stables, rapides, efficaces et hautement automatisés. Cette thèse a pour but de développer la bibliothèque d'intégrales Golem95. Cette bibliothèque est un programme écrit en Fortran95, qui contient tous les ingrédients nécessaires pour calculer une intégrale scalaire ou tensorielle à une boucle avec jusqu'à six pattes externes. Golem95 utilise une méthode traditionnelle de réduction (réduction à la Golem) qui réduit les facteurs de forme en des intégrales de base redondantes qui peuvent être scalaires (sans paramètres de Feynman au numérateur) ou tensorielles (avec des paramètres de Feynman au numérateur); ce formalisme permet d'éviter les problèmes de l'instabilité numérique engendrés par des singularités factices dues à l'annulation des déterminants de Gram. En plus, cette bibliothèque peut être interfacée avec des programmes du calcul automatique basés sur les méthodes d'unitarité comme GoSam par exemple. Les versions antérieures de Golem95 ont été conçues pour le calcul des amplitudes sans masses internes. Le but de ce travail de thèse est de généraliser cette bibliothèque pour les configurations les plus générales (les masses complexes sont incluses), et de fournir un calcul numériquement stable dans les régions problématique en donnant une représentation intégrale unidimensionnelle stable pour chaque intégrale de base de Golem95.

Les interrupteurs moléculaires sont des composés capables de commuterréversiblement entre deux ou plusieurs états stables en réponse à un stimulusextérieur. Lʼobjectif de la thèse est la conception dʼinterrupteurs moléculairesprésentant des contrastes optiques non-linéaires (ONL) et la mise évidence desparamètres structuraux et électroniques menant à dʼimportants contrastes depremière hyperpolarisabilité (β) via une approche multidisciplinaire qui combine lasynthèse de nouveaux composés, la caractérisation de leurs réponses optiqueslinéaires et non-linéaires par spectroscopie dʼabsorption UV-visible et par diffusionhyper-Rayleigh et lʼutilisation des méthodes de la chimie théorique afin de prédire etdʼinterpréter les propriétés moléculaires. Ces phénomènes de commutationsréversibles et les changements de propriétés qui les accompagnent présentent denombreux intérêts, tant technologiques comme lʼélaboration dʼordinateursmoléculaires quʼau niveau des organismes vivants où de nombreuses fonctionsbiologiques sont basées sur un phénomène de commutation. Les principaux résultatsde nos travaux se situent au niveau de lʼinterprétation des réponses ONL et de leurscontrastes en fonction de la nature, de la position et du caractère donneur/accepteurdes substituants présents sur le squelette des interrupteurs moléculaires. / Molecular switches are compounds presenting the ability to commutereversibly between two or more states in response to external stimuli. The goal of thework is the design of molecular switches exhibiting contrasts of their second-ordernonlinear optical (NLO) properties and the highlight of the structural and electronicparameters leading to large contrasts of first hyperpolarizability (β) via amultidisciplinary approach combining the synthesis of new compounds, thecharacterization of their linear (by UV-Visible absorption spectroscopy) and nonlinearoptical properties (by hyper Rayleigh scattering), and the theoretical simulations inorder to predict and interpret molecular properties. These reversible switchingprocesses and the resulting variations of molecular properties have many interests intechnological area such as the development of molecular computers or in lifesciences since many biological functions are based on commutation mechanisms.The major results of our investigations are the interpretation of the NLO responsesand contrasts as a function of the nature, the positioning, and the donor/acceptorcharacter of the substituents.

Les composés organiques et organométalliques représentent des matériaux prometteurs pour leurs applications dans divers domaines tels que l'optique non linéaire, l'optoélectronique, la photonique et le stockage des données par voie optique. Dans ce travail,nous avons étudié les propriétés optiques non linéaires(ONL) de deux familles de composés à savoir des molécules organiques à base de BODIPY et des complexes organométalliques à base de ruthénium (II)et de fer (II). Pour cette étude nous avons utilisé un laser pulsé en régime picoseconde qui délivre deux longueurs d'ondes : 1064 nm et 532 nm. Nous avons utilisé 1064nm pour les techniques de la génération de la seconde harmonique (SHG) et la génération de la troisième harmonique (THG) et 532 nm pour celle de Zscan.Les résultats obtenus sont intéressants et originaux et montrent bien que la réponse non linéaire dépend du nombre de groupements donneurs d’électrons pour les molécules organiques à base de BODIPY. Le même comportement a été observé dans le cas des complexes organométalliques à base de ruthénium (II) et de fer (II) mettant en évidence la modulation de la réponse optique non linéaire en fonction de la nature du métal de transition utilisé(Ru(II)ou Fe(II)) et de la nature des ligands auxiliaires autour du fragment organométallique (Ru(II)). / Organic and organometallic compounds represent an important potential in many fields such as optics, optoelectronics, photonics and optical data storage. In this work, we have studied the nonlinear optical properties of two types of compounds; organic molecules based on BODIPY and organometallic complexes based on ruthenium (II) and iron (II). For this, the experimental techniques used were based on SHG, THG and onZ-scan techniques. For this study, we used a pulsed picosecond laser delivering two wavelengths: 1064 nm and 532 nm. 1064 nm for SHG and THG techniques and 532 nm for Z-scantechnique were used, respectively. The results obtained are interesting and original and show that the nonlinear optical response of organic molecules based on BODIPY depends in particular on the number of electron donor groups. The same behavior has been observed in the case of organometallic complexes based on ruthenium (II) and iron (II), highlighting the modulation of the nonlinear optical response as a function of the nature of the transition metal used (Ru ( II) or Fe (II)) and the nature of the ancillary ligands around the organometallic moiety (Ru (II)).

Le futur collisionneur du CERN (le LHC) possède un fantastique potentiel de découverte à condition d'avoir une prédiction quantitative de la QCD. Pour ce faire, il est nécessaire d'effectuer des calculs dans l'approximation NLO de manière à réduire la dépendance de la section efficace en fonction des échelles non physiques. Pour obtenir des résultats dans cette approximation, il faut calculer les sections efficaces des sous-processus partoniques contribuant à la réaction étudiée à l'ordre le plus bas ainsi que les corrections virtuelles (une boucle) et réelles. Le calcul des corrections virtuelles reste très compliqué si le nombre de particules externes est supérieur à quatre ou si les particules externes (internes) sont massives.<br />Dans cette thèse est proposée une méthode automatique pour effectuer les calculs à une boucle et à cinq pattes, et qui peut être généralisée aux cas de particules massives.<br />Dans une première partie, nous décrirons divers outils et méthodes nécessaires à de tels calculs. Nous les appliquerons ensuite au calcul de la réaction (gluon + gluon -> photon + photon + gluon), qui intéresse les expérimentateurs des expériences ATLAS et CMS comme bruit de fond à la recherche du Higgs, notamment pour décrire correctement la queue de la distribution transverse du boson de Higgs. Sera alors présenté le résultat explicite de cette amplitude pour chaque configuration d'hélicités sous une forme compacte et une représentation clairement invariante de jauge. Nous terminerons par une étude phénoménologique de cette réaction.

<P> Amphiphilic molecules contain a hydrophilic headgroup and a hydrophobic tail. The headgroup is polar or ionic and likes water, the tail is typically an aliphatic chain that cannot be accommodated in a polar environment. The prevailing molecular asymmetry leads to a spontaneous adsorption of amphiphiles at the air/water or oil/water interfaces. As a result, the surface tension and the surface rheology is changed. Amphiphiles are important tools to deliberately modify the interfacial properties of liquid interfaces and enable new phenomena such as foams which cannot be formed in a pure liquid.</P> <P> In this thesis we investigate the static and dynamic properties of adsorption layers of soluble amphiphiles at the air/water interface, the so called Gibbs monolayers. The classical way for an investigation of these systems is based on a thermodynamic analysis of the equilibrium surface tension as a function of the bulk composition in the framework of Gibbs theory. However, thermodynamics does not provide any structural information and several recent publications challenge even fundamental text book concepts.</P> <P>The experimental investigation faces difficulties imposed by the low surface coverage and the presence of dissolved amphiphiles in the adjacent bulk phase. In this thesis we used a suite of techniques with the sensitivity to detect less than a monolayer of molecules at the air-water interface. Some of these techniques are extremely complex such as infrared visible sum frequency generation (IR-VIS SFG) spectroscopy or second harmonic generation (SHG). Others are traditional techniques, such as ellipsometry employed in new ways and pushed to new limits. Each technique probes selectively different parts of the interface and the combination provides a profound picture of the interfacial architecture. </P> <P>The first part of the thesis is dedicated to the distribution of ions at interfaces. Adsorption layers of ionic amphiphiles serve as model systems allowing to produce a defined surface charge. The charge of the monolayer is compensated by the counterions. As a result of a complex zoo of interactions there will be a defined distribution of ions at the interface, however, its experimental determination is a big scientific challenge. We could demonstrate that a combination of linear and nonlinear techniques gives direct insights in the prevailing ion distribution. Our investigations reveal specific ion effects which cannot be described by classical Poisson-Boltzmann mean field type theories.</P> <P>Adsorption layer and bulk phase are in thermodynamic equilibrium, however, it is important to stress that there is a constant molecular exchange between adsorbed and dissolved species. This exchange process is a key element for the understanding of some of the thermodynamic properties. An excellent way to study Gibbs monolayers is to follow the relaxation from a non-equilibrium to an equilibrium state. Upon compression amphiphiles must leave the adsorption layer and dissolve in the adjacent bulk phase. Upon expansion amphiphiles must adsorb at the interface to restore the equilibrium coverage. Obviously the frequency of the expansion and compression cycles must match the molecular exchange processes. At too low frequencies the equilibrium is maintained at all times. If the frequency is too fast the system behaves as a monolayer of insoluble surfactants. In this thesis we describe an unique variant of an oscillating bubble technique that measures precisely the real and imaginary part of the complex dilational modulus E in a frequency range up to 500 Hz. The extension of about two decades in the time domain in comparison to the conventional method of an oscillating drop is a tremendous achievement. The imaginary part of the complex dilational modulus E is a consequence of a dissipative process which is interpreted as an intrinsic surface dilational viscosity. The IR-VIS SFG spectra of the interfacial water provide a molecular interpretation of the underlying dissipative process.</P> / <P>Amphiphile Moleküle vereinen zwei gegensätzliche Strukturelemente. Sie bestehen aus einer polaren oder ionischen Kopfgruppe und einem unpolaren Molekülteil, häufig einer Kohlenwasserstoffkette. Die vorliegende molekulare Asymmetrie bewirkt eine spontane Adsorption der Amphiphile an der Wasser/Luft Grenzschicht. Als Folge verändern sich Oberflächenspannung und Grenzflächenrheologie. Amphiphile Moleküle werden benutzt, um die Eigenschaften flüssiger Grenzflächen zu verändern und begegnen uns z.B. in Form von Seifen oder anderen waschaktiven Substanzen im täglichen Leben.</P> <P>Der erste Teil dieser Doktorarbeit widmet sich der Verteilung von Ionen an geladenen flüssigen Grenzflächen. Adsorbtionsschichten ionischer Amphiphile bieten Modellsysteme zur Untersuchung dieses klassischen Bereiches der Kolloid- und Grenzflächenforschung. Durch die Adsorption der Amphiphile in der Grenzschicht werden definierte Oberflächenladungen erzeugt, welche durch die angrenzenden Gegenionen in der Sublage kompensiert werden.</P> <P>In dieser Arbeit wird gezeigt, dass eine Kombination aus linearen und komplexen nichtlinearen optischen Methoden, die experimentelle Bestimmung der Verteilung der Gegenionen an geladenen Grenzflächen ermöglicht. Unsere Messungen zeigen ionenspezifische Effekte, die sich nicht in Reihenfolge des Periodensystems ordnen lassen. Insbesondere wurde ein Phasenübergang in der Verteilung der Gegenionen von einem Zustand, in dem sich die Ionen in der Sublage befinden, zu einem Zustand bestehend aus direkt kondensierten Ionen beobachtet. Dieser Phasenübergang geschieht innerhalb einer geringen Erhöhung der Oberflächenladung und lässt sich nicht mit klassischen Theorien beschreiben.</P> <P>Der zweite Teil dieser Arbeit widmet sich der Stabilität von Schaumlamellen. Eine Schaumlamelle ist ein dünner Wasserfilm, der durch die Adsorption von oberflächenaktiven Molekülen an beiden Seiten stabilisiert wird. In Zusammenhang von Schäumen muss zwischen zwei Prozessen unterschieden werden: Der Schaumbildung und der Schaumstabilität. Die zugrundeliegenden Mechanismen der Schaumbildung sind weitestgehend verstanden, die der Schaumstabilität jedoch noch nicht.</P> <P>Um die Stabilität von Schäumen zu untersuchen, müssen Nichtgleichgewichtszustände erzeugt und die anschließende Relaxation in das Gleichgewicht beobachtet werden. In dieser Arbeit wurde ein neues Verfahren entwickelt, welches es ermöglicht, das Elastizitätsmodul von Grenzflächen in einem Frequenzbereich von 1-500 Hz zu bestimmen. Dies bedeutet eine Erweiterung um zwei Dekaden gegenüber herkömmlichen Methoden. Die Idee ist denkbar einfach: In einer mit Flüssigkeit gefüllten Kammer wird über die Bewegung eines Piezos eine Luftblase in Schwingung versetzt und mit einem in der Kammer befindlichen Drucksensor die Schwingungsantwort der Blase aufgezeichnet. Unsere Untersuchungen zeigen, dass die Voraussetzung für die Ausbildung einer stabilen Schaumlamelle das Vorkommen einer intrinsischen Oberflächenviskosität ist. Eine anschauliche Erklärung verdeutlicht dies: Eine viskose Oberfläche ist in der Lage, eine eingehende Störung lokal zu dämpfen, im Gegensatz zu einer komplett elastischen Oberfläche, wo sich die Störung über die gesamte Schaumlamelle verbreiten kann.</P> <P> Untersuchungen mittels der IR-VIS SFG Spektroskopie ergaben, dass die Struktur des Wassers bei der Beschreibung der Schaumstabilität auf molekularer Ebene eine entscheidende Rolle spielt: Die Oberflächenviskosität ist mit einem dissipativen Vorgang innerhalb der Grenzschicht verbunden. Dieser dissipative Vorgang konnte auf molekularer Ebene durch das Aufbrechen von Wasserstoffbrückenbindungen identifiziert werden. Ausschlaggebend war dabei der Austausch der adsorbierten Amphiphile in der Grenzfläche und der angrenzenden Sublage.</P>

<p>Quantum chemical computations provide convenient and effective ways for molecular design using computers. In this dissertation, the molecular designs of optimal nonlinear optical (NLO) materials were investigated through three aspects. First, an inverse molecular design method was developed using a linear combination of atomic potential approach based on a Hückel-like tight-binding framework, and the optimizations of NLO properties were shown to be both efficient and effective. Second, for molecules with large first-hyperpolarizabilities, a new donor-carbon-nanotube paradigm was proposed and analyzed. Third, frequency-dependent first-hyperpolarizabilities were predicted and interpreted based on experimental linear absorption spectra and Thomas-Kuhn sum rules. Finally, molecular interferometers were designed to control charge-transfer using vibrational excitation. In particular, an ab initio vibronic pathway analysis was developed to describe inelastic electron tunneling, and the mechanism of vibronic pathway interferences was explored.</p> / Dissertation

This thesis deals with the investigation of the first hyperpolarizabilities (β) of a large number of molecules linked to other molecules either covalently or noncovalently. Chapter 1 gives a brief introduction to supramolecular chemistry and Nonlinear Optics (NLO). A survey of literature pertinent to noncovalently interacting supramolecular assembly and their NLO properties as well as NLO properties of oligomeric systems has been presented. The scope of the present investigation has been described at the end of the chapter. Chapter 2 discusses all the methods used in carrying out this thesis work. The first hyperpolarizabilities (β) of all the compounds have been measured by the hyper Rayleigh scattering (HRS) technique; the experimental details of which are written in this chapter. Various spectroscopic techniques such as NMR, IR, UV-Vis, etc. that were used in the investigation have been presented. The subsequent chapters 3-5 deal with the actual results obtained in this work. In chapter 3 first hyperpolarizabilities of o-, m-, and p-aminobenzoic acids and their oligomers viz., dimer, trimer and tetramer (covalently linked) have been studied. The compounds are synthesized and characterized by various spectroscopic methods and their β values have been measured by HRS. The hyperpolarizability increases in going from the monomer to the dimer but decreases subsequently from the dimer to the trimer to the tetramer. This unexpected trend in β has been attributed to the formation of molecular aggregates in the trimers and tetramers. Further evidences of aggregation come from the results of1H NMR spectroscopy and conductivity measurements. In chapter 4, synthesis, characterization and HRS investigation to probe the formation, dissociation and binding constants of hydrogen bonded supramolecular complexes (noncovalent interaction) formed in solution between 6-amino-2-(pivaloylamino)pyridine and ferrocene functionalized barbituric acid and 5-methoxy-N,N′-bis(6-amino-2-pyridinyl)-1,3-benzenedicarboxamide and ferrocenyl barbituric acid have been described. From the HRS data the stoichiometry of the supramolecular complexes has been determined and compared to that from the NMR data. Some of the complex stoichiometries that are measured by HRS have not been seen in the NMR data and vice versa. The results have been rationalized in terms of the strengths and weaknesses of various spectroscopic methods as applied to this problem. Many fold increase in the β value has been realized in the supramolecular complex formation process. Depolarized HRS experiments have been carried out to obtain structural information on the complexes. In the last chapter the synthesis, characterization and measurements on the first hyperpolarizabilities of unsubstituted tetraphenylporphyrin and its metallated complexes have been presented. Synthesis of supramolecular complexes of ferrocenyl barbituric acid with functionalized porphyrin compounds has been carried out although the amount of the final complex was insufficient for HRS measurements. This chapter ends with a perspective for the future work in the direction.