Cette thèse caractérise les propriétés optiques des matériaux plasmoniques microstructurés et procède à l’évaluation des paramètres analytiques afin de les employer comme plateforme de biodétection en spectroscopie de résonance des plasmons de surface (SPR). Aux dimensions micrométriques, les matériaux plasmoniques présentent des caractéristiques optiques propres aux nano- et macromatériaux. La cartographie physicooptiques en SPR de matériaux méso- et microscopiques s’est effectuée à l’aide de films structurés de motifs périodiques triangulaires et circulaires fabriqués par une technique modifiée de lithographie par nanosphères (nanosphere lithography, NSL). À partir de cette vue d’ensemble, quelques films structurés ont été sélectionné en fonction d’aspects analytiques tels que la sensibilité et la résolution face aux variations d’indice de réfraction (RI) pour déterminer le potentiel de ces matériaux comme plateforme de biodetection. Les propriétés optiques distinctes des films microstructurés proviennent d’interactions résonantes entre les modes de plasmons de surface (SP) localisé et délocalisé identifiés par la relation de dispersion en SPR ainsi que l’imagerie Raman. Les conditions de résonance des modes SP dépendant de paramètres expérimentaux (λ, θ, η) tel qu’observés numériquement par rigorous coupled wave analysis (RCWA) et empiriquement. Ces travaux démontrent la nature plasmonique distincte des micro-matériaux et leur potentiel d’intégration aux techniques analytiques SPR existantes. Les matériaux plasmoniques micrométriques furent également étudiés pour l’implémentation de la SPR à une pointe de microscopie à force atomique (atomic force microscopy, AFM) combinant ainsi la spectroscopie à l’imagerie topographique. Des travaux préliminaires se sont concentrés sur la signature spectroscopique de leviers en silicium (Si) et en nitrure de silicium (Si3N4), l’impact d’un revêtement d’or sur les pointes et l’influence de milieu environnant. Une image d’origine plasmonique a été obtenue avec des leviers en Si3N4 revêtus d’or en transmission dans un environnement aqueux, indiquant ainsi le potentiel de ces pointes comme micro-biocapteur SPR. Ces résultats préliminaires servent de fondement pour orienter les prochaines investigations dans ce projet. / This thesis characterizes the optical properties of microstructured plasmonic materials and evaluates analytical parameters to use them as biosensing platforms in surface plasmon resonance (SPR) spectroscopy. At microscopic dimensions, plasmonic materials present optical characteristics unique to nano- and macromaterials. A SPR physico-optic mapping of meso- and microscopic materials was performed using structured films with triangular and circular periodic patterns fabricate by modified nanosphere lithography (NSL) technique. From this overview, a few structured films were selected based on analytical aspects such as sensitivity and resolution with respect to the refractive index (RI) to determine the potential of these materials as biosensing platforms. The distinct plasmonic properties of microstructured films emerge from resonant interactions between localized and propagating surface plasmons (SP) modes identified by the SPR dispersion relation and by Raman imaging. The conditions of SP modes resonant interactions depend on experimental parameters (λ, θ, η) as observed numerically in rigorous coupled wave analysis (RCWA) and empirically. These works show the distinct plasmonic nature of micromaterials and their potential integration to existing SPR techniques. Plasmonic micromaterials were also studied for the implementation of SPR to an atomic force microscopy (AFM) cantilever, hence combining spectroscopy to topographic imaging. Preliminanry works were focused on the spectroscopic response of silicon (Si) and silicon nitride (Si3N4) cantilever, the impact of gold coating on the cantilever is tip, and the influence of the adjacent environment. An image of plasmonic nature was obtained in transmission spectroscopy with gold coated Si3N4 cantilever in water environment, thus indicating the potential of these cantilevers as micro-SPR sensing probes. These preliminary results provide a basis to guide future investigations in this project.

In this thesis devices for controlling the flow of surface plasmon polaritons are described. Dielectric and metallic nanostructures were designed for this purpose, and characterized by leakage radiation microscopy in real and in reciprocal spaces. Manipulation of surface plasmons by dielectric lenses and gradient index elements is presented, and negative refraction, steering and self-collimation of surface plasmons in one- and two-dimensional plasmonic crystals is demonstrated. The achieved degree of control was applied for routing of nanoparticles by optical forces, as well as for two methods of enhancing the figures of merit of plasmonic refractive index sensors, based on the one hand on Fano resonances natural to leakage radiation microscopy, and on the other hand on anisotropie plasmonic bandstructures.

Le but de cette thèse est de développer les outils numériques et semi-analytiques qui nous permettent d’étudier des guides non-linéaires complexes et réalistes qui pourraient être fabriqués et caractérisés expérimentalement.Nous présentons une étude complète d’une version améliorée du guide d’onde plasmonique non-linéaire à une dimension, en ajoutant deux couches tampons de diélectrique linéaire entre le cœur non-linéaire isotrope et les deux gaines métalliques. Ses couches réduisent les pertes et permettent leur diminution avec la puissance contrairement aux guides simples. De plus, les principaux modes plasmoniques non-linéaires peuvent présenter une transition spatiale vers des modes de types différents, qui peut être contrôlée par la puissance.Par la suite, nous étudions un nouveau guide plasmonique non-linéaire à fente utilisant un métamatériau, soit dans le cœur non-linéaire soit dans les gaines linéaires. Nous avons mis au point une méthode semi-analytique et une méthode numérique afin d’étudier les solutions stationnaires non-linéaires dans ce nouveau guide non-linéaire anisotrope. Nous avons montré analytiquement et numériquement que le cœur non-linéaire anisotrope peut être conçu afin d’atteindre de forts effets non-linéaires à faible puissance. Pour certains métamatériaux dans les gaines linéaires, la figure de mérite de ce guide d’onde augmente de plus de 50 fois par rapport aux guides isotropes.Pour conclure, nous présentons une nouvelle méthode basée sur la méthode des éléments finis de type vectoriel couplée à l’algorithme à puissance fixée pouvant calculer rigoureusement les effets non-linéaires dans des guides d’onde plasmoniques 2D. / The main goal of this PhD is to develop the semi-analytical and the numerical tools that allow us to study complicated and realistic nonlinear plasmonic waveguides which can be fabricated and characterized experimentally.First, we present a full study of an improved version of the one-dimensional nonlinear plasmonic slot waveguide, by adding two linear dielectric buffer layers between the isotropic nonlinear core and the two metal claddings. These additional layers reduce the overall losses and allow the losses to decrease with the power for some configurations unlike the usual slot. Furthermore, the main plasmonic modes can exhibit nonlinear spatial modal transitions towards new families of modes that can be controlled with the power.Second, we propose and study new one-dimensional nonlinear plasmonic slot waveguides with metamaterial regions either in the nonlinear core or in the linear claddings. For the metamaterial nonlinear core, we developed semi-analytical and fully numerical methods in order to study the nonlinear stationary solutions propagating in this anisotropic nonlinear waveguide. We have demonstrated both analytically and numerically that the anisotropic nonlinear core can be designed in order to achieve strong nonlinear effects at low power.For the structures with metamaterial linear claddings, the figure of merit can be extremely enhanced by more than 50 times compared with the simple one. Finally, we present the full derivation of a new nonlinear full vectorial finite element method based on the fixed power algorithm in order to quantify rigorously the nonlinear characteristics of realistic two-dimensional nonlinear plasmonic structures.

Dans ce travail de thèse, le microscope à force atomique (AFM) a été utilisé comme outil de manipulation de haute précision pour construire des nanostructures plasmoniques avec des géométries définies et un réglage précis de la distance interparticulaire et également comme technique de spectroscopie d'absorption. Différentes études concernant les phénomènes pertinents pour la manipulation des nanoparticules et émergeant à l'interface substrat-nanoparticules, ont été réalisées. Des expériences de frottement menées sur diverses surfaces d'oxydes ont révélé un nouveau mécanisme de frottement à l’échelle nanométrique, expliqué par un modèle de potentiel d'interaction de type Lennard-Jones modifié. Les propriétés de frottement et d'adhésion de CTAB adsorbé sur silice sont également présentées. Des nano-bâtonnets d'or fonctionnalisés par du CTAB ont été manipulés par AFM afin de construire des nanostructures plasmoniques. La dernière partie de la thèse présente les efforts expérimentaux et théoriques pour démontrer la faisabilité de l'utilisation d'un AFM comme une technique de spectroscopie optoélectronique à base de force. / In this thesis work the atomic force microscope (AFM) was employed first as a high precision manipulation tool for building plasmonic nanostructures with defined geometries and precise tuning of interparticle distance and second as an absorption spectroscopy technique. Different studies regarding phenomena emerging at sample nanoparticle interface relevant for nanoparticle manipulation were performed. Friction experiments conducted on various oxide surfaces revealed a novel nanoscale stick slip friction mechanism, explained by a modified Lennard-Jones-like interaction potential model. Frictional and adhesion properties of CTAB adsorbed on silica are also reported. CTAB functionalized gold nanorods were used for building specific plasmonic particulate nanostructures. The final part of the thesis presents experimental and theoretical efforts to demonstrate the feasibility of using an AFM as a force-based optoelectronic spectroscopy technique.

Les nanoparticules (NPs) d'Ag sont très utilisées dans le secteur de la santé, dans l'industrie alimentaire et dans les produits de consommation pour leurs propriétés antimicrobiennes. Le grand rapport surface sur volume des NPs d'Ag permet une augmentation importante du relargage d'Ag comparé au matériau massif et donc une toxicité accrue vis à vis des micro-organismes sensibles à cet élément. Ce travail de thèse présente une évaluation des propriétés antimicrobiennes de petites NPs d'Ag (<20 nm) enrobées dans des matrices de silice sur la photosynthèse d'algues vertes. Deux techniques d'élaboration par voie physique ont été utilisées pour fabriquer ces nanocomposites: (i) l'implantation ionique à basse énergie et (ii) la pulvérisation d'Ag couplée avec la polymérisation plasma. Les propriétés structurales et optiques de ces nanostructures ont été étudiées par microscopie électronique à transmission, réflectivité et ellipsométrie. Cette dernière technique, couplée à un modèle basé sur l'approximation quasi-statique de type Maxwell-Garnett, a permis la détection de petites variations dans la taille et la densité des NPs d'Ag. Le relargage d'argent de ces NPs d'Ag enrobées dans des diélectriques a été mesuré par spectrométrie de masse après immersion dans de l'eau tamponnée. La toxicité à court terme de l'Ag sur la photosynthèse d'algues vertes, Chlamydomonas reinhardtii, a été évaluée par fluorométrie. L'enrobage des nanoparticules dans un diélectrique réduit leur interaction avec l'environnement, et les protège d'une oxydation rapide. La libération d'Ag bio-disponible (impactant sur la photosynthèse des algues) est contrôlée par la profondeur à laquelle se trouvent les NPs d'Ag dans la matrice hôte de silice. Cette étude permet d'envisager le design de revêtements à effet biocide contrôlé. En couplant les propriétés antimicrobiennes de ces NPs d'Ag enrobées à leur qualité d'antenne plasmonique, ces nanocomposites peuvent être utilisés pour détecter et prévenir les premières étapes de la formation de biofilms sur des surfaces. Ainsi, une dernière partie de ce travail est dédiée à l'étude de la stabilité et de l'adsorption de protéines fluorescentes Discosoma rouges recombinantes (DsRed) sur ces surfaces diélectriques avec la perspective du développement de dispositifs SERS. / Silver nanoparticles (AgNPs) because of their strong biocide activity are widely used in health-care sector, food industry and various consumer products. Their huge surface-volume ratio enhances the silver release compared to the bulk material, leading to an increased toxicity for microorganisms sensitive to this element. This work presents an assessment of the biocide properties on algal photosynthesis of small (<20 nm) AgNPs embedded in silica layers. Two physical approaches were used to elaborate these nanocomposites: (i) low energy ion beam synthesis and (ii) combined silver sputtering and plasma polymerization. These techniques allow elaboration of a single layer of AgNPs embedded in silica films at defined nanometer distances (from 0 to 7 nm) beneath the free surface. The structural and optical properties of the nanocomposites were studied by transmission electron microscopy, reflectance spectroscopy and ellipsometry. This last technique, coupled to modelling based on the quasi-static approximation of the classical Maxwell-Garnett formalism, allowed detection of small variations over the size and density of the embedded AgNPs. The silver release from the nanostructures after immersion in buffered water was measured by inductively coupled plasma mass spectrometry. The short-term toxicity of Ag to the photosynthesis of green algae, Chlamydomonas reinhardtii, was assessed by fluorometry. Embedding AgNPs reduces their interactions with the buffered water, protecting the AgNPs from fast oxidation. The release of bio-available silver (impacting on the algal photosynthesis) is controlled by the depth at which AgNPs are located for the given host silica matrix. This provides a procedure to tailor the biocide effect of nanocomposites containing AgNPs. By coupling the controlled antimicrobial properties of the embedded AgNPs and their quality as plasmonic antenna, these coatings can be used to detect and prevent the first stages of biofilm formation. Hence, the last part of this work is dedicated to a study of the structural stability and adsorption properties of Discosoma recombinant red (DsRed) fluorescent proteins deposited on these dielectric surfaces with perspectives of development of SERS devices.

Photosynthesis involves the absorption of photons by light-harvesting pigments and the subsequent transfer of excitation from the absorption centre to the reaction centre. This highly efficient phenomenon of excitation transfer has traditionally been explained by the Forster mechanism of incoherent hopping of excitation from one chromophore to another. Recently 2D electronic spectroscopic evidences were gathered by Fleming and coworkers on the photosynthetic Fenna-Matthews-Olson (FMO) complex in green sulfur bacteria [1]. Subsequent simulation studies by the same group [2] led to the proposition of a quantum-mechanical, coherent, wave-like transfer of excitation among the chromophores. However, Fleming's conclusions regarding retention of coherence appeared surprising because, the complex would interact with the numerous degrees of freedom of the protein scaffold surrounding it, leading to decoherence, which is expected to be rapid. Thus, we were interested in proposing an analytical treatment to rationalize the excitation transfer. Traditional approaches employed for studying excitation energy transfer involve the master equation techniques where the system-bath coupling is perturbative and is truncated after a few orders. It is important to note that the system-bath coupling causes both decoherence and population relaxation. Such a perturbative approximation is difficult to justify for the photosystem, as the system-bath coupling and the interchromophoric electronic coupling have comparable values. Also, these treatments are largely numerical studies and demand involved calculations. Thus, exact calculations for such a system (7-level) are very difficult. Consequently, we were interested in developing an analytical approach where the coupling is treated as non-perturbative. We devised a novel analytical treatment which employs a unitary transformation analogous to the one used for the theory of nonadiabatic effects in chemical reactions [3]. Our treatment rests on an adiabatic basis which are eigenstates calculated at each nuclear position (i.e. at each configuration of the bath) bearing a parametric dependence in Qi, where Qi denotes the shift of the exciton at site `i' due to the environment. The treatment is justified because in the case of coherent transfer, the excitation would travel mostly amongst the adiabatic states and the effects of non-adiabaticity are small. We observed that the system-bath coupling, after the unitary transformation, could be decoupled at the lowest order into two parts: a) an adiabatic contribution, which accounts solely for decoherence (this is evaluated almost exactly in our approach) and b) a non-adiabatic contribution which accounts for population relaxation from one adiabatic state to another (treated by a Markovian master equation). When we applied our technique to the FMO complex, our prediction for population evolution at the chromophores showed excellent correspondence with those obtained by Nalbach and coworkers using path-integral calculations [4], which are exact. These were calculations where the environment was modelled using a Drude spectral density. Our method allowed the calculations to be readily performed for different temperatures as well. It should be specifically emphasized that, unlike the involved and cumbersome path-integral calculations by Nalbach and coworkers [4] or the hierarchical equation calculations by Ishizaki et al. [2], our method is simple, easy to apply and computationally expedient. Further it became evident that the ultra-efficiency of energy transfer in photosynthetic complexes is not completely captured by coherence alone but is the result of an interplay of coherence and the dissipative influence of the environment (also known as ENAQT or Environment Assisted Quantum Transport [5]). An added advantage of our analytical treatment was the flexibility it offered. Thus, we could use our formalism to perform expedient analyses on the behavior of the system under various conditions. For example, we may wish to evaluate the consequences of introducing correlations among the bath degrees of freedom on the efficiency of transfer to the reaction centre. To this end, we applied our formalism by introducing correlations among the bath degrees of freedom and then by introducing anticorrelations among the bath degrees of freedom. The conclusions were interesting, for they suggested that the efficiency of transfer to the reaction centre was enhanced by the presence of anti-correlations, when compared with an uncorrelated bath. Uncorrelated baths, in turn, had a higher efficiency of energy transfer than correlated baths [6]. Thus, the population evolution is fastest for the anti-correlated bath, followed by the uncorrelated bath and is slowest for the correlated bath. Similar conclusions have been reached at by Tiwari et al. [7]. We could also extend the formalism for studying the system under different spectral densities for the environment, apart from just the Drude spectral density which is popularly used in literature associated with FMO calculations. For instance, the FMO system could be analyzed for the Adolphs-Renger spectral density [3, 8]. Once again our results showed excellent agreement with those reported by Nalbach. We also analyzed the FMO system under the spectral density proposed by Kleinekathofer and coworkers [9]. It was found that these latter spectral densities had more profound participation from the environment, therefore coherences were destroyed more effectively and population relaxation was faster. The excitation transfer to the final site (site closest to the reaction centre in the FMO complex) was found to be faster for the Adolphs and Renger spectral density and the spectral density proposed by Kleinekathofer and coworkers, when compared to the Drude spectral density. Also, the excitation transfer was fastest when we modelled the environment using the Kleinekathofer spectral density. This reinforced the previous conclusions that the dissipative effects of the environment promote a faster energy transport. Being an almost analytical approach, our technique could be applied to systems with larger number of levels as well. A good example of such a case is the MEH-PPV polymer. 2D electronic-spectroscopic experiments performed on this polymer in solution speculate that the excitation energy transfer might be coherent even at physiological temperatures [10]. A prototype for studying this system might be a conjugated polymer with around 80-100 chromophores. Linewidths and Lineshapes in the vicinity of Graphene It has been reported that a vibrating dipole may de-excite by transferring energy non-radiatively to a neighboring metal surface [11]. It is also understood that due to its delocalized pi-cloud, graphene has a continuum of energy states and can behave like a metal sheet and accept energies. Thus, we proposed that if a vibrationally excited dipole de-excites in the vicinity of a graphene sheet, graphene may get electronically excited and thus serve as an effective quencher for such vibrational excitations. Depending on the distance of the dipole from the graphene sheet, the transfer might be intense enough to be spectroscopically probed. We have investigated the rate of such an energy transfer. We use the Dirac cone approximation for graphene, as this enables us to obtain analyt-ical results. The Fermi Golden rule was used to evaluate the rate of energy transfer from the excited dipole to the graphene sheet [12]. The calculations were performed for both the instances: a) energy transfer from a dipole to undoped graphene and, b) energy trans-fer from a dipole to doped graphene. For undoped graphene, the carrier (electron) charge density in the conduction band is zero and we would only have transitions from the valence band to the conduction band. As a consequence of absence of carrier charge density in CB (conduction band), the screening of Coulombic interactions in the graphene plane is ineffective. Thus, one could use the non-interacting polarizability for undoped graphene in the rate expression [13]. However, when we consider the case of doped graphene where EF is shifted upwards into CB, the conduction band electrons will contribute to screening. In this case, we have two sets of transitions: a) from ki in VB (valence band) to kf in CB and b) ki in CB to kf in CB, where ki and kf are the wavevectors which correspond to the initial and final electronic states in graphene. So we have used the polarizability propagator in the random phase approximation [14] to calculate the rate following the approach of [13]. It is also known that the imaginary part of the frequency domain dipole-dipole corre-lation function is a measure of the lineshape [15]. We were, thus, interested in evaluating the lineshape for these transitions. For evaluating the correlation function, we used the partitioning technique developed by L•owdin [16] and subsequently extracted the lineshape from its imaginary part. Using this method, we calculated lineshape for the vibrational excitation of CO molecule in the vicinity of an undoped graphene lattice. The linewidth for this system also was obtained. It could be seen that the vibrational linewidth for 1 CO in the vicinity (5 A) of undoped graphene (EF = 0:00eV ) is small (0:012 cm ) but could be observed experimentally. The lineshape calculations were also extended to cases where it is possible to have atomic transitions by placing an electronically excited atom in the vicinity of the graphene sheet. We considered the following two cases: a) 3p ! 2s transition in hydrogen atom, at a distance of 12 A from the graphene sheet and, b) 4p ! 3s transition in hydrogen atom, at a distance of 20 A from the graphene sheet. The linewidths for atomic transitions could be easily probed in these cases ( 55 cm 1 for 3p ! 2s and 56 cm 1 for 4p ! 3s). In the preceding calculations, the transi-tion dipoles were considered perpendicular to the graphene surface. It is worthwhile to note that if the transition dipoles are considered parallel to the graphene surface, the respective linewidths would be half of those obtained for the case where the transition dipoles are perpendicular. Another interesting possibility would be to consider a lanthanide metal complex placed within a few nanometers from graphene. Lanthanides are known to have sharp f-f transitions [17] and consequently, one could easily observe the effects of broadening due to energy transfer to the electronic system of graphene. Energy Eigenmodes for arrays of Metal Nanoparticles In the final part of the thesis we consider organized assemblies of metal nanoparti-cles, specifically helical and cylindrical assemblies and investigate the plasmonic excitation transfer across these assemblies. These were motivated by recent studies which reported growth of chiral asymmetric assemblies of nanoparticles on D and L- isomers of dipheny-lalanine peptide nanotubes [18]. The plasmons in the helical/cylindrical assemblies are expected to couple with each other via electromagnetic interactions. We construct the Hamiltonian for such systems and evaluate the eigenmodes and energies pertaining to these modes in the wave vector space. We also perform calculations for the group velocity for each eigenmode as this gives us an idea of which eigenmode transports excitation the fastest.

Pas de résumé en français / Plasmonic circuitry is considered as a promising solution-effectivetechnology for miniaturizing and integrating the next generation ofoptical nano-devices. The realization of a practical plasmonic circuitry strongly depends on the complete understanding of the propagation properties of two key elements: surface plasmons and electrons. The critical part constituting the plasmonic circuitry is a waveguide which can sustain the two information-carriers simultaneously. Therefore, we present in this thesis the investigations on the propagation of surface plasmons and the co-propagation of surface plasmons and electrons in single crystalline metal nanowires. This thesis is therefore divided into two parts. In the first part, we investigate surface plasmons propagating in individual thick penta-twinned crystalline silver nanowires using dual-plane leakage radiation microscopy. The effective index and the losses of the mode are determined by measuring the wave vector content of the light emitted in the substrate. Surface plasmon mode is determined by numerical simulations and an analogy is drawn with molecular orbitals compound with similar symmetry. Leaky and bound modes selected by polarization inhomogeneity are demonstrated. We further investigate the effect of wire geometry (length, diameter) on the effective index and propagation losses. On the basis of the results obtained during the first part, we further investigate the effect of an electron flow on surface plasmon properties. We investigate to what extend surface plasmons and current-carrying electrons interfere in such a shared circuitry. By synchronously recording surface plasmons and electrical output characteristics of single crystalline silver and gold nanowires, we determine the limiting factors hindering the co-propagation of electrical current and surface plasmons in these nanoscale circuits. Analysis of wave vector distributions in Fourier images indicates that the effect of current flow on surface plasmons propagation is reflected by the morphological change during the electromigration process. We further investigate the possible crosstalk between co-propagating electrons and surface plasmons by applying alternating current bias

Les guides d’ondes plasmoniques à rubans dielectriques (DLSPPW) sont récemment apparus comme une des solutions possible pour le transport de signaux optiques et électriques sur puce. Néanmoins, dans le contexte particulier des interconnections optiques, des fonctionalitées avancées telles que filtrage, commutation, et routage sont nécessaires afin de remplacer dans le futur les composants electroniques équivalents trop gourmands en énergie et aussi réduire leur empreinte. Après une présentation des intérêts et limitations de la technique de micro- scopie à fuite radiative, nous montrons plusieurs composants actifs utilisant pour diélectrique des polymères thermo-sensibles controlés électriquement par eet Joule. Par la suite nous démontrons la faisabilité de systèmes tout optique que ce soit par dopage du polymère par des nanoparticules metalliques ou par eet thermo-plasmonique d’un second mode plasmon permettant un échauement localisé de forme choisie. L’activation dynamique de nos composants thermo-optiques est réalisée grâce à un montage fibre-à-fibre créé spécialement nous permettant d’investiguer le temps de réponse d’un chauage plasmonique ainsi que la transmission de signal télécom. Des améliorations de performances du concept DLSPPW original sont proposées par l’ajout d’un mur métallique sur le côté du ruban de polymère. Ce système peut alors fonctionner comme un convertisseur de polarisation compacte et athermique / The Dielectric Loaded Surface Plasmon Polariton Waveguides (DLSPPWs) have recently emerged as a possible solution to carry both optical and electrical signals on- chip. However, in the particular context of optical interconnects, advanced functionalities such as filtering, switching, and routing are required in order to replace in the future the equivalent electronic components which are too much power consumer and also to reduce their footprints. After presenting the interest and limitation of the leakage radiation microscopy method used all along this work, we show several active devices using thermo-sensitive polymers as the dielectric load driven electrically by Joule heating. Then we demonstrate the feasibility of all-optical systems by either doping the dielectric with metallic nanoparticles or by plasmo-thermal eect of a second plasmonic mode providing a localized heating of controlled shape. The dynamic activation of our thermo- optical devices is performed using a homemade fiber-to-fiber setup which allows us to investigate the response time of a plasmo-thermal heating as well as true datacom transmission. Some improvements of the original DLSPPWs performances are proposed by adding a metallic wall on one side of the polymer ridge. This system can act as a compact and athermal polarization converter

Raman optical activity (ROA) is a powerful probe of the structure and behaviour of biomolecules in aqueous solution for a number of important problems in molecular biology. Although ROA is a very sensitive technique for studying biological samples, it is a very weak effect and the conditions of high concentration and long data collection time required limit its application for a wide range of biological samples. These limitations could possibly be overcome using the principle of surface enhanced Raman scattering (SERS). The combination of ROA with SERS in the form of surface enhanced ROA (SEROA) could be a solution for widening the application of ROA. In the last few years, the generation of reliable SEROA spectra of biomolecules has been problematic due to non-homogenous colloidal systems forming and low signal-to-noise ratios which complicated detection of the true SEROA signal from the analyte. L- and D-enantiomers give full or partially mirror image chiroptical spectra, this property of enantiomers can be employed to prove the chiroptical activity of the SEROA technique. In this thesis we employed a hydrophilic polycarbopol polymer as stabilising media which has led to the first report of mirror image SEROA bands for enantiomeric structures. This new technique of incorporating the hydrogel polymer as a means to stabilise the colloidal system has proven to be reliable in obtaining high quality SEROA spectra of D- and L-enantiomers of ribose and tryptophan. In an extension of the hydrogel-stabilised SEROA work, we also demonstrate that single nanoparticle plasmonic substrate such as silver silica nanotags can enhance the weak ROA effect. These dye tagged silica coated silver nanoparticles have enabled a chiral response to be transmitted from a chiral analyte to the plasmon resonance of an achiral metallic nanostructure. The measurement of mirror image SERROA bands for the two enantiomers of each of ribose and tryptophan was confirmed for this system. The generation of SEROA for both systems was achieved and confirmed SEROA as a new sensitive tool for analysis of biomolecular structure. In a related project, Raman and ROA spectra were measured for adenosine and seven of its derivative ribonucleotides. Both of these spectroscopic techniques are shown to be sensitive to the site and degree of phosphorylation, with a considerable number of marker bands being identified for these ribonucleotides. Moreover, the SERS studies of these ribonucleotides were also performed. The obtained SERS spectra were shown similar features that confirm these analytes interact with the surface in a similar manner, hence limiting the structural sensitivity of this method towards phosphate position. Short dipeptides such as diketopiperazine (DKP) have been investigated during the last decades as both natural and synthetic DKPs have a wide variety of biological activities. Raman and ROA spectra of linear and cyclic dialanine and diserine were measured to charecterize their solution structures. Density functional theory (DFT) calculations were carried out by a collaborator to assist in making vibrational band assignments. Considerable differences were observed between the ROA bands for the cyclic and linear forms of both dialanine and diserine that reflect large differences in the vibrational modes of the polypeptide backbone upon cyclicization. In this study, the ROA spectra of cyclic dialanine and diserine have been reported for the first time which demonstrated that ROA spectroscopy when utilised in combination with computational modelling clearly provides a potential tool for characterization of cyclic peptides.

Organic solar cells have great potential for cost-effective and large area electricity production, but their applicability is limited by the relatively low efficiency. In this dissertation I report investigations of novel materials and the underlying principles of organic solar cells, carried out at the University of St Andrews between 2011 and 2015. Key results of this investigation: • The charge carrier mobility of organic semiconductors in the active layer of polymer solar cells has a rather small influence on the power conversion efficiency. Cooling solar cells of the polymer:fullerene blend PTB7:PC₇₁BM from room temperature to 77 K decreased the hole mobility by a factor of thousand but the device efficiency only halved. • Subphthalocyanine molecules, which are commonly used as electron donor materials in vacuum-deposited active layers of organic solar cells, can, by a slight structural modification, also be used as efficient electron acceptor materials in solution-deposited active layers. Additionally these acceptors offer, compared to standard fullerene acceptors,advantages of a stronger light absorption at the peak of the solar spectrum. • A low band-gap polymer donor material requires a careful selection of the acceptor material in order to achieve efficient charge separation and a maximum open circuit voltage. • Metal structures in nanometer-size can efficiently enhance the electric field and light absorption in organic semiconductors by plasmonic resonance. The fluorescence of a P3HT polymer film above silver nanowires, separated by PEDOT:PSS, increased by factor of two. This could be clearly assigned to an enhanced absorption as the radiative transition of P3HT was identical beside the nanowires. • The use of a processing additive in the casting solution for the active layer of organic solar cells of PTB7:PC₇₁BM strongly influences the morphology, which leads not only to an optimum of charge separation but also to optimal charge collection.