Tesi sul tema "Optical nanofibers"

Cette thèse a consisté à mettre en place une nouvelle expérience utilisant des atomes froids en interaction avec la lumière guidée par une nanofibre optique. Nous avons tout d'abord développé un banc de fabrication de nanofibres. En chauffant et étirant une fibre optique commerciale, on obtient un cylindre de silice de 400 nm de diamètre. La lumière guidée dans ces nanofibres est fortement focalisée sur toute la longueur de la fibre et exhibe de forts champs évanescents, ce qui permet d'obtenir une grande profondeur optique avec un faible nombre d'atomes. Après avoir inséré une nanofibre au milieu d'un nuage d'atomes, nous avons observé le phénomène de lumière lente dans les conditions de transparence électromagnétiquement induite. Nous avons aussi stoppé la lumière guidée et mémorisé l'information qu'elle contenait. Nous avons montré que ce protocole de mémoire optique fonctionne pour des impulsions lumineuses contenant moins d'un photon en moyenne. Ce système pourra donc être utilisé comme une mémoire quantique, un outil essentiel pour les futurs réseaux de communication quantique. Enfin, nous avons piégé les atomes dans un réseau optique au voisinage de la nanofibre grâce à de la lumière guidée par celle-ci. Par rapport à notre première série d'expériences, le nuage ainsi obtenu a un temps de vie plus long (25 ms) et interagit plus fortement avec la lumière guidée (OD ~ 100). Ce nouveau système devrait permettre d'implémenter efficacement d'autres protocoles d'optique quantique, comme la génération de photons uniques et l'intrication de deux ensembles atomiques distants
We built a new experiment using cold atoms interacting with the light guided by an optical nanofiber. We first developed a nanofiber manufacturing bench. By heating and stretching a commercial optical fiber, a silica cylinder of 400 nm diameter is obtained. The light guided in these nanofibers is strongly focused over the whole length and exhibits strong evanescent fields. We then prepared a vacuum chamber and the laser system necessary for the manipulation of cold atoms. After inserting a nanofiber amid a cloud of cold atoms, we observed the phenomenon of slow light under the conditions of electromagnetically induced transparency: the light guided by the fiber is slowed down to a speed 3000 times smaller than its usual speed. We also stored the light guided by an optical fiber. After several microseconds, the information stored as a collective atomic excitation could be retrieved in the fiber. We have shown that this optical memory works for light pulses containing less than one photon on average. This system may therefore be used as a quantum memory, an essential tool for future quantum communication networks. Finally, we trapped atoms in an array in the vicinity of the nanofiber thanks to the light guided by the latter. Compared to our first set of experiments, the resulting cloud has a longer lifetime (25 ms) and interacts more strongly with the guided light (OD ~ 100). This new system should allow to efficiently implement other quantum optics protocols, such as the generation of single photons, or the entanglement of two remote atomic ensembles

Electrospinning has been recognized as an efficient technique for the fabrication of polymer fibers. These electrospun fibers have many applications across a broad range of industries. In this research, optical transparent composites were successfully fabricated by embedding polyacrylonitrile (PAN) hollow nanofibers into poly (methyl methacrylate) (PMMA) matrix. The hollow PAN nanofibers were prepared by coaxial electrospinning. The PAN was used as the shell solution, and the mineral oil was used as the core solution. The resulting fibers were then etched with octane to remove the mineral oil from the core. The hollow PAN fibers were then homogeneously distributed in PMMA resins to fabricate the composite. The morphology, transmittance and mechanical properties of the PAN/PMMA composite were then characterized with an ESEM, TEM, tensile testing machine, UV-vis spectrometer and KD2 Pro Decagon device. The results indicated that the hollow nanofibers have relatively uniform size with one-dimensional texture at the walls. The embedded PAN hollow nanofibers significantly enhanced the tensile stress and the Young's modulus of the composite (increased by 58.3% and 50.4%, respectively), while having little influence on the light transmittance of the composite. The KD2 Pro device indicated that the thermal conductivity of the PMMA was marginally greater than the PAN/PMMA composite by 2%. This novel transparent composite could be used for transparent armor protection, window panes in vehicles and buildings, and airplane windshield etc.

La plupart des objets quantiques individuels développés jusqu’à aujourd’hui ne permettent pas de satisfaire toutes les conditions nécessaires pour la construction d’un simulateur quantique. Une possibilité pour obtenir un système quantique robuste est de combiner plusieurs de ces approches. Dans cette thèse, nous décrivons les résultats obtenus sur deux systèmes expérimentaux développés dans ce but.La première partie de cette thèse décrit un système hybride d’atomes neutres couplés à des qubits supraconducteurs, en construction à l’Université du Maryland. La solution envisagée pour placer un ensemble d’atomes froids à proximité de la surface supraconductrice est de piéger les atomes dans le champ évanescent se propageant autour d’une fibre optique nanométrique. Nous avons développé un dispositif permettant la production de fibres optiques nanométriques de transmission optique supérieure à 99.95% dans le mode fondamental. Nous avons également optimisé la transmission de quelques modes d’ordres supérieurs, ce qui pourra s’avérer utile pour le piégeage d’atomes.La seconde partie de cette thèse décrit un système développé à l’Institut d’Optique et comprenant des atomes neutres piégés dans des matrices de pinces optiques. Dans ce cas, nous excitons les atomes dans des états de Rydberg afin de bénéficier de fortes interactions interatomiques. Nous avons caractérisé les interactions de van der Waals et les interactions résonantes entre deux atomes individuels, et démontré le caractère cohérent de l’interaction dipolaire. Nous avons enfin simulé la dynamique d’une chaine élémentaire de spins dans une matrice de trois atomes
Most platforms that are being developed to build quantum simulators do not satisfy simultaneously all the requirements necessary to implement useful quantum tasks. Robust systems can be constructed by combining the strengths of multiple approaches while hopefully compensating for their weaknesses. This thesis reports on the progress made on two different setups that are being developed toward this goal.The first part of this thesis focuses on a hybrid system of neutral atoms coupled to superconducting qubits that is under construction at the University of Maryland. Sub-wavelength diameter optical fibers allow confining an ensemble of cold atoms in the evanescent field surrounding the fiber, which makes them ideal for placing atoms near a superconducting surface. We have developed a tapered fiber fabrication apparatus, and measured an optical transmission in excess of 99.95% for the fundamental mode. We have also optimized tapered fibers that can support higher-order optical modes with high transmission, which may be useful for various optical potential geometries.The second part of this thesis focuses on a system of neutral atoms trapped in arrays of optical tweezers that has been developed at the Institut d’Optique. Placing the atoms in highly excited Rydberg states allows us to obtain strong interatomic interactions. Using two individual atoms, we have characterized the pairwise interactions in the van der Waals and resonant dipole-dipole interaction regimes, providing a direct observation of the coherent nature of the interaction. In a three-atom system, we have finally simulated the dynamics of an elementary spin chain

The project has two main objectives. First, the demonstration of the existence of single photon emitters in WSe2 monolayers. We recognized localized defect-bound excitons as responsible for this. Second, the demonstration of the evanescent coupling of a localized defect-bound exciton emission to a tapered optical nano fiber. To achieve these goals, we produced a detailed study ofWSe2, starting from the fabrication process in the clean room, up to the characterization ofthe emission spectrum and the proof of the existence of single photon emitters. Then, before fabricating the nanofibers and demonstrating the coupling result, we tested the feasibility ofthe evanescent coupling with COMSOL and MATLAB simulations. In particular, we performed a detailed optical characterization of two samples of WSe2 monolayers produced via exfoliation in clean room. We used an all dry deterministic transfer to encapsulate the samples in two layers of hexagonal boron nitride (hBN). We performed micro-photoluminescence, lifetime and degree of second-order temporal coherence measurements. We focused our attention in localized defect-bound excitons due to the high intensity PL signal and sharp linewidth. Moreover, in this work we have demonstrated the evanescent coupling of a single localized defect-bound exciton emitter with a tapered optical nano fiber we produced. For the fabrication of the nanofiber, through COMSOL and MATLAB simulations we found the right size to have a sufficiently intense evanescent field to allow coupling to the emitter. We managed, through several repetitions, to produce autonomously the nanofiber of the desired size. Finally we were able to demonstrate the feasibility of the evanescent coupling of the emission to the fiber from a chosen localized defect-bound exciton. Thus, our results provide evidence of the possibility to integrate quantum emitters in 2D materials with photonic structures.

Les interactions opto-acoustiques sont des phénomènes physiques à l’interface entre les domaines de l'optique et de l'acoustique. Cette thèse porte sur une investigation théorique et expérimentale d’effets opto-acoustiques basés sur la diffusion Brillouin dans des nanofibres optiques de silice. Grâce à leurs dimensions transverses inférieures aux longueurs d’onde optiques infrarouges, ces guides possèdent des propriétés uniques, ouvrant la voie à des applications pour la réalisation de capteurs, le traitement du signal et l'information quantique. Nous présentons dans ce manuscrit un nouveau procédé de fabrication de nanofibres optiques à haute transmission, basé sur une approche qui améliore la flexibilité dans la conception des guides. Cette avancée permet notamment de concevoir des guides sur mesure pour favoriser certains effets opto-acoustiques, tels que la diffusion Brillouin intermodale ou stimulée. La caractérisation du spectre Brillouin des nanofibres est réalisée pour la première fois dans le régime de diffusion stimulée, mettant en avant un forte efficacité de l’interaction sur les différentes résonances acoustiques. Le gain Brillouin intrinsèque dans une nanofibre a été mesuré et est jusqu'à 40 fois supérieur au gain d'une fibre standard SMF-28. À notre connaissance, cela représente la première démonstration d'un effet laser Brillouin dans une nanofibre. Une investigation théorique et expérimentale d’une interaction spin-orbite opto-acoustique par diffusion Brillouin dans une nanofibre optique est réalisée. Le phénomène est une conséquence directe de la conservation du moment angulaire. Ce principe fondamental impose ici un échange entre le degré de spin de la lumière incidente, incarné par sa polarisation, le moment angulaire orbital de l'onde-vortex acoustique TR21, et le spin de l'onde Brillouin diffusée. Enfin, nous implémentons une mémoire opto-acoustique Brillouin sensible à la polarisation dans une nanofibre, qui permet d'envisager le stockage de l’état de polarisation de la lumière au sein d'une onde acoustique et un traitement opto-acoustique de l'information
Opto-acoustic interactions are physical phenomena at the interface between the fields of optics and acoustics. This thesis focuses on a theoretical and experimental investigation of Brillouin scattering opto-acoustic effects in silica optical nanofibers. Due to their transverse dimensions being smaller than optical wavelengths, these waveguides exhibit unique properties, paving the way for applications in sensing, signal processing, and quantum information. In this manuscript, we present a new high-transmission optical nanofiber fabrication model based on an approach that enhances design flexibility for waveguides. This advancement allows for the custom design of waveguides to favor specific opto-acoustic effects, such as intermodal or stimulated Brillouin scattering. For the first time, the Brillouin spectrum characterization of nanofibers is conducted in the stimulated scattering regime, highlighting a strong interaction efficiency across different acoustic resonances. The intrinsic Brillouin gain in a nanofiber has been measured to be up to 40 times higher than that of a standard SMF-28 fiber, enabling the demonstration of a Brillouin laser effect in the nanofiber. A theoretical and experimental investigation of opto-acoustic spin-orbit interaction via Brillouin scattering in an optical nanofiber is also carried out. The phenomenon is a direct consequence of the fundamental principle of angular momentum conservation, which involves an exchange between the spin degree of the incident light, embodied by its polarization, the orbital angular momentum carried by the TR21 acoustic vortex, and the spin of the scattered light. Finally, we implement a polarization-sensitive Brillouin opto-acoustic memory in a nanofiber, opening the way to storing information on the polarization state of light within an acoustic wave

Le couplage de guides d'ondes nanoscopiques et d'atomes froids a récemment ouvert de nouvelles voies de recherche. Le guide d'onde dans notre cas est une nanofibre qui confine la lumière transversalement à une échelle inférieure à la longueur d'onde. La lumière guidée présente un fort champ évanescent permettant une interaction atome-photon exaltée au voisinage de la nanofibre. Dans notre expérience, un nuage atomique froid est d'abord superposé à une nanofibre optique. Puis, en utilisant un piège dipolaire via le champ évanescent de la nanofibre, les atomes froids sont piégés à proximité de sa surface. Avec cette plateforme, nous avons obtenu des épaisseurs optiques élevées OD ~ 100 et de longues durées de vie ~ 25 ms en utilisant un schéma de piégeage qui préserve les propriétés internes des atomes. Une direction intéressante est alors d'explorer les effets collectifs résultant de l'ordre spatial des atomes. Lorsque la période du réseau est proche de la longueur d'onde de résonance, une réflexion de Bragg aussi élevée que 75% est observée. Cette réflexion dépend de la polarisation de la sonde par rapport aux réseaux atomiques - une signature de la chiralité dans les systèmes à guide d'ondes nanoscopiques. La possibilité de contrôler le transport de photons dans les guides d'ondes couplés à des systèmes de spin permettrait de nouvelles fonctionnalités pour les réseaux quantiques et l'étude d'effets collectifs résultant d'interactions à longue distance
The coupling of cold atoms to 1D nanoscale waveguides have opened new avenues of research. The waveguide in our case is a nanofiber, which confines light transversally to a subwavelength scale. The guided light exhibits a strong evanescent field allowing enhanced atom-photon interaction in the vicinity of nanofiber. In our experiment, a cold atomic cloud is first interfaced with an optical nanofiber. By using an optical lattice in the evanescent field, the atoms are then trapped in 1D atomic arrays close to the nanofiber. In this platform, we reach high optical depth OD ~ 100 and long lifetimes ~ 25 ms by using a dual-color compensated trapping scheme that preserves the internal properties of atoms. In this thesis, we explore collective effects emerging from the spatial ordering of atoms. When the period of the lattice is made close to commensurate with the resonant wavelength, Bragg reflection, as high as 75%, is observed. The reflection shows dependency on orientation of the probe polarization relative to the atomic arrays - a chiral signature in nanoscale waveguide-QED systems. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum networking capabilities and the study of many-body effects arising from long-range interactions

Les sources de paires de photons corrélés sont des composants clés nécessaires aux réseaux de télécommunications quantiques. Réaliser directement ces sources à partir de fibres optiques permet de minimiser les pertes d'insertion. Nous proposons de concevoir une telle source à partir d'une fibre optique étirée. La fibre étirée possède un diamètre pouvant descendre à moins de 500 nm sur une longueur de quelques centimètres. Le faible diamètre de la section étirée favorise les effets non linéaires, tandis que les sections non étirées permettent de connecter avec de très faibles pertes cette fibre étirée avec les fibres des réseaux de télécommunication.Dans cette thèse, nous présentons donc une conception d’une nouvelle source de photons corrélés totalement fibrée à base de fibres standard de télécommunications (SMF28) étirées. Pour produire ces paires de photons nous utiliserons la fluorescence paramétrique due à la brisure de symétrie à la surface de la nanofibre en silice.Nous avons développé une technique de mesure par microscopie optique, qui permet de mesurer tout le profil de la fibre étirée avec une résolution nanométrique bien au-delà de la limite de diffraction.En parallèle, nous avons modélisé la susceptibilité non linéaire de surface de second ordre en prenant en compte l’aspect vectoriel de la propagation du champ optique dans une microfibre à deux ou trois couches. Dans un second temps, nous définissons les accords de phase modaux qui sont nécessaires pour l’obtention d’une forte fluorescence paramétrique. Nous dimensionnons cette nanofibre pour une bonne optimisation de l’efficacité de génération des paires. L'ensemble du processus de création de photons sera modélisé
Sources of correlated photon pairs are key components required for quantum telecommunications networks. Implementing these sources directly with optical fibers minimizes the insertion losses. We propose to design such a source from a tapered optical fiber.The tapered fiber has a diameter lower than 500 nm over a length of a few centimeters. The small diameter of the tapered section favors the non-linear effects, while the unstretched sections make it possible to connect this tapered fiber with the fibers of the telecommunication networks with very low losses.In this thesis, we present a design of a new source, fully fibered of correlated photons based on standard telecommunications tapered fibers (SMF28). To produce these pairs of photons we will use the parametric fluorescence due to symmetry breaking at the surface of a silica nanofiber.We have developed an optical microscopy measurement technique to measure all the profile of tapered fibers with nanometer resolution far beyond the diffraction limit.In parallel, we modeled the second-order nonlinear surface susceptibility by taking into account the vector aspect of the propagation of the optical field in a two or three-layered microfiber. In a second step, we define modal phase matchings that are necessary to obtain a strong parametric fluorescence. We size this nanofiber for a good optimization of pairs generation efficiency. The entire process of photon creation will be modeled

Cette thèse est consacrée à l'étude du couplage d'émetteurs de photons uniques avec des nanostructures photoniques en utilisant les propriétés du champ proche d'une structure photonique en vue de la réalisation d'une source à photons uniques intégrée et compacte pour des applications quantiques. La première partie de mon travail de thèse a été consacrée à l'optimisation des nanocristaux de pérovskites. Bien que les nanocristaux de pérovskites soient des sources de photons uniques très prometteuses, ils nécessitent encore des améliorations : dans ce travail, je passe en revue les principales propriétés de ces émetteurs et je présente une caractérisation complète des nanocristaux de pérovskites avec une photo-stabilité améliorée, un clignotement réduit et un fort dégroupement de photons. Dans la deuxième partie de la thèse, je me concentre sur le couplage des émetteurs quantiques avec diverses structures photoniques : à savoir les nanofibres optiques effilées et les guides d'ondes à échange d'ions. La méthode de fabrication et les propriétés optiques des nanofibres sont décrites en détail et le couplage d'un nanocristal de pérovskite unique avec une nanofibre est réalisé, ce qui constitue une preuve de principe d'une source hybride et intégrée de photons uniques. Enfin, je montre comment le champ proche autour des guides d'ondes d'échange d'ions peut être utilisé avec la polymérisation en champ proche pour piéger des émetteurs quantiques sur les guides d'ondes
This thesis is devoted to the study of the coupling of single-photon emitters with photonic nanostructures by using the properties of the near field of a photonic structure in view of the realization of a compact integrated single-photon source for quantum applications. The first part of my thesis work was consecrated to the optimization of perovskites nanocrystals. Although perovskites nanocrystals are very promising single-photon sources, they still need improvements: in this work, I review the main properties of these emitters and present a full characterization of perovskite nanocrystals with improved photo-stability, reduced blinking ad strong antibunching. In the second part of the thesis, I focus on the coupling of quantum emitters with various photonic structures: namely the tapered optical nanofibers and the ion-exchange waveguides. The fabrication method and the optical properties of the nanofibers are described in detail and the coupling of a single perovskite nanocrystal with a nanofiber is achieved, which constitutes a proof of principle of a hybrid integrated single-photon source. Finally, I show how the near field around ion Exchange waveguides can be employed together with near-field polymerizations to trap single-photon emitters onto the waveguides

Cette thèse de doctorat porte sur l'étude d'effets optiques non linéaires d’ordres 2 et 3 dans des nanofibres optiques de silice qui sont des fibres optiques étirées jusqu'à atteindre des diamètres de l'ordre de la longueur d'onde.La première application étudiée est la réalisation de convertisseurs de longueur d’onde dans le visible en régime sub-nanoseconde, domaine peu couvert par les sources impulsionnelles actuelles. Le principe de ces convertisseurs repose sur la diffusion Raman stimulée dans le champ évanescent d’une nanofibre optique de silice baignée dans un liquide. En définissant et optimisant leur domaine de fonctionnement, nous avons atteint des efficacités de conversion externes de l'onde de pompe à 532 nm vers le premier ordre Stokes de l'éthanol à 630 nm proches de 60%. Les performances de nos convertisseurs sont très répétables et ouvrent la voie à une nouvelle famille de convertisseurs de longueur d'onde très compacts, efficaces, fiables et entièrement fibrés.La seconde application visée concerne l'étude d'une source de paires de photons corrélés émettant autour de 1,5 μm pour les télécommunications quantiques. Notre source est basée sur le mécanisme de fluorescence paramétrique à la surface d’une nanofibre optique de silice. Dans l'accord de phase modal étudié, l'onde de pompe est émise sur le mode TM01 à 775 nm et les paires de photons corrélés sont générées autour de 1,5 microm sur le mode fondamental HE11, avec l'avantage de pouvoir se recoupler avec un minimum de pertes dans un réseau fibré. Nos études ont principalement porté sur le choix de la fibre standard permettant d'optimiser l'efficacité du mécanisme, la conception de la nanofibre et de ses tapers ainsi que la mise en place d'expériences préliminaires pour l'excitation de modes d'ordre supérieur
In this PhD thesis we study 2nd and 3rd order optical non-linearities in optical nanofibers, which are obtained by stretching standard fibers until their diameter becomes of the order of magnitude of the wavelength. The first application is the realization of wavelength converters in the visible range in the sub-ns regime, range which is only minimally covered by pulsed sources. The principle of these converters is to use stimulated Raman scattering in the evanescent field immersed in a liquid. By defining and optimizing their operating range, we have reach external conversion efficiencies from the pump at 532 nm to the first Stokes order of ethanol at 630 nm near to 60%. The performances of our converters are very repeatable and open the way to a new family of very compact, reliable and all-fibered components.The second application is the study of a source of correlated photon pairs for quantum telecommunications. Our source is based of parametric fluorescence on the surface of a silica nanofiber. In the phase-matching we propose, the pump wave is emitted on the mode TM01 at 775 nm and the photon pairs are emitted around1.5 μm in the fundamental mode, enabling a recoupling with only a few losses in the optical network. Our study mainly concern the choice of the standard fiber enabling to optimize the efficiency of the mechanism, the conception of the nanofiber and its tapers as well as the implementation of preliminary experiments for the excitation of high ordrer modes

O desenvolvimento da fotônica integrada vem recebendo muita atenção nos últimos anos. Sua alta funcionalidade e velocidade de transmissão de sinais possibilitam a aplicação em diversas áreas, que vão desde comunicações até biologia. O uso de polímeros em circuitos fotônicos integrados tem se mostrado interessante, pois compostos orgânicos podem ser facilmente incorporados a matrizes poliméricas. Isso faz com que as propriedades físicas do polímero possam ser modificadas de acordo com os materiais incorporados. Além disso, a técnica da fotopolimerização por absorção de dois fótons torna possível a produção de microestruturas poliméricas tridimensionais com alta resolução. A incorporação dessas microestruturas a circuitos fotônicos pode trazer um novo ramo de funcionalidades devido à facilidade de modificação das propriedades dos polímeros. Além disso, a tridimensionalidade das estruturas permite a realização de conexões ópticas em três dimensões, o que colabora para o aumento da compacticidade dos dispositivos fotônicos. No entanto, para que estas microestruturas possam ser efetivamente incorporadas aos circuitos fotônicos é necessário desenvolver formas de conectá-las a fontes externas de excitação, bem como a instrumentos de análise de sinais. Os tapers de fibras ópticas, também conhecidos como microfibras ou nanofibras, são bons candidatos para realizar essa tarefa devido a suas dimensões reduzidas, as quais são compatíveis com o tamanho das microestruturas. Neste trabalho desenvolvemos métodos para realizar a conexão óptica entre microestruturas poliméricas e tapers de fibras ópticas. As microestruturas foram produzidas através da técnica de fotopolimerização por absorção de dois fótons e corantes orgânicos foram incorporados à matriz polimérica para conferir propriedades fluorescentes às estruturas. Os tapers foram produzidos a partir de fibras ópticas convencionais por uma técnica de aquecimento e estiramento. Para realizar a conexão óptica, dois métodos foram desenvolvidos. No primeiro deles as microestruturas foram excitadas através de uma lente objetiva e sua emisão foi coletada por um taper. No segundo método, tanto a excitação quanto a coleta foram realizadas por tapers de fibras ópticas. Em ambos os casos as fibras foram posicionadas através de micromanipuladores. Os resultados obtidos indicam que os tapers são ferramentas adequadas para realizar tanto a excitação quando a coleta da emissão de microestruturas, pois permitem excitação individual e coleta localizada. Produzimos microestruturas com múltiplas dopagens e pudemos concluir que a excitação localizada de diferentes partes da estrutura, bem como a correta escolha do comprimento de onda de excitação, são mecanismos que levam a alterações no espectro de emissão, o que torna estas estruturas candidatas a fontes de luz sintonizáveis que podem ser incorporadas a dispositivos on-chip. Por fim, desenvolvemos um método de produção de microestruturas conectadas a tapers. Este trabalho abre caminho para a incorporação de microestruturas poliméricas a circuitos fotônicos e demonstra que tapers de fibras ópticas são ferramentas eficientes para a realização de microconexões ópticas.
The development of integrated photonics has received a great deal of attention in the last few years. Its high functionality and signal transmission speed allow applications in several fields, from telecommunications to biology. The use of polymeric platforms in integrated photonic circuits is interesting because organic compounds can be easily incorporated to polymeric matrixes, which makes it easy to change the physical properties of the polymer according to the embed materials. Furthermore, the two-photon polymerization technique allows the production of three-dimensional polymeric microstructures with high resolution. The incorporation of these microstructures to photonic circuits paves the way for a new field of funcionalities due to the ease of modification of the polymers properties. Besides that, the structures three-dimensionality allows the performance of optical connections in three dimensions, which can improve the compacticity of the photonic devices. However, for the effective incorporation of these microstructures to photonic circuits, it is necessary to develop ways to connect them to external excitation sources, as well as analysis instruments. Optical fiber tapers, also known as microfibers or nanofibers, are good candidates for this task due to their reduced dimensions that are compatible with the size of the microstructures. In this work we developed methods for the performance of optical connections of polymeric microstructures through fiber tapers. The microstrutures were produced through the two-photon polymerization technique and organic dyes were incorporated to the polymeric matrix in order to introduce fluorescent properties. The fiber tapers were produced from conventional optical fibers through a heat-and-draw approach. To perform the optical connections, two methods were developed. In the first one, the microestructures were excited through a microscope objective and emission collection was performed by a fiber taper. In the second approach, excitation and collection were performed by fiber tapers. In both methods, the tapers were set up by micromanipulators. The obtained results indicate that tapers are a suitable tool to perform optical excitation and emission collection in microstructures, as they allow individual excitation and localized collection. Multiple doped microstructures were produced and we could imply that the localized excitation of different parts of the structures, as well as the correct choice of the excitation wavelength, are tools that lead to changes in the emission spectrum, which makes these structures candidates to tunable light sources that can be incorporated to on-chip devices. At last, we developed a method for the production of microstructures connected to fiber tapers. This work paves the way for the incorporation of polymeric microstructures to photonics circuits and demonstrates that fiber tapers are efficient tools to perform optical microconnections.

Cette thèse traite des interactions entre des photons guidés par une nanofibre optique et des réseaux d'atomes piégés. Notre montage expérimental consiste en un piège dipolaire bicolore compensé, généré dans le champ évanescent d'une nanofibre et permettent de piéger des atomes de césium de part et d'autre de la fibre. Une épaisseur optique de plus de 130 est obtenue avec quelques milliers d'atomes seulement. Nous démontrons la capacité de préparer les atomes piégés dans un sous-niveau Zeeman unique, bien qu'avec une efficacité limitée. Cette étape est importante pour la réalisation de mémoires quantiques avec de longs temps de vie avec notre plateforme fibrée. Le résultat principal que nous présentons est la réalisation d'une excitation collective unique dans l'ensemble d'atomes. L'excitation est annoncée par la détection d'un photon émis dans le mode guidé. Nous sommes alors capables de lire l'état atomique et récupérer un photon unique dans le mode guidé avec une efficacité jusqu'à 25%. Ce résultat consiste en une première démonstration d'un état atomique intriqué, couplé préférentiellement à un guide d'onde, une étape importante dans le contexte de l’électrodynamique quantique avec des guides d'ondes
This thesis focuses on the study of interactions between photons guided by an optical nanofiber and arrays of trapped atoms. Our experimental setup consists in a two-color compensated dipole trap located in the evanescent field of an optical nanofiber in a ultra-high vacuum chamber. Cold cesium atoms are trapped in two 1D arrays above and below the nanofiber. An optical depth of over 130 is achieved with only a few thousand atoms. We demonstrate the ability to prepare the trapped atoms in a single Zeeman sub-level, albeit with limited efficiency. This is an important step towards the realization of a long-lived quantum memory with our fibered platform. The main result of this thesis concerns the initialization of a single collective excitation coupled to the nano-waveguide. The excitation is heralded by the detection of a Raman scattered photon in the nanofiber. We are then able to readout the atomic state and retrieve a single photon in the guided mode with an efficiency of up to 25%. This result is the first demonstration of an atomic entangled state preferentially coupled to a waveguide. It is a milestone in the context of the emerging waveguide-QED approach, with applications to quantum networking, quantum non-linear optics and quantum many-body physics

Les travaux présentés dans cette thèse portent sur l’étude expérimentale de systèmes hybrides dans lesquels des nanoémetteurs sont couplés à des nanofibres optiques. Un système hybride vise à combiner les atouts des éléments qui le constituent. Une nanofibre offre une interface lumière/matière unique: directement intégrable au réseau de fibres optiques, elle confine la lumière "à la limite de diffraction" sur toute sa longueur. De plus, le confinement transverse de la lumière dans une fibre sub-longueur d’onde implique un champ électrique « exotique », en particulier la présence d’une composante longitudinale du champ électrique. Dans cette thèse nous tirons parti de ces propriétés et nous présentons une expérience mettant en jeu un phenomène de bielle-manivelle optique afin de modifier la polarisation du rayonnement d’un émetteur à la surface de la nanofibre. Sur la base du système nanoparticule + nanofibre optique, nous présentons également une “règle optique” permettant de localiser la nanofibre à 5 nanomètres près. Ceci ouvre une voie dans l’étude optomécanique des nanofibres optiques
In this thesis, we present an experimental study of hybrid systems where nano-emitters are coupled to optical nanofibers. The strong transverse confinement of light in sub-wavelength fibres implies an “exotic” electric field (longitudinal electric field component, inhomogeneous polarisation etc.) that we use in order to alter the radiation properties of nano-emitter placed at the surface of the nanofiber. Based on the same system : nano-particle + nanofibre, we developped an “optical ruler” to localise the nanofiber with nanometer precision. This open the way to the study of nanofibre optomechanics

[ES] Los biosensores son dispositivos analíticos con aplicabilidad en diferentes campos y con numerosas ventajas frente a otros métodos analíticos convencionales, como son el uso de pequeños volúmenes de muestra y reactivos, su sensibilidad y su rápida respuesta, sin necesidad de pretratamiento de la muestra, equipos caros o personal especializado. Sin embargo, se trata de un campo de investigación relativamente nuevo en el que todavía queda mucho camino por andar. Esta Tesis doctoral pretende aportar un granito de arena a este campo de conocimiento mediante el estudio del potencial de diferentes materiales porosos como transductores para el desarrollo de biosensores ópticos con respuesta en tiempo real y sin marcajes. Los materiales propuestos van desde aquellos artificialmente sintetizados, como silicio poroso (SiP), nanofibras (NFs) poliméricas o membranas poliméricas comerciales, hasta materiales naturales con propiedades fotónicas que todavía no habían sido explotadas para el sensado, como son los exoesqueletos de biosílice de diatomeas. Todos ellos tienen en común la simplicidad en su obtención, evitando costosos y laboriosos procesos de nanofabricación. Para su estudio, se analizará su respuesta óptica y, en aquellos casos en los que ésta permita llevar a cabo experimentos de detección, se desarrollarán estrategias para su biofuncionalización y su implementación en experimentos de biosensado. En el caso del SiP y las NFs se han optimizado los parámetros de fabricación para obtener una respuesta óptica adecuada que permita su interrogación. A continuación, se ha llevado a cabo su biofuncionalización empleando métodos covalentes y no covalentes, así como diferentes bioreceptores (aptámeros de ADN y anticuerpos) para estudiar su potencial y sus limitaciones como biosensores. En el caso de las membranas comerciales y el exoesqueleto de sílice de diatomeas, se ha caracterizado su respuesta óptica y se han llevado a cabo experimentos de sensado de índice de refracción para estudiar su sensibilidad. Así mismo, se ha desarrollado un método de funcionalización de la superficie del exoesqueleto de diatomeas basado en el uso de polielectrolitos catiónicos. Como resultado, se ha demostrado el potencial tanto de NFs para el desarrollo de biosensores, como el de membranas comerciales para sensores cuya aplicación no requiera una elevada sensibilidad pero sí un bajo coste. Además, se ha puesto de manifiesto el gran potencial del exoesqueleto de diatomeas para el desarrollo de sensores basados en su respuesta óptica. Por el contrario, las limitaciones encontradas en el desarrollo de biosensores basados en SiP han evidenciado la necesidad de un estudio riguroso y la optimización de la estructura de materiales porosos previamente a ser usados en (bio)sensado.
[CA] Els biosensors són dispositius analítics amb aplicabilitat en diferents camps i amb nombrosos avantatges enfront d'altres mètodes analítics convencionals, com són l'ús de xicotets volums de mostra i reactius, la seua sensibilitat i la seua ràpida resposta, sense necessitat de pretractament de la mostra, equips cars o personal especialitzat. No obstant això, es tracta d'un camp d'investigació relativament nou en el qual encara queda molt camí per fer. Aquesta Tesi doctoral pretén aportar el seu òbol a aquest camp de coneixement mitjançant l'estudi del potencial de diferents materials porosos com a transductors per al desenvolupament de biosensors òptics amb resposta en temps real i sense marcatges. Els materials proposats van des d'aquells artificialment sintetitzats, com a silici porós (SiP), nanofibras (NFs) polimèriques o membranes polimèriques comercials, fins a materials naturals amb propietats fotòniques que encara no havien sigut explotades per al sensat, com són els exoesquelets de biosílice de diatomees. Tots ells tenen en comú la simplicitat en la seua obtenció, evitant costosos i laboriosos processos de nanofabricació. Per al seu estudi, s'analitzarà la seua resposta òptica i, en aquells casos en els quals aquesta permeta dur a terme experiments de detecció, es desenvoluparan estratègies per a la seua biofuncionalizació i la seua implementació en experiments de biosensat. En el cas del SiP i les NFs s'han optimitzat els paràmetres de fabricació per a obtenir una resposta òptica adequada que permeta la seua interrogació. A continuació, s'ha dut a terme la seua biofuncionalizació emprant mètodes covalents i no covalents, així com diferents bioreceptors (aptàmers d'ADN i anticossos) per a estudiar el seu potencial i les seues limitacions com a biosensors. En el cas de les membranes comercials i l'exoesquelet de sílice de diatomees, s'ha caracteritzat la seua resposta òptica i s'han dut a terme experiments de sensat d'índex de refracció per a estudiar la seua sensibilitat. Així mateix, s'ha desenvolupat un mètode de funcionalizació de la superfície de l'exoesquelet de diatomees basat en l'ús de polielectròlits catiònics. Com a resultat, s'ha demostrat el potencial tant de NFs per al desenvolupament de biosensors, com el de membranes comercials per a sensors amb una aplicació que no requerisca una elevada sensibilitat però sí un baix cost. A més, s'ha posat de manifest el gran potencial de l'exoesquelet de diatomees per al desenvolupament de sensors basats en la seua resposta òptica. Per contra, les limitacions trobades en el desenvolupament de biosensors basats en SiP han evidenciat la necessitat d'un estudi rigorós i l'optimització de l'estructura dels materials porosos prèviament a ser usats en (bio)sensat.
[EN] Biosensors are analytical devices with application in diverse fields and with several advantages relative to other conventional methods, such as the use of small volumes of sample and reagents, their sensitivity and their fast response, without the need of the sample pretreatment, expensive equipments or specialised technicians. Nevertheless, this is a relatively new research field in which there is a long way to go yet. This doctoral Thesis aims at doing its bit to this field of knowledge by studying the potential of different porous materials as transducers for the development of real-time and label-free optical biosensors. The proposed materials range from those artificially synthesised, such as porous silicon (pSi), polymeric nanofibres (NFs) or commercial polymeric membranes, to natural materials with photonic properties that had not been exploited for sensing yet, such as biosilica exoskeletons of diatoms. All of them have in common its simple production, avoiding expensive and laborious nanofabrication processes. For their study, their optical response will be analysed and, in those cases in which such optical response allows performing detection experiments, strategies for their biofunctionalisation and their implementation in biosensing experiments will be developed as well. Regarding pSi and NFs, the fabrication parameters were optimised to get a suitable optical response for their interrogation. Afterwards, their surface functionalisation was carried out by covalent and non-covalent methods, as well as different bioreceptors (DNA aptamers and antibodies), to study their potential and their constraints as biosensors. Concerning commercial membranes and the biosilica exoskeleton of diatoms, their optical response was characterised and refractive index sensing experiments were carried out to study their sensitivity. Additionally, a biofunctionalisation method for the surface of the diatoms exoskeleton was developed based on the use of cationic polyelectrolytes. As a result, it was demonstrated the potential of NFs for the development of biosensors, as well as the potential of commercial membranes for developing sensors for an application that does not require a high sensitivity but a low cost. Furthermore, the great potential of biosilica exoskeleton of diatoms for the development of sensors based on their optical response has been revealed. By contrast, the constraints found in the development of pSi illustrate the importance of an accurate study and optimisation of porous materials structure before using them for (bio)sensing.
Martínez Pérez, P. (2021). Development and Optimization of Experimental Biosensing Protocols Using Porous Optical Transducers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172541
TESIS

The main aim of this thesis work is to investigate the electrical, optical and thermal impact characteristics of cobalt oxide doped antimony tin oxide (CoO-ATO) in the form of thin films and nanofiber membranes. CoO-ATO is a novel composite material that has the potential to be used as reinforced aircraft coatings, military garment coatings, or more specifically as an anti-reflective (AR) top coating for photovoltaic (PV) cells. This work will be critical in determining the effectiveness of using a CoO-ATO layer in these applications. Electrospun nanofibers and spin coated thin films consisting of a polymeric solution of CoO-ATO will be used. Thin films are created using spin coating techniques, and nanofiber membranes are created using an electrospinning technique. Polystyrene (PS) will be used as a solute, and chloroform as a solvent, to create the solution. It is hypothesized that coatings of this material will have improved optical characteristics as compared to traditional ATO coatings and minimum impact from thermal cycling making it a favorable candidate for PV cells. This work will do an electrical, optical and thermal cycling impact characterization of CoO-ATO thin films and nanofiber membranes for a doping range of x% CoO where x ranged from 0.2

Nous étudions expérimentalement deux mémoires quantiques pour la lumière utilisant la transparence électromagnétiquement induite (EIT) dans des nuages froids de césium.Nous expliquons la pertinence des mémoires quantiques pour le développement de réseaux quantiques à longue distance, et décrivons la théorie de l’EIT en soulignant les paramètres essentiels pour l’implémentation de mémoires quantiques.Notre premier cas d’étude est un piège magnéto-optique en espace libre. Notre principal résultat est la démonstration du caractère multimode de ce système pour le stockage quantique de la lumière. Pour cela, nous utilisons des faisceaux de Laguerre-Gauss (LG), porteurs de moment angulaire orbital (OAM). Dans une première étape, nous avons montré que l’état de moment orbital d’impulsions lumineuses en régime de photons uniques est préservé lors du stockage dans la mémoire. Ensuite, nous avons implémenté un bit quantique comme une superposition de modes LG ayant des hélicités opposées. Nous avons développé un système original pour mesurer ces bits quantiques qui nous a permis de caractériser l’action de la mémoire. Nous avons ainsi pu montrer que le stockage quantique de ces bits quantiques.Le second système, également un nuage d’atomes froids, a la particularité que les atomes sont piégés optiquement autour d’un nano-guide d’onde. Ce design innovant permet une plus grande interaction entre lumière et matière, et facilite l’interfaçage des photons dans et hors de la mémoire. Nous décrivons la construction de ce dispositif et les premiers pas vers son utilisation en tant que mémoire quantique
We present an experimental study of two optical quantum memory systems based on electromagnetically induced transparency (EIT) in cold cesium atoms.We explain the relevance of quantum memories for the development of large-scale quantum networks, we give a comprehensive theory of the EIT phenomenon and underline the role of relevant parameters regarding the implementation of quantum memories.The first system under study is prepared in a free-space magneto-optical trap. The main result of this thesis is the demonstration of the spatial multimode capability of this system at the quantum level. For this, we used Laguerre-Gaussian (LG) light beams, i.e. beams possessing a non-zero value of orbital angular momentum (OAM). In a first step, we showed that the orbital angular momentum of stored light pulses is preserved by the memory, deep in the single photon regime. In a second step, we encoded information in the orbital angular momentum state of a weak light pulse and defined a qubit using two LG beams of opposite helicities. We developed an original setup for the measurement of this OAM qubit and used it to characterize the action of the memory during the storage of such a light pulse. Our results show that the memory performs the quantum storage of such a qubit.The second system under study, also a cloud of cold atoms, has the specificity that the atoms are trapped optically in the vicinity of a nano-waveguide. This innovative design ensures a higher light-matter interaction and facilitates the interfacing of photons into and out of the memory. We describe the building of this setup and the first steps towards quantum memory implementations

We aimed to provide optimal and controlled growth mechanisms that determine the fate of cells by designing a novel polymeric, bio-functionalised 3-dimensional artificial Nanofibrous Extracellular Matrix (NF-ECM) that recapitulates the natural microenvironment of cells. We initially reviewed current cell-expansion methods, and clinically feasible protocols for tissue engineering applications. They are often based on conventional 2-dimensional tissue culture plates that usually require xenogenic coating substrates or feeder-cells to maintain their characteristics. Propagating cells in a 3-dimensional architecture, rather than in the conventional 2-dimensional flat monolayers, can be advantageous for many regenerative applications and biological or disease modelling studies. Furthermore, such 3-dimensional culture systems might be crucial in developing a bioreactor-based design that provides finely controlled environmental conditions that would reliably propagate 3-dimensional multilayered cell organisation or spheroids on a large scale. Furthermore, the ability to expand cells in the absence of animal-derived products is a necessary condition for clinical application.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Dentistry and Oral Health
Griffith Health
Full Text

This thesis introduces reader to current knowledge of nanomaterials and their usage. It summarises production methods and usage of different materials in nuclear power plants, nuclear research and nuclear medicine. Theoretical part of this thesis is dedicated to possible usage of carbon nanotubes for neutron beam collimation and guides. In experimental part different materials were tested in measuring box connected to horizontal radial channel of VR-1 nuclear reactor and their influence on neutron flux was measured. Tested samples were non-oriented carbon nanotubes, carbon nanofibers, alumina nanowires, oriented carbon nanotubes with several angles of rotation and these samples were compared with results of graphite.

Blood vessel mimics (BVMs) are simple tissue engineered blood vessel constructs intended for preclinical testing of vascular devices. This thesis developed and implemented methods to characterize two of these components. The first aim of this thesis investigated the effect of cell culture duration and flow conditions on endothelial cell gene expression, especially regarding endothelial-to-mesenchymal transition (EndMT). A trend of decreased endothelial marker gene expression and increased mesenchymal marker gene expression would indicate EndMT. qPCR analysis revealed that increased cell culture duration did not result in EndMT, and in fact increased endothelial marker expression as cell culture duration increased. Disturbed flow conditions decreased endothelial marker and increased mesenchymal marker expression relative to static culture. The second aim of this thesis developed methods to determine cytotoxicity of, and endothelial cell adhesion to, novel BTEAC salt scaffolds. Immunostaining was used to visualize these scaffold effects. The cytotoxicity elution assay showed that BTEAC salt scaffolds were not more cytotoxic than the standard PLGA scaffold. Direct contact assays spanning several timepoints also found that BTEAC salt scaffolds were not more cytotoxic than standard scaffolds but had higher endothelial cell adhesion and coverage than standard scaffolds. Overall, this thesis developed and implemented methods to characterize the endothelial cells used in the BVM model.

碩士
國立成功大學
材料科學及工程學系碩博士班
96
Electrospun nanofibers from optical polymers, such as PMMA (polymethyl methacrylate) exhibit remarkable interaction with ambient light as shown in their UV-vis spectra. Diameters of electrospun PMMA nanofibers determined by SEM images illustrate the linear dependence on the absorption peaks. UV-vis absorption spectra of these PMMA nanofibers with difference deposited thickness, incident angles, and the media within fiber spacing were also carefully investigated. In addition, the software simulation was also conducted in order to further explain the light absorption* phenomenon of PMMA nanofibers. Fluorescent dyes, including Coumarin 6 and Ru(bpy)3Cl2, were utilized to examine the possible light trapping by the electrospun nanofibers. PMMA/Coumarin 6 and PMMA/Ru(bpy)3Cl2 composite nanofibers were electrospun and investigated in terms of the fluorescence enhancement as a function of deposited thicknesses. The adsorption and emission spectra of dye-doped PMMA nanofibers with various PMMA/dye concentrations and deposited thickness were analyzed. Fluorescence intensities were carefully normalized by PMMA weight per unit area, so that the emission enhancement could be quantified and compared. According to the experimental results, the fluorescence enhancement from dye-doped PMMA nanofibers did reveal the relationship with the deposited thicknesses of electrospun nanofibers. Especially in the UV region, the electrospun PMMA nanofibers successfully confined the incident irradiations within the nanostructures.

碩士
中原大學
電子工程研究所
106
In recent years, mechanical vision image detection has become more and more developed. With image analysis to make the product in the production line more clearly, quality management can be more smoothly and save more time. Therefore, in order to realize fully automated equipment in the factory, the development of product inspection machines has become an important indicator of quality control. In this paper, we use OpenCV as the development environment, and use carbon nanofiber products as the research object. In the production process, we aim to distinguish some of the defective classes, so that the production quality is regulated. Because the production of the carbon nanofiber is not perfect, if bad products are put into the end equipment, the production process will inevitably encounter unexpected errors and degrade products. We use image processing techniques (such as Gaussian Blur filter to remove noise from the captured image) to detect whether the carbon fiber in the image is a normal product or not; we aim to solve that detection problem by using computer algorithms instead of a human check. We define four undesirable conditions for quality management analysis: bifurcation defects, burr defects, large-width defects and small-width defects. These four categories are likely to cause unpredictable errors in the production process that hinder normal production. If these defects can be eliminated before the subsequent production stage, the production quality will be increased. With this detection algorithm for various kinds of defects, the current state of production quality can be under control.

碩士
國立臺灣科技大學
材料科學與工程系
106
Nanomaterials have numerous commercial and technological applications in chemical, biomedical, optoelectronics, electronics and space industries. Once nanomaterials are released into the environment via manufacturing, use or disposal, their transport is the critical parameter in assessing their exposure and impact on the public health and the ecosystem, therefore understanding the fate of nanomaterials in the environment is critical. This research goal aims at developing nanomaterials derived from natural resources, both reinforcement and matrix are biobased and biodegradable. Cellulose nanofibers from wood, plants and agricultural by-products is an abundant renewable resources. The fabrication of cellulose based-nanocomposite film without affecting the optical, mechanical and thermal properties of cellulose triacetate (CTA), one of the most widely used polymers, and cellulose nanofiber (CNF), which represent the world’s most abundant bio-based nanofiller, is investigated. In this study, using recycled the polarizers industrial CTA film waste – recycled triacetate cellulose (rTAC), the conventional waste disposal could be improved for the environmental issues. Furthermore, the reinforcement from the raw material, which was the extraction of nanofibers consisted of sudachi residue (lemon peel) after juice extraction. Cellulose nanofiber suspension was solvent-exchanged with acetone-methanol by series of centrifuging and re-dispersing steps. After that, using the solution casting method including the mixture of rTAC film and nanofibers that was prepared by stirring in combination with ball milling technique to achieve full dispersed solution, was coated on the glass to obtain a thin film. And for comparative purposes, industrial cellulose nanofiber (OJI-CNF) in its pristine form, is also reported. The structure of nanofibers and the dispersion effect of both CNFs in TAC were observed by scanning electron micrograph (SEM) and transmission electron microscopy (TEM). The optical, mechanical and thermal properties of the nanocomposite films were characterized experimentally. The results showed that by varying nanofiber contents (1~7wt%), the haze was slightly increased while the transmittance was not be affected compared to that of rTAC film (92.7%). On the other hand, OJI-CNF showed a lower transparency significantly when increasing nanofiber contents, compared to lemon peel-CNF, indicated that the poor dispersion due to the aggregates of OJI-CNF in solution. It was found that the addition of CNFs increased the tensile stress by 60%; the tensile strain by 150% and the yield stress by 50%. The dynamic mechanical properties (creep behavior) results were also positive; the creep compliance improved for all nanocomposites compared to rTAC film. These both nanofibers contributed to a significant reduction in the thermal expansion properties of rTAC film while maintaining their ease of bending.

碩士
國立中興大學
化學工程學系所
102
In this thesis, we highlight on the techniques of producing nanofied- cellulose and its modification. Since cellulose abundant exists in the world which also be equipped with a lot of oustanding characteristics so that''s why we nanofied the ordinary cellulose for the sake of enhancing its advantages, and we abbriviate this kind of cellulose as TOCN(TEMPO- oxidized cellulose nanofibers). After modification, we analyzed the ratio of modified to unmodified cellulose by titration. Furthermore, observations were performed by utilizing SEM, FT-IR, NMR and XRD. In SEM, we detected cellulose was successfully nanofied, and also found the appearance of -COONa function group with the aid of FT-IR and NMR. In addition,XRD analysis showed that there was no significant change in the cryatal structure between the modified and unmodified cellulose, and the degree of crystallinity only slightly decline.Moreover, we deducednanocellulose''s molecular weight by measuring its viscosityand the results indicated that the extent of the degradation caused by the modification process is low.Consiquently, the molecular weight of nanofied cellulose remained approximately 90,000, and we can also derive the original cellulose''s molecular weight is around 130,000. In the thesis, we produced highly transparent paper film by TOCN. At first, we dispersed TOCN into DI waterwith vary energy levels of the ultrasonic homogenizer ,measuring particle size by DLSand light transmittance by UV-vis. Wediscovered that the TOCN has better light transmittance as we exploited 200W as ultrasonic homogenizer''s energy level than 160W did, which pointed out that the paper film possesses more transparency. On the other hand, we unearthed that the film''s transparency varies with the pH value, since it may declines as we fixed TOCN in more acidic environment. Hence, the cellulose film can reach the optimum transparency of 87% as the condition comes to 200W energy level in neutral surrounding. Next, we modified TOCN by surface-initiated ATRP by PSt to change its hydrophility. We harnessed UV-vis ,confirming that it only had slightly decrease in transmittance. Finally, by contact angle analysis we discovered the angle increased from 60 to about 90 degrees. Because of its distinguished light transmittance, flexure and hydrophobicity after modification, it is a promising and potential material for making optical components. With surface modification by TEMPO (2,2,6,6-tetramethylpiperidine- 1-oxyl), the hydroxyl group at C6 on cellulose changed to sodium carboxylate group by redox reaction produces TOCN, and we also test TOCN''s dispersibility in different solvents. After esterification reaction performed by BIB (2-bromoisobutyrylbromide), TOCN surface was grafted by initiator of ATRP. We investigated the difference of functional groups in the modification process by ESCA (Electron spectroscopy for chemical analysis) and EA (Element analysis) to make sure modified consequences. Then surface-initiated ATRP grafted polystyrene from TOCN. Because of the carboxylate groupandthebenzene ring, it is equiptted with adsorbability. Selecting trichlorobenzene as the source of organic contaminant , the adsorbability increased as TOCN grafted.Besides, the heavy metal adsorbability almost remains the same after grafting. Therefore, this kind of modified TOCN is also potential and it may be servedas a dual fucntional filter adsorber in the future .

Tese de Doutoramento em Física
Com o objectivo de obter uma multiplicidade de propriedades ópticas e electrónicas específicas, podemos produzir nanoestruturas artificiais controlando o seu material, tamanho e forma. Recentemente temos assistido à exploração de como a combinação de diferentes tipos destas estruturas podem vir a reforçar as suas respectivas caracteristicas. Isto é realizado com o objectivo de uma possivel produção de vários materiais a serem usados na próxima geração de dispositivos optoelectrónicos e nanofotónicos. Como tal, neste trabalho explorámos como a combinação de materiais bidimensionais, Grafeno e MoS2, juntamente com Pontos Quânticos ou Nanoplaquetas permitem criar nanoestruturas artificiais e como alteram as suas características. Sendo que interacção entre a estrutura e excitações elementares em nanoestruturas semicondutoras e orgânicas podem afectar as suas propriedades ópticas lineares e não lineares, explorámos o seu acoplamento através de interacções excitão-plasmão ou excitão-excitão. A investigação deste acoplamento foi realizada utilizando : espectroscopia Raman, contagem de fotões únicos correlacionada com o tempo (TCSPC), espectroscopia de absorção transitória (TA) e geração de segunda harmónico resolvido no tempo (TR2HG) numa tentativa de caracterizar os processos físicos subjacentes e avaliar o possível potencial destas estruturas híbridas. Além disso, foi realizada uma avaliação de nanofibras biocompatíveis com capacidade de gerar segundo harmónico (2HG). Sendo que os resultados obtidos corroboram a nossa proposta de que estas nanofibras formadas por moléculas não lineares push-pull cristalizadas dentro de uma matriz biopolimérica são materiais promissores para aplicações nanofotónicas e possivel recolha de energia. Por fim foi realizada uma caracterização do índice de refracção não-linear do Grafeno com uso de uma nova abordagem. Através da modulação de fase cruzada através do do efeito óptico Kerr ultra-rápido, caracterizamos a resposta não linear de terceira ordem do grafeno. Verificamos que as alterações não lineares induzidas no grafeno por um campo forte ultra-rápido podem alterar temporariamente o índice de refracção visto por um segundo campo mais fraco, sendo que existe uma forte dependência da frequência analisada. Este efeito é prometedor por exemplo para o desenvolvimento de um interruptor óptico ultra-rápido baseado no grafeno.
Artificial nanostructures can be engineered to obtain a variety of specific optical and electronic properties, depending on their material, size and shape. More recently researchers have begun to explore how combining different types of these structures might reinforce their respective strengths to attain promising materials for the next generation of optoelectronic and nanophotonics devices. For that, we explored how combining two-dimensional materials, Graphene and MoS2, with Quantums Dots (QD) or Nanosplatelets (NP) to create artificial nanostructures might reinforce their respective strengths. organic nanostructures can affect their linear and nonlinear optical properties we explored the effect of coupling them via exciton-plasmon or exciton-exciton interactions. We have probed this coupling using Raman spectroscopy, Time-Correlated Single Photon Counting (TCSPC), Ultrafast Transient Absorption Spectroscopy (TAS) and Time-Resolved Second Harmonic Generation (TR2HG) in an attempt to characterize the underlying physical processes and evaluate the potential technological significance of these hybrids structures. In addition, an evaluation of biocompatible second harmonic generation (2HG) nanofibers was realized and the produced results support the proposal that electrospun nanofibers formed by nonlinear pushpull molecules crystallized inside a biopolymer matrix are promising hybrid functional materials for nanophotonics and energy harvesting applications. Furthermore, a characterization of the nonlinear refractive index of graphene was made with the implementation of a new approach. By means of the cross phase modulation via the ultrafast optical Kerr effect method, we characterize the third-order nonlinear response of graphene. We find that in graphene the nonlinear changes induced by a strong pump ultrashort field can temporally alter the refractive index seen by a weaker probe field and observe a strong dependence on frequency. This effect hold promise for developing a high-speed all-optical switch based on graphene.
Fundação para a Ciência e a Tecnologia

First we investigate the generation of non-classical states of light by means of pulsed parametric down-conversion, and second their complete diagnostics and characterisation by means of pulsed homodyne detection. We introduce a new characterisation technique of quantum states of light (starting with the case of the single photon) that combines techniques from the fields of quantum optics and ultrafast coherent control: the idea is to generate femtosecond quantum light states with a broad spectrum, and then, through adaptive mapping of their spectro/temporal mode onto the reference field, to completely retrieve the "shape" of the state under investigation, even with no prior information at hand. The possibility of accessing the arbitrarily-shaped spectro/temporal structure of ultrashort quantum light states will allow a leap forward to the encoding and manipulation of quantum information.

碩士
逢甲大學
光電學系
106
Since bands of optical communication is often in 1.5-µm wave length region, to build a reference frequency which is accurate and easy to use in this band is a very important job. To achieve this goal, we demonstrate an all-fiber system based on optical nanofiber (ONF) to probe the saturation absorption of the P(9) line of the acetylene ν1+ν3 band, which is the strongest line of ν1+ν3band at room temperature. The diameter and length of the nanofiber waist are 600 nm and 3.65 mm, respectively, which allows most of the light energy to leak out of the surface of the fiber and interact with the gas molecules. Since the optical backscattering reflection(OBR) of the ONF interferes with the probe beam, the saturation absorption signal is deteriorated and is hard to be observed. To reduce the interference between the OBR and probe beam, we introduce a large optical path difference. In addition, we observed that, for the ONF with 85% transmittance, an incident light of 6.66 mW would result in 591 μW of OBR. Finally, the saturated absorption spectrum becomes more apparent by using frequency derivative spectroscopy.

Cellulose is a potential source of nano-material not only because it possesses excellent mechanical and optical properties, but also because it is environmentally benign. In this study, nanofibres derived from wheat straw, an agriculture residue, was utilized in producing flexible and optically transparent nanocompostie films. The composites were produced using a bi-phase impregnation technique that coats the dried nanofibre films with clear polyurethane acrylate resins using UV radiation induced curing. The nanocomposite films thus produced possess excellent tensile properties (161MPa in strength and 9GPa in Young’s Modulus), superior thermal stability (above 300°C), low coefficient of thermal expansion (8-9ppm/K), good light transparency (80%), excellent flexibility and abrasion resistance. These nanocomposite films are aimed to replace the conventional glass substrates made in batches to a polymer based substrates that can be efficiently produced in a roll-to-roll process for the base of the future flexible flat panel displays.