Un nombre croissant d’applications telles que le micro-usinage ou le diagnostique de composants électroniques nécessitent de fortes puissances moyennes dans différentes gammes de longueurs d’onde (infra-rouge à 1030 nm, vert à 515 nm ou ultra-violet à 343 nm). Ces fortes puissances moyennes lasers ne sont généralement atteignables qu’à l’aide d’architecture laser de type MOPA (Master Oscillator Power Amplifier). C’est dans cette optique que la société Eolite Systems veut développer ses propres oscillateurs car elle maitrise déjà l’amplification à l’aide de fibres de type barreau à large aire modale. Le développement d’oscillateurs picosecondes de fortes puissances moyennes est ainsi une brique essentielle dans la chaîne d’amplification globale. Dans le cadre d’un contrat CIFRE entre Eolite Systems et le Laboratoire Onde et Matière d’Aquitaine de l’Universitéde Bordeaux 1, nous avons développé différents laser dont la puissance moyenne est supérieure à 10W, à une cadence de 74 MHz. La durée des impulsions générées s’étend de 20 ps à 130 fs. Le fonctionnement de ces différents lasers repose sur l’utilisation de la rotation non-linéaire de polarisation dans la fibre optique qui, dans le régime de fonctionnement à dispersion normale, permet d’atteindre le verrouillage en phase des modes et ainsi la génération d’impulsions d’énergie de l’ordre de 150nJ. Nous avons développé un code de simulation numérique afin de rendre compte de la dynamique des impulsions dans la cavité. Les résultats obtenus à l’aide de ce code sont en bon accord avec ceux obtenus lors des différentes expériences. / A growing number of applications such as micro-machining of electronical components need high average power in a various range of wavelengths (infrared at 1030 nm, green at 515 nm and ultravioletat 343 nm). These high average power lasers are generally design using a MOPA (MasterOscillator Power Amplifier) scheme. Following this idea, Eolite systems wants to develop its own oscillators since it already masters the different difficulties when trying to reach high average power,especially by using rod-type fibers with a large mode area. The development of high power picosecondfiber oscillators is a essential piece in the global amplification scheme. In the frame of a CIFRE contract between Eolite Systems and the Laboratoire Onde et Matière d’Aquitaine of the Universitéde Bordeaux 1 we have developed different laser oscillators with an average power of more than10 W at a repetition rate of 74 MHz. The pulse duration generated is ranging from 20 ps down to130 fs. The pulsed regime was initiated using non-linear polarization evolution in the fiber and in anormal dispersion laser cavity. This lead to the generation of pulse energies in the range of 150 nJ for the different architectures. We also developed a numerical code in ordre to fully understand the influence of the different elements in the laser cavity. The results are in good agreement with those obtained with the experimental setup.

Le travail présenté dans cette thèse, s’inscrit dans le domaine d'étude de l'interaction des rayonnements ionisants avec les liquides polaires. Bénéficiant de l’accélérateur d'électrons picoseconde ELYSE, les études ont été menées en utilisant les techniques de la radiolyse impulsionnelle associées à la spectrophotométrie d’absorption résolue en temps dans le domaine de la picoseconde. Ce travail est réparti sur deux chapitres distincts. Le premier aborde l’étude la variation temporelle du rendement radiolytique de l’électron solvaté dans l'eau et les alcools simples. Grâce au système de détection original monté sur l’accélérateur ELYSE, composé d’une lampe flash spécialement conçue pour cette détection et d’une streak-camera utilisée pour la première fois en spectroscopie d’absorption, il a été possible d'enregistrer la totalité du déclin du rendement radiolytique de l’électron solvaté d’une façon continue dans un intervalle de temps allant de la dizaine de picoseconde à quelques centaines de nanoseconde. La capture de l’électron solvaté par le méthylviologène, a été mise à profit pour réévaluer le coefficient d’extinction molaire du spectre d'absorption de l’électron solvaté dans l’eau et l’éthanol à partir des points isobestiques qui apparaissent à l'intersection des spectres d'absorption de l’électron solvaté qui disparaît et du méthylviologène qui se forme au cours de la réaction.Le deuxième chapitre est consacré à l’étude des carbonates organiques liquides, tels que le diméthyle carbonate (DMC), le diéthyle carbonate (DEC) et le propylène carbonate (PC). Cette famille de carbonate qui n’a jamais été étudiée auparavant par radiolyse pulsée, entre dans la composition des électrolytes des batteries notamment au lithium. Les études ont été focalisées sur le PC au vu de ces caractéristiques physico-chimiques, notamment sa constante diélectrique très élevée (64) et son très fort moment dipolaire de 4,9 D. Les premiers résultats ont été obtenus d’abord sur des solutions aqueuses contenant du propylène carbonate afin d'observer les réactions de réduction et d'oxydation du PC par les espèces radiolytiques de l'eau (électron solvaté et radicaux OH). Puis après l’identification (spectrale et cinétique) de l’espèce formée par interaction avec le radical OH comme étant le radical PC• résultant de l'abstraction d'un H de la molécule de PC et l’espèce formée par interaction avec l’électron aqueux comme étant l'anion PC-, d’autres mesures ont été effectuées dans le liquide pur ainsi qu’en présence de certains intercepteurs d’électrons (biphényle, anthracène, naphtalène). Elles ont permis d'accéder au rendement radiolytique de PC- ainsi qu'à l'évaluation de son potentiel redox. Les premiers résultats sur le DEC et le DMC sont aussi exposés dans cette partie, portant dans un premier lieu sur le solvant pur et puis en présence de biphényle. / This work is part of the study area of the interaction of radiation with polar liquids. Using the picosecond electron accelerator ELYSE, studies were conducted using the techniques of pulse radiolysis combined with absorption spectrophotometry Time-resolved in the field of a picosecond.This work is divided into two separate chapters. The first study addresses the temporal variation of the radiolytic yield of solvated electron in water and simple alcohols. Due to original detection system mounted on the accelerator ELYSE, composed of a flash lamp specifically designed for the detection and a streak-camera used for the first time in absorption spectroscopy, it was possible to record the time-dependent radiolytic yields of the solvated electron from ten picoseconds to a few hundred nanoseconds. The scavenging of the electron solvated by methyl viologen, was utilized to reevaluate the molar extinction coefficient of the absorption spectrum of solvated electron in water and ethanol from isobestic points which corresponds to the intersection of the absorption spectra of solvated electron which disappears and methyl viologen which is formed during the reaction.The second chapter is devoted to the study of liquid organic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). This family of carbonate wich compose the electrolytes lithium batteries, has never been investigated by pulse radiolysis. The studies were focused on the PC in the light of these physicochemical characteristics, including its very high dielectric constant (64) and its strong dipole moment of 4.9 D. The first results were obtained on aqueous solutions containing propylene carbonate to observe the reactions of reduction and oxidation of PC by radiolytic species of water (solvated electron and OH radicals). Then, after the identification (spectral and kinetic) of the species formed by interaction with the OH radical as the PC• radical resulting from the abstraction of a H from the molecule of PC and the species formed by the interaction with electron as the anion aqueous PC-, other measurements were made in the pure liquid and in the presence of some electron interceptors (biphenyl, anthracene, naphthalene). They give access to the radiolytic yield of PC- and the evaluation of its redox potential. The first results of the DEC and the DMC are also outlined in this section, the pure solvent and then in the presence of biphenyl.

O desenvolvimento da Odontologia Restauradora culminou com a era das restaurações estéticas adesivas e da intervenção minimamente invasiva, para as quais técnicas inovadoras e materiais de última geração vêm sendo constantemente introduzidos. As técnicas conservadoras visam não somente a remoção do substrato dental cariado, mas também o preparo das paredes da cavidade para a realização da restauração adesiva. Este estudo visou avaliar a possibilidade de introdução dos lasers de pulsos ultracurtos na Odontologia Restauradora, com o intuito de suprir os requisitos básicos para a realização de uma restauração conservadora adequada. A intenção foi de manter os benefícios já conhecidos relacionados à remoção seletiva de cárie com os lasers de alta potência, bem como superar as desvantagens relacionadas às fontes lasers atualmente disponíveis para este fim, como aumento excessivo de temperatura e adesão prejudicada da superfície irradiada à resina composta. Para a melhor avaliação da interação entre os lasers de pulsos ultracurtos e o substrato dental, os experimentos foram realizados em três fases. A Fase 1 visou avaliar o efeito de diferentes comprimentos de onda (355 nm, 532 nm, 1045 nm e 1064 nm), durações de pulso (pico e femtossegundos) e protocolos de irradiação (velocidade de escaneamento da superfície, espessura do espécime, método de refrigeração e taxa de repetição de pulso) em esmalte e dentina. Para a Fase 2, os parâmetros de irradiação que apresentaram resultados mais favoráveis na Fase 1 foram analisados para relacionar o aumento de temperatura com a taxa de ablação e a eficiência de ablação para cada parâmetro. A Fase 3 teve como objetivo analisar a interface adesiva e os valores de microtração da dentina irradiada com os parâmetros selecionados e estudados na Fase 2, utilizando sistemas adesivos do tipo condicione e lave e autocondicionante com diferentes protocolos de adesão (Clearfil SE Bond com e sem Primer, Adper Single Bond com e sem condicionamento ácido). Os resultados obtidos na Fase 1 indicam que a dentina e o esmalte irradiados com lasers de femtossegundos de 1045 nm e picossegundos de 1064 nm apresentam superfície rugosa livre de carbonização. Os protocolos de irradiação selecionados mostram que a irradiação deve ser conduzida com maior velocidade de escaneamento da superfície, e não há necessidade de refrigeração durante a irradiação. Todos os parâmetros utilizados promoveram ablação seletiva do substrato dental, e apresentaram maior taxa de ablação para dentina que para esmalte. A Fase 2 permitiu observar que todos os parâmetros de irradiação selecionados não provocaram aumento de temperatura maior que 6,1 ºC para esmalte e 4,6 ºC para dentina, quando o aumento de temperatura foi aferido no lado oposto ao irradiado, em espécimes de 1 mm de espessura e sem refrigeração. Exceção foi observada para a maior potência do laser de picossegundos, para a qual a temperatura aumentou até 12 ºC em esmalte e 15 ºC em dentina. Os valores obtidos no ensaio de microtração variaram de acordo com os parâmetros de irradiação e o sistema adesivo. A adesão à dentina irradiada com lasers de pulsos ultracurtos apresentou valores de resistência adesiva semelhantes ou significantemente maiores que os obtidos nos grupos controle, para todos os parâmetros de irradiação selecionados. Os resultados obtidos neste estudo indicam que os lasers de pulsos ultracurtos apresentaram resultados favoráveis para o preparo cavitário em esmalte e dentina em relação à morfologia produzida na superfície e ao aumento de temperatura provocado durante a irradiação. A resistência adesiva à dentina irradiada foi semelhante, ou mesmo significantemente maior que a obtida nos grupos controle. Portanto, os lasers de pulsos ultracurtos são considerados uma técnica promissora para a realização de intervenção minimamente invasiva com lasers de alta potência. / The development of restorative dentistry has reached the era of esthetic adhesive restorations and minimally invasive approach, for which innovative techniques and advanced materials are constantly introduced. Conservative techniques aim not only to remove carious dental substrate, but also to prepare cavity surfaces for adhesive restoration. The main objective of this study was to evaluate the possibility of introducing ultra-short pulsed lasers in Restorative Dentistry, in attempt to fulfill the basic requirements of adequate conservative restoration, by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages related to current laser sources available for this purpose, such as temperature increase and damaged adhesion to resin composite. In order to better evaluate the interaction between ultra-short pulsed lasers and dental substrates, experimental procedures were divided in three phases. Phase 1 aimed to evaluate the effect of different wavelengths (355 nm, 532 nm, 1,045 nm, and 1,064 nm), pulse durations (pico and femtoseconds) and irradiation protocols (surface scanning speed, sample thickness, cooling method, pulse repetition rate) on enamel and dentin. For Phase 2, laser parameters with most favorable results in Phase 1 were evaluated to relate temperature increase to ablation rate or ablation efficiency. Phase 3 aimed to analyze adhesive interface and microtensile bond strength to dentin irradiated with the selected parameters by using etch-and-rinse and self-etch adhesive systems with different bonding protocols (Clearfil SE Bond with and without Primer, Adper Single Bond with and without acid etching). The results of Phase 1 indicate that dentin and enamel irradiated with 1,045-nm fs-laser and 1,064-nm ps-laser present a rough surface without carbonization. Irradiation should be conducted with higher scanning speed, and no additional cooling during irradiation was necessary. All parameters provided selective tissue ablation, with higher ablations rate for dentin than enamel. Phase 2 indicated that all parameters tested provoked temperature increase of up to 6.1 ºC for enamel and 4.6 ºC for dentin, when temperature increase was measured at the back side of 1-mm thick samples without cooling during irradiation, except for higher power for ps-laser, for which temperature increased up to 12 ºC for enamel and 15 ºC for dentin. Microtensile bond strength values varied according to laser parameters and adhesive systems used. Adhesion to dentin irradiated with ultra-short pulsed lasers resulted in similar or significantly higher bond strength values than control groups, for all laser parameters analyzed. Based on the results of this study, ultra-short pulsed lasers presented favorable results for cavity preparation in dentin and enamel regarding surface morphology and temperature increase. Adhesion to irradiated dentin was either similar or superior to traditional techniques. Thus, ultra-short pulsed lasers are considered a promising technique for the promotion of laser-supported minimally invasive approach.

Microbial resistance to the current available antibiotics is considered a global health problem, especially for the Multi-Drug Resistant pathogens (MDR) including methicillin resistant Staphylococcus aureus. Recently nanoparticles (NPs) have been involved in variety of antimicrobial applications due to their unique properties of antibacterial effects. However, the molecular mechanisms behind their antibacterial activity are still not fully understood. In this study, we produced silver Ag NPs (average size 27 nm) and silver-Titanium Ag-TiO2 NPs (average size 47 nm) using picosecond laser ablation. Our results showed that both laser NPs had obvious size-dependent antibacterial activity. The laser Ag NPs with a size of 19 nm and Ag-TiO2 NPs with a size 20 nm presented the highest bactericidal effect. The laser generated Ag and Ag-TiO2 NPs with concentrations 20, 30, 40, and 50 Î1⁄4g/ml showed strong antibacterial effect against three bacterial strains: E. coli, P. aeruginosa, and S. aureus, and induced the generation of reactive oxygen species (ROS), lead to cell membrane interruption, lipid peroxidation, DNA damages, glutathione depletion and the eventual cell death. Both types of laser NPs at two concentrations (2.5 and 20 Î1⁄4g/ml) showed low cytotoxicity to the in vitro cultured five types of human cells originated from the lung (A549), kidney (HEK293), Liver (HepG2), skin (HDFc) and blood vessel cells (hCAECs). The antibacterial activity of the laser generated Ag and Ag-TiO2 NPs had lasted for over one year depending on the degree of air exposure and storage conditions. Frequent air exposure increased particle oxidation and reduced the antibacterial durability of the laser generated Ag NPs. The laser generated Ag NPs had lower antibacterial activity when stored in cold compared to that stored at room temperature. The antibacterial activity of laser generated Ag and Ag-TiO2 NPs were also compared with four types of commercial based-silver wound dressings (Acticoat TM, Aquacel® Ag, Contreet ®Foam, and Urgotul® SSD) against E. coli to inform future application in this area. In conclusion, laser generated Ag and Ag-TiO2 NPs have strong bactericidal effect and low toxicity to human cells which could be a type of promising antibacterial agents for future hygiene and medical applications.

O desenvolvimento da Odontologia Restauradora culminou com a era das restaurações estéticas adesivas e da intervenção minimamente invasiva, para as quais técnicas inovadoras e materiais de última geração vêm sendo constantemente introduzidos. As técnicas conservadoras visam não somente a remoção do substrato dental cariado, mas também o preparo das paredes da cavidade para a realização da restauração adesiva. Este estudo visou avaliar a possibilidade de introdução dos lasers de pulsos ultracurtos na Odontologia Restauradora, com o intuito de suprir os requisitos básicos para a realização de uma restauração conservadora adequada. A intenção foi de manter os benefícios já conhecidos relacionados à remoção seletiva de cárie com os lasers de alta potência, bem como superar as desvantagens relacionadas às fontes lasers atualmente disponíveis para este fim, como aumento excessivo de temperatura e adesão prejudicada da superfície irradiada à resina composta. Para a melhor avaliação da interação entre os lasers de pulsos ultracurtos e o substrato dental, os experimentos foram realizados em três fases. A Fase 1 visou avaliar o efeito de diferentes comprimentos de onda (355 nm, 532 nm, 1045 nm e 1064 nm), durações de pulso (pico e femtossegundos) e protocolos de irradiação (velocidade de escaneamento da superfície, espessura do espécime, método de refrigeração e taxa de repetição de pulso) em esmalte e dentina. Para a Fase 2, os parâmetros de irradiação que apresentaram resultados mais favoráveis na Fase 1 foram analisados para relacionar o aumento de temperatura com a taxa de ablação e a eficiência de ablação para cada parâmetro. A Fase 3 teve como objetivo analisar a interface adesiva e os valores de microtração da dentina irradiada com os parâmetros selecionados e estudados na Fase 2, utilizando sistemas adesivos do tipo condicione e lave e autocondicionante com diferentes protocolos de adesão (Clearfil SE Bond com e sem Primer, Adper Single Bond com e sem condicionamento ácido). Os resultados obtidos na Fase 1 indicam que a dentina e o esmalte irradiados com lasers de femtossegundos de 1045 nm e picossegundos de 1064 nm apresentam superfície rugosa livre de carbonização. Os protocolos de irradiação selecionados mostram que a irradiação deve ser conduzida com maior velocidade de escaneamento da superfície, e não há necessidade de refrigeração durante a irradiação. Todos os parâmetros utilizados promoveram ablação seletiva do substrato dental, e apresentaram maior taxa de ablação para dentina que para esmalte. A Fase 2 permitiu observar que todos os parâmetros de irradiação selecionados não provocaram aumento de temperatura maior que 6,1 ºC para esmalte e 4,6 ºC para dentina, quando o aumento de temperatura foi aferido no lado oposto ao irradiado, em espécimes de 1 mm de espessura e sem refrigeração. Exceção foi observada para a maior potência do laser de picossegundos, para a qual a temperatura aumentou até 12 ºC em esmalte e 15 ºC em dentina. Os valores obtidos no ensaio de microtração variaram de acordo com os parâmetros de irradiação e o sistema adesivo. A adesão à dentina irradiada com lasers de pulsos ultracurtos apresentou valores de resistência adesiva semelhantes ou significantemente maiores que os obtidos nos grupos controle, para todos os parâmetros de irradiação selecionados. Os resultados obtidos neste estudo indicam que os lasers de pulsos ultracurtos apresentaram resultados favoráveis para o preparo cavitário em esmalte e dentina em relação à morfologia produzida na superfície e ao aumento de temperatura provocado durante a irradiação. A resistência adesiva à dentina irradiada foi semelhante, ou mesmo significantemente maior que a obtida nos grupos controle. Portanto, os lasers de pulsos ultracurtos são considerados uma técnica promissora para a realização de intervenção minimamente invasiva com lasers de alta potência. / The development of restorative dentistry has reached the era of esthetic adhesive restorations and minimally invasive approach, for which innovative techniques and advanced materials are constantly introduced. Conservative techniques aim not only to remove carious dental substrate, but also to prepare cavity surfaces for adhesive restoration. The main objective of this study was to evaluate the possibility of introducing ultra-short pulsed lasers in Restorative Dentistry, in attempt to fulfill the basic requirements of adequate conservative restoration, by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages related to current laser sources available for this purpose, such as temperature increase and damaged adhesion to resin composite. In order to better evaluate the interaction between ultra-short pulsed lasers and dental substrates, experimental procedures were divided in three phases. Phase 1 aimed to evaluate the effect of different wavelengths (355 nm, 532 nm, 1,045 nm, and 1,064 nm), pulse durations (pico and femtoseconds) and irradiation protocols (surface scanning speed, sample thickness, cooling method, pulse repetition rate) on enamel and dentin. For Phase 2, laser parameters with most favorable results in Phase 1 were evaluated to relate temperature increase to ablation rate or ablation efficiency. Phase 3 aimed to analyze adhesive interface and microtensile bond strength to dentin irradiated with the selected parameters by using etch-and-rinse and self-etch adhesive systems with different bonding protocols (Clearfil SE Bond with and without Primer, Adper Single Bond with and without acid etching). The results of Phase 1 indicate that dentin and enamel irradiated with 1,045-nm fs-laser and 1,064-nm ps-laser present a rough surface without carbonization. Irradiation should be conducted with higher scanning speed, and no additional cooling during irradiation was necessary. All parameters provided selective tissue ablation, with higher ablations rate for dentin than enamel. Phase 2 indicated that all parameters tested provoked temperature increase of up to 6.1 ºC for enamel and 4.6 ºC for dentin, when temperature increase was measured at the back side of 1-mm thick samples without cooling during irradiation, except for higher power for ps-laser, for which temperature increased up to 12 ºC for enamel and 15 ºC for dentin. Microtensile bond strength values varied according to laser parameters and adhesive systems used. Adhesion to dentin irradiated with ultra-short pulsed lasers resulted in similar or significantly higher bond strength values than control groups, for all laser parameters analyzed. Based on the results of this study, ultra-short pulsed lasers presented favorable results for cavity preparation in dentin and enamel regarding surface morphology and temperature increase. Adhesion to irradiated dentin was either similar or superior to traditional techniques. Thus, ultra-short pulsed lasers are considered a promising technique for the promotion of laser-supported minimally invasive approach.