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Made available in DSpace on 2014-06-12T18:02:45Z (GMT). No. of bitstreams: 2 arquivo2425_1.pdf: 3082700 bytes, checksum: 92455b1966dd234a3bd5c8a909cf80c9 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / Universidade Federal de Pernambuco / Nesta dissertação são apresentados resultados experimentais que demonstram a operação de um laser aleatório constituído por um meio fortemente espalhador que contém partículas dopadas com íons de neodímio. As partículas, de formas irregulares e tamanho da ordem de 30 m, foram obtidas após pulverizarmos vidros fluoroindatos dopados com três diferentes concentrações em mol% de Nd3+: 0,5; 1,0; e 3,0. Apresentamos resultados de emissão por conversão ascendente de freqüência envolvendo Nd3+ (processo anti-Stokes). O bombeamento óptico é feito por um laser de corante centrado em 575 nm (pulsos de 10 ns; taxa de repetição de 5 Hz), em ressonância com a transição 4 I9/2 → 2 G7/2 do Nd3+. A emissão do laser aleatório ocorre em 381 nm, sendo mais eficiente na amostra que contém 3% de Nd3+. A emissão anti-Stokes ocorre devido a um processo de transferência de energia entre íons de Nd3+. Os comportamentos espectral e temporal são analisados para a caracterização do laser aleatório

Distributed Temperature Sensing (DTS) has been used in a variety of different applications. Its ability to detect temperature fluctuations along fiber optic lines that stretch for several kilometers has made it a popular topic in various fields of science, engineering, and technology. From pre-fire detection to ecological monitoring, DTS has taken a vital role in scientific research. DTS uses the principle of backscattering by three different spectral components, e.g., Rayleigh scattering, Brillouin scattering, and Raman scattering. Although there have been various improvements to DTS, its slow response time and poor spatial resolution have been hard to overcome. Its repetition rate is low because the pulse must travel the distance of the fiber optic line and return to the detector to record the temperature change along the fiber. A spatial resolution of 7.4 cm with a response time as low as 1 second and a temperature resolution of the 0.196 ℃ is achieved from the current Raman-based DTS system. This research proves that high-spatial resolution can be obtained with the use of a Silicon Avalanche Photodetector with a 1 GHz bandwidth. / MS / Sensors have been used for a variety of purposes such as to measure temperature and strain. Recent literature suggests that distributed temperature sensing (DTS) is a unique approach to measure temperature. DTS allows continuous, real-time measurements along a fiber optic cable. My research focused on improving the DTS system. A high-resolution Raman-based DTS was developed by 1) enhancing its spatial resolution, 2) shortening response time, 3) improving temperature resolution, and 4) extending the sensing distance. By enhancing these parameters, it will provide a wide range of new possibilities to the field of optical fiber sensing.

In this work we investigate how to control the optical and mechanical properties of photonic materials. Firstly we investigated the highly efficient 480 and 800 nm upconversion emissions from Tm3+/Yb3+ co-doped water-free low silica calcium aluminosilicate and tellurite glasses under resonant (976 nm) and anti-Stokes (1064 nm) excitations. As a result of these efficient upconversion processes, luminescent switches with the pump intensity and temperature (the latter under anti-Stokes excitation) have been observed. These switches were explained and discussed using rate equations analysis and saturation effects. Fitting the experimental data point provided the value of the energy transfer parameter related to the 2F5/2, 3H4->2F7/2, 1G4 transition. This switching mechanism could be used in the development of sensors and networks for optical processing and optical communications. Following the study of optical control of mechanical and optical proprieties, we investigated how to use femtosecond laser to write waveguides in Nd3+ doped YAG ceramics by multiple inscriptions of filaments, and if they are resistant to annealing temperatures. We studied two types of structures: “double-filament” and “square-filament” in Nd:YAG samples. We also reported, for the first time to our knowledge, on the fabrication of channel-buried optical waveguides in a Nd:YVO4 crystal by femtosecond laser inscription showing both TM and TE confinements. The optical waveguides obtained in this material emerge as promising candidates for highly efficient self-Raman integrated laser sources. And finalizing, we show the improvement of ultrafast laser written optical waveguides in Yb:YAG ceramics by tailoring the presence of heat accumulation effects. We showed how laser annealing can strongly reduce the concentration of defects and also reduce compressive estresse, leading to an effective 50% reduction in the propagation losses and to more extended and symmetric propagation modes. Micro-luminescence and micro-Raman imaging experiments have been carried out to elucidate the potential application of the obtained waveguides as integrated laser sources as well as to elucidate the waveguiding mechanisms. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho investigamos como controlar as propriedades ópticas e mecânicas de materiais fotônicos. Primeiramente investigamos as emissões por conversão ascendente de energia (CAE) em 480 e 800 nm altamente eficientes de vidros LSCAS (Low Silica Calcium Aluminosilicate) e TL (telurito) co-dopados com Yb3+/Tm3+ sob excitações ressonante (976 nm) e anti-Stokes (1064 nm). Como resultados desses processos eficientes de CAE, foram obtidos switches de luminescência com a intensidade de excitação e a temperatura (este último sob excitação anti-Stokes). Estes switches foram explicados e discutidos usando análises com equações de taxas e efeitos de saturação. Ajustes dos dados experimentais forneceram o valor do parâmetro de transferência de energia associado à transição 2F5/2, 3H4->2F7/2, 1G4. Este mecanismo de switching pode ser usado no desenvolvimento de sensores e redes para processamento óptico e comunicação óptica. Continuando o estudo de controle de propriedades ópticas e mecânicas, investigamos como é possível usar laser de femtosegundo para fabricar guias de ondas em cerâmica de YAG dopada com Nd3+ por meio da inscrição de filamentos, e se eles são resistentes a temperaturas de annealing altas. Estudamos dois tipos de estruturas na amostra de Nd:YAG: “filamento-duplo” e “filamento-quadrado”. Apresentamos também, pela primeira vez para nosso conhecimento, a fabricação de guias de ondas usando inscrição direta com laser de femtosegundo em amostra cristalina de Nd:YVO4, nas quais mostramos confinamentos de ambos os modos TM e TE. Os guias de ondas ópticos obtidos nesse material surgem como candidatos promissores para a fabricação de lasers de auto-Raman integrados com alta eficiência. Por fim, mostramos o aperfeiçoamento de guia de ondas fabricado com lasers de femtosegundos em cerâmica de Yb:YAG controlando a presença de defeitos por meio da acumulação de calor. Mostramos como annealing térmico produzido pelo laser pode fortemente reduzir a concentração de defeitos e o estresse compressivo da rede, resultando numa redução efetiva de 50% das perdas na propagação e modos mais estendidos e simétricos. Experimentos de micro-luminescência e micro-Raman foram utilizados para elucidar a aplicação potencial dos guias de ondas obtidos, como fontes lasers integradas bem como para possibilitar o entendimento das mudanças ocorridas nos guias de ondas.

La peau est un organe qui enveloppe le corps, elle est une barrière naturelle importante et efficace contre différents envahisseurs. Pour le traitement des maladies dermatologiques ainsi que dans l'industrie cosmétique, les applications topiques sur la peau sont largement utilisées. Ainsi beaucoup d'efforts ont été investis dans la recherche sur la peau visant à comprendre l'absorption moléculaire et les mécanismes rendant efficace la pénétration. Cependant, il reste difficile d'obtenir une visualisation 3D de haute résolution combinée à une information chimique- ment spécifique et quantitative dans la recherche sur la peau. La spectroscopie et la microscopie non-linéaire, incluant la fluorescence excitée à 2-photon (TPEF), la diffusion Raman spontanée, la diffusion Raman cohérente anti-Stokes (CARS) et la diffusion Raman stimulée (SRS), sont introduits dans ce travail pour l'identification sans ambiguïté de la morphologique de la peau et la détection de molécules appliquées de façon topique. Plusieurs méthodes quantitatives basées sur la spectroscopie et la microscopie non-linéaire sont proposées pour l'analyse chimique en3D sur la peau artificielle, ex vivo et in vivo sur la peau humaine. De plus, afin de s'adapter aux applications cliniques à venir, un design endoscopique est étudié pour permettre l'imagerie non-linéaires dans les endoscopes flexibles. / Skin is an organ that envelops the entire body, acts as a pivotal, efficient natural barrier to- wards various invaders. For the treatment of major dermatological diseases and in the cosmetic industry, topical applications on skin are widely used, thus many efforts in skin research have been aimed at understanding detailed molecular absorption and efficient penetration mechanisms. However, it remains difficult to obtain high-resolution visualization in 3D together with chemical selectivity and quantification in skin research. Nonlinear spectroscopy and microscopy, including two-photon excited fluorescence (TPEF), spontaneous Raman scattering, coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), are introduced in this work for unambiguous skin morphological identification and topical applied molecules detection. Sev- eral quantitative methods based on nonlinear spectroscopy and microscopy are designed for 3D chemical analysis in reconstructed skin, ex vivo and in vivo on human skin. Furthermore, to adapt to forthcoming clinical applications, an endoscopic design is investigated to bring nonlin- ear imaging in flexible endoscopes.

L’étude expérimentale des processus physico-chimiques de la combustion nécessite de disposer de diagnostics non-intrusifs. Le présent manuscrit reporte le développement du diagnostic laser de mesure de température DRASC (Diffusion Raman anti-Stokes Cohérente) en régime d’impulsions laser femtoseconde pour lequel la configuration à sonde à dérive de fréquence (CPP) a permis d’effectuer des mesures instantanées de température à 1kHz. Un travail à la fois théorique, numérique et expérimental a permis d’extraire la température des spectres DRASC instantanés acquis dans des mélanges air/argon (300-600K) et en flamme prémélangée CH4/Air avec une précision de l’ordre de 1% à 2100 K. La validité de ces résultats est obtenues par des confrontations numérique/expérimental pour différentes grandeurs d’influence. Cette étude permettra dans un proche futur d’appliquer le diagnostic DRASC fs CPP dans des flammes turbulentes représentatives d’écoulements réels observés en combustion aéronautique. / The experimental study of the physico-chemical processes of combustion requires the use of non-intrusive diagnostics. This manuscript reports the development of the CARS (Coherent Anti-Stokes Raman Scattering)) laser diagnostic in the femtosecond pulse regime for which the Chirped Pulse Probe (CPP) configuration enabled instantaneous measurements of temperature at 1kHz. A theoretical, numerical and experimental study allowed highlighting the possibility to measure temperature from the data processing of instantaneous DRASC spectra acquired in air/argon mixtures (300-600K) and in premixed flame CH4/Air with an accuracy of 1% at 2100 K. Validity of these results was obtained from numerical/experimental confrontations for different scalar parameters configurations. This study would enable in the near future the application of the CPP fs CARS diagnostic in turbulent flames representative of real flows observed in aeronautical combustion.

<p>Nonlinear optical microscopy serves as a great tool for biomedical imaging due to its high resolution, deep penetration, inherent three dimensional optical sectioning capabilities and superior performance in scattering media. Conventional nonlinear optical microscopy techniques, e.g. two photon fluorescence and second harmonic generation, are based on detecting a small light signal emitted at a new wavelength that is well separated from the excitation light. However, there are also many other nonlinear processes, such as two-photon absorption and self-phase modulation, that do not generate light at new wavelengths and that have not been extensively explored for imaging. This dissertation extends the accessible mechanisms for contrast to the later nonlinear optical processes by combining femtosecond laser pulse shaping and homodyne detection. We developed a rapid pulse shaper with a relatively simple and compact instrument design that modifies the spectrum of individual laser pulses from an 80 MHz mode-locked laser. The pulse shaper enables simultaneous two-photon absorption and self-phase modulation imaging of various nanoparticles in-vitro with high sensitivity. We also applied this imaging technique to study the nonlinear optical response in graphene. Because our technology detects the nonlinear signature encoded within the laser pulse itself, we achieve intrinsic contrast of biological and non-biological samples in highly scattering media. These capabilities have significant implications in biomedical imaging and nanophotonics.</p> / Dissertation

<p>Conventional rocket propellants such as monomethyl hydrazine (MMH) and hydrazine have been used for decades due to their high specific impulse and performance. However, interest in greener alternatives, including HAN or HAN-based propellants, has grown due to high levels of toxicity and difficulties in the handling and storage of conventional fuels. Included among potential propellants are monopropellants nitromethane (NM) and isopropyl nitrate (IPN) and their blends. Though large-scale investigations on the ignition and combustion of these fuels have been done, the ignition and combustion processes of these monopropellant fuels are still not well understood. Droplet studies have been traditionally and extensively employed to decipher the influence of ambient conditions and fuel properties on ignition and combustion of different fuels. These fundamental studies allow for the isolation of different factors such as ambient temperature and initial droplet size among others, to provide a deeper understanding of their effects in overall spray combustion.</p> <p> </p> <p>The research described here seeks to add to the knowledge on the ignition and combustion processes of NM and IPN through single droplet ignition and combustion studies. To this end, the first effort has been to establish a suitable method of studying the ignition and combustion of droplets in conditions similar to those in practical systems. Droplet ignition delay measurements for NM and IPN droplets have also been conducted, and the influence of ambient temperature and droplet size has been studied. The double flame structures of NM and IPN, representative of hybrid combustion, have also been observed. In addition, the applicability of the hybrid combustion model, developed to predict mass burning rates for hypergolic fuels exhibiting hybrid burning including MMH, UDMH and hydrazine, has been assessed. Lastly, the ability of the quasi-steady droplet ignition model to predict ignition delays of IPN and NM monopropellant droplets is also discussed.</p>

Lung carcinoma is the most prevalent type of cancer in the world, considered to be a relentlessly progressive disease, with dismal mortality rates to patients. Recent advances in targeted therapy hold the premise for the delivery of better, more effective treatments to lung cancer patients, that could significantly enhance their survival rates. Optimizing care delivery through targeted therapies requires the ability to effectively identify and diagnose lung cancer along with identifying the lung cancer cell type specific to each patient, \textit{small cell carcinoma}, \textit{adenocarcinoma}, or \textit{squamous cell carcinoma}. Label free optical imaging techniques such as the \textit{Coherent anti-stokes Raman Scattering microscopy} have the potential to provide physicians with minimally invasive access to lung tumor sites, and thus allow for better cancer diagnosis and sub-typing. To maximize the benefits of such novel imaging techniques in enhancing cancer treatment, the development of new data analysis methods that can rapidly and accurately analyze the new types of data provided through them is essential. Recent studies have gone a long way to achieving those goals but still face some significant bottlenecks hindering the ability to fully exploit the diagnostic potential of CARS images, namely, the streamlining of the diagnosis process was hindered by the lack of ability to automatically detect cancer cells, and the inability to reliably classify them into their respective cell types. More specifically, data analysis methods have thus far been incapable of correctly identifying and differentiating the different non-small cel lung carcinoma cell types, a stringent requirement for optimal therapy delivery. In this study we have addressed the two bottlenecks named above, through designing an image processing framework that is capable of, automatically and accuratly, detecting cancer cells in two and three dimensional CARS images. Moreover, we built upon this capability with a new approach at analyzing the segmented data, that provided significant information about the cancerous tissue and ultimately allowed for the automatic differential classification of non-small cell lung carcinoma cell types, with superb accuracies.

Aseptic loosening of artificial joints is caused by an osteolytic reaction to wear debris mediated by macrophages and other cells. Imaging these wear particles within cells can be a key process in understanding particle-cell interactions. However, the compounds used in surgical implants are not easily visualised as no tagging molecule can be added without altering the properties of the material. We were interested in using a label free optical technique known as coherent anti-Stokes Raman scattering spectroscopy (CARS) to image these particles in cells. In this thesis we studied how to use CARS to image physiologically relevant wear particles within cells. We characterised the responses from our CARS system and found them to be in good agreement to the Raman spectra we obtained for the same materials. We showed that the forward scattered CARS signal was consistently larger than the backwards scattered signal for the same size particles, and also generated a larger contrast, especially between sub-micron sized particles and the non-resonant background. Wear particles of polyethylene isolated from a pin-on-plate wear simulator were shown to be in a similar size range to those retrieved from revision tissue. When incubated in our model macrophage cells we were able to image areas of CARS signal that indicated the location of these particles in the cell. Furthermore, using multiple CARS images taken at different Raman resonances we were able to distinguish between three different polymeric compounds added to cells, showing the specificity of the technique. The inherent 3D sectioning capabilities of multiphoton microscopy were used to generate projected images of the cells and contents, as well as estimating the particle loads within cells. These results show that CARS could be an important tool in imaging intra-cellular polyethylene and characterising the interactions of wear particles with cells and the surrounding tissue.