Essa dissertação de mestrado é dedicada ao estudo, desenvolvimento e caracterização da resposta dinâmica de transdutores de deformação mecânica e de temperatura baseados em grades de Bragg inscritas em fibras ópticas (FBG). Como não se encontram referências diretas na literatura da área sobre a caracterização da resposta dinâmica de sensores de temperatura e deformação a FBG, percebeu-se a importância de realizar um trabalho com ênfase nesse aspecto. O desenvolvimento de transdutores FBG de deformação e de temperatura com resposta dinâmica rápida é de grande importância, já que as grades de Bragg são afetadas, de maneira intrínseca, simultaneamente pelas duas grandezas e que existe um amplo leque de aplicações em que uma delas, ou ambas, variam rapidamente. Nesses casos, diferenças em termos de tempos de resposta entre os sensores utilizados para medição de deformação e os usados para compensação de temperatura podem acarretar em erros significativos nas medidas, o que pode até inviabilizar o uso dos sensores a grades de Bragg em tais aplicações. Este trabalho apresenta um compêndio da teoria da tecnologia das FBG para aplicação em sensores ópticos de deformação e de temperatura. Buscando contribuir para o domínio das técnicas de fabricação de sensores a FBG no Brasil, também são apresentados os resultados experimentais da utilização de grades de Bragg inscritas em fibras ópticas fabricadas no laboratório da Subdivisão de Sensores (EFO-S), da Divisão de Fotônica do Instituto de Estudos Avançados (IEAv) do Comando-Geral de Tecnologia Aeroespacial (CTA), como elementos sensores em ensaios de deformação e de temperatura. Os resultados de caracterizações, tanto de FBG produzidas no IEAv quanto de sensores de deformação e de temperatura comerciais das empresas Micron Optics e Fiber Sensing, foram obtidos por meio de três interrogadores diferentes e são comparados e apresentados neste trabalho. Em uma análise realizada dos resultados apresentados de sensores a FBG, utilizados para medição de temperatura e de deformação mecânica em alguns arranjos experimentais, foram observados comportamentos dinâmicos não lineares que apresentam-se como um obstáculos a serem vencidos para a viabilização da aplicação desta técnica à medição desses parâmetros quando os mesmos são rapidamente variáveis. / This dissertation is devoted to the study, development and characterization of the dynamic response of mechanical strain and temperature transducers based on Bragg gratings inscribed in optical fibers (FBG). Since there are no direct references in the literature on the characterization of the dynamic response of FBG based temperature and strain sensors, it was realized the importance of conducting a study with emphasis on this aspect. The development of FBG strain and temperature transducers with fast dynamic response is of great importance, since the Bragg gratings are intrinsically and simultaneously affected by the two quantities and there is a wide range of applications in which one or both quantities vary rapidly. In such cases, differences in response times between the sensors used for measurement of strain and used for temperature compensation can result in significant errors, which may even preclude the use of FBG sensors in such applications. This work presents a compendium of the theory related to FBG technology for application in optical strain and temperature sensors. Seeking to master the techniques of manufacture of the FBG sensors in Brazil, experimental results from the use of FBG manufactured in the laboratory of Sensors Subdivision (EFO-S), of Photonics Division of Institute of Advanced Studies (IEAv) of General Command for Aerospace Technology (CTA) as sensor elements in strain and temperature trials are also presented. The results of both characterizations, of FBG produced in IEAv and strain and temperature commercial sensors, produced by Micron Optics and Fiber Sensing manufacturers, were obtained from three different interrogators and are compared and presented in this paper. In an analysis of the results of FBG sensors used for measuring temperature and mechanical deformation in some experimental arrangements, nonlinear dynamic behaviors were observed. Such behaviors present themselves as an obstacle to be overcome to achieve the feasibility of applying this technique to measurement of these parameters when they are rapidly changing.

The different topics covered in this thesis include photosensitivity in germanosilicate fibers/glasses and application of fiber Bragg grating sensors in simultaneous strain and temperature discrimination. Fiber Bragg Gratings are wavelength dispersive refractive index structures manufactured through ultra-violet (UV) exposure of optical fibers. Their applications range from wavelength division multiplexing filters, dispersion compensators and fiber laser resonators for telecommunication applications to different types of point or distributive sensors for a variety of applications. One aim of this thesis has been to understand the mechanism of photosensitivity in germanosilicate fibers/preforms. Studies undertaken in this part of the thesis include thermal dynamics of Fiber Bragg Gratings and nano-indentation on ultra-violet irradiated germanosilicate glass preforms. An interesting, periodic appearance of a new peak has been observed in the reflected spectrum of Bragg grating inscribed in a germanosilicate fiber during thermal treatment. The new peak occurs on the longer wavelength side of the spectrum during heating and on the shorter wavelength side during cooling, following an identical reverse dynamics. A commercial grating with 99.9% reflectivity also shows a similar decay dynamics. The observed temperature induced distortion in refractive index modulation profile has been understood in the light of compaction-densification model. It is proposed that during the fabrication process of a grating, the modulation in the thermal expansion coefficient brought about by the interference fringes results in a non-uniform expansion throughout the grating length which in turn results in the distortion of the refractive index profile with increase/decrease in temperature. Since the reflection spectrum of a grating can be approximated as the Fourier transform of the refractive index profile, any distortion in the index profile results in the observed anomalous behaviour in the reflection spectrum. Nano-indentation studies have been performed to measure the changes in mechanical properties of a glass preform subjected to different levels of ultra-violet exposure. The results reveal that short term exposure leads to an appreciable increase in the Young’s modulus suggesting the densification of the glass, confirming the compaction-densification model. However, on prolonged exposure, the Young’s modulus decreases, which provides the first direct evidence of dilation in the glass leading into the Type IIA regime. The present results rule out the hypothesis that continued exposure leads to an irreversible compaction and prove that index modulation regimes are intrinsic to the glass matrix. In the second part of the thesis, three different schemes have been proposed for the use of Fiber Bragg Gratings as strain-temperature discriminating sensors: (a) The first method is based on the measurement of the different characteristic wavelength shifts of two types of gratings. Strain and temperature sensitivities of a Type I Bragg grating (G1) in germania doped silica fiber, fabricated under normal conditions, and zero strain, are compared with that of a Bragg grating inscribed under pre-strained condition (G2). Experimental results show that both, strain and temperature sensitivities of G1 and that of G2 are different. Based on this study, we have proposed an approach which enables simultaneous discrimination of axial strain and temperature. (b) In the second method, a single sensing element has been used to encode strain and temperature into an additional parameter other than the wavelength shift. The thermal out-diffusion of germanium from the core of a photosensitive fiber under elevated temperature is exploited to form a Fabry-Perot filter with a single Fiber Bragg Grating. The filter is fabricated using the standard phase-mask technique and one-time exposure. Energy Dispersive X-Ray analysis is used to measure the out-diffusion. The filter is used as a sensor for simultaneous measurement and discrimination of strain and temperature. The proposed technique, where a single grating is used to discriminate the parameters, provides a large advantage over other existing methods. (c) In the third method, a compact design based on cross-wire arrangement of Fiber Bragg Gratings having identical Bragg resonance and different reflectivity is proposed for simultaneously sensing strain (uniaxial) and temperature. Two gratings are assembled orthogonal to each other on an aluminium base. The cross-wire design allows the two sensors to experience the same temperature but different strain. The gratings are identified by their respective reflectivity and, strain and temperature are resolved from the shift in Bragg wavelength. The proposed design exploits the fact that strain is a vector and temperature is a scalar parameter. This sensor has wide industrial application in discriminating strain from temperature effects.

The research that is presented in this thesis can be divided into two major parts. The first part concerns longitudinally pumped, bulk Er-Yb lasers. In these lasers, the main limitation is the thermal shortcomings of the phosphate glass host material. From the laser experiments and the spectroscopic measurements on crystalline host materials, as well as an investigation to bring further light to the physical background of the involved dynamics, the thesis presents some novel results that contribute to the search for a crystalline replacement. The second part concerns novel laser concepts applied to Yb-doped double tungstate lasers. Different crystal orientations are investigated, such as an athermal orientation for reduced thermal lensing and a conical refraction orientation for complete polarization tuning. Furthermore, the introduction of volume Bragg gratings in the cavity enables wide spectral tuning ranges and extremely low quantum defects. Regarding the first part, the main results are the achievement of 15 % slope efficiency in a monolithic, continuous-wave Yb:GdCOB laser and the achievement of Q-switching of the same laser. The Q-switched pulse durations were around 5-6 ns and the Q-switched slope efficiency was 11.6 %. For both lasers, a maximum output power of 90 mW was obtained, which is close to ordinary glass lasers under similar conditions. A spectroscopic investigation into the Er,Yb-codoped double tungstates was also performed and the results have enabled mathematical modeling of the fluorescence dynamics in these materials. Finally, the temperature dependence of the dynamics in Er,Yb:YAG was studied and the results have given some insight into the physical background of the mechanisms involved. Regarding the second part, different end-pumped Yb:KReW laser cavities were constructed to demonstrate the different concepts. With a laser crystal cut for propagation along the athermal direction at 17º angle clockwise from the dielectric direction Nm, the thermal lens could be reduced by 50 %. In these experiments the maximum output power was 4 W at 60 % slope efficiency. In another cavity incorporating a volume Bragg grating in a retroreflector set-up, the wavelength could be continuously tuned between 997 - 1050 nm. The spectral bandwidth was 10 GHz and the peak output power was 3 W. The same output power could also be obtained at 1063 nm with the grating positioned as an output coupler instead. If, on the other hand, the grating was positioned as an input coupler, 3.6 W output power at 998 nm was obtained at a quantum defect of only 1.6 %. Furthermore, using a crystal oriented for propagation along an optic axis, internal conical refraction could be used to establish arbitrary control of the polarization direction as well as the extinction ratio. Even unpolarized light could be enforced despite the highly anisotropic medium. With this configuration, the maximum output power was 8.6 W at 60 % slope efficiency which equals the performance of a reference crystal with standard orientation. The completely novel concepts of laser tuning with Bragg grating retroreflectors, of low quantum defect through Bragg grating input couplers and of polarization tuning by internal conical refraction can all easily be applied to several other laser materials as well. / QC 20100713

In this thesis, we explore the four aspects of fiber Bragg grating sensors: mathematical modeling of Fiber Bragg Grating response/spectral characteristics, fabrication using phase mask, application and interrogation. Applications of fiber Bragg gratings, also known as in-fiber gratings, with emphasis on their sensing capabilities, interrogation of an array of sensors and their performance in structural health monitoring scenario are documented. First, we study the process of photosensitivity phenomenon in glasses, in particular GeO2:SiO2 glasses. For mathematical modeling we consider the 1-D refractive index profile along the propagation axis of an optical fiber drawn from the preform of such glasses. These 1-D index structures exhibit a bandgap for propagation along the fiber axis. We show how the bandgap is dependent on the two structural parameters: index periodicity and effective refractive index. The mathematical model provides the characteristics of three sensor parameters -resonance wavelength also known as the Bragg wavelength (λB ), filter bandwidth (ΔλB ), and reflectivity (R). We show that the evolution of the index structure in germanosilicate glasses is dependent on the inscription parameters such as exposure time, intensity of the laser used for inscribing, the interference pattern, and coherence of the laser system. In particular, a phase mask is used as the diffffacting element to generate the required interference pattern, that is exposed on the photosensitive fiber. We present a mathematical model of the electromagnetic diffraction pattern behind the phase mask and study the effect of the limited coherence of the writing laser on the interference pattern produced by the diffracting beams from the mask. Next, we demostrate the sensing capabilities of the fiber Bragg gratings for measuring strain, temperature and magnetic fields. We report linearity of 99.7% and sensitivity of 10.35pm/◦C for the grating temperature sensor. An array of gratings assigned with non-overlapping spectral windows is inscribed in a single fiber and applied for distributed sensing of structural health monitoring of an aircraft’s composite air-brake panel. The performance of these sensors is compared with the industry standard resistance foil gauges. We report good agreement between the two gauges (FBG and RSG). In some applications it is more desirable to know the spectral content, rather than the magnitude of perturbation. Fiber Bragg gratings sensors can be used to track events that occur in a very small span of time and contain high frequencies. Such applications demand very high speed wavelength demodulation methods. We present two interrogation techniques: wavelength-shift time-stamping (WSTS) and reflectivity division multiplexing (RDM). WSTS interrogation method employs the multiple threshold-crossing technique to quantize the sensor grating fluctuations and in the process produces the time stamps at every level-cross. The time-stamps are assembled and with the a priori knowledge of the threshold levels, the strain signal is reconstructed. The RDM methodology is an extension of the WSTS model to address multiple sensors. We show that by assigning unique reflectivities to each of the sensors in an array, the time-stamps from each of the sensors can be tagged. The time-stamps are collected by virtue of their corresponding pulse heights, and assembled to reconstruct the strain signal of each of the array sensor. We demonstrate that the two interrogation techniques are self-referencing systems, i.e., the speed at which the signals are reconstructed is instantaneous or as fast as the signal itself.

Bragg scattering of optical waves in thick gratings at extreme angles, where the scattered wave propagates parallel (extremely asymmetric scattering - EAS) or nearly parallel (grazing angle scattering - GAS) to the grating boundaries, is associated with many unique and practically important resonant phenomena. It has been demonstrated that one of the main physical mechanisms for these resonant phenomena is the diffractional divergence of the scattered wave inside and outside the grating region. This thesis fills the gaps in the theoretical and experimental understanding of Bragg scattering in gratings at extreme angles by investigating EAS and GAS in structures where diffractional divergence of waves is significantly affected by anisotropy and/or non-uniformities of the dielectric permittivity. Unusually high sensitivity of wave scattering in thick periodic gratings to small step-like variations of mean structural parameters at the grating boundaries is predicted and described for the case when the scattered wave (the +1 diffracted order) propagates almost parallel to the front grating boundary (the geometry of GAS). A unusual pattern of strong multiple resonances for bulk electromagnetic waves is predicted and analysed numerically in thick periodic holographic gratings in a guiding slab with mean permittivity that is greater than that of the surrounding media. It is demonstrated that these resonances are related to resonant generation of a new type of eigenmodes in a thick slab with a periodic grating. These eigenmodes are generically related to the grating -- they do exist not if the grating amplitude is zero. A new type of resonant coupling of bulk radiation into the conventional guided modes of a slab with a thick holographic grating is predicted and explained theoretically. It occurs in the presence of strong frequency detunings of the Bragg condition by means of interaction of the strongly non-eigen +1 diffracted order with the slab-grating boundaries. Therefore, it is only in the presence of step-like variations of the mean permittivity at the grating boundaries that this type of resonant coupling can occur. A new method for the analysis of EAS and GAS in anisotropic gratings is developed. This method is based on the consideration of the diffractional divergence of the scattered wave and the two-wave approximation in anisotropic gratings. Special efforts are focused on the analysis of EAS and GAS of extraordinary waves in uniaxial gratings. In particular, it is demonstrated that increasing curvature of the normal surface in the direction of propagation of the scattered wave results in increase of its diffraction divergence and the resonant amplitude. A theoretical model is developed for comparison of the theoretical predictions with data obtained from experimental observations of EAS in a holographic grating written in a photorefractive medium. The developed model is applied for the interpretation of experimental observations of EAS in BaTiO3 photorefractive crystals. Good agreement with the theoretical predictions is demonstrated.

Made available in DSpace on 2016-03-15T19:38:55Z (GMT). No. of bitstreams: 1 CLAUDIA BARROS DOS SANTOS DEMORI.pdf: 3640553 bytes, checksum: 13700107293ec12ced27c0e70d6fb334 (MD5) Previous issue date: 2015-08-25 / This work shows an Erbium doped-fiber Laser with many frequencies and many operation regimes based on integration of two paired arrayed waveguide gratings (AWGs) into a ring cavity. The AWGs are highlighted, since 2000, as key technology for multifrequencies lasers for optical communications, spectroscopy, image, astronomy and others applications. Fundamentally, gratings work splitting waveguide signal and since insertion in the cavity they allow simultaneous operating of tens of wavelength. We explore each one of these wavelength withing Erbium gain region, doing channels in different regimes of operation. These regimes may be continuous or pulsed. The advantage is that each channel may be modulated independently. Simultaneous operation with high repetition rates at 10 and 40 GHz were demonstrated, as continuous wave. The laser is stable, versatile and multifunctional. It is possible that more operating regimes, as passive mode-locking, be explored. We showed by this work efficient way to passive mode-locking by carbon nanotubes as saturable absorbers. Soon, the passive mode-locking is a potential regime for the demonstrated laser. As the new bi-dimensional materials, that look efficient for passive mode-locking and in the future, hybrid mode-locking, as graphene and black phosphor. / Esta tese trata de demonstrar um Laser de fibra dopada com Érbio com múltiplas frequências e múltiplos regimes de operação simultâneos baseados na integração de duas grades de difração pareadas (Arrayed Waveguide Gratings, AWGs) dentro de uma cavidade de laser de fibra. As AWGs são apontadas, desde o ano 2000, como tecnologia fundamental em lasers de múltiplas frequencias para as comunicações ópticas, para espectroscopia, imageamento, astronomia, e outras aplicações. Fundamentalmente, as grades funcionam como divisores do sinal óptico e quando inseridas dentro da cavidade de um laser de fibra permitem a operação simultânea de dezenas de comprimentos de onda. Neste trabalho, exploramos cada comprimento de onda, dentro da região de ganho do Érbio, com um regime de operação diferente. Esse regime pode ser pulsado ou contínuo. A vantagem do laser apresentado é que cada comprimento de onda é um canal que pode ser modulado de forma independente. Pôde-se demonstrar operação simultânea com regimes a altas taxas de repetição como 10 GHz e 40 GHz, assim como CW. O laser é estável, versátil e multifuncional. É possível que mais regimes de operação, como o regime de acoplamento de modos passivo sejam explorados. Mostramos ao longo deste trabalho maneiras eficientes de acoplar modos passivamente, utilizando nanotubos de carbono como absorvedores saturáveis, logo a técnica de acoplamento de modos passivo é um dos regimes em potencial para este laser. Assim como, o uso de novos materiais bidimensionais, que se mostram eficientes para o acoplamento de modos passivo e futuramente híbrido, como o grafeno e o fósforo negro.

[pt] Nesse trabalho, descreve-se o desenvolvimento de uma calibração do sistema de interrogação dos espectros das redes de Bragg baseando-se em uma simulação numérica adotada de testes experimentais. O objetivo é calibrar a técnica de demodulação óptica utilizando dois filtros de transmissão fixos, procurando-se principalmente a posição verdadeira dos sensores. O espectro refletido de uma rede tem uma forte dependência com o espectro da luz incidente que resultará em uma deformação no espectro refletido da rede, gerando um desvio no sensor detectado. A metodologia é gerar uma perturbação na fonte de luz e analisar a leitura do espectro da rede. Esse desvio gerado na leitura espectral é associado à potência óptica lida nos fotodetectores com a posição do comprimento de onda do sensor; as leituras indicadas são proporcionais ao grau de superposição entre os espectros do sensor e dos filtros. A calibração é enfatizada em simulações comparando-se com resultados experimentais e será recuperado principalmente o espectro deformado da rede por um espectro indicado que fornecerá a informação correta da posição do sensor. A simulação conclui em uma recuperação do espectro deformado, diminuindo incertezas de medição e da posição do sensor comparando-se com medidas experimentais proporcionando bons resultados. / [en] The development of a calibration system for Fiber Bragg Grating sensors based on two fixed spectral filters has been described basing in adopted numeric simulation of experimental tests. The objective is to gage the technique of optical demodulação using two fixed transmission filters, being sought mainly the true position spectral of sensors. The reflected spectrum of a Bragg Grating has a strong dependence with the spectrum of the incident light that will result in a deformation to the reflected spectrum, generating a deviation in the sensor detected. The methodology will be to generate a disturbance in the light source and to analyze the reading of the spectrum Bragg Grating. That deviation in the position is associated to the potency optical work in the photodetectors with the position of wavelength sensor; the suitable readings in the photodetectors are proportional to the overlap degree among the spectra of the sensor and filters. The calibration will be emphasized in simulations being compared with experimental results, and to recover mainly the deformed spectrum of Bragg Grating sensor for a suitable spectrum that will give the correct information at the position of sensor. The simulation ends in a recovery of the deformed spectrum, reducing measurement uncertainties and of the position of sensor, being compared with experimental results.

Esta tese descreve a fabricação, caracterização e possíveis aplicações de compósitos poliméricos nanoestruturados obtidos pela técnica de automontagem. Três sistemas distintos foram analisados: i) nanocompósitos contendo azopolímeros e azocorantes, ii) nanocompósitos contendo compostos de coordenação macrocíclicos (ftalocianinas), e iii) nanocompósitos contendo materiais do tipo doador-receptor, à base de poli(p-fenileno vinileno) (PPV) e azocorantes. Nos compósitos contendo azobenzeno, exploramos as propriedades de birrefringência e a formação de grades de relevo fotoinduzidas. Dois compostos contendo azobenzeno foram utilizados: um copolímero com cromóforos de azobenzeno ligados covalentemente à cadeia principal (Ma-co-DR13) e um azocorante comercial de baixo peso molecular, Brilliant Yellow (BY). Verificou-se através de experimentos de armazenamento óptico que o tempo de escrita até a saturação é muito maior (cerca de 30 min.) que em filmes de azopolímeros produzidos por outras técnicas como casting, em que este tempo é da ordem de dezenas de segundos. O longo tempo foi atribuído às fortes interações eletrostáticas entre as camadas dos filmes automontados, restringindo o processo de reorientação molecular, necessário à indução da birrefringência. Verificamos também que a presença de água entre as camadas do filme exerce influência significativa sobre o tempo de escrita. O tempo característico de escrita diminui de 8 min. para um filme seco para 2 min. após imersão em água. Este efeito é completamente reversível, ou seja, o tempo característico volta a aumentar se o filme for mantido em dessecador durante alguns dias. Grades de relevo foram inscritas nos filmes de BY e analisadas com micro-espectroscopia Raman. Os resultados mostraram um grau variável de fotodegradação no processo de inscrição das grades, dependendo do policátion ou dos parâmetros de fabricação dos filmes, como o pH das soluções. Qualitativamente, a menor ocorrência de fotodegradação foi observada em filmes de poli(alilamina hidroclorada) (P AH) e BY, preparados em soluções de pH = 10. Para os filmes fabricados com ftalocianina tetrasulfonada de ferro (FeTsPc), a combinação das técnicas de espectroscopia no UV-VIS. e no infavermelho (modos transmissão e reflexão) revelou a existência de ligações não-usuais específicas entre o átomo central de ferro da FeTsPc e os grupos não ionizados (NH2) da PAH, usada como policátion. A existência dessas interações ainda não havia sido relatada na literatura e é devida à estrutura de camadas extremamente finas de PAH e FeTsPc. A espessura média de uma bicamada de PAHlFeTsPc foi estimada em cerca de 10 \'Angstron\'. No terceiro tópico abordado, estudamos o processo de transferência de energia entre camadas automontadas de poli(p-fenileno vinileno) (PPV) e do azocorante BY. A transferência de energia pôde ser controlada não só pela variação da distância entre doador e receptor, mas principalmente pelo foto alinhamento das moléculas do BY (receptor) numa direção perpendicular à direção preferencial de emissão do PPV. Esse fotoalinhamento diminui a transferência de energia entre PPV e BY, resultando em um aumento de até 4 vezes na intensidade da fotoluminescência do filme. / This thesis describes the fabrication and possible applications of layer-by-Iayer (LBL) nanostructured films for three distinct systems comprising i) azopolymers and azodyes, ii) organometallic molecules (phthalocyanines) and iii) luminescent polymers and azodyes. Optically induced birefringence and surface relief gratings (SRGs) were studied in the azobenzene-containing composites, using a side-chain azopolymer (Ma-co-DR13) and a commercially available azodye, viz. Brilliant Yellow (BY). Optical storage experiments showed that the writing time required to induce birefringence (up to the saturation) in LBL films of Ma-co-DR13 is ca. 30 min, which is considerably longer than the times required in cast films of azopolymers (tens of seconds). The long writing time was attributed to the electrostatic interactions between the layers in the LBL film, which preclude photoisomerization or the reorientational processes for the azobenzene molecules.ln addition, entrained water in the films was found to affect the writing time. For example, the characteristic writing time decreases from 8 min. for a dry film to ca.2 min. for a film immersed for some minutes in water. This effect was completely reversible. Surface relief gratings were inscribed on LBL films from BY and analyzed with micro-Raman spectroscopy. The Raman spectra revealed that the process for SRG inscription is not entirely light-driven, with the occurrence of photodegradation. Such photodegradation can be minimized upon the appropriate choice of the polycations as well as the experimental conditions used for film fabrication. The lowest level of photodegradation was observed for films of poly(allylamine hydrochloride) (PAH) and BY fabricated from pH 10 solutions. Organometallic supramolecular composites were built using iron tetrasulfonated phthalocyanine (FeTsPc) and P AH as polycation. The combination of electronic and vibrational spectroscopic techniques showed the presence of unusual specific interactions between the central atom of FeTsPc and non-protonated groups from P AH (NH2). These interactions are believed to occur due to the intimate contact between the materials in the very thin PAH/FeTsPc LBL films, whose thickness was 10 ?Angstron? per bilayer. In the poly(p-fenilene vinylene) (PPV) (donor) and BY (acceptor) system, the resonant energy transfer process was exploited to control luminescence. The quenching in luminescence could be controlled by varying the distance between the PPV and BY layers, similarly to what has been reported in the literature. The novelty in this work, however, was the fine-tuning of luminescence achieved with the photoalignment of the acceptor molecules (BY). For example, the intensity of the photoluminescence increased 4 times upon the photoalignment for 10 min. of the BY chromophores.

Made available in DSpace on 2017-07-24T19:22:01Z (GMT). No. of bitstreams: 1 Camilo Andres P Mora.pdf: 2179325 bytes, checksum: 956a5f1d8568fa3876b0879ad21942c4 (MD5) Previous issue date: 2014-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to investigate the shrinkage-strainand degree of conversion inside the rootcanal"in situ"of resin cements used to lute fiber posts (Whitepost DC, FG). Thirty maxillary canines with similar root length average were selected (14 mm ± 1 mm). Each root canal was treated with crown-down technique and filled with gutta-percha, leaving 4 mm of apical seal.One week later, the roots were prepared following fiber post system manufacturer’s instructions. For the cementation, teeth were randomly divided into 2 groups (n = 15) according to the resin cement used: Group 1: dual-cured resin cement RelyX™ ARC – Adper Scotchbond™ Multipurpose Plus Adhesive (3M/ESPE) and Group 2: dual-cured resin cement RelyX™ U200 (3M/ESPE). Two fiber optic sensors with recorded Bragg gratings were attached to the coronal section (not in contact with the root) of each post before inserting the resin cement inside the root canal. These sensors measured the deformations of the cement over the coronal and apical section of the root (μe). Once measured, the specimens were sectionated in order to obtain slides on its cervical and apical sections. The degree of conversion of the cements on each third was analyzed by μ-Raman micro-spectroscopy. The data were statitsticallyanalyzed by two-way ANOVA (p = 0.05). The dual-curedconventional resin cement tested in this study showed the highest values of shrinkage-strain and degree of conversion; cervical region showed higher values than apical region in both of resin cements. / O objetivo deste estudo foi conhecer o comportamento e a magnitude das deformações que ocorrem durante a polimerização “in loco” no interior do canal radicular, em cimentos resinosos durante a fixação de pinos de fibra de vidro Whitepost DC (FGM) e verificar o grau de conversão dos mesmos. Foram selecionados 30 caninos superiores (n=10) com comprimento radicular médio de 14 mm medidos da junção cemento-esmalte (JCE). Os canais foram tratados endodonticamente ea guta-percha foi removida deixando 4 mm do selamento apical. Após uma semana os canais foram preparados. Para a cimentação, os dentes foram divididos aleatoriamente em 2 grupos, segundo o cimento resinoso utilizado: Grupo ARC: cimento resinoso dual RelyX™ ARC – Adesivo Adper Scotchbond™ Multipurpose Plus (3M/ESPE) e Grupo U200: cimento resinoso dual RelyX™ U200 (3M/ESPE). Antes da inserção do cimento resinoso no interior do canal radicular foram posicionados no pino dois sensores de fibra óptica com redes de Bragg gravadas e colados na região que não entrou em contato com as paredes do canal; um na posição mais apical e outro na mais cervical do pino. Os sensores realizaram a mensuração das deformações do cimento em uma porção coronária e apical do canal radicular, para se obter valores em micro-strain (μe). Logo depois, os espécimes foram cortados em fatias para mensuração do grau de conversão dos cimentos, nos terços apical e cervical por meio da espectroscopia μ-Raman. Os dados obtidos foram analisados estatisticamente por meio do teste ANOVA de dois fatores (p=0,05).Os sensores de fibra óptica com redes de Bragg mostraram-se eficientes na mensuração de contração de polimerização de cimentos resinosos. O cimento resinoso convencional testado no estudoapresentou maiores valores de contração de polimerização e grau de conversão, quando comparado com o cimento resinoso autoadesivo. O terço cervical apresentou maiores valores de contração de polimerização e grau de conversão, quando comparado com o terço apical independentedo tipo de cimento.

Ce travail de thèse concerne l'amélioration du pouvoir de résolution de la microscopie optique en champ lointain. Nous avons développé des techniques qui tirent profit de la relation liant le champ électromagnétique émis par un objet à l’éclairement utilisé. En utilisant plusieurs images obtenues pour différents éclairements, et à l’aide d’un algorithme d'inversion approprié, il est possible d'accéder à des fréquences spatiales de l'objet habituellement filtrées par le microscope.Ce concept est d’abord appliqué à une technique de microscopie cohérente : la tomographique optique de diffraction. Elle permet d’obtenir numériquement une carte quantitative de la permittivité diélectrique de l'objet, avec une résolution supérieure à celle d'un microscope classique, à partir de plusieurs hologrammes de l'échantillon. Dans ce cadre, nous montrons que le phénomène de diffusion multiple permet d’atteindre des résolutions encore plus spectaculaires s’il est pris en compte. Nous étudions ensuite la microscopie de fluorescence par éclairement structuré, que nous proposons d’améliorer de deux manières différentes. Dans la première, nous utilisons un algorithme d’inversion capable de retrouver simultanément la densité de fluorescence et les éclairements utilisés. Grâce à celui-ci, nous pouvons remplacer l’illumination périodique et contrôlée généralement utilisée, par des speckles aléatoires formés avec un montage remarquablement simple. Nous montrons expérimentalement l'efficacité de cette approche. Dans un second temps, nous proposons de remplacer la lamelle de verre sur laquelle est repose l’échantillon par un réseau diélectrique nanométrique. Celui-ci crée à sa surface une grille de lumière de période inférieure à la limite de diffraction, ce qui permet d’améliorer d’avantage la résolution finale de l’image reconstruite. Nous détaillons la conception, la fabrication et la caractérisation expérimentale de ce substrat nanostructuré. / This PhD work focuses on the resolution improvement of far-field optical microscopy. We have studied and developed different techniques that take advantage of the relationship between the sample, the illumination and the diffracted (or emitted) field, in order to increase final band-pass of the image beyond that imposed by the diffraction phenomenon. In In these approaches, several images of the same sample are recorded under different illuminations. An inversion algorithm in then used to reconstruct a super-resolved map of the sample from the set of measurements.This concept is first applied to coherent microscopy. In tomographic diffraction microscopy, many holograms of the same unstained sample are obtained under various incidences, then used to numerically reconstruct a quantitative map of permittivity of the sample. The resolution is usually better than that of classical wide-field microscopy. We show theoretically and experimentally that, far from being a drawback, the presence of multiple scattering within the sample can, if properly accounted for, lead a to an even better resolution.We then study structured illumination fluorescence microscopy. We present two different ways for improving this method. The first one takes advantage of an inversion algorithm, which is able to retrieve the fluorescence density without knowing the illumination patterns. This algorithm permits one to replace the periodic light pattern classically used in structured illumination microscopy by unknown random speckle patterns. The implementation of the technique is thus considerably simplified while the resolution improvement remains. In the second approach, we propose to replace the coverslip on which the sample usually lays, by a sub-lambda grating. The latter is used to form, in near field, a light grid with sub-diffraction period that is able to probe the finest details of the sample. The design, fabrication and optical characterization of this key structure are detailed.