Orientador: Keizo Yukimitu / Banca: Eudes Borges de Araújo / Banca: Noelio Oliveira Dantas / Resumo: Vidros teluretos são estudados devido as suas interessantes características ópticas (altos índice de refração, comparados aos vidros silicatos), apresentando-se como materiais promissores para o uso em fibras ópticas baseados nas propriedades ópticas lineares e nãolineares. Espectros de absorção na região do infravermelho e no UV - Vis indicam que a incorporação do lítio no vidro baseado no telúrio provoca a formação de pirâmides trigonais TeO3 e também a formação de bipirâmides trigonais dos grupos TeO4 simétricas. Porém, em ambos os sistemas ternários, TeO2-Li2O-TiO2 (TLT) e TeO2-Li2O-WO3 (TLW), ocorre uma progressiva mudança na coordenação dos átomos de Te (TeO3 para TeO4) quando os óxidos de TiO2 e WO3 substituem o óxido de Li2O na composição da matriz vítrea. Essas informações estruturais também são correlacionadas com a expressão para o índice de refração devido ao modelo de Wemple: n2-1=(EdEo)/(E2o-E2) , onde Eo é a energia relacionada à freqüência de absorção óptica, E é a energia da onda incidente, Eda "energia de dispersão", determinada pela equação Ed = BNcZaNe, com B sendo uma constante, Nc o número de coordenação do cátion, Za é a valência do ânion e Ne é o número de elétrons de valência do ânion. Os valores de Ed tendem a aumentar com o aumento da concentração de TiO2. Entretanto, os valores de E0 e Ed do sistema TLW são maiores do que os valores do sistema TLT. Como a polarizabilidade eletrônica (α) é diretamente responsável pelo comportamento do índice de refração, e os grupos estruturais TeO4 por possuírem maiores magnitudes de αsão os responsáveis pelos altos valores do índice de refração dos vidros teluretos. Por outro lado, como os grupos TeO3 têm menor polarizabilidade eletrônica, a sua presença provoca a diminuição dos valores de n. / Abstract: Tellurite glasses are being studied due to their interesting optical characteristics, presenting as promising material for use in optical fiber based on linear and non-linear optical properties. Spectra of absorption in the region of the infrared and UV-Vis indicate that the incorporation of lithium in tellurium based glass causes the formation of pyramids trigonais TeO3 and also the trigonal bipyramids of symmetrical TeO4 groups. However, in both ternary systems, TeO2-Li2O-TiO2 (TLT) e TeO2-Li2O-WO3 (TLW), occur a gradual change in the coordination of atoms of Te (TeO3 to TeO4) when oxides of TiO2 and WO3 replace the oxide Li2O in the composition of the vitreous matrix. Such structural information is also correlated with the expression for the refractive index due to the Wemple's model: n2-1 = [EdEo]/[Eo 2- E2], where Eo is the energy of optical absorption, E is the incidente wave energy and Ed is the "dispersion energy" determined by the equation: Ed =BcNcZaNe , with Bc = 0.39 eV, Nc is the number of cation coordination, Za is the anion valence and Ne is the effective number of anion valence electrons. The values of Ed tend to increase with increasing concentration of TiO2. Meanwhile, the value of E0 and Ed of the system TLW are greater than the values of the system TLT. As the electronics polarizability (α) is directly responsible for the behavior of the refractive index, and structural groups TeO4, due to their larger magnitudes of α, are responsible for high values of the refractive index of the tellurite glasses. Moreover, as the groups TeO3 have lower electronics polarizability, its presence causes a decreasing of the refraction index values n. / Mestre

>Magister Scientiae - MSc / Recent research shows that the study of optical properties of organic material natural dyes has gained much consideration. The specific functional groups in several natural dyes remain essential for the large nonlinear absorption expressed in terms of nonlinear optical susceptibilities or other mechanism of absorption such as two photon absorption (TPA), reverse saturable absorption (RSA) or intensitydependent refractive index characteristic. In this thesis we highlight the optical limiting responses of selected natural dyes as nonlinear response in the femtosecond regime. This technique refers to the decrease of the transmittance of the material with the increased incident light intensity.Three dyes derived from beetroot, flame flower and mimosa flower dyes were investigated. The results showed a limiting behaviour around 795 mW for the beetroot and the flame dye while there is total transmission in the flame dye sample. The performance of the nonlinearity i.e. the optical limiting is related to the existence of alternating single and double bonds (i.e. C-C and C=C bonds) in the molecules that provides the material with the electron delocalization, but also it is related to the light intensity.Beside nonlinearity study, crystallographic investigation was carried out for more possible applicability of the selected dyes and this concerned only the mimosa and flame flower dye thin film samples since the beetroot thin film was very sensitive to strong irradiation (i.e. immediately destroyed when exposed to light with high intensity). For more stability,dye solutions were encapsulated in gels for further measurements.

Neste trabalho investigamos as duas contribuições mais importantes ao índice de refração não-linear, n2, em sólidos dopados: o efeito de Lente Térmica (LT) e o efeito de Lente de População (LP). Nós estudamos cristais fluoretos dopados com Cr+3 e vidros fluoretos dopados com Nd+3. As medidas de n2 foram feitas com a técnica de Z-scan resolvida no tempo, que é uma técnica simples mas muito sensível. Também realizamos medidas usando a técnica de Lente Térmica de modo descasado onde usou-se dois feixes de laser (um de excitação e outro de prova). Nós mostramos que pode-se separar temporalmente as contribuições a n2 devido a LT e LP, através da variação da freqüência do chopper / In this work we investigated the two more important contributions to the index of no-lineal refraction, n2, in ion doped solid: the effects of Thermal Lens (LT) and Population Lens (LP). We studied Cr+3 doped fluoride crystals and Nd+3 doped fluoride glasses. The n2 measurements were made with the time-resolved Z-scan technique that is a simple but very sensitive technique. We also performed time¬ resolved Mode-mismatched Thermal Lens measurements, where two laser beams were used (one excitation beam and another probe beam). We showed that it is possible to temporally separate the contributions of LT and LP for n2, through the variation of the chopper frequency

Orientador: Edison Bittencourt / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-06T05:15:57Z (GMT). No. of bitstreams: 1 Fregolente_PatriciaBogalhosLucente_M.pdf: 761293 bytes, checksum: da2a8c420bdda1b10fb1d7888911e1b9 (MD5) Previous issue date: 2006 / Resumo: Atualmente, o mercado procura materiais com qualidades ópticas que satisfaçam as exigências dos usuários e que possuam facilidades de processamento. De forma geral, para um polímero apresentar boas propriedades ópticas, este necessita ter boas características como alto índice de refração, alta transmitância da luz, baixo peso específico, resistência ao impacto, estabilidade dimensional pós cura e estabilidade por exposição à luz e ao calor. Industrialmente, utiliza-se para a fabricação de lentes oftálmicas, a técnica de polimerização térmica, ou cura térmica. Dessa maneira, necessita-se de um tempo de cura muito longo (cerca de 20 horas) para evitar defeitos nas lentes. Entretanto, a cura através de irradiação de luz ultra-violeta (UV) permite obter os mesmos tipos de materiais e com características semelhantes com um tempo de processo reduzido em até poucos minutos. No presente trabalho, para confecção das lentes foram estudados os seguintes monômeros e oligômeros: metacrilato de metila (MAM), 1,6-Hexanediol diacrilato (HDODA), diacrilato uretano alifático tetrafuncional (Ebecryl 284) e diacrilato epóxi bisfenol-A (Ebecryl 3700) e para cada formulação o fotoiniciador 2- hidroxi-2-metil-1-fenilpropanona (Darocure 1173). O tempo de fotocura da mistura dura entre 4 a 7 minutos, de acordo com a espessura do molde. As lentes obtidas foram caracterizadas por medidas de dureza Shore D, transmitância nas regiões visível, UVA e UVB, índice de refração, análises térmicas para determinação da temperatura de transição vítrea. As lentes foram recobertas por uma resina multifuncional através do método de deposição por spin-coating e curada por UV. A caracterização dessa camada foi realizada por testes de dureza superficial utilizando graduações de grafites além de um planejamento experimental para observar as variáveis do processo de spin-coating que mais interferem na formação do recobrimento. As lentes produzidas apresentam ótimas qualidades ópticas e mecânicas e esta tecnologia de fotocura apresenta grande potencial para ser aplicada e produzir lentes em escala industrial / Abstract: The materials used for ophthalmic lenses need to present some optical qualities and to satisfy the requirements of the users. Various characteristics are required for the transparent synthetic resins as optical material. A polymer, to have good optical properties, needs to be colorless and tranparent, present good characteristics as high refractive index, high light transmittance, low specific weight, impact resistance, and stability to the exposition to the light and the heat. Industrially, for the manufacture of opthalmic lenses is used the technique of thermal polymerization, or thermal cure. This way, it is needed a long time of cure (about 20 hours) to prevent defects in the lenses. The monomers and monofunctional and multi-functional oligomers that have been studied for production of the lenses are methyl methacrylate (MAM), 1,6-hexanediol diacrylate (HDODA), aliphatic uretane diacrylate and bisphenol A epoxy diacrylate. The photoinitiator 2-hydroxi-2-methyl-1-fenilpropanone was added to each mixture, varying its concentration of 1 to 3%. The cure through ultraviolet irradiation (UV) allows to get the same kind of materials than thermal cure with similar characteristics but with a time of processing of the order of few minutes. In the present work, characteristics as refractive index (n), heat resistance, light transmittance and hardness of the produced lenses were studied from mixtures of acrylates and multi-functional methacrylates through photopolymerization with UV lamp at room temperature. The pencil hardness test was used for characterize the surface coating by spin-coating method, beyond an experimental design to observe the variables of the process that influence the formation of the coating / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Orientador: Hugo E. Hernandez Figueroa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T23:26:41Z (GMT). No. of bitstreams: 1 Sartori_EduardoJose_D.pdf: 11903812 bytes, checksum: 6e06f001155d33b841c61ae93464c897 (MD5) Previous issue date: 2009 / Resumo: Metamateriais são estruturas ou arranjos geométricos feitos a partir de materiais comuns, dielétricos, condutores, magnéticos ou por combinação destes. Os metamateriais caracterizam-se principalmente por apresentarem propriedades especiais de permissividade ( e) e permeabilidade ( µ) não encontradas nos materiais em estado natural, cujo principal efeito é o índice negativo de refração (n < 0). Essas características permitem seu emprego em diversos tipos de aplicações em eletromagnetismo e óptica, tais como filtros passa-faixa e rejeita-faixa, espelhos dielétricos, super lentes etc. Normalmente, o equacionamento envolvido no cálculo de parâmetros dos metamateriais são complexos e, na maioria das vezes, necessitam de apoio computacional. Por este motivo, o presente trabalho traz um estudo experimental sobre dois tipos de comportamento metamaterial, o de permissividade quase-zero e negativa, analisando seu desempenho sob vários aspectos geométricos e de características dos materiais envolvidos, além de propor uma metodologia de desenvolvimento, a qual possibilita um rápido dimensionamento de diversos tipos de grades metamateriais, baseada em cálculos simples ou consulta direta a tabelas e curvas de projeto. / Abstract: Metamaterials are structures or geometric arrangements made from common materials, dielectrics, conductors, magnetic or a combination of these. Metamaterials are characterized mainly because of their special characteristics of permittivity ( e) and permeability ( µ), not found in the materials at natural state, whose main effect is the negative index of refraction (n <0). These characteristics allow its use in several types of applications in electromagnetism and optics, such as band-pass and band-stop filters, dielectric mirrors, super lenses etc.. Typically, the equations involved in the calculation of parameters of metamaterials are complex and, in most cases, require high capability computational methods. For this reason, this work presents an experimental study on two types of metamaterial behavior, near-zero and negative permittivity, examining its performance in several geometric aspects and characteristics of the materials involved, and propose a development methodology, which allows a fast scaling of various types of metamaterials grids, based on simple calculations or direct consultation tables and curves design. / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17578号 / 工博第3737号 / 新制||工||1570(附属図書館) / 30344 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 川上 養一, 准教授 後藤 康仁 / 学位規則第4条第1項該当

Abstract While numerous publications deal with the properties and applications of porous silicon (PS), some of the related topics are not complete or could be investigated from different aspects. Therefore, the main objective of this thesis is to provide novel information associated with the optical and chemical properties of PS. For the investigations, various PS samples are manufactured by electrochemical dark etching of boron-doped p+-type Si wafers. Amongst others, (i) the wavelength-dependent refractive indices of freestanding PS monolayers having different porosities were obtained from optical transmission and reflection spectra in the 700–1700 nm wavelength range, and compared to those calculated from Bruggeman's effective medium approximation (EMA). The refractive indices of the PS samples are shown to be described well with the EMA. In addition, optical scattering at the air-PS interface was demonstrated. (ii) Multilayer stacks are created by alternating the porosities of PS layers within the same sample to form Bragg filters. The Bragg conditions of the filters are calculated and compared to optical transmission measurements. (iii) The oxidation of PS membranes in dry air is investigated with emphases on the reaction kinetics and on the structural changes of the porous matter. As revealed, oxidation proceeds faster in PS than in Si bulk. The formed SiO2 is amorphous and causes stress in the lattice of the residual Si skeleton. (iv) The effect of oxidation extent of PS layers on the growth mechanism of multi-walled carbon nanotubes (CNTs) is investigated. The density of the CNT network is found proportional to the oxidation extent of the substrates. (v) Finally, the chemically-reductive nature of PS is studied and exploited via the immersion plating method to deposit palladium and silver nanoparticles in the nanopores and on the surface of PS samples. The presented novel results have potential in silicon-based technologies, including integrated active and passive optical components (waveguides, filters, antireflection coatings, optical gas/liquid sensors), electronic devices (electrochemical gas/liquid sensors, diodes, field effect devices) and selective chemical catalysis (substrates, growth templates).

A multilayered system is a good model for many optical systems. An optical coherence tomography (OCT) system can provide fundamental information about the refractive index distribution of the sample and enables images to be corrected for geometric accuracy, but this requires the separation of refractive index and physical thickness for each layer from the measured optical paths. In this thesis a novel approach for simultaneous extraction of index and thickness of multi layer systems and the last medium index of refraction in a single experiment using only the object’s spectral response available by any Fourier Domain OCT system without using any additional outside measurements is introduced. The method is based on a novel matrix equation that uses the reflected spectrum from the object and the measured optical thickness. In the presence of slight error of measuring optical thickness, the parameters extraction has wavenumber dependency. A novel method is used to select the suitable set of spectral components that reduces the extracted parameters error. The parameters extraction method is followed by a fitting process for optimized results. The method works the best for low contrast index distribution even in the presence of relatively large optical thickness measurement error.

The mapping of the refractive index of cells has been extensively studied since 1950s. This optical parameter constitutes a key biophysical property strongly correlated to fundamental cell parameters such, e.g., intracellular mass distribution and protein concentration. Experimental studies evidence that the cell refractive index (Refractive Index) provides critical insights to understand diverse cellular structures and interpret pathological states, including diverse stages of diseases. However, measuring the refractive indices of biological specimens satisfying clinical requirements is currently challenging, since there is a lack of spectral signatures of sub-cellular components in the visible range due to their transparent nature. Designing methods capable of extracting visible fingerprints of cellular components remains attracting large research interests. In this work, I have contributed to this project by fabricating and characterizing a black nanostructured membrane that dynamically interacts with cancerous cells and furnishes label-free structural color generation by exploiting the inherent contrast mechanisms of them. Thus, adequately meeting morphology differentiation to assist in biomedical research. I have tested the system with HCT116 colorectal cancer cells. In addition, this special membrane allows refractive index recovery and cell thickness mapping with commonly available bright-field microscopy equipment. Therefore, it is of considerable clinical importance to allow the generation of qualitative information about cell morphology to add in medicine and biophysics research.

The role of energy in wealth and development is evident but the manner that a population’s access to energy effects overall growth is unclear. Understanding the role of energy in society can impact policies to push improvement in underdeveloped countries. Therefore, it is necessary to know how energy improves quality of life and what improvements need to be made to provide the necessary resources to underdeveloped populations. The first half of the thesis focuses on the role of energy use in society and its effect on human development. It is established that underdeveloped countries are in fact positively affected from increased energy access. Additionally, that the use of renewables will improve all the aspects of human development: health, wealth, and education. These results suggest that policy makers should focus on increasing clean energy in developing countries to also improve overall development. The second half shifts to the design and characterization of a water tunnel and the role it has in understanding fluid flow for near-wall visualization. Using refractive index matching (RIM) this experimental method can be used to study micro-surfaces that could improve efficiency in transportation or renewable energy. The water tunnel herein can achieve turbulent flows, unlike previous RIM designs.