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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Investigation of optical loss changes in siloxane polymer waveguides during thermal curing and aging

Hegde, Shashikant G. 02 January 2008 (has links)
In high performance electronic systems, with increasing chip speed and larger number of processors, the system performance is being limited by off-chip metal interconnects. In such systems, polymer optical waveguides are being considered to replace electrical interconnects because of their high capacity for bandwidth and less constraints on interconnect length. The optical loss in the polymer optical waveguides is the key criterion used to evaluate their performance, and is significantly affected by thermal curing and aging. The evolution of degree-of-cure is determined from differential scanning calorimetry and compared to optical absorption from spectroscopy. Optical loss due to scattering mechanisms is related to local density fluctuations, which is studied using dielectric analysis. Based on the optical loss trends in uncladded and cladded waveguides, the underlying mechanisms for the optical loss variations are proposed and a cure process schedule to realize the lowest optical loss is recommended. Process-induced thermal stresses can also affect the polymer waveguide by introducing stress birefringence. The stress-optical coefficients of the siloxane polymer are extracted and employed in a numerical modeling method to determine the stress-induced birefringence in an optical waveguide system. The thermal-aging dependent optical loss is determined for waveguide samples at several different accelerated temperature conditions. To get the field-use conditions, the temperature distribution in the vicinity of the embedded laser and the polymer waveguide is determined. Using such thermal experimental data, the analytical reliability models were employed to relate the optical loss with time, and provide a practical way of determining whether the optical waveguides would perform within the optical loss budget during field-use conditions.
222

Optical interconnects on printed circuit boards

Wang, Fengtao 03 August 2010 (has links)
The ever-increasing need for higher bandwidth and density is one of the motivations for extensive research on planar optoelectronic structures on printed circuit board (PCB) substrates. Among these applications, optical interconnects have received considerable attention in the last decade. Several optical interconnect techniques, such as free space, guided wave, board level and fiber array interconnects, have been introduced for system level applications. In all planar optoelectronic systems, optical waveguides are crucial elements that facilitate signal routing. Low propagation loss, high reliability and manufacturability are among the requirements of polymer optical waveguides and polymer passive devices on PCB substrates for practical applications. Besides fabrication requirements, reliable characterization tools are needed to accurately and nondestructively measure important guiding properties, such as waveguide propagation loss. In three-dimensional (3D) fully embedded board-level optical interconnects, another key challenge is to realize efficient optical coupling between in-plane waveguides and out-of-plane laser/detector devices. Driven by these motivations, the research presented in this thesis focuses on some fundamental studies of optical interconnects for PCB substrates, e.g., developing low-loss optical polymer waveguides with integrated efficient out-of-plane couplers for optical interconnects on printed circuit board substrates, as well as the demonstration of a novel free-space optical interconnect system by using a volume holographic thin film. Firstly, the theoretical and experimental investigations on the limitations of using mercury i-line ultraviolet (UV) proximity photolithography have been carried out, and the metallization techniques for fine copper line formation are explored. Then, a new type of low-loss polymer waveguides (i.e., capped waveguide) is demonstrated by using contact photolithography with considerable performance improvement over the conventional waveguides. To characterize the propagation properties of planar optical waveguides, a reliable, nondestructive, and real-time technique is presented based on accurately imaging the scattered light from the waveguide using a sensitive charge coupled device (CCD) camera that has a built-in integration functionality. To provide surface normal light coupling between waveguides and optoelectronic devices for optical interconnects, a simple method is presented here to integrate 45° total internal reflection micro-mirrors with polymer optical waveguides by an improved tilted beam photolithography (with the aid of de-ionized water) on PCBs. A new technique is developed for a thin layer of metal coating on the micro-mirrors to achieve higher reflection and coupling efficiency (i.e., above 90%). The combination of the capped waveguide technique and the improved tilted UV exposure technique along with a hard reusable metal mask for metal deposition eliminates the usage of the traditional lift-off process, greatly simplifies the process, and reduces fabrication cost without sacrificing the coating quality. For the study of free-space optical interconnects, a simple system is presented by employing a single thin-film polymeric volume holographic element. One 2-spherical-beam hologram is used to link each point light source with the corresponding photodetector. An 8-channel free-space optical interconnect system with high link efficiency is demonstrated by using a single volume holographic element where 8 holograms are recorded.
223

Silicon integrated nanophotonic devices for on-chip optical interconnects

Lin, Che-Yun 12 July 2012 (has links)
Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research. / text
224

A waveguide-based lens-less x-ray microscope / Ein linsenloses Röntgenmikroskop auf Basis von Röntgenwellenleitern

Ollinger, Christoph German Josef 11 July 2006 (has links)
No description available.
225

Direct Patterning of Optical Coupling Devices in Polymer Waveguides

Finn, Andreas 26 May 2014 (has links) (PDF)
The aim of the present work was to design and fabricate all purpose, positioning-tolerant and efficient interconnects between single-mode fibers and integrated waveguides out of polymers. The developed structures are part of the optical packaging of integrated optical chips. Integrated optics have gathered tremendous interest throughout recent years from research as well as from the industry, and most likely the demand will further grow in the future. Today’s trend is to establish optical data communication not only in far-distance transmission but also in end-user or so called fiber-to-home configurations, or, in the near future, also on board or even chip level. In addition, integrated optical sensors are gaining more and more importance. In the future, lab-on-a-chip systems may be able to simplify and accelerate analysis methods within health care or allow for a continuous monitoring of almost any environmental variable. All these applications call for robust optical packaging solutions. Many integrated optical chips are using a silicon-on-insulator design. Technologies which were originally intended for the manufacturing of integrated circuits can be utilized for the fabrication of such silicon-on-insulator chips. Point-of-care testing, which is a considerable part of bio-sensing, in some cases only allows the use of disposable transducer elements. The fabrication of these transducers, also including almost all other system parts, may be possible using polymers. Alternative fabrication methods like nanoimprint lithography can be applied for the patterning of polymers. With these, the extension of already known working principles or even entirely new device architectures become feasible for mass production. The direct patterning of polymers by means of nanoimprint was used to fabricate interconnects for integrated waveguides. In contrast to conventional lithography approaches, where a patterned resist layer is used as a masking layer for subsequent process steps, direct patterning allows the immediate use of the structures as functional elements. Firstly, nanoimprint allows diffraction-unlimited patterning with nanometer resolutions as well as the replication of complex three-dimensional patterns. These unique properties were used within this work to pattern shallow gratings atop an integrated waveguide within only one single manufacturing step. The gratings are used as coupling elements and can be utilized either to couple light from external elements to the chip or vice versa. Considerations regarding the optical effects on single-mode polymer waveguides as well as grating couplers were obtained from simulation. They are specific to the chosen design and the used polymer and cannot be found elsewhere so far. Compared to similar designs and fabrication strategies proposed in literature, the ones followed here allow for a higher efficiency. The dimensions and process windows obtained from simulation did serve as a basis for the subsequent fabrication of the grating couplers. All steps which are necessary to turn the calculated design into reality, ranging from master fabrication, to working mold cast and imprint, are shown in detail. The use of a working mold strategy is of crucial importance for the fabrication process and is discussed in detail. The use of a working mold preserves a costly master and further allows for a cost-efficient production. Parameters which are relevant for the production as well as for the final polymer patterns were analyzed and discussed. On the basis of the obtained data, a process optimization was performed. The optical characterization was also part of the presented work. A comparison with the results obtained from simulation is included and additional effects were revealed. Most of them may be subject to further improvement in future designs. In summary, the present work contributes to the field of optical packaging. It shows a viable route for the design and fabrication of interconnects of single-mode polymer waveguides. The presented design can be used as a building block which can be placed at almost any positions within an integrated optical chip. The fabrication method includes a minimum number of process steps and is still able to increase performance compared to similar approaches. Moreover, all process steps allow for scaling and are potential candidates for mass production.
226

High temperature thickness monitoring using ultrasonic waves

Pezant, Joannes Charles 19 November 2008 (has links)
The time required for inspection and maintenance of piping systems and vessels needs to be reduced to both minimize down time and decrease operational costs of petrochemical plants. Current ultrasonic inspection systems are not suited for on-line monitoring, with the main issues being the resistance of transducers and their coupling to high temperatures and the removal of insulation to access structures. The use of welded cylindrical rods is thus proposed, but measurements are threatened by "trailing echo" generation in waveguides. The introduction of a taper angle is investigated to attenuate these undesired echoes. While clean signals can always be obtained by increasing the taper angle in long rods, that is not always the case for short rods, which are considered here. In addition, temperature variations have a non-negligible impact on the arrival time of the backwall echo when performing measurements with a waveguide, and on-line compensation is essential. Since the interface echo between the rod and the pipe wall may be suppressed after the welding operation, a notch is machined at the end of the rod to create a reflected echo, which can be used for on-line compensation. Finally, the implementation of waveguides is considered for both pulse-echo and pitch-catch modes. In the pitch-catch mode, the backwall echo and the notch echo are received by different transducers and signals of interst are both first arrivals. As a result, trailing echoes do not impede measurements and their attenuation becomes unnecessary. In contrast, pulse-echo measurements are sensitive to trailing echoes and the waveguide's design plays an essential role in the feasibility of measurements. However, the environment also imposes a set of constraints on waveguide dimensions that complicates the implementation of pulse-echo measurements. Being more flexible, the pitch-catch configuration is chosen for final implementation. Experiments are performed to verify the concept feasibility, and the accuracy of measurements with thickness and temperature changes is also confirmed.
227

Produção de Interferômetros Mach-Zehnder utilizando guias de onda do tipo pedestal e filmes finos de Bi₂O₃-WO₃-TeO₂ para aplicações em sensores ópticos integrados. / Production of Mach-Zehnder Interferometer using pedestal type optical waveguides and Bi₂O₃-WO₃-TeO₂ thin films for applications in integrated optical sensors.

Mauricio Eiji Camilo 06 June 2014 (has links)
Neste trabalho foram produzidos Interferômetros Mach-Zehnder (IMZ) a partir de guias de onda do tipo pedestal com filmes finos de Bi₂O₃-WO₃-TeO₂ (BWT) como camada de núcleo para aplicações em sensores ópticos integrados. A influência dos parâmetros e dos materiais utilizados nas etapas de processo foi verificada. Os valores de índice de refração efetivo e coeficiente de absorção em função do comprimento de onda foram obtidos para os filmes finos BWT. Os guias de onda pedestais foram caracterizados por Microscopia Eletrônica de Varredura, medidas de perda por propagação e perfis de campo próximo em 633 nm e 1050 nm. Os valores mínimos obtidos nas perdas por propagação foram de ~1,5 dB/cm em 633 nm e 3,0 dB/cm em 1050 nm. As medidas de perfis de campo próximo mostraram que guias de onda com larguras superiores a 7 m apresentaram comportamento multimodo. Foram obtidos IMZs que apresentaram guiamento de luz por toda a estrutura, com comportamento multimodo. Sensores ópticos de pressão e temperatura foram produzidos. A fabricação de diafragmas através do processo de corrosão úmida do silício é apresentada no sensor de pressão. Sensores ópticos de temperatura foram produzidos com filamentos metálicos. As cavidades ópticas não foram obtidas nesse sensor. A potência de luz na saída dos sensores de temperatura foi medida em função da diferença de potencial aplicada no filamento metálico. Os resultados apresentados mostram que guias de onda do tipo pedestal produzidos com núcleo de BWT são promissores para aplicações em sensores ópticos integrados. / In this work Mach-Zehnder Interferometers (MZI) were produced from the pedestal-type waveguides with Bi₂O₃-WO₃-TeO₂ (BWT) thin films as the core layer for applications in integrated optical sensors. The influence of the parameters and materials used in the process steps was verified. The values of the effective refractive index and absorption coefficient as a function of wavelength were obtained for the BWT thin films. The pedestal waveguides were characterized by Scanning Electron Microscopy, by propagation loss measurements and near-field profiles at 633 nm and 1050 nm. The minimum values obtained by propagation losses were ~ 1.5 dB/cm at 633 nm and 3.0 dB/cm at 1050 nm. The measures of near-field profiles showed that waveguides with widths larger than 7 m presented multimode behavior. The MZIs obtained presented guiding light through the structure, with multimode behavior. Optical pressure sensors and temperature sensors were produced. The production of diaphragms using the wet etching process of silicon is presented on the pressure sensor. Optical temperature sensors were made with metallic filaments. Optical cavities were not obtained in this sensor. The light power in the output of the temperature sensors was measured as the voltage applied to the metal filament. The results show that the waveguides produced with pedestal-type and BWT thin films as core layer are promising for applications in integrated optical sensors.
228

Caracterização de superfícies de vidros expostas a vapores de KNO3 /

Saggioro, Bruno Zaniboni. January 2005 (has links)
Orientador: Ervino Carlos Ziemath / Banca: Dimas Roberto Vollet / Banca: Eduardo Bellini Ferreira / Resumo: Superfícies de vidro plano comercial (flotado) e de vidros sintetizados no laboratório com diferentes concentrações em massa de SnO2 foram expostos aos "vapores" resultantes da decomposição de KNO3 fundido a uma temperatura um pouco abaixo da temperatura de transição vítrea. Medidas de EDS mostram um aumento da concentração dos íons K+ na superfície com o aumento do tempo de exposição aos vapores. Alguns destes íons migraram para o interior dos vidros, conforme mostram as medidas do perfil de concentração. Os coeficientes de difusão foram determinados utilizando a técnica de Bolztzman-Matano. Esta mudança na concentração de K+ provocou modificações estruturais na superfície, alterando algumas de suas propriedades físico-químicas. Espectros de reflexão no infravermelho foram realizadas nestas amostras e mostraram que as alterações mais pronunciadas ocorreram na banda em tono de 950 cm-1. A dureza Vickers aumenta com o tempo de exposição. O índice de refração foi determinado pelos métodos de Brewster e refratometria Abbe. Constatou-se que quanto maior o tempo de exposição aos vapores, maior o valor do índice de refração das amostras. Foi verificado se esta nova técnica de troca iônica, isto é, por exposição a vapores, é propicia na preparação de dispositivos baseados em guias de ondas planares, utilizando a técnica de acoplamento de prisma. Vidros sintetizados também foram submetidos a testes de dilatometria com o intuito de determinar a temperatura de transição vítrea e calcular o coeficiente de expansão térmica. Medidas de densidade foram realizadas utilizando o principio de Arquimedes. Há diversas evidências experimentais que o estanho incorporado à estrutura vítrea atua como cátion formador de vidros, e que inibe a difusão iônica. / Abstract: Surfaces of commercial plane glass (floated) and glasses synthesized in laboratory with different concentrations of SnO2 were exposed to "vapors" resulting from the decomposition of molten KNO3 at temperatures somewhat below the glass transitions. EDS measurements show an increase of the K+ concentration at the surfaces during the time of exposition to the vapors. Some of these ions migrate into the near surface layers of the samples, according to the measured concentration profiles. Diffusion coefficients were determined using the Bolztzman-Matano technique. The changes in concentration promote structural modifications at the surfaces, changing some of the physico-chemical properties of the glasses. Reflectance spectra in the infrared were carried out in these samples and one observe that the most pronounced change occurred around 950 cm-1. The Vickers hardness increases with the exposition time. The refractive index was determined by Brewster method and by Abbe refractometry. The longer the time of exposition to the vapors, the higher was the refractive index of the samples. This new technique of ionic exchange, that is, the exposition to vapors, was tested to verify if it is appropriate to prepare planar waveguide devices, and the coupling prism method was employed. Synthesized glasses were also subjected to dilatometric tests in order to determine the glass transition temperature, Tg, and the average thermal expansion coefficient, a. Density measurements were performed using Archimedes principle. There are several experimental evidences that tin is incorporated in the glass structure as a glass former cation, and it hinders ionic diffusion. / Mestre
229

Desenvolvimento de materiais nanoestruturados à base de óxido de nióbio para aplicação em fotônica / Nanostructured niobium based materials for photonic applications

Felipe Thomaz Aquino 12 September 2013 (has links)
No presente trabalho foram realizadas a síntese e caracterizações estruturais, ópticas e espectroscópicas de materiais nanocompósitos na forma de guias de onda planares e pós de (100-x)SiO2-xNb2O5 dopados com íons lantanídeos pelo método sol-gel, para aplicação em Fotônica. Foi observada separação de fase controlada e cristalização, com distribuição e tamanho de partículas, bem como a fase cristalina de Nb2O5 formada, dependentes da composição (%Nb) e temperatura de tratamento térmico. Caracterizações estruturais revelaram a formação de duas fases cristalinas de Nb2O5, ortorrômbica (fase T) e monoclínica (fase M), com distribuição de tamanhos de nanopartículas da ordem de 7 a 30 nm. Essas duas fases cristalinas apresentaram-se na forma de nanocristais dispersos em uma matriz amorfa, formando sistemas nanocompósitos transparentes. A formação dessas diferentes fases cristalinas influenciou diretamente nas propriedades luminescentes dos materiais que apresentaram uma intensa emissão na região do Infravermelho próximo (com máximo de emissão em 1530 nm) sob excitação em 980 nm, com valores de largura de banda variando de 48 a 84 nm. A dependência dos espectros de emissão (largura inomogênea e componentes Stark), valores de largura de banda e tempos de vida do estado excitado 4I13/2 em relação às diferentes fases cristalinas de Nb2O5 formadas, permitiram a conclusão de que os íons Er3+ estão ocupando preferencialmente ambientes de baixa energia de fônon à base de Nb2O5. Estudos espectroscópicos dos nanocompósitos dopados com íons Eu3+ possibilitaram maiores evidências da ocupação dos íons lantanídeos em diferentes sítios de simetria no Nb2O5. A co-dopagem dos nanocompósitos com íons Er3+ e Yb3+ permitiu uma intensificação na emissão na região do Infravermelho próximo, correspondente à transição 4I13/24I15/2, decorrente da maior seção de choque dos íons Yb3+ em 980 nm e um processo eficiente de transferência de energia entre os íons Yb3+ e os íons Er3+ distribuídos nas matrizes estudadas. Essa transferência de energia eficiente intensificou também as emissões tanto na região do verde como do vermelho, decorrente de processos de conversão ascendente. Um estudo detalhado da dinâmica do processo de conversão ascendente foi realizado para os pós e guias de onda. No presente trabalho também foram obtidos guias de onda planares (100-x)SiO2-xNb2O5 dopados com íons Er3+ e co-dopados com íons Er3+ e Yb3+, com excelentes propriedades estruturais, morfológicas, ópticas e espectroscópicas para aplicação como amplificadores ópticos, tais como, superfícies livres de trinca, distribuição uniforme dos valores de índice de refração através da superfície e em função da profundidade, baixa rugosidade, alta porcentagem de confinamento da luz, uma excelente transparência das matrizes no visível e infravermelho próximo, bem como emissão em região usada para transmissão de sinal óptico em telecomunicações. Os guias de onda apresentaram intensas emissões tanto na região do Infravermelho próximo quanto no visível, decorrente de processos de conversão ascendente, apresentando ainda uma interessante variação das cores verde e vermelha, dependendo-se da potência de excitação utilizada e da proporção em mol (%) de Nb adicionada. Após a constatação dos excelentes resultados obtidos nos guias dopados com íons Er3+ e Yb3+, foram preparados nanocompósitos co-dopados com Tm3+ e Yb3+ na forma de pós e guias de onda planares, que apresentaram uma largura de banda de 120 nm na região do infravermelho próximo (com máximo de emissão em 1650 nm) e emissões na região do azul (475 nm) e no infravermelho (785 nm), decorrentes de processos de conversão ascendente. Por fim, foi realizada inscrição bem sucedida de canais nos guias de onda planares utilizando um laser de Ti:safira de femtosegundos. Em suma, os materiais nanocompósitos (100-x)SiO2-xNb2O5 apresentam um grande potencial de aplicação, especialmente em fotônica como amplificadores ópticos (EDWA) em telecomunicações, em circuitos fotônicos, lasers na região do visível (explorando conversão ascendente de energia), marcadores ópticos, dependendo fundamentalmente dos íons lantanídeos utilizados na dopagem. No caso especifico de amplificadores ópticos para telecomunicações, pôde-se concluir que as propriedades mais adequadas foram observadas nos materiais nanocompósitos (100-x)SiO2-xNb2O5 guias de onda planares contendo as proporções 80Si-20Nb e 70Si-30Nb tratados termicamente a 900oC co-dopados com íons Er3+/Yb3+ e Tm3+/Yb3+ / In the present work are reported the synthesis and structural, optical and spectroscopic characterizations of lanthanide doped (100-x)SiO2-xNb2O5 nanocomposites materials as planar waveguides and powders prepared by the sol gel method for photonic applications. The controlled phase separation and crystallization observed, as well as the particle size and distribution depended on the composition (%Nb) and the annealing temperature. The structural characterization revealed the formation of two Nb2O5 crystalline phases, orthorhombic (T-phase) and monoclinic (M-phase), with nanoparticle size distribution from 7 to 30 nm. The two crystalline phases were observed as nanocrystals dispersed in an amorphous matrix, constituting transparent nanocomposite systems. The formation of the different crystalline phases affected directly the materials luminescent properties which showed an intense near infrared emission (with maximum peak at 1530 nm) under 980 nm excitation, with bandwidth values from 48 to 84 nm. The dependence of emission spectra (inhomogeneous broadening and Stark components), the bandwidth values and the 4I13/2 excited state lifetimes dependence upon the different Nb2O5 crystalline phases formation, led to the Er3+ ions preferential occupation on low phonon energy, Nb2O5-rich environment. Spectroscopic studies with Eu3+-doped nanocomposites provided additional evidences of the lanthanide occupation of different symmetry sites on the Nb2O5-rich environment. The nanocomposites co-doping with Er3+ and Yb3+ ions allowed intensification on the near infrared emission, corresponding to the 4I13/24I15/2 transition, which resulted from the higher cross section of Yb3+ ions at 980 nm and an efficient energy transfer process between the Yb3+ ions and the Er3+ ions. This efficient energy transfer process also intensified the emissions both in green and red range, deriving from upconversion processes. A detailed study on the upconversion processes was made for nanocomposites and waveguides. In the present work, Er3+-doped and Er3+ and Yb3+ co-doped planar waveguides (100-x)SiO2-xNb2O5 with excellent optical, morphological and spectroscopic properties were also obtained, such as, crack free surfaces, a uniform refractive index profile across the surface and the thickness, low rugosity, high light confinement, low optical losses, and an excellent infrared and visible range matrix transparency, as well as emission used on optical telecommunication transmission. The waveguides showed emission both on near infrared and visible range, resulting from upconversion processes, showing an interesting color tuning phenomena in the green and red ranges, dependent on the excitation power and Nb content (mol%). After the excellent results verified with Er3+ and Yb3+, Tm3+ and Yb3+ co-doped nanocomposites and planar waveguides were prepared, which showed a bandwidth of 120 nm in the infrared range (with maximum peak at 1650 nm) and blue (475 nm) and near infrared (785 nm) emissions deriving from upconversion processes. Finally, channel writing using a femtosecond Ti:sapphire laser was successfully performed on the planar waveguides. Therefore, the (100-x)SiO2-xNb2O5 nanocomposite materials have shown great potential application, especially in photonic, such as, optical amplifiers (EDWA), photonic circuits, visible range lasers (exploring upconversion processes), and optical markers, depending on the lanthanide doping. In the specific case of optical amplifiers for telecommunication application, it could be concluded that the most adequate properties were observed on the ions Er3+/Yb3+ and Tm3+/Yb3+ co-doped (100-x)SiO2-xNb2O5 nanocomposites at 80Si-20Nb and 70Si-30Nb ratios, annealed at 900°C
230

Produção e caracterização de filmes finos amorfos de germanato codopados com Tm3+ e Yb3+ contendo nanopartículas metálicas para a produção de guias de onda. / Production and characterization of Tm3+ and YB3+ codoped germanate amorphous thin films containing metallic nanoparticles for the production of waveguides.

Thiago Alexandre Alves de Assumpção 24 September 2015 (has links)
O trabalho em questão mostra a possibilidade de produção de guias de onda por meio de filme finos de GeO2-PbO codopados com Tm3+/Yb3+, com e sem nanopartículas (NPs) de ouro, a partir da técnica de RF Magnetron Sputtering. Foram usados nos processos de fabricação dos guias de onda do tipo RIB e PEDESTAL, as mesmas técnicas empregadas na fabricação de dispositivos de microeletrônica, tais como, litografia e corrosão por plasma. A influência dos parâmetros dos processos de produção é reportada e a caracterização dos guias foi realizada por diversas técnicas. Dentre elas, destacamos a microscopia eletrônica de varredura (MEV) para a observação do perfil dos guias, as rugosidades de superfície e as espessuras das camadas utilizadas para a confecção dos mesmos. Medidas de transmitância óptica realizadas nos filmes permitiram a determinação do coeficiente de absorção óptica e do índice de refração, de aproximadamente 2,0, além da confirmação das espessuras dos filmes obtidos por Sputtering. Guias do tipo RIB foram descartados por dificuldades enfrentadas durante o processo de fabricação. Medidas ópticas de perdas por propagação, realizadas em guias do tipo PEDESTAL, mostraram que os melhores guias produzidos apresentaram perdas em torno de 5 dB/cm em 633 e 1050 nm, e medidas de perfil de campo próximo, além da simulação dos modos propagados, o comportamento de guiamento multímodo. Ganho óptico em torno de 13,5 dB/cm (em 805 nm) foi obtido em guia com largura de 30 ?m e potência de bombeio estimada de ~75 mW. Guias contendo NPs de ouro foram produzidos por meio de metodologia adequada que permitiu a nucleação das NPs (tamanho médio de 20 nm) e um ganho 22 dB/cm em 805 nm, portanto, duas vezes superior ao mesmo guia sem NPs (30 ?m de largura). Os resultados apresentados demonstram que guias de onda GeO2-PbO codopados com Tm3+/Yb3+, com ou sem NPs metálicas, são promissores para aplicações em dispositivos fotônicos, com a criação de dispositivos amplificadores integrados para operação na 1° janela de telecomunicações. / The work in question shows the possibility of producing waveguides by means of Tm3+/Yb3+ codoped GeO2-PbO thin films, with or without gold nanoparticles (NPs), by using the RF Magnetron Sputtering technique. For the production of RIB and PEDESTAL type waveguides, the techniques employed in the manufacture of microelectronics devices, such as plasma etching and lithography, were employed. The influences of the production process parameters are reported and the waveguides characterization was performed by several techniques. Among them, we highlight the scanning electron microscopy (SEM), which was used to observe the profile of the waveguides, the surface roughness and thickness of the layers used for their production. Measurements of thin films optical transmittance allowed the determination of the optical absorption coefficient and refractive index of approximately 2.0, and also the confirmation of the thin films thicknesses obtained by Sputtering. RIB type waveguides were discarded due to the difficulties during the manufacturing process. Optical measurements of propagation losses, held in the PEDESTAL type guides, showed losses around 5 dB/cm at 633 and 1050 nm, for the best waveguides produced, and near-field profile measurements in addition to the simulation of the propagating modes, showed multimode coupling behavior. Optical internal gain around 13.5 dB/cm (at 805 nm) was obtained in waveguide with 30 µm width at ~75 mW estimated power pumping. Waveguide containing gold NPs were produced using adequate methodology that allowed the NPs nucleation (average size of 20 nm) and 22 dB/cm gain at 805 nm, therefore, twice higher than the value obtained for the same waveguide without NPs (30 ?m width). These results show that Tm3+/Yb3+ codoped GeO2-PbO waveguides, with or without metallic NPs, are promising for applications in photonic devices, with the creation of integrated amplifiers devices for operation in the first telecommunications window.

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