Les travaux réalisés dans ce manuscrit portent sur la fabrication de fibres optiques microstructurées (FOMs) à cœur suspendu en verre de tellurite pour la génération de supercontinuum au-delà de 2µm. Pour atteindre notre but nous avons tout d'abord réalisées les études des propriétés thermiques et optiques des verres TeO2-ZnO-R2O et TeO2-WO3-R2O (où R= Li, Na et K). La composition du verre 80TeO2-10ZnO-10Na2O (% molaire) a été sélectionnée pour la fabrication des FOMs destinées aux caractérisations du développement des effets non linéaires. La synthèse sous atmosphère sèche et oxydante nous a permis de réduire la concentration des groupements hydroxyles d’un facteur 30 par rapport à la fabrication du verre sous air. L’utilisation d'agents déshydratants (ZnF2 et TeCl4) permet d'abaisser encore la concentration des groupements OH jusqu’à quelques ppm. La composition du verre 80TeO2-5ZnO-5ZnF2-10Na2O donne une fibre transparente jusqu’à 4 µm laissant apparaître l’influence de l’absorption multiphonon. Utilisant les précurseurs commerciaux les plus purs nous avons pu réaliser une fibre de tellurite avec de très faibles pertes à 0,1 dB/m.Nous avons fabriqué des FOMs à cœurs suspendus avec des diamètres de cœurs variant de 2,7 µm à 3,5 µmet permettant de gérer la dispersion chromatique et de ramener la longueur d'onde du zéro dispersion entre 1500 nm et 1660 nm. Pour optimiser la génération du supercontinuum nous avons utilisé des sources laser pulsées pico- et femtosecondes pour pomper les fibres en régime de dispersion anormale. En parallèle aux mesures expérimentales, nous avons effectué des modélisations numériques basées sur la résolution de l'équation de Schrödinger non-linéaire généralisée. Les résultats expérimentaux, en bon accord avec les simulations, nous ont permis d'obtenir un élargissement spectral s’étalant de 850 nm à 2850 nm avec un niveau de puissance de sortie de 112 mW, dont l'extension à plus grandes longueurs d'ondes dans l'infrarouge est encore pour l'instant fortement limitée par l’absorption des groupements hydroxyles. Cependant la déshydratation du matériau, même si elle doit encore être améliorée a permis de montrer que lors de pompage à 2000-2200 nm le supercontinuum peut atteindre 4000-4500 nm, gamme de longueurs d’onde à partir de laquelle l’absorption multiphonon commence à être perceptible / The work reported in this thesis deals with the fabrication of suspended core tellurite microstructured optical fibers (MOFs) for supercontinuum generation beyond 2 µm. In order to reach our aim, we first studied thermal and optical properties of TeO2-ZnO-R2O and TeO2-WO3-R2O (where R = Li, Na and K) glasses. The glass 80TeO2-10ZnO-10Na2O (molar %) has been chosen in order to make MOFs for characterization of the generated non linear optical effects. Synthesis performed under dry and oxidative atmosphere allowed us to reduce the hydroxyl groups concentration by a factor of 30 compared to fabrication in air atmosphere. Use of dehydrating agents (ZnF2 and TeCl4) allowed to reduce again the OH groups concentration down to a few ppm. The glass composition 80TeO2-5ZnO-5ZnF2-10Na2O increases the fiber transparency up to 4 µm letting the influence of multiphonon absorption appear. Using the purest commercial raw powders, we have fabricated one tellurite fiber exhibiting very low losses (0,1 dB/m). We have fabricated suspended core MOFs with a core diameter varying from 2,7 µm up to 3,5 µm allowing to deal with the chromatic dispersion and to shift the zero dispersion wavelength down to the 1500-1660 nm range. In order to optimize the supercontinuum generation, we have used pico- and femtosecondes pulsed laser sources to pump the fibers in anomalous dispersion regime. In parallel to the experimental measurements, we have performed numerical simulations based on the resolution of the generalized nonlinear Schrödinger equation. The experimental results, in good agreement with the simulations, allowed us to point out a spectral broadening expending from 850 nm up to 2850 nm with a total output power of 112 mW, with an extinction near the longest infrared wavelengths which is again strongly limited by the hydroxyl groups absorption. However, the dehydrated material, even though it needs to be improved further, allowed to show that by pumping at 2000-2200 nm, the supercontinuum can reach 4000-4500 nm, the wavelength range from which the multiphonon absorption starts to be perceptible

Made available in DSpace on 2017-07-21T19:25:46Z (GMT). No. of bitstreams: 1 Joao Luiz Gomes Junior.pdf: 5004861 bytes, checksum: 0e45ece35c737cce76186e1babb5e257 (MD5) Previous issue date: 2015-03-26 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / In this work, the correlation between the structural morphology with thermal, optical and mechanical properties of (1 – x – y)TeO2-xLi2O-yMoO3 glasses was studied. The analysis was divided into three sets of samples, varying according to the composition for technique. The results reveal different behaviors for each set vitreous stabilities. The Raman spectroscopy and FTIR results showed a similar structural change between each set with decrease NBOs and new peaks position. The Raman and FTIR spectra results showed that with increasing content x and y, concomitantly, occur the conversion of TeO4 to TeO3+1 units, then, in addition to TeO3 units. Furthermore occurs change coordination in the structural units Mo atoms 4 to 6 and these structural changes. Li addition causes these structural changes. This fact confirmed by the Band Gap energy values, which increase with the increase of x and y, it decreases the optical basicity and refractive index values. By optical absorption measurements determined the Band Gap energy values of all samples. It was concluded that occur direct transitions allowed in all sets. The behavior of increasing Band Gap values and decreasing Optical basicity confirmed the decreasing in the NBO content leading to an indication of a more polymerized network for a variation of x mol%. Finally the behaviors elastic modulus and hardness, which shows decreased stiffness of the material with the incorporation of Li2O and MoO3 concomitantly, is presented. x / Este trabalho apresenta as correlações entre a morfologia estrutural e as propriedades térmicas, ópticas e mecânicas nos vidros (1 – x – y)TeO2 – xLi2O – yMoO3. Dividiram-se as análises em três conjuntos de amostras, de acordo com variação da composição, para cada técnica utilizada. Os resultados revelam diferentes comportamentos de estabilidades vítreas para cada conjunto. As medidas por espectroscopia de Raman e FTIR mostram mudanças estruturais similares entre cada conjunto com diminuição dos NBOs e novas posições de picos. Os resultados de Raman e FTIR mostram que com o aumento em conteúdo x e y ocorre a transformação de unidades TeO4 para TeO3 + 1 e, em seguida, para TeO3 além disso ocorre a mudança de coordenação do átomo de Mo de 4 para 6 e estas alterações estruturais têm sido relacionados com a adição de átomos de Li. Este fato é confirmado pelos valores de energia de Band Gap, que aumentam com o incremento de x e y, e diminuição dos valores de basicidade óptica e índice de refração. As energias de Band Gap, para todas as amostras, foram determinadas por medidas de absorção óptica na região do Ultravioleta. Foi concluído que ocorrem transições diretas permitidas em todos os conjuntos. E por fim apresenta-se os comportamentos de dureza e Módulo elástico, o que revela diminuição da rigidez do material com a incorporação de Li2O e MoO3 concomitantemente.

Made available in DSpace on 2017-07-21T19:25:51Z (GMT). No. of bitstreams: 1 Anderson Goncalves.pdf: 4030302 bytes, checksum: 6c04b9e37c0aaf5b0f1e9c3ecb66a216 (MD5) Previous issue date: 2016-02-22 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / In this work were studied the tellurite glasses of the glass system (100-x-y)TeO2-yLi2O-xBaO obtained by melt quenching method and characterized by techniques X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, linear refractive index and density measurements. The results of DRX measurements allowed classifying the samples with a standard characteristic diffraction amorphous structures. The DSC results show that the samples located close to the center of the glass-forming region have the highest values for the thermal stability, these being greater than 100 °C. Results of Raman spectroscopy show that there is a decrease in the connectivity of the network glass formed and of the TeO4 units with decreasing amount of tellurium. The units of TeO3+1 show an increase while for TeO3 units there is not a well defined behavior. The FTIR results show a decrease in TeO4 units and increase in TeO3 units with decreasing amount of tellurium. The Band Gap (Eg) energy values obtained are in agreement with those found in the literature for tellurite glasses. The results also indicate that electronic transitions that occur are of the type permitted indirect, still being observed an increase in Eg values as tellurium replaced. The structural changes create Non Bridging Oxygen (NBO), but the connection between the NBO and Te atoms is weak, which do not influence in Eg behavior. This influence starts to be strong above a certain value of BaO content (which depends on the Li2O content). While these values to the energy band gap increase, the values of the linear refractive index decreases, agreeing with what is presented in the literature. For polarizability ion oxide, only the samples with 5% Li2O shows behavior consistent with what is reported in the literature, inversely proportional to the Band Gap values and proportional to the refractive index. / Neste trabalho foram estudados os vidros teluretos do sistema vítreo (100-x-y)TeO2-yLi2O-xBaO obtidos pelo método de melt quenching e caracterizados pelas técnicas de Difração de Raios X (DRX), Calorimetria Diferencial de Varredura (DSC), Espectroscopia Raman, Espectroscopia no Infravermelho por Transformada de Fourier (FTIR), Espectroscopia UV-Vis, medidas de índice de refração linear e densidade. Os resultados das medidas de DRX permitiram classificar as amostras que apresentavam um padrão de difração característico de estruturas amorfas. Os resultados de DSC mostraram que as amostras localizadas próximas ao centro da região de formação vítrea apresentaram os maiores valores para a estabilidade térmica, sendo estes maiores que 100 °C. Os resultados de espectroscopia Raman mostraram que ocorre uma diminuição na conectividade da rede vítrea formada e das unidades de TeO4 com a diminuição da quantidade de telúrio. As unidades de TeO3+1 apresentaram um aumento, enquanto que para as unidades de TeO3 não há um comportamento bem definido. Os resultados de FTIR mostraram uma diminuição nas unidades de TeO4 e um aumento nas unidades de TeO3 com a diminuição da quantidade de telúrio. Os valores de energia de Band Gap (Eg) obtidos estão de acordo com os encontrados na literatura para vidros teluretos. Os resultados também indicam que as transições eletrônicas que ocorrem são do tipo permitida indireta, sendo observado ainda um aumento nos valores de Eg à medida que o telúrio é substituído. As modificações estruturais que ocorreram criam oxigênios não ligados (NBO – non-bridging-oxygen), mas os mesmos são fracamente conectados aos átomos de Te, não influenciando tanto nos valores de Eg até certa quantidade de BaO (que depende da quantidade de Li2O). Enquanto estes valores para a energia de Band Gap aumentam, os valores para o índice de refração linear diminuem, concordando com o que é apresentado pela literatura. Para a polarizabilidade do íon óxido, apenas as amostras com 5% de Li2O apresentaram comportamento coerente com o que é reportado na literatura, sendo inversamente proporcional ao Band Gap e proporcional ao índice de refração.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-14Bitstream added on 2014-06-13T18:53:40Z : No. of bitstreams: 1 sidel_sm_me_ilha.pdf: 1806167 bytes, checksum: 2a4e01caec0f051d6145b4716b656d11 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Neste trabalho foram estudados os vidros teluretos do sistema (20-x)Li2O-80TeO2- xWO3 com diferentes valores de x. Os resultados das medidas de DRX dos vidros como preparados confirmaram o comportamento amorfo das matrizes vitreas, e para os vidros tratados termicamente em diferentes temperaturas, acima de Tg, evidenciou-se a formacao das fases cristalinas durante o processo de cristalizacao. No vidro com x=0 (TL) foi observado a presenca das fases cristalinas -TeO2, -TeO2 e Li2Te2O5, e para os vidros com x=5 e 10 (TLW-5 e TLW-10) foi observado somente as duas primeiras fases cristalinas. Esse resultado sugere que o WO3 entra na estrutura como formador vitreo e inibe o crescimento da fase cristalina Li2Te2O5. Os parametros termicos, como a Tg, Tx e Tp, e o processo de cristalizacao dos vidros foram estudados por meio das medidas de DSC, e foram calculados os valores da energia de ativacao (E) e do parametro de Avrami. As curvas de DSC foram obtidas para taxas de aquecimento entre 2.5 e 12.5 K.mol-1 e particulas com tamanho 45-63 Êm. A energia de ativacao e o indice de Avrami foram calculados para cada fase cristalina e os picos de DSC foram ajustados utilizando funcoes gaussianas. As curvas de DSC das amostras tratadas termicamente apresentaram os picos de cristalizacao, referentes a cada fase cristalina, separadamente. Nas curvas de DSC do vidro TLW-5 foram observados tres picos de cristalizacao, embora as medidas de DRX tenham apresentado apenas duas fases cristalinas. Deste modo, a existencia deste terceiro pico de cristalizacao nas curvas de DSC do vidro TLW-5 confirmam o processo de transformacao da fase -TeO2 em -TeO2, conforme sugerido pelos dados de DRX e tambem pelos espectros de FT-IR. Nos espectros de infravermelho das tres matrizes vitreas foram verificadas as bandas de absorcao referentes as vibracoes das unidades tetragonais TeO4 e as bandas referentes as ligacoes W-O. / In this work the tellurite glasses of the system (20-x)Li2O-80TeO2-xWO3 with different x values were studied. The results of the XRD measurements for glasses as quenched confirmed the amorphous behavior of the glass matrix, and for the glasses thermally treated at different temperatures above Tg evidenced the phases crystalline formed during the crystallization process. In the glass with x=0 (TL) the presence of the -TeO2, -TeO2 and Li2Te2O5 crystalline phases was observed and for the glasses with x=5 and 10 (TLW-5 and TLW-10) were observed only the first two crystalline phases. This result suggests that WO3 enters in the structure as glass former and it inhibits the growth of the crystalline phase Li2Te2O5. The thermal parameters, as Tg, Tx and Tp, and the crystallization process of the glasses were studied through the DSC measurements, the values of the activation energy (E) and the Avrami s parameter were calculated. The DSC curves were obtained for heating rates between 2.5 and 12.5 K.mol-1, and 45-63 ìm particles size. The activation energy and the Avrami s parameter were calculated for each crystalline phase and the peaks of DSC were fitted using Gaussian functions. The DSC curves of the samples thermally treated showed the crystallization peaks, regarding each crystalline phase, separately. In the DSC curves of TLW- 5 glass three crystallization peaks were observed, although the measurements of XRD have presented only two crystalline phases. In this way the existence of this third crystallization peak in the DSC curves of the glass TLW-5 confirms the process of transformation of the phase -TeO2 in -TeO2, as suggested by XRD data and also for the FT-IR spectra. In the infrared spectra of the three glass matrix the absorption bands regarding the vibrations of the tetragonal units TeO4 and the bands regarding the connections W-O were observed.

Orientador: Keizo Yukimitu / Banca: Victor Ciro Solano Reynoso / Banca: Sandro Márcio Lima / Resumo: Neste trabalho foram estudados os vidros teluretos do sistema (20-x)Li2O-80TeO2- xWO3 com diferentes valores de x. Os resultados das medidas de DRX dos vidros como preparados confirmaram o comportamento amorfo das matrizes vitreas, e para os vidros tratados termicamente em diferentes temperaturas, acima de Tg, evidenciou-se a formacao das fases cristalinas durante o processo de cristalizacao. No vidro com x=0 (TL) foi observado a presenca das fases cristalinas -TeO2, -TeO2 e Li2Te2O5, e para os vidros com x=5 e 10 (TLW-5 e TLW-10) foi observado somente as duas primeiras fases cristalinas. Esse resultado sugere que o WO3 entra na estrutura como formador vitreo e inibe o crescimento da fase cristalina Li2Te2O5. Os parametros termicos, como a Tg, Tx e Tp, e o processo de cristalizacao dos vidros foram estudados por meio das medidas de DSC, e foram calculados os valores da energia de ativacao (E) e do parametro de Avrami. As curvas de DSC foram obtidas para taxas de aquecimento entre 2.5 e 12.5 K.mol-1 e particulas com tamanho 45-63 ƒÊm. A energia de ativacao e o indice de Avrami foram calculados para cada fase cristalina e os picos de DSC foram ajustados utilizando funcoes gaussianas. As curvas de DSC das amostras tratadas termicamente apresentaram os picos de cristalizacao, referentes a cada fase cristalina, separadamente. Nas curvas de DSC do vidro TLW-5 foram observados tres picos de cristalizacao, embora as medidas de DRX tenham apresentado apenas duas fases cristalinas. Deste modo, a existencia deste terceiro pico de cristalizacao nas curvas de DSC do vidro TLW-5 confirmam o processo de transformacao da fase -TeO2 em -TeO2, conforme sugerido pelos dados de DRX e tambem pelos espectros de FT-IR. Nos espectros de infravermelho das tres matrizes vitreas foram verificadas as bandas de absorcao referentes as vibracoes das unidades tetragonais TeO4 e as bandas referentes as ligacoes W-O. / Abstract: In this work the tellurite glasses of the system (20-x)Li2O-80TeO2-xWO3 with different x values were studied. The results of the XRD measurements for glasses as quenched confirmed the amorphous behavior of the glass matrix, and for the glasses thermally treated at different temperatures above Tg evidenced the phases crystalline formed during the crystallization process. In the glass with x=0 (TL) the presence of the -TeO2, -TeO2 and Li2Te2O5 crystalline phases was observed and for the glasses with x=5 and 10 (TLW-5 and TLW-10) were observed only the first two crystalline phases. This result suggests that WO3 enters in the structure as glass former and it inhibits the growth of the crystalline phase Li2Te2O5. The thermal parameters, as Tg, Tx and Tp, and the crystallization process of the glasses were studied through the DSC measurements, the values of the activation energy (E) and the Avrami’s parameter were calculated. The DSC curves were obtained for heating rates between 2.5 and 12.5 K.mol-1, and 45-63 ìm particles size. The activation energy and the Avrami’s parameter were calculated for each crystalline phase and the peaks of DSC were fitted using Gaussian functions. The DSC curves of the samples thermally treated showed the crystallization peaks, regarding each crystalline phase, separately. In the DSC curves of TLW- 5 glass three crystallization peaks were observed, although the measurements of XRD have presented only two crystalline phases. In this way the existence of this third crystallization peak in the DSC curves of the glass TLW-5 confirms the process of transformation of the phase -TeO2 in -TeO2, as suggested by XRD data and also for the FT-IR spectra. In the infrared spectra of the three glass matrix the absorption bands regarding the vibrations of the tetragonal units TeO4 and the bands regarding the connections W-O were observed. / Mestre

Ces travaux de thèse portent sur la synthèse et purification de matériaux vitreux utilisés pour le développement de fibres optiques à profils opto-géométriques variés, adaptées à la génération de supercontinuum (SC) entre 1 et 5 μm.Concernant la purification, plusieurs pistes ont été suivies, le meilleur résultat étant obtenu pour la purification du système vitreux TeO2-ZnO-Na2O au moyen du fluorure de zinc. Les mesures d'atténuation sur fibre mono-indice révèlent l'élimination presque complète des absorptions liées aux groupements OH entre 3 et 4 μm (taux d'impuretés OH dans la matrice inférieur à 1 ppm massique). Ces verres purifiés sont utilisés pour la fabrication de fibres optiques microstructurées (FOMs). Un élargissement spectral couvrant la fenêtre 0.6 μm - 3.3 μm est obtenu dans une fibre effilée à coeur suspendu. Aussi, une source compacte basée sur la génération de SC dans une FOM en tellurite est développée et appliquée à la détection de gaz (du méthane) entre 2 et 3 μm. Cependant un phénomène de vieillissement, lié à une interaction du coeur de la fibre avec la vapeur d'eau atmosphérique via la microstructure, et entraînant une augmentation des pertes optiques entre 3 et 4 μm, est mis en évidence dans ces fibres à coeur suspendu. Pour pallier ce problème, des fibres tout-solide à saut d’indice sont développées. La méthode de fabrication des préformes en verre, combinant les techniques de built-in casting et de rod-in-tube, est alors adaptée aux techniques de purification. Une fibre à saut d'indice à petit coeur en verres TNaGZ et TZNF purifiés a notamment été étirée et utilisée pour la génération d’élargissements spectraux dans différents régimes de dispersion. / This PhD thesis work focuses on the synthesis and purification of vitreous materials used for the development of waveguides with varied profiles, dedicated to supercontinuum (SC) generation between 1 and 5 μm.Concerning the purification of tellurite glasses, several leads were followed, but best results are obtained for the purification of the TeO2-ZnO-Na2O glassy system by the means of zinc fluoride. Attenuation measurements performed on several meter-long single-index fiber samples reveal the nearly complete elimination of water-related absorptions between 3 and 4 μm (OH ions concentration lower than 1 ppm mass.). Such water-purified glasses were firstly dedicated to microstructured optical fibers (MOFs) fabrication for SC generation. Spectral broadening between 0.6 and 3.3 μm is obtained in a suspended-core taper. Moreover, a compact source based on supercontinuum generation in tellurite MOFs is developed for a gas detection application in the 2-3 μm domain. However an aging process, due to water contamination and leading to the apparition of additional optical losses between 3 and 4 μm, has been identified in those suspended-core fibers. In order to avoid such transmission degradation, all-solid step-index fibers are developed. The preforms fabrication method, which combines the built-in casting and the rod-in-tube, is adapted to the purification techniques. An all-solid small-core waveguide made from purified TNaGZ and TZNF glasses is fabricated and moreover used for spectral broadening experiments in different dispersion regimes.

Orientador: Luiz Carlos Barbosa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-05T01:53:17Z (GMT). No. of bitstreams: 1 FernandezChillcce_Enver_D.pdf: 7309346 bytes, checksum: be836197654a767d0622dc9b2349506e (MD5) Previous issue date: 2005 / Resumo: Sistemas de transmissão de informação de grande capacidade, isto é, em termos de velocidade e transmissão de informação por longas distâncias, na área das comunicações ópticas demanda a fabricação de amplificadores de grande largura de banda. Logo, há necessidade de fabricar dispositivos com estas características. Dispositivos amplificadores baseados em vidros teluritos se enquadram dentro deste grupo de amplificadores de grande largura de banda e estes poderiam resolver este tipo de demanda. Nas últimas décadas muitas pesquisas voltaram-se ao desenvolvimento de amplificadores baseados em vidros teluritos e a caracterização deste tipo de materiais é importante hoje em dia. Neste trabalho apresenta-se primeiramente a caracterização estrutural, térmica, mecânica e óptica dos vidros teluritos devido à influência de composição dos constituintes TeO2, Na2O, WO3, Nb2O5. Logo a partir de vidros com composições adequadas, conseguiu-se fabricar tubos e barras com a finalidade de construir as pré-formas das fibras dos vidros teluritos. Apresentam-se métodos inéditos de sucção e centrifugação para a fabricação de barras e tubos de vidros teluritos. São demonstrados pela primeira vez os processos de fabricação das fibras ópticas convencionais (casca-núcleo) e fotônicas (micro-estruturas) dopadas com íons de Er 3+ e co-dopadas com íons de Tm3+ . Reportamos medidas de largura de banda de emissão, obtidas a partir dos espectros de emissão espontânea amplificada (ASE). Conseguimos mostrar uma largura de banda de emissão de 187nm usando uma fibra óptica dopada com 7500ppm de Er2O3 e co-dopada com 5000ppm de Tm2O3, a qual representa um dos maiores valores já reportadas até o momento. Foram realizadas medidas experimentais de tempo de vida do nível 4I13/2 dos íons de Er3+, usando lasers de bombeio de 790 (400mW) e 980nm (120mW), para fibras dopadas com íons de Er3+ e co-dopadas com diversas concentrações dos íons de Tm3+. Medidas da eficiência quântica de probabilidade de transição radiativa são demonstradas a partir de medidas do tempo de vida experimental e tempo de vida calculado, este último usando a teoria de Judd-Ofelt. O estudo do processo de transferência de energia (TE1) entre os níveis de 4I13/2 e 3F4 é realizado com a finalidade de analisar a eficiência quântica de amplificação em 1550nm / Abstract: In optical communications, high capacity information transmission systems demand broadband optical amplifiers. Therefore, it has become increasingly necessary to manufacture devices with such characteristics. Optical amplifier devices based on Tellurite glasses are ideal for manufacturing broadband optical amplifiers. In the last few decades, most researchers have focused on developing amplifiers based on Telluirte glass. As a consequence, Tellurite glass characterization is essential nowadays. In this work, we will report the structural, thermal, mechanical and optical characterization of tellurite glass as a function of TeO2, Na2O, WO3, Nb2O5 composition. From an optimum composition Tellurite glass, it was possible to fabricate tubes and rods for optical fiber pre-forms. Moreover, the novel methods of suction and centrifugation used to fabricate Tellurite glass tubes and rods are shown. For the first time we are reporting the fabrication of conventional core-clad and photonic Tellurite optical fibers with an Er3+-Tm3+ co-doped core. Also, we will report bandwidth measurements from amplified spontaneous emission (ASE) spectra. We have shown a 187nm (the highest broadband value reported) using a 7500ppm Er2O3- 5000ppm Tm2O3 co-doped tellurite optical fiber. In addition, measurements of 4I13/2 level lifetimes for Er3+ - doped tellurite optical fibers and Er3+ -Tm3+ co-doped tellurite optical fibers were taken using 790nm (420mW) and 980nm (120mW) pump lasers. We report the quantum efficiency measurements of radiative transition probability obtained from calculated and measured lifetimes. The calculated lifetime was obtained using the Judd-Ofelt teory. Finally, the study of energy transfer (ET) processes between 4I13/2 and 3F4 levels was carried out in order to observe the amplification quantum efficiency around 1550nm band / Doutorado / Física da Matéria Condensada / Doutor em Ciências

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-06-15T11:35:12Z No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:06:49Z (GMT) No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) / Made available in DSpace on 2018-09-03T16:06:49Z (GMT). No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) Previous issue date: 2018-03-02 / Vidros transparentes do sistema vítreo 0.95TeO2-(0.05-x)Sb2O3–xCuO contendo nanopartículas de cobre foi preparado com sucesso pelo método convencional de fusão – resfriamento dos materiais precursores, utilizando a rota redox do óxido de antimônio. Esta técnica de preparação de vidros permite a produção de nanopartículas metálicas durante a fusão dos materiais, através da reação de oxidação Sb3+ → Sb5+ + 2e-, que permite a redução de íons metálicos. A investigação estrutural foi realizada por calorimetria exploratória diferencial (DSC), difração de raios X (DRX) e espectroscopia Raman. Imagens de microscopia eletrônica de transmissão (TEM) e espectroscopia UV-visível evidenciaram a formação de clusters de nanopartículas de cobre cúbicas, distribuídas aleatoriamente em meio a matriz vítrea. A eficácia dos efeitos plasmônicos das nanopartículas de cobre promoveu a intensificação da fluorescência dos íons érbio. A interação da radiação excitante e amostra levou ao processo de excitação térmica, promovendo o aumento da população de níveis de energia específicos dos íons érbio, com consequente resposta óptica, evidenciada pela estrutura vibrônica presente no espectro de fluorescência dos vidros de teluritos contendo nanopartículas de cobre dopados com íons érbio. Além disso, os efeitos plasmônicos das nanopartículas de cobre na intensificação das emissões no infravermelho e conversão ascendente nos vidros de teluritos co-dopados com íons Yb3+/Ce3+/Er3+ sob excitação em 980 nm também foram investigados. As contribuições dos íons Yb3+ e Ce3+ também foram discutidas. A eficiência da ressonância do plasmon de superfície localizado (LSPR) das nanopartículas de cobre promoveu um melhoramento de cerca de 47% da emissão em 1550 nm dos íons Er3+. Além disso, o tempo de decaimento da transição Er3+: 4I13/2 → 4I15/2 aumentou em cerca de 50% na amostra contendo nanopartículas de cobre. Finalmente, os vidros de teluritos contendo nanopartículas de cobre apresentaram resultados interessantes quando utilizados como substratos para obtenção de espectros Raman intensificados por superfície (espectros SERS), sendo obtidos satisfatoriamente espectros SERS para soluções de 2,2’-bipiridina 1,0 × 10-5 mol.L-1 e do corante azul do Nilo 1,0 × 10-7 mol.L-1. / Transparent 0.95TeO2-(0.05-x)Sb2O3-xCuO glassy system containing copper nanoparticles were successfully prepared by the conventional melt quenching method of starting materials, using the antimony oxide redox route. This technique allows the production of metallic nanoparticles during melting, through the reaction Sb3+ → Sb5++ 2e-, which leads to the reduction of metallic ions. The structural investigation was carried out by differential scanning calorimetry (DSC), X ray diffraction (XRD) and Raman spectroscopy. Transmission electron microscopy image (TEM) and UV-visible spectroscopy evidenced the formation of cubic copper nanoparticles, randomly embedded in the glassy matrix. The effectiveness of the plasmonic effects of the copper nanoparticles provided the enhancement of the fluorescence of the erbium ions. The interaction between excitant radiation and sample led to the thermal excitation, which increased the population of specific energy levels of erbium ions, with consequent optical response into vibronic structure, as can be seen in the erbium-doped tellurite glasses containing copper nanoparticles. Furthermore, the plasmonic effects of the copper nanoparticles on the enhancement of the infrared and upconversion emissions intensities in the Er3+/Yb3+/Ce3+ co-doped transparent tellurite glasses under 980 nm laser diode excitation were investigated. The roles of Yb3+ and Ce3+ as sensitizers are also discussed. The effectiveness of localized surface plasmon resonance (LSPR) of the copper nanoparticles provided an improvement about 47% of the 1550 nm luminescence intensity of the Er3+ ions. Moreover, the lifetime of the Er3+: 4I13/2 → 4I15/2 transition increased around 50 % in the copper nanoparticle containing samples. Finally, the tellurite glasses containing copper nanoparticles showed interesting results as substrates for obtainment of surface enhanced Raman spectra (SERS spectra) and SERS spectra were satisfactorily obtained for 2,2'-bipyridine 1.0 × 10 -5 mol.L-1 and Nile blue dye 1.0 × 10-7 mol.L-1 solutions.

Transparent glasses embedded with TTB structured ferroelectric nano/micro crystals (K3Li2Nb5O15, Ba5Li2Ti2Nb8O30) were fabricated in various tellurite and borate based glass matrices and characterized for their physical properties. Nanocrystals of K3Li2Nb5O15 were successfully grown inside tellurite glass matrix via conventional heat-treatment route. Eventhough, tellurite glasses preferentially crystallize only on the surface, bulk uniform crystallization was achieved in the (100-x) TeO2 - x(1.5K2O-Li2O-2.5Nb2O5) system. Heat capacity studies revealed them to be thermodynamically less fragile than any other tellurite glasses ever reported in the literature. Pyroelectric and ferroelectric effects as well as second harmonic generation were demonstrated for the heat treated (glass nanocrystal composites) samples in this system. The conventional method of melt-quenching of constituent oxides could not yield Ba5Li2Ti2Nb8O30 crystallites. So, Ba5Li2Ti2Nb8O30 microcrystals were successfully formed in tellurite glass matrix by mixing pre-reacted Ba5Li2Ti2Nb8O30 ceramic powders with TeO2. The glass transition temperature was found to be the highest ever reported and this system was kinetically strong based on the fragility parameter. Dielectric studies revealed a frequency and temperature independent nature of the dielectric constant and very low dielectric loss. The SHG measurement which was carried out as a function of temperature demonstrated the incidence of blue second harmonic generation in the microcrystals present in the glass matrix. Ba5Li2Ti2Nb8O30 nanocrystals were successfully crystallized in the transparent glass system (100-x)Li2B4O7 – x(Ba5Li2Ti2Nb8O30). Dielectric constant increased while the dielectric loss decreased with the increase in Ba5Li2Ti2Nb8O30 content. Nuclear magnetic resonance spectroscopic studies were carried out to have an insight into the structure of this system. Transmission studies and refractive index measurements were performed and various optical parameters were calculated. Dielectric and transport properties were studied for the glasses and glass nano/microcrystal composites of all the systems reported in this thesis. Li+ ion was found to be responsible for conduction in all these systems. Evolution of self-organized nanopatterns of K3Li2Nb5O15 crystals has been demonstrated in the glass system (100-x) TeO2 - x(1.5K2O-Li2O-2.5Nb2O5) by excimer laser irradiation. The second harmonic signal observed by the Maker fringe technique has been attributed to the presence of well-aligned nano-sized grating structures in the glass system. Glasses belonging to the systems TeO2-K3Li2Nb5O15, TeO2-Ba5Li2Ti2Nb8O30 and V2Te2O9 undergo spinodal decomposition on exposing to KrF pulsed excimer laser. The spinodally phase separated structures were observed on all the surfaces of the samples. Ring shaped patterns were observed on several locations of the samples at higher frequency of laser pulses probably owing to the shock waves produced by the high intense laser beam. Line shaped patterns were found to originate on the sample surfaces when irradiated for longer periods.

The main motivation of this thesis is to study the long standing problem of mixed alkali effect (MAE) in oxyfluro vanadate glass systems from the point of view of structural arrangement and to investigate the effect of two rare earth ions, namely, erbium and europium on the structure of tellurium dioxide based glass. In glass science, it is well known that when one alkali in a glass matrix is gradually replaced by another alkali, leads to a non-linear variation in some of the physical properties. There are many a theories trying to explain this effect. Recently the renewed interest lies in explaining MAE in-terms of structural consideration. Rare earth (RE) ion doped glasses are of interest in a variety of applications in photonics because of the special optical properties exhibited by these materials. Atomic like f-f transitions of RE ions depend on the local environment of the these ions. A particular glass matrix may be able to bring out the optical properties of a RE ion better than the other matrix. In this regard structural characterization of a glass matrix with different RE ions for optical properties is of importance. Spectroscopic tech-niques are best suited to investigate structural arrangement in glasses and in this thesis we have used techniques like Raman, electron paramagnetic resonance (EPR), impedance, photoluminescence and UV- visible absorption spectroscopies. The thesis comprises of five chapters and an appendix. Chapter 1 consists of brief introduction of general properties of glasses and their behavior under different spectroscopic techniques. Chapter 2 deals with the sample preparation and the experimental techniques used in this work. Chapter 3 elaborates on the Raman and EPR spectroscopic studies on the structural arrangement of the mixed alkali oxyfluro vanadate glass systems. Chapter 4 focuses on the ac and electrical modulus analysis to study the MAE in the above samples. Chapter 5 deals with the optical spectroscopic techniques used to study the compatibility of RE ions (erbium and europium) with the tellurium dioxide based glass matrix. Chapter 1: Disordered materials pose a challenge to understand their structure mainly because of their random arrangement of the constituent units. In this chapter the glassy systems and the different experimental techniques used to study them are discussed in general. The behavior of glassy systems to the external stimuli in various frequency ranges is highlighted. A short review of mixed alkali effect in glasses mainly covering the advances in the last two decades is given. Brief outline of the theory of Raman, EPR and ac impedance spectroscopy are given. Chapter 2: This chapter discusses the major experimental techniques used in the thesis to study the glass systems at block diagram level. The Raman and EPR spectrometers are discussed. Experimental technique used in ac impedance measurement is outlined. Different methods of preparing glass are listed and melt quenching technique is discussed in detail. Chapter 3: This chapter discusses the results and analysis of Raman and EPR study in oxyfluoro vanadate glasses emphasizing MAE. The glass having batch formula 40V2O5 - 30BaF2 - (30 - x) LiF - xRbF (x = 0 – 30) is prepared by melt quenching technique. Raman spectroscopic study in back scattering geometry is performed to see the effect of alkali ions on the V – O bond length of VO6 polyhedra in the glass. The de-convoluted Raman peaks corresponding to V = O and VO2 are considered and the effect of alkali mixture on these bonds are studied. • The peak shift of V = O and VO2 bonds shows that V = O is affected only a little by the replacement of lithium (Li) by rubidium (Rb), while VO2 bond gets affected to a larger extent. • From the peak shift the most probable value of the bond length and the spread in it are estimated. The bond length corresponding to V = O is found to increase and that of VO2 decrease as a consequence of alkali replacement. • From the FWHM of the corresponding Raman peaks, it is concluded that O - Rb coordination sphere around VO6 polyhedra is more homogeneous than either O – Li or O - Li /Rb coordination. These results are published in J. Non-Cryst. Solids 370 (2013) 6. EPR studies on the samples are carried out in X band frequency and spin – Hamilto-nian parameters were extracted by simulating and fitting the EPR spectra to experimental data using EasySpin which is a Matlab toolbox. • it is observed that the ratio 4gjj=4g?, which is a measure of tetragonality of octa-hedral crystal symmetry of V2O5, varies non-monotonically with Rb content. • A model based on this observation is proposed. The essential idea of this model is that Rb atoms that are substituted for Li atoms initially prefer terminal positions over planar positions. Continued substitution then replaces planar Li atoms. It is seen that this model of “preferential substitution” explains the observation very well. • Another observation is that the EPR signal intensity, which is due to concentration of V4+ ions, also shows non-monotonous behavior with Rb content. This is also explained using preferential substitution, taking into consideration the oxidation states of the vanadium ions. • The value of 4gjj=4g?, is a minimum for all rubidium environments around V2O5, which infers that Rb coordination is more symmetric than all Li or Li−Rb. • A good correlation is found between Raman and EPR study of the above system. These results are published in J. Phys. Chem. A 118 (2014) 573. Chapter 4: The chapter brings out the results of ac conductivity and electrical mod-ulus study of MAE in the glass system mentioned above. The Agilent 4294A precision impedance analyzer operating in frequency range 40 Hz to 110 MHz, is used for per-forming impedance and capacitance experiments carried out in this thesis. Impedance measurements in our studies are performed in sandwich geometry. • Room temperature dc conductivity shows a decrease as Li is replaced by Rb and reaches its minimum - five orders less than its all Li value at 0.33 molar fraction of Rb, which is attributed to MAE. This observation is explained using the structural aspect. • Using the linear response theory the number of mobile ions participating in the conduction is estimated. • Imaginary part of the electrical modulus is fitted to Kohlrausch – Williams – Watts (KWW) relation by using a complex nonlinear least squares fitting procedure given by Bergmann. • The stretching parameter b estimated from the above procedure is found to exhibit MAE. The observed variation in b with Rb mole fraction is explained by taking into considerations the contributions from fast and slow processes, and coupling between different relaxing sites. The manuscript is under preparation. Chapter 5: This chapter illustrates the optical study of RE doped TeO2 based glasses to determine the suitability of a particular RE ion with a given glass matrix. TeO2 based glasses having a general formula (in mol %) 65TeO2 – 5BaF2 – 30ZnF2 (TBZ) were prepared by usual melt quenching technique. RE doping was done at the expense of TeO2. 3 mol % of Eu or Er are added to prepare RE doped glass. Raman, PL, UV-visible absorption studies are carried out on the glass samples. • From the peak shift, intensity variation and FWHM of the Raman spectra of the glass samples it is observed that Eu doped TBZ glass has a greater tendency towards depolymerizing the glass matrix by influencing the conversion of TeO4 units into the formation of TeO3 units. • PL spectra of the glass samples shows emission due to different possible transitions. Position of the peak of the de-convoluted spectra shows the position of the particular Stark component and the FWHM is a measure of the inhomogeneous broadening. • The UV-visible absorption spectra are used to calculate the optical density and fitted to the Mott equation to determine the band edge of the glass samples. It is seen that Eu doped TBZ glass has a lesser band gap than that of Er doped glass. The manuscript is submitted to Bul. Mat. Sci. Appendix : This consists of a collection of details of EDS study carried on the VBL series glasses and some MATLAB codes used to simulate the EPR spectrum for VBL series glasses.