Orientador: Pascoal Jose Giglio Pagliuso / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-06T01:46:23Z (GMT). No. of bitstreams: 1 Bittar_EduardoMatzenbacher_M.pdf: 1910389 bytes, checksum: 05b3ae1670a1bb296e2272ede7101d48 (MD5) Previous issue date: 2006 / Resumo: Primeiramente sintetizados por Remeika et al., para M = Rh, em 1980, os compostos intermetálicos ternários do tipo R3M4S n13, onde R = íon de terra rara e M = metal de transição (por exemplo, Rh, Ir e Co), cristalizam-se em uma estrutura cúbica. Apesar de possuírem uma estrutura cristalina relativamente simples, esses sistemas apresentam uma série de propriedades físicas interessantes que resultam da combinação de interações microscópicas fundamentais tais como: interaçãoes magnéticas tipo RKKY (Ruderman-Kittel-Kasuya-Yosida), efeitos de campo cristalino, acoplamento elétron-fónon e efeito Kondo. Dentro dessas séries, podemos encontrar, por exemplo, materiais supercondutores, férmions pesados, metais com ordenamentos magnéticos e paramagnéticos. Neste trabalho descrevemos o processo de síntese e as propriedades físicas para a série inédita com M = Co, que apesar de possuir suas estruturas catalogadas, jamais teve suas propriedades físicas reportadas (ao menos que tenhamos conhecimento). Monocristais de R3Co4Sn13, onde R = La, Ce, Pr, Nd e Gd, foram crescidos pela técnica de fluxo metálico. A estrutura cristalina desses compostos intermetálicos foi determinada por difração de raios X. Eles se cristalizam em uma estrutura cúbica tipo Yb3Rh4Sn13, grupo espacial Pm-3n, que apresenta 40 átomos por célula unitária. Medidas de susceptibilidade magnética, calor específico e resistividade elétrica foram realizadas nesses monocristais. Esses compostos ordenam-se antiferromagneticamente em baixas temperaturas (TN < 15 K) para R = Nd e Gd, enquanto o Pr3Co4Sn13 é paramagnético até 2 K. O composto de Ce3Co4Sn13 apresenta um comportamento tipo férmion pesado e o La3Co4Sn13 é um paramagneto de Pauli que sofre uma transição supercondutora em 2,3 K. Através de um modelo de campo médio (desenvolvido por colaboradores) que considera interações magnéticas entre primeiros vizinhos e efeitos de campo cristalino cúbico, ajustou-se simultaneamente as curvas de susceptibilidade magnética e calor específico obtendo-se os parâmetros A4 e A6 que caracterizam o potencial do campo cristalino cúbico para a série de intermetálicos R3Co4Sn13. Observou-se que estes parâmetros independem da terra rara, sofrendo variação apenas para o composto de Ce / Abstract: Firstly synthesized by Remeika et al., for M = Rh, in 1980, the intermetallic compounds R3M4Sn13, where R = rare-earth ion and M = transition-metal (for exemple, Rh, Ir and Co), crystallizes with a cubic structure. These compounds include, for instance, superconducting materials, heavy-fermions, magnetic materials and paramagnetic metals. Complex magnetic ordering, crystalline electrical field effects (CEF) and Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic interaction are interesting physical phenomenal found in systems of these family, despite of their simple cubic structure. These facts make this series an excellent class of compounds to explore the interplay between these physical properties. In this work we describe the synthesis process and the physical properties of a novel serie of R3M4Sn13 for M = Co and R = La, Ce, Pr, Nd and Gd. R3Co4Sn13 single crystals were grown from metallic flux. Measurements of X-ray diffraction, magnetic susceptibility, heat capacity and electrical resistivity were performed. They crystallize in a cubic Yb3Rh4Sn13 type structure, space group Pm-3n, which has 40 atoms per unit cell. These compounds order antiferromagnetically at low temperature (TN < 15 K) for R = Nd and Gd, while Pr3Co4S n13 is paramagnetic down to 2K. The Ce3C o4Sn13 compound display heavy fermion behavior at low temperature and La3Co4Sn13 is a Pauli paramagnetic which superconducts at 2.3 K. With a mean field model (developed by collaborators) which considers magnetic interactions for the first neighbors and a cubic CEF, we fit simultaneously the magnetic susceptibility and heat capacity data obtaining the CEF parameters A4 and A6 that characterize the CEF potential for the R3Co4Sn13 intermetallic series. We observed that theses parameters are rare-earth independents, being the Ce-base compound the only exception / Mestrado / Física da Matéria Condensada / Mestre em Física

Orientadores: Ítalo Odone Mazali, Fernando Aparecido Sigoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T16:11:21Z (GMT). No. of bitstreams: 1 Mello_LauraBissolide_M.pdf: 5917459 bytes, checksum: 84ba21daf327140c83f0038b51e81366 (MD5) Previous issue date: 2013 / Resumo: No presente trabalho, buscou-se avaliar as mudanças promovidas pela substituição parcial e total de TiO2 por GeO2 em vidros niobofosfato co-dopados com Er/Yb previamente estudados pelo grupo. Uma série de sistemas vítreos de composições 20Na2O-30Nb2O5-(5-y-z)Al2O3-30P2O5-(15-x)TiO2-xGeO2-yEr2O3-zYb2O3 com x = (0; 5; 10; 15), y = (0; 1), z = (0; 2) mol%, obtidos por fusão-resfriamento, foram investigados quanto à sua estrutura, propriedades ópticas e de luminescência. Análises de FTIR e Raman sugerem que a estrutura de vidro não se altera de forma significativa ao longo da série de substituições de TiO2 por GeO2 e, consequentemente, a coordenação dos elementos devem se manter semelhantes. Na literatura reporta-se que íons Ge têm preferencialmente coordenação 4; entretanto, nos sistemas estudados, sugere-se que o Ge apresente coordenação 6, semelhante à do Ti substituído. Esta proposição é confirmada pelos espectros de P MAS-NMR, os quais indicam que os vidros possuem cadeias majoritariamente do tipo pirofosfato, sem mudança no grau de polimerização com as substituições. Também pôde-se confirmar a manutenção da coordenação com os resultados obtidos da fotoluminescência dos sistemas vítreos co-dopados, nos quais os tempos de vida de emissão do íon Er (5 ms) e parâmetros de intensidade de Judd-Ofelt dos diferentes sistemas vítreos são muito semelhantes entre si, e o processo de emissão de upconversion dos vidros dopados envolve 1,5 fótons. Quanto ao comportamento térmico, observa-se que os vidros contendo maior proporção de GeO2 têm maior estabilidade térmica e são, portanto, mais resistentes à desvitrificação quando comparado às composições contendo mais TiO2 / Abstract: The aim of this work was to study the changes promoted by partial and complete substitution of TiO2 by GeO2 in Er/Yb co-doped niobophosphate glasses previously studied by the group. A series of glasses with composition 20Na2O-30Nb2O5-(5-y-z)Al2O3-30P2O5-(15-x)TiO2-xGeO2-yEr2O3-zYb2O3 with x = (0; 5; 10; 15), y = (0; 1), z = (0; 2) mol%, prepared by quenching-melt process, were investigated with respect to their structural, optical and luminescence properties. FTIR and Raman analysis suggest that the glassy chains didn¿t suffer relevant modifications with the TiO2 substitutions by GeO2 and as a consequence, the coordination of the ions weren¿t affected. The coordination of the Ge ion is reported as mainly thetraedral; however, in the present work, is suggested that Ge ion has an octahedral coordination, as well the TiO2 substituted. This proposition is confirmed by the P MAS-NMR spectra, which showed mainly pyrophosphate chains of the different glasses, without changings in their polymerization after the substitutions. The similar ions coordination was also confirmed by the photoluminescence behavior of the different co-doped samples, which showed equal Er emission decay lifetimes (5 ms) and Judd-Ofelt intensity parameters, and the upconversion emission process involved 1,5 photons. Regarding the thermal behavior, it is noted that the glasses containing higher proportions of GeO2 have higher thermal stability and are therefore more resistant to devitrification when compared to compositions containing more TiO2 / Mestrado / Quimica Inorganica / Mestra em Química

Dans de nombreux systèmes de traitement de l'information, le signal est numérisé, traité informatiquement, puis reconverti dans le domaine analogique. La faible bande passante de ces étapes de conversion numérique/analogique limite considérablement le débit d'informations traitées. Une solution purement analogique améliorerait donc considérablement le temps de traitement et la bande passante. Notre approche consiste à transférer le signal RF à traiter sur une porteuse optique puis à procéder à son traitement dans le domaine optique. L'étape de traitement est assurée par la traversée d'un cristal dopé en ions terres rares convenablement "programmé". Cette étape de programmation consiste à graver dans le profil d'absorption du cristal une fonction caractéristique de l'opération de traitement du signal à réaliser. Deux opérations ont ainsi été implémentées : 1) le renversement temporel de signaux RF : c'est l'opération consistant à générer analogiquement le signal renversé temporellement s(−t) d'un signal incident s(t). La fonction à graver dans le profil d'un cristal d'Er:YSO est alors un réseau spectral de pas variable. 2) l'analyse spectrale large bande instantanée : c'est l'opération permettant d'accéder au contenu spectral d'un signal. On impose au protocole de fournir instantanément le spectre d'un signal large bande. La fonction à graver dans le profil d'un cristal de Tm:YAG est alors un réseau spectro-spatial de pas variable. / Many signal processing devices rely on the digitalization of the incoming signal. After being processed by a computer, the signal needs to be converted back to its original analog form. Due to the limited bandwidth of analog-to-digital and digital-to-analog stages, the data flow rate is significantly limited. A purely analog solution would then significantly improve the processing time and bandwidth. In our approach, we first transfer the incoming RF signal on an optical carrier, allowing us to process it in the optical domain. For the processing stage, we propose to engrave the absorption profile of a rare earth ion-doped crystal with different shapes (each shape is specific to one processing operation). In this work, two operations are implemented: 1) time reversal of RF signals: we analogically generate the time reversed replica s(−t) of an incoming signal s(t). For this purpose, the shape to be engraved in the absorption profile of a Er:YSO crystal is a non-periodic spectral grating. 2) instantanous broadband spectral analysis: we want to instantaneously access the spectral components of a broadband signal. For this purpose, the shape to be engraved in the absorption profile of a Tm:YAG crystal is a spectro-spatial grating with a variable period.

La propriété de creusement spectral, que l’on retrouve dans certains cristaux dopés aux ions de terres rares refroidis à basse température offre des possibilités prometteuses pour le traitement analogique de signaux radiofréquence. En effet, celle-ci permet de programmer des fonctions de traitement dans le spectre d’absorption du cristal.Partant des premières démonstrations de principe d’un analyseur spectral radiofréquence large bande instantanée, l’objectif est d’en améliorer les performances, ce qui requiert une modélisation précise de l’interaction laser-matière et de l’ensemble des perturbations inhérentes à la montée en maturité technologique du dispositif. Nous avons par conséquent développé un modèle et cherché à étendre son domaine de validité pour qu’il s’applique à un maximum de protocoles.Nous l’avons ensuite appliqué à un matériau en particulier, à savoir un cristal de Tm³ ⁺ :YAG. Après avoir effectué une série de mesures des différentes caractéristiques intrinsèques à ce cristal, nous avons choisi un protocole d’application relativement proche de celui de l’analyseur spectral que nous cherchons à optimiser, à savoir la création de réseaux spectraux large bande. La comparaison des résultats expérimentaux à ceux de notre modèle nous a permis de démontrer sa validité.Nous avons finalement appliqué notre modèle au cas précis de l’analyseur spectral radiofréquence. Les simulations nous ont permis de déterminer théoriquement comment optimiser ses performances, en particulier la dynamique, avec des paramètres réalistes, atteignables expérimentalement. / The Spectral Hole Burning property, found in some rare-earth ion-doped crystals at low temperature is particularly relevant for analogic processing of radiofrequency signals. Indeed, it enables processing functions to be programmed in the crystal’s absorption spectrum.Starting with the first demonstrations of a wideband radiofrequency spectrum analyser, we aim at improving its performances, which requires an accurate modelling of the light-matter interaction and all the perturbations arising from the upgrade in TRL (Technology Readiness Level). Therefore, we have developed a model and extended its validity domain to a broad variety of SHB-based protocols.We applied this model on a particular material, namely a Tm³ ⁺:YAG crystal. After measuring experimentally the relevant intrinsic parameters of this crystal, we applied our model to a protocol which is quite similar to the one of the spectrum analyser we aim at optimizing, namely the engraving of wideband spectral gratings. The comparison of our experimental results to the simulations from our model proved its validity.Finally we applied it to the exact case of the radiofrequency spectrum analyser. With the simulations, we determined how to improve its performances, and particularly increase the dynamic range with realistic experimental parameters.

<p>Rare-earth ions (REIs) in solids are attractive optical centers due to their stable optical transitions and long lifetimes. Miniaturizing solid-state devices incorporated with REIs as quantum centers can play a key role in the implementation of future multiplexed quantum optical networks. Among the solid-state host materials for REIs, the Dissertation specifically studies silicon nitride (SiN) and crystalline lithium niobate (LN) materials. </p> <p><br></p> <p>SiN and Si are a CMOS-compatible material, and leveraging the well-developed technologies from the microelectronics industry is important for practical purposes because the cost of fabrication can be significantly reduced. Also, a recent study showed that the inhomogeneous broadening of Er-doped crystalline Si can be as low as 1GHz. Moreover, low-loss waveguide and high Q resonators were reported, making it a promising host for strong light-atom interactions. </p> <p><br></p> <p>On the other hand, LN is a promising host material for REIs due to its unique piezoelectric, electro-optic, nonlinear, and acousto-optic properties. Until recently, direct etching of LN has not been realized. But recently developed lithium niobate on insulator (LNOI) platform and direct LN etching techniques made it possible to fabricate low loss and strong confinement waveguides. Furthermore, LN has been used for quantum light storage and on-chip photon generation and wavelength conversion. Motivated by these recent advances and the interesting properties of LN, the Dissertation investigates thin-film crystalline LN. </p> <p><br></p> <p>In this dissertation, the methods and processes of fabricating long waveguides and ring resonators in 1)silicon nitride and 2)lithium niobate are introduced and the study of optical characterizations of Yb3+ ions in two different solid-state host materials are presented, specifically including photoluminescence (PL) spectroscopy, lifetime measurement, absorption and other characterization of light-atom interactions. </p> <p><br></p> <p>Furthermore, a study of Tm3+ ion arrays in thin-film LN is presented, specifically including the PL lifetime comparison between the periodically ordered sample and the randomly ordered sample and the scattering/reflection measurement from periodic ion arrays, both indicating the early evidence of cooperative effects of arrays in solids. Also, the theory of collective emission from atomic arrays is presented. Finally, I propose future plans to improve the fabrication process in these materials and possible future research directions based on the Dissertation.</p>

We are living in an age where the demand for energy is growing rapidly. This means that supplies to easily accessible oil and natural gas is unlikely to keep up with the demand as times goes on. The world will have to use energy more efficiently and increase its use of other sources of energy. This study is aiming at developing materials that will improve the power conversion efficiency of photovoltaic cells by using up and down-converting phosphor materials. ZnTiO3-Zn2TiO4 composite and ZnTiO3 phosphors doped with Er3+,Yb3+, Eu3+ and Al3+, which display up and down-converted luminescence were synthesized by a simple high temperature conventional solid state reaction method. The structure, particle morphology, absorption, photoluminescent properties and elemental distribution were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR absorption spectrometer, photoluminescence (PL) spectroscopy and time of flight secondary ion mass spectroscopy (TOF-SIMS), respectively. ZnTiO3-Zn2TiO4 composite doped with different concentration of Er3+ ions was synthesized via solid state chemical reaction method at 1100 ℃. The X-ray diffraction (XRD) confirmed the crystallization of both the hexagonal ZnTiO3 and cubic spinel Zn2TiO4 phases of the composite. The SEM images of ZnTiO3-Zn2TiO4:Er3+ composite showed that the particle morphology was made up of faceted hexagons. Furthermore, the ZnTiO3-Zn2TiO4:Er3+ phosphors were excited in the near-infrared (NIR) region using a laser diode with a wavelength of 980 nm and displayed both green and red up-conversion emission bands in the visible range at 543, 553, 650 – 670 nm. These emission bands correspond to 2H11/2, 4S1/2→ 4 I15/2 and 4F9/2→ 4 I15/2 transitions of Er3+ ions. However, the interaction mechanisms involved in the upconversion process of ZnTiO3-Zn2TiO4:Er3+ phosphor is discussed with the help of an energylevel schematic diagram and the number of the photons involved in the up-conversion luminescence process were of a double photon mechanism. The decay lifetimes were studied by fitting the luminescence decay curve with a single-component exponential decay. Er3+ and Yb3+ incorporated zinc titanate (ZnTiO3) phosphor powders were synthesized using conventional solid-state reaction method at 800 ℃. A ZnTiO3:Er3+,Yb3+ phosphor that resembled an ecandrewsite single phase with space group R-3 (148) was obtained, as proven by X-ray diffraction (XRD). The SEM image showed a surface morphology composed of agglomerated irregular shaped particles. The energy band gap of ZnTiO3 was engineered by incorporating different concentration of the dopant ions. After irradiating ZnTiO3:Er3+with a 980 nm laser beam, the phosphor up-converted the photon energy to display green and red emissions in the visible range that were positioned at 527, 545 and 665 nm. Enhancement of the luminescence intensity of ZnTiO3:Er3+ phosphor was achieved by variation of Er3+ concentration. Co-doping with Yb3+ ions proved to be effective in enhancing the luminescence intensity of the optimized Er3+ ion emission and new emission bands at 410 and 480 nm, through an energy transfer mechanism were observed. The enhancement of the lifetime of the up-conversion luminescence was also achieved by co-doping ZnTiO3:Er3+ phosphor with Yb3+ ion. The energy transfer mechanisms involved in Er3+ - Yb3+ co-doped ZnTiO3 phosphor was illustrated and discussed in detail. The ZnTiO3:Er3+, Yb3+ thin films were successfully deposited by pulsed laser deposition (PLD) by varying the silicon (100) substrate temperature. The distribution of the ions in the films was investigated and the TOF-SIMS showed that the ions were homogeneously distributed throughout the ZnTiO3 host lattice which indicated a successful incorporation of the Er3+ and Yb3+ ions. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO3:Er3+, Yb3+ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. The ZnTiO3:Er3+, Yb3+ thin films also exhibited up-conversion emission from Er3+ electronic transitions, with violet, blue, green and red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4 I15/2, 4F7/2 → 4 I15/2, 2H11/2 → 4 I15/2, 4S3/2 → 4 I15/2 and 4F9/2 → 4 I15/2 transitions, respectively. These up-conversion emissions were enhanced by increasing the silicon substrate temperature during the deposition. ZnTiO3 host co-doped with Eu3+ and Al3+ was synthesized by solid state reaction to convert the UV photons to visible photons. Charge compensation effects of Al3+ incorporated ZnTiO3:Eu3+ as a co-dopant ion was reported in detail. The structural and morphological characterization show that the addition of Eu3+ and Al3+ does not affect the phase formation and the surface morphology of the host. The visible emission intensity of Eu3+ ions for an optimal concentration of 2 mol% under 395 nm excitation, was enhanced by incorporating Al3+. The energy level diagram showing the charge compensation mechanism was proposed for the co-doped system. / College of Engineering, Science and Technology

An zwei verschiedenen Kristall-Typen, an Tb3Ga3O12 (TGG) und an KTaO3, konnten die prinzipiellen Vorteile der ODMR-Technik (optisch detektierte magnetische Resonanz) gegenüber der konventionellen ESR (Elektronenspinresonanz) durch die erzielten interessanten Untersuchungsergebnisse belegt werden. Die ODMR-Technik ermöglichte Spinresonanz-Untersuchungen an TGG. Dieses Material ist durch sein paramagnetisches Grundgitter für konventionelle ESR nicht zugänglich. Das für den "bulk"-Paramagnetismus verantwortliche Tb3+ konnte in allen Kristallen nachgewiesen werden. Die Identifizierung erfolgte durch Untersuchungen der Proben über MCD (magnetic circular dichroism), ODMR via MCD, ODMR via den Faraday-Effekt und zusätzlichen theoretischen Betrachtungen mit Hilfe von Kristallfeld-Rechnungen. Bei dem zweiten in TGG identifizierten Zentrum handelt es sich um Ce3+, dessen ODMR interessanterweise vor dem starken paramagnetischen Hintergrund durch das Tb-Untergitter beobachtbar ist. Dieser Defekt ist nur in den Ca/Ce-dotierten Proben mit Ce-Überschuß nachweisbar - was vermuten läßt, daß Ce zur Ladungskompensation der Ca2+-Defekte auf Tb3+- und Ga3+-Plätzen nur vierwertig eingebaut wird. Ist die Ce-Dotierung dagegen höher als zur Ladungskompensation nötig, so wird es vorwiegend dreiwertig eingebaut. Es wurde durch Vergleich von MCD-, LD- und Spektren der optischen Absorption gezeigt, daß Ce3+ das photochrome Zentrum ist, welches für einen speziellen photorefraktiven Effekt in TGG verantwortlich ist. Der zweite Teil dieser Arbeit gilt der Untersuchung von Fe-dotiertem KTaO3 mit den Methoden der ODMR. Im Vergleich zum TGG konnte hier eine überraschend große Anzahl verschiedener Zentren identifiziert und über deren Spinresonanz und optische Eigenschaften charakterisiert werden. Für das aus ESR-Untersuchungen bereits bekannte axiale Fe3+-Oi -Zentrum wurde anhand dessen tagged MCD-Messungen gezeigt, daß die optischen Übergänge dieses unsere Kristalle dominierenden Defektes erstaunlich weit in den roten Spektralbereich hineinreichen. Der Nachweis der optischen Orientierbarkeit dieses molekülartigen Defekt-Komplexes stellt ein weiteres sehr interessantes Ergebnis dieser Arbeit dar. Das in den "as grown" Kristallen metastabil vorhandene (ebenfalls axiale) Fe4+-Oi konnte zum ersten Mal beobachtet werden. Durch Oxidationsbehandlungen (Absenken des Fermi-Niveaus) der Fe-dotierten KTaO3 -Proben läßt sich erreichen, daß Fe4+-Oi bei tiefen Temperaturen als stabiler Zustand vorhanden ist. In reduzierten Proben konnte ein weiteres in zwei Ladungsstufen auftretendes Zentrenpaar identifiziert werden. Das axiale Fe3+-Vo war durch ESR-Untersuchungen bereits bekannt und ist bei X-Band MW-Frequenzen allein über die ESR vom Fe3+-Oi nicht zu unterscheiden. Der MCD des Fe3+-Vo mit einer Bande bei 370 nm unterscheidet sich jedoch sehr deutlich von den bis ins Rote reichenden MCD-Banden des Fe3+-Oi. Je nach Reduktionsgrad der Probe ist der Defekt in der Ladungsstufe Fe2+-Vo zugleich präsent oder kann durch eine Umladungsbeleuchtung erzeugt werden. Dieses neu entdeckte Zentrum besitzt eine dem Fe4+-Oi ähnliche ODMR-Winkelabhängigkeit. Zusätzlich zu den vielen axialen Fe-Zentren zeigte sich auch ein Fe3+-Zentrum in lokaler rhombischer Symmetrie. Die Betrachtung der für diesen Defekt signifikanten Spin-Hamilton-Parameter von Helium bis Raumtemperatur ermöglichte es, die zwei in der Literatur diskutierten Fe3+rh-Zentren auf ein einziges Zentrum zurückzuführen. Das nur metastabil und mit axialer Symmetrie auftretende O--Zentrum wurde auch in nicht Fe-dotierten KTaO3-Kristallen entdeckt. Neben der Untersuchung der erwähnten Defekte wurde eine erhöhte Aufmerksamkeit den in der Polarisationsspektroskopie (prinzipbedingt) häufig auftretenden Artefakten gewidmet.

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No. of bitstreams: 1 alyssonmirandadefreitas.pdf: 61947422 bytes, checksum: fabd334a3f9ff790ff3a3b4c6d2016d5 (MD5) Previous issue date: 2015-03-30 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, propomos uma nova matriz vítrea, denominada de PZABP, de composição nominal 60P205 . 15ZnO . 5A/203 . 10Ba0 . 10Pb0, em mol %, nanoestruturada com nanocristais de ZnTe e dopada com íons de Yb3+ e avaliamos a viabilidade de utilização deste material para aplicações em dispositivos fotônicos, tais como, lasers de alta potência, fibras ópticas lasers, lasers de pulsos ultra-curtos e lasers sintonizáveis na região do infravermelho. As amostras foram produzidas através do método de fusão-resfriamento, sendo confeccionado dois conjuntos. Um deles, PZABP + xYb, foi dopado apenas com íons de Yb3+ em concentrações que variam de 0% a 10%, em wt%, com acréscimos de 1%. Outro conjunto, PZABP + 1ZnTe + xYb, foi dopado com 1% de nanocristais semicondutores de ZnTe e íons de Yb3+ em concentrações que variam de 0% a 5%, em wt%. As propriedades ópticas das amostras e as interações entre os íons de Yb3+ vizinhos e entre os nanocristais de ZnTe e os íons Yb3+ foram estudadas através das técnicas de Absorção Óptica, Fotoluminescência e Fotoluminescência Resolvida no Tempo. A Espectroscopia de Lente Térmica e a técnica de Capacidade Térmica Volumétrica, também conhecida como pc, foram utilizadas para caracterizar as propriedades térmicas das amostras. Alguns dos principais parâmetros que analisam o desempenho e o limiar de ação laser do material foram estimados a partir da determinação das seções de choque de absorção e emissão dos íons de Yb3+ quando inseridos nessa matriz. De forma geral, a matriz vítrea PZABP demonstrou-se um excelente material hospedeiro para os íons de Yb3+ por apresentar uma ampla janela óptica, ser tolerante a altas concentrações de dopantes e não formar aglomerados de íons de Yb3+, garantindo assim uma boa qualidade óptica para aplicações em fotônica. Parâmetros importantes como o tempo de vida e a eficiência quântica do material apresentaram valores comparáveis aos encontrados na literatura. Foi verificado que a presença dos nanocristais de ZnTe intensificou a emissão dos íons de Yb3+, indicando que houve transferência de energia entre os nanocristais e os íons. Com relação a análise térmica, foram encontrados valores desejáveis para aplicações que envolvem ambientes superaquecidos. A alta difusividade e condutividade térmica das amostras as permitem dissipar calor rapidamente e a baixa variação do caminho óptico com a temperatura (ds/dT) indica que o feixe não sofre desvios muito acentuados no interior da cavidade óptica. Os parâmetros de emissão laser encontrados estão comparáveis aos de outras matrizes vítreas já estudadas, embora a presença dos nanocristais de ZnTe pareça prejudicar esses parâmetros. Portanto, de acordo com os resultados encontrados e com base nas possíveis melhoras que podem ser realizadas, concluímos que a matriz vítrea PZABP nanoestruturada com nanocristais semicondutores de ZnTe e dopada com íons de Yb3+ é um material viável para aplicações em dispositivos fotônicos de alta potência. / In this work, we have proposed a new glass matrix, called PZABP, with nominal composition 60P205 . 15ZnO . 5A/203 . 10Ba0 . 10Pb0, in mol %, nanostructured with ZnTe semiconductor nanocrystals and doped with Yb3+ ions, then, we analized its availability to photonics devices application like high power lasers, optical fiber lasers, ultra-short pulses lasers and tunable lasers in the infrared region. The samples were produced by fusion method, being made two sets. One, PZABP + xYb, was doped with Yb3+ ions at various concentrations from 0% to 10%, in wt%.The other one, PZABP + 1ZnTe + xYb, was doped with semiconductors nanocrystals of ZnTe and Yb3+ ions at concentrations from 0% to 5%, in wt%. The optical properties of the samples and the interactions between neighbors Yb3+ ions and between semiconductors nanocrystals of ZnTe and Yb3+ ions were studied by Optical Absorption, Photoluminescence and Time Resolved Photoluminescence techniques. Thermal Lens Spectroscopy and Heat Volumetric Capacity, also know as pc, were used to characterize the thermal properties of the samples. The main parameters that avail the performance laser and the threshold action laser were estimated by the determination of absorption and emission cross section of the Yb3+ ions when they are inserted in this matrix. The PZABP glass matrix showed to be an excellent host material to Yb3+ ions because it present a large optical window, it is tolerant to high dopants concentration and not showed Yb3+ clusters. Important parameters like lifetime and quantum efficience showed values comparable to others found in the literature. It was verified that the presence of ZnTe nanocrystals had enhanced the emission of the Yb3+ ions, indicating that have occurred energy transfer between ZnTe nanocrystals and Yb3+ ions. Thermal properties have presented interesting values to applications that involved superheated environment. The high thermal diffusivity and high thermal conductivity allow the sample to dissipate the heat quickly. The low variation of the optical path with the temperature (ds/dT) indicate that the laser beam not strongly deviates into the optical cavity. The laser performance parameters obtained are comparable to the other glass matrix found in the literature, although the presence of the ZnTe nanocrystals seems to prejudice these parameters. According with the results found and the improvement that could be done, we have conclude that the glass matrix PZABP nanostructured with semiconductores nanocrystals of ZnTe and doped with Yb3+ ions is a viable material to application in high power photonics devices materials.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-27T20:21:11Z No. of bitstreams: 1 marcelinocordeironeto.pdf: 92399516 bytes, checksum: 0d59ef50bab71144a1450179047a4f30 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-07T21:07:35Z (GMT) No. of bitstreams: 1 marcelinocordeironeto.pdf: 92399516 bytes, checksum: 0d59ef50bab71144a1450179047a4f30 (MD5) / Made available in DSpace on 2017-08-07T21:07:35Z (GMT). No. of bitstreams: 1 marcelinocordeironeto.pdf: 92399516 bytes, checksum: 0d59ef50bab71144a1450179047a4f30 (MD5) Previous issue date: 2014-05-06 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo desta tese é analisar se as propriedades ópticas apresentadas neste trabalho qualificam o sistema vítreo PZABP, com composição nominal 60P2O5.15ZnO.5Al2O3.10BaO.10PbO (% mol), dopado com íons terras-raras trivalentes, itérbio (Yb3+) e európio (Eu3+) e, também, com nanopartículas semicondutoras de telureto de zinco (ZnTe) como potencialmente útil para construção de dispositivos de emissão de luz na região de 920 nm a 1060 nm. A teoria de Judd-Ofelt é usada nos cálculos dos parâmetros de intensidade Ωλ(λ = 2,4,6). Técnicas de microscopia de força atômica (AFM), absorção óptica (AO), fotoluminescência (FL) e fotoluminescência resolvida no tempo (FLRT) caracterizam o sistema vítreo. A finalidade do ZnTe é aumentar a seção de choque de absorção do sistema vítreo PZABP e transferir energia para os íonsEu3+ e/ouYb3+. A formação de dois tipos de nanopartículas semicondutoras de telureto de zinco ZnTe-propriedades de bulk e pontos quânticos – foram identificados. FL e FLRT sugerem transferência de energia dos íons de Eu3+ e/ou ZnTe para os íons deYb3+. / The aim of this thesis is to analyze if the optical properties presented in this work qualify the glass system PZABP, with nominal composition 60P2O5.15ZnO.5Al2O3.10BaO.10PbO(% mol), doped with trivalent rare earth ions, ytterbium (Yb3+) and europium (Eu3+) as well as zinc telluride (ZnTe) as potentially useful for light emission devices in the infrared region from 920 nm to 1060 nm. The Judd-Ofelt theory is used to calculate the intensity parameters Ωλ(λ = 2,4,6). Atomic force microscopy (AFM), optical absorption (OA), photoluminescence (PL) and time-resolved photoluminescence (TRPL) techniques characterized the vitreous system. The formation of two kinds of ZnTe semiconductor nanoparticles - bulk-like and quantum dots –were identified. PL and TRPL suggest the energy transfer from Eu3+ ions and/orZnTetoYb3+ ions.

<p>  </p> <p>A harmonic oscillator is a ubiquitous tool in various disciplines of engineering and physics for sensing and energy transduction. The degrees of freedom, low noise oscillation, and efficient input-output coupling are important metrics when designing sensors and transducers using such oscillators. The ultimate examples of such oscillators are quantum mechanical oscillators coherently transducing information or energy. Atoms are oscillators whose degrees of freedom can be controlled and probed coherently by means of light. Elegant techniques developed during the last few decades have enabled us to use atoms, for example, to build exquisite quantum sensors such as clocks with the precision of <1 second error over the lifetime of the universe, to store and transduce information of various forms and also to develop quantum processors. Similar to atoms, mechanical oscillators can also be controlled ultimately to their single vibrational quanta and be used for similar sensing and transduction applications.</p> <p><br></p> <p>In this thesis, we explore both atomic and mechanical systems and develop a toolbox to build an effective atom-light interface and light-oscillator interface for controlling such atomic and mechanical oscillators and use them in sensing and storage applications. Primarily, we study two disparate platforms: 1) rare-earth ions in solids integrated into photonic chips as a compact and heterogeneous platform and 2) nanoscopic and macroscopic oscillators interfaced with light and magnetic field to isolate them from environmental noise. </p> <p><br></p> <p>Rare earth (RE) ions in crystals have been identified as robust optical centers and promising candidates for quantum communication and transduction applications. Lithium niobate (LN), a novel crystalline host of RE ions, is considered as a viable material for photonic system integration because of its electro-optic and integration capability. This thesis first experimentally reports the activation and characterization of LN crystals implanted with Yb and Er ions and describes their scalable integration with a silicon photonic chip with waveguide and resonator structures. The evanescent coupling of light emitted from Er ions with optical modes of waveguide and microcavity and modified photoluminescence (PL) of Er ions from the integrated on-chip Er:LN-Si-SiN photonic device with quality factor of 104 have been observed at room temperature. This integrated platform can ultimately enable developing quantum memory and provide a path to integrate more photonic components on a single chip for applications in quantum communication and transduction.</p> <p><br></p> <p>Optomechanical systems are also considered as candidates for light storage and sensing. In this thesis, we also present results of the theoretical study of coherent light storage in an array of nanomechanical resonators. The majority of the thesis is focusing on an optomechanical sensing experiment based on levitation. An oscillator well isolated from environmental noise can be used to sense force, inertia, torque, and magnetic field with high sensitivity as the interaction with these quantities can change the amplitude or frequency of the oscillator’s vibration, which can be accurately measured by light. It has been proposed that such levitated macroscopic objects could be used as quantum sensors and transducers at their quantum ground states. They are also proposed as a platform to test fundamental physics such as detecting gravitational waves, observing macroscopic quantum entanglement, verifying the spontaneous collapse models, and searching for dark matter.</p> <p><br></p> <p>In particular, we consider superconducting levitation of macroscopic objects in vacuum whose positions are measured by light. We build an optomechanical platform based on a levitated small high reflective (HR)-coated mirror above a superconductor disk. We use this levitated mirror at ambient conditions to detect the magnetic field with a sensitivity on the order of <em>pT/sqrt(Hz).</em> Moreover, the levitated mirror is used as the end mirror of a Fabry–Pérot cavity to create an optical resonance that could be used to study coherent radiation pressure forces. The platform provides a sensitive tool to measure the various forces exerted on the mirror and it offers the possibility of the coherent optical trapping of macroscopic objects and precision gravity sensing. Moreover, we study the nonlinear dissipation and mode coupling of a levitated HR-coated magnetic mirror above a superconducting disk in vacuum conditions. We observe that by exciting one vibrational mode of the mirror, the vibrational noise of another mode can be significantly suppressed by a factor of 60. We attribute this unique noise suppression mechanism to the mode coupling and nonlinear dissipation caused by the driven magnetic inhomogeneity of the levitated object. Such a suppression mechanism can enable cooling certain modes independent of their detection and position in the spectrum, which may be promising for precision sensing applications.</p>