Les ions de terres rares en matrice cristalline, refroidis à très basse température, offrent des propriétés remarquables pour le traitement analogique du signal sur porteuse optique. L’élargissement inhomogène du spectre d’absorption peut en effet atteindre plusieurs centaines de gigahertz alors que la largeur homogène des raies d’absorption des ions individuels ne dépasse pas quelques kilohertz. Par pompage optique il est alors possible de modifier à volonté le profil du spectre d’absorption. On dispose ainsi d’un filtre programmable présentant à la fois une très grande bande passante, donnée par la largeur inhomogène, et une excellente résolution, fixée par la largeur homogène. Une raie d’absorption étroite correspond à un état de superposition quantique de longue durée de vie. C’est sous cet angle, celui des transitoires cohérents, et spécifiquement celui des échos de photons que nous abordons les propriétés du filtre programmable. Dans la première partie de la thèse, le filtre est programmé comme un élément dispersif. Il permet d’atteindre des taux de dispersion inaccessibles aux dispositifs optiques conventionnels, tels que les fibres optiques. Nous l’utilisons comme un composant de lentille temporelle, en vue de produire des signaux de forme arbitraire. Par rapport à des dispositifs d’optique conventionnels, on gagne plusieurs ordres de grandeurs en termes de produit temps x bande passante. Après avoir exploité l’écho de photon dans un contexte de filtrage linéaire, nous tirons parti de ses propriétés de très forte non-linéarité dans la seconde partie de la thèse. Cette fois nous cherchons à capturer un signal lumineux de très faible intensité, à le convertir en état de superposition atomique, puis à le restituer dans son état lumineux initial. Cela suppose en particulier d’empêcher les effets d’émission spontanée ou stimulé qui nuisent à la fidélité de la restitution. Pour ce faire, nous proposons un nouveau protocole que nous avons appelé « Revival Of Silenced Echo » (ROSE) / Rare earth ions doped crystals, when cooled at very low temperature, exhibit outstanding properties for optically-carried analogical signal processing. The absorption spectral broadening can reach several hundred of Gigahertz, while the homogeneous width of each individual ion does no exceed a few kilohertz. With the help of optical pumping, one may modify the absorption profile at will. The resulting programmable filter simultaneously offers a very large bandwidth, given by the inhomogeneous width, and a very good resolution, fixed by the homogeneous width. Narrow absorption line is related to long lifetime quantum superposition. We contemplate the programmable filter properties, keeping in mind this coherent transient picture, specifically related to photon echoes. In the first part of the dissertation, the programmable filter is programmed as a dispersive element. This gives access to dispersion rate values out of reach of conventional optical devices, such as optical fibers. We use the filter as a temporal lens component, with an eye to generating arbitrary waveforms. Thereby, we gain several orders of magnitude against conventional optical devices in terms of time x bandwidth product. After taking advantage of photon echoes in the linear filtering context, we capitalize on their strongly non-linear properties in the second part of the dissertation. This time we want to capture a very weak optical signal, to convert it into an atomic superposition state, and to restore it in its initial state of light. Faithful retrieval of the incoming signal relies on the elimination of spontaneous and stimulated emission. To this end, we propose a new protocol we have named « Revival Of Silenced Echo » (ROSE).

Neste trabalho é apresentado um estudo espectroscópico sobre vidros de germanato contendo nanopartículas (NPs) metálicas e semicondutoras dopados com íons de terras-raras (TRs) Eu3+, Nd3+ e Er3+ visando o desenvolvimento de novos materiais para aplicações em fotônica. Estes vidros apresentam larga janela de transmissão (400-4500 nm), alto índice de refração (~ 1,9), baixa energia de fônon (700 cm-1), alta resistência mecânica e durabilidade química. Com a finalidade de verificar a nucleação das NPs metálicas e semicondutoras, foram realizadas análises por Microscopia Eletrônica de Transmissão (MET) que indicaram a presença de NPs metálicas e semicondutoras. As técnicas de espectroscopia de fluorescência de raios X por energia dispersiva (EDS energy dispersive spectroscopy) e difração de elétrons comprovaram a natureza química das NPs. As medidas de absorção óptica evidenciaram a incorporação dos íons de TRs na forma trivalente, fenômeno responsável pela luminescência nos vidros, e permitiram as medidas das bandas de absorção relacionadas à ressonância dos plasmons superficiais e das bandas de absorção características de NPs de natureza semicondutora. Medidas de emissão foram realizadas através de diferentes procedimentos, que variaram de acordo com a natureza das TRs. Foram medidas intensas bandas de emissão da luz vermelha do Eu3+ relacionadas com as transições 7F J (J=0 a 6) -> 5D0, bandas de emissão associadas à conversão ascendente de freqüências do Er3+ em 530, 550 e 670nm relacionadas com as transições 2H 11/2 -> 4I 15/2 , 4S 3/2 -> 4I 15/2 e 4F 9/2 -> 4I 15/2 respectivamente, e bandas de emissão de luz na região do infravermelho do Nd3+ em 900, 1076 e 1350 nm relacionadas com as transições 4F 3/2 -> 4I 9/2 , 4F 3/2 -> 4I 11/2 e 4F 3/2 -> 4I 13/2 . Foi observado aumento significativo da luminescência da luz vermelha do Eu3+ nas amostras contendo NPs de prata, ouro, e prata juntamente com ouro. Nas amostras contendo NPs de silício foi observado aumento significativo da emissão associada à conversão ascendente de freqüências do érbio. Os aumentos ocorridos na luminescência das amostras contendo NPs metálicas são provavelmente causados pelo aumento do campo local nas proximidades dos íons de TRs e pela transferência de energia entre as NPs e os íons deTRs. Os aumentos ocorridos na luminescência das amostras contendo NPs semicondutoras são provavelmente causados pela transferência eficiente de energia entre as NPs e os íons de TRs originada da recombinação de éxcitons dentro das NPs semicondutoras. Portanto, a presença das NPs desempenha um papel importante para o aumento da luminescência, permitindo o desenvolvimento de novos materiais com aplicações em nanofotônica. / This work presents a spectroscopic study about Eu3+, Nd3+ and Er3+ rare-earth doped germanate glasses containing metallic and semiconductor nanoparticles (NPs) aiming the development of new materials for photonic applications. These glasses have a large transmission window (400-4500 nm), high refractive index (~ 1.9), low phonon energy (700 cm-1), high mechanic resistance and chemical durability. Transmission Electronic Microscopy analysis was performed to verify the metallic and semiconductor NPs nucleation, and indicated the presence of metallic and semiconductor NPs. X ray fluorescence by energy dispersive spectroscopic (EDS) and electron diffraction analysis showed the chemical nature of the NPs. Optic absorption measurement proved the trivalent incorporation of the rare-earth ions, the responsible phenomenon for the luminescence of the glasses that allowed the measurement of the absorption bands related to the superficial plasmon resonance. Emission measurements were performed with different procedures, related to nature of the rare-earth. High emission bands of Eu3+ were measured related to the 7F J (J=0 to 6) -> 5D 0 transitions; emission bands associated to the frequency upconversion of Er3+ in 530, 550 and 670nm related to the 2H 11/2 -> 4I 15/2, 4S 3/2 -> 4I 15/2 e 4F 9/2 -> 4I 15/2 transitions were observed, and as well as emission bands of Nd3+ in 900, 1076 and 1350 nm related with the 4F 3/2 -> 4I 9/2, 4F 3/2 -> 4I 11/2 e 4F 3/2 -> 4I 13/2 transitions. A significant enhancement of the red light luminescence of Eu3+ was observed in the samples containing silver, gold, and silver together with gold NPs. For the samples containing silicon NPs it was observed a considerable enhancement of the frequency upconversion emission of the erbium. The luminescence enhancement of the samples with metallic NPs is due to the enhancement of the local field nearby the rare-earth ions and/or to the energy transfer between the NPs and the rare-earth ions. The luminescence enhancement of the samples with semiconductor NPs are due to the efficient energy transfer between the NPs and the rare-earth ions originated from the excitons recombination inside the semiconductor NPs. Therefore, the presence of the NPs plays an important role on the luminescence enhancement, allowing de development of new materials for nanophotonic applications.

Recentemente, grande interesse tem sido demonstrado por cerâmicas transparentes dopadas com íons terras raras trivalentes, como meios ativos para lasers na região espectral do infravermelho próximo. Em particular, cerâmicas dopadas com altas concentrações de Nd3+ e Yb3+ são muito estudadas pela possibilidade de gerar emissão laser de alta potência em torno de 1,0 mm. Embora a cerâmica transparente de titanato zirconato de chumbo e lantânio (PLZT), com composição La/ Zr/Ti = 9/65/35, seja originalmente reconhecida por suas propriedades ferroelétricas e eletro-ópticas, a mesma também apresenta características interessantes como matriz hospedeira de íons oticamente ativos. Recentemente, de Camargo et al. realizaram vários estudos espectroscópicos que comprovam a potencialidade laser de amostras dopadas com Yb3+, Er3+, Tm3+ e em especial Nd3+. Apesar de a cerâmica PLZT:Nd ser a mais promissora, se comparada a líder de mercado YAG:Nd (sistema ítrio-alumínio garnet dopado com neodímio), ainda não foi possível obter ação laser da primeira, devido à presença de fases espúrias (imperceptíveis a olho nu), que comprometem a qualidade óptica do material, especialmente para concentrações de dopagem maiores que 1,0% peso de Nd2O3. Uma vez que a qualidade estrutural tem implicação direta na qualidade óptica/espectroscópica de materiais ópticos, faz-se necessário estender os estudos visando otimizar a obtenção de amostras transparentes com mais altos níveis de dopagem. Neste trabalho apresenta-se um método alternativo para a dopagem da matriz PLZT com os íons TR = Nd3+ e Yb3+, e utiliza-se de várias técnicas (DR-X, DTA-TG, FT-IR, Raman, RMN e Luminescência), para caracterizar os compostos precursores e/ou produtos. O novo método baseia-se na obtenção prévia de óxidos precursores dopados, seguida da utilização destes para o preparo das cerâmicas PLZT:TR. As caracterizações foram conduzidas em função da concentração de dopantes (0,1 4,0% peso TR2O3), comparativamente ao método de dopagem convencional utilizado nos trabalhos anteriores. A espectroscopia de ressonância magnética nuclear em sólidos em 207Pb, mostrou-se uma ferramenta bastante útil na elucidação de questões estruturais desses sistemas tão complexos. Como os íons paramagnéticos Nd3+ e Yb3+ não podem ser diretamente acessados por RMN, a estratégia para caracterizar suas distribuições espaciais foi investigar suas respectivas mímicas diamagnéticas Y3+ e Sc3+ (núcleos 45Sc e 89Y). Resultados de DR-X apresentam menor formação de fase secundária nas amostras preparadas via método alternativo, sendo identificado as fases secundárias como (La,Nd)2(Zr,Ti)2O7 (estrutura do tipo pirocloro), ZrO2 em fase parcialmente monoclínica e cúbica e ZrO2 em fase cúbica, das amostras dopadas com Nd3+, Y3+ e Yb3+, respectivamente. De acordo com os resultados de DR-X, experimentos de RMN permitiram melhor avaliação quanto a inserção do íon dopante a medida que há formação de fase secundária e mostraram que a inserção dos íons dopantes é homogênea, bem como resultados de luminescência, com o limite de solubilidade do íon dopante sempre menor do que o necessário para que seja observado supressão da luminescência dos íons emissores. / In recent years, there has been a great interest for rare-earth (RE) doped transparent ceramics as near-infrared laser active media. Particularly, Nd3+ and Yb3+-doped ceramics are of special interest due to the possibility of generating high power emissions at around 1.0 mm. Even though lead lanthanum zirconate titanate (PLZT) ceramics, with composition La/Zr/Ti = 9/65/35, are mostly known by their ferroelectric and electro-optic properties, recent works by de Camargo et al. have also indicated their potentiality as laser active media. In this regard, the most promising system is PLZT:Nd (as compared to YAG:Nd - neodymium-doped yttrium aluminium garnet), however, laser action of the former has not yet been possible, the reason lying in the presence of secondary phases (invisible to the naked eye) that compromise the optical quality of the ceramics, especially for samples with concentration higher than 1.0 wt% Nd2O3. Since the structural quality of samples has a direct implication on their spectroscopic and optical qualities, the goals pursued in this work are to present means to obtain highly transparent samples with higher incorporation of dopants, as well as to understand some fundamental questions regarding the microstructure of PLZT:RE ceramics. Thus, an alternative method, based on the obtainment of RE-doped precursor oxides, is presented for the synthesis of PLZT:RE and several techniques (XRD, DTA-TG, FT-IR, Raman, NMR and Luminescence) are used to characterize the samples, as a function of doping concentration (0,1 4,0 wt% RE2O3). These studies are done in comparison to the conventional method used in previous works. Solid state NMR spectroscopy of 207Pb proved to be a very useful tool for the understanding of these complex systems. Because Nd3+ and Yb3+ are paramagnetic and thus inaccessible by NMR, the strategy used for the characterization of their spatial distribution was to study samples doped with their respective diamagnetic mimics Sc3+ and Y3+ (45Sc and 89Y nuclei). XRD results have shown formation of less secondary phase for samples prepared by alternative method, being identified as secondary phase pyrochlore structure (La,Nd)2(Zr,Ti)2O7, partially monoclinic/cubic ZrO2 and cubic ZrO2 of the samples doped with Nd3+, Y3+ and Yb3+ respectively. NMR measurements allowed to make proposals about dopant ion insertion while secondary phase is formed and showed homogeneous distribution of dopant into the matrix, aswell luminescence measurements with maximum dopant solubility being less than enough to show any suppression of luminescence.

Neste trabalho é apresentado um estudo espectroscópico sobre vidros de germanato contendo nanopartículas (NPs) metálicas e semicondutoras dopados com íons de terras-raras (TRs) Eu3+, Nd3+ e Er3+ visando o desenvolvimento de novos materiais para aplicações em fotônica. Estes vidros apresentam larga janela de transmissão (400-4500 nm), alto índice de refração (~ 1,9), baixa energia de fônon (700 cm-1), alta resistência mecânica e durabilidade química. Com a finalidade de verificar a nucleação das NPs metálicas e semicondutoras, foram realizadas análises por Microscopia Eletrônica de Transmissão (MET) que indicaram a presença de NPs metálicas e semicondutoras. As técnicas de espectroscopia de fluorescência de raios X por energia dispersiva (EDS energy dispersive spectroscopy) e difração de elétrons comprovaram a natureza química das NPs. As medidas de absorção óptica evidenciaram a incorporação dos íons de TRs na forma trivalente, fenômeno responsável pela luminescência nos vidros, e permitiram as medidas das bandas de absorção relacionadas à ressonância dos plasmons superficiais e das bandas de absorção características de NPs de natureza semicondutora. Medidas de emissão foram realizadas através de diferentes procedimentos, que variaram de acordo com a natureza das TRs. Foram medidas intensas bandas de emissão da luz vermelha do Eu3+ relacionadas com as transições 7F J (J=0 a 6) -> 5D0, bandas de emissão associadas à conversão ascendente de freqüências do Er3+ em 530, 550 e 670nm relacionadas com as transições 2H 11/2 -> 4I 15/2 , 4S 3/2 -> 4I 15/2 e 4F 9/2 -> 4I 15/2 respectivamente, e bandas de emissão de luz na região do infravermelho do Nd3+ em 900, 1076 e 1350 nm relacionadas com as transições 4F 3/2 -> 4I 9/2 , 4F 3/2 -> 4I 11/2 e 4F 3/2 -> 4I 13/2 . Foi observado aumento significativo da luminescência da luz vermelha do Eu3+ nas amostras contendo NPs de prata, ouro, e prata juntamente com ouro. Nas amostras contendo NPs de silício foi observado aumento significativo da emissão associada à conversão ascendente de freqüências do érbio. Os aumentos ocorridos na luminescência das amostras contendo NPs metálicas são provavelmente causados pelo aumento do campo local nas proximidades dos íons de TRs e pela transferência de energia entre as NPs e os íons deTRs. Os aumentos ocorridos na luminescência das amostras contendo NPs semicondutoras são provavelmente causados pela transferência eficiente de energia entre as NPs e os íons de TRs originada da recombinação de éxcitons dentro das NPs semicondutoras. Portanto, a presença das NPs desempenha um papel importante para o aumento da luminescência, permitindo o desenvolvimento de novos materiais com aplicações em nanofotônica. / This work presents a spectroscopic study about Eu3+, Nd3+ and Er3+ rare-earth doped germanate glasses containing metallic and semiconductor nanoparticles (NPs) aiming the development of new materials for photonic applications. These glasses have a large transmission window (400-4500 nm), high refractive index (~ 1.9), low phonon energy (700 cm-1), high mechanic resistance and chemical durability. Transmission Electronic Microscopy analysis was performed to verify the metallic and semiconductor NPs nucleation, and indicated the presence of metallic and semiconductor NPs. X ray fluorescence by energy dispersive spectroscopic (EDS) and electron diffraction analysis showed the chemical nature of the NPs. Optic absorption measurement proved the trivalent incorporation of the rare-earth ions, the responsible phenomenon for the luminescence of the glasses that allowed the measurement of the absorption bands related to the superficial plasmon resonance. Emission measurements were performed with different procedures, related to nature of the rare-earth. High emission bands of Eu3+ were measured related to the 7F J (J=0 to 6) -> 5D 0 transitions; emission bands associated to the frequency upconversion of Er3+ in 530, 550 and 670nm related to the 2H 11/2 -> 4I 15/2, 4S 3/2 -> 4I 15/2 e 4F 9/2 -> 4I 15/2 transitions were observed, and as well as emission bands of Nd3+ in 900, 1076 and 1350 nm related with the 4F 3/2 -> 4I 9/2, 4F 3/2 -> 4I 11/2 e 4F 3/2 -> 4I 13/2 transitions. A significant enhancement of the red light luminescence of Eu3+ was observed in the samples containing silver, gold, and silver together with gold NPs. For the samples containing silicon NPs it was observed a considerable enhancement of the frequency upconversion emission of the erbium. The luminescence enhancement of the samples with metallic NPs is due to the enhancement of the local field nearby the rare-earth ions and/or to the energy transfer between the NPs and the rare-earth ions. The luminescence enhancement of the samples with semiconductor NPs are due to the efficient energy transfer between the NPs and the rare-earth ions originated from the excitons recombination inside the semiconductor NPs. Therefore, the presence of the NPs plays an important role on the luminescence enhancement, allowing de development of new materials for nanophotonic applications.

[Mathematical symbols can be only approximated here. For the correct display see the Abstract in the PDF files linked below] This work has demonstrated that hyperfine decoherence times sufficiently long for QIP and quantum optics applications are achievable in rare earth ion centres. Prior to this work there were several QIP proposals using rare earth hyperfine states for long term coherent storage of optical interactions [1, 2, 3]. The very long T_1 (~weeks [4]) observed for rare-earth hyperfine transitions appears promising but hyperfine T_2s were only a few ms, comparable to rare earth optical transitions and therefore the usefulness of such proposals was doubtful. ¶ This work demonstrated an increase in hyperfine T_2 by a factor of 7 × 10^4 compared to the previously reported hyperfine T_2 for Pr^[3+]:Y_2SiO_5 through the application of static and dynamic magnetic field techniques. This increase in T_2 makes previous QIP proposals useful and provides the first solid state optically active Lamda system with very long hyperfine T_2 for quantum optics applications. ¶ The first technique employed the conventional wisdom of applying a small static magnetic field to minimise the superhyperfine interaction [5, 6, 7], as studied in chapter 4. This resulted in hyperfine transition T_2 an order of magnitude larger than the T_2 of optical transitions, ranging fro 5 to 10 ms. The increase in T_2 was not sufficient and consequently other approaches were required. ¶ Development of the critical point technique during this work was crucial to achieving further gains in T_2. The critical point technique is the application of a static magnetic field such that the Zeeman shift of the hyperfine transition of interest has no first order component, thereby nulling decohering magnetic interactions to first order. This technique also represents a global minimum for back action of the Y spin bath due to a change in the Pr spin state, allowing the assumption that the Pr ion is surrounded by a thermal bath. The critical point technique resulted in a dramatic increase of the hyperfine transition T_2 from ~10 ms to 860 ms. ¶ Satisfied that the optimal static magnetic field configuration for increasing T_2 had been achieved, dynamic magnetic field techniques, driving either the system of interest or spin bath were investigated. These techniques are broadly classed as Dynamic Decoherence Control (DDC) in the QIP community. The first DDC technique investigated was driving the Pr ion using a CPMG or Bang Bang decoupling pulse sequence. This significantly extended T_2 from 0.86 s to 70 s. This decoupling strategy has been extensively discussed for correcting phase errors in quantum computers [8, 9, 10, 11, 12, 13, 14, 15], with this work being the first application to solid state systems. ¶ Magic Angle Line Narrowing was used to investigate driving the spin bath to increase T_2. This experiment resulted in T_2 increasing from 0.84 s to 1.12 s. Both dynamic techniques introduce a periodic condition on when QIP operation can be performed without the qubits participating in the operation accumulating phase errors relative to the qubits not involved in the operation. ¶ Without using the critical point technique Dynamic Decoherence Control techniques such as the Bang Bang decoupling sequence and MALN are not useful due to the sensitivity of the Pr ion to magnetic field fluctuations. Critical point and DDC techniques are mutually beneficial since the critical point is most effective at removing high frequency perturbations while DDC techniques remove the low frequency perturbations. A further benefit of using the critical point technique is it allows changing the coupling to the spin bath without changing the spin bath dynamics. This was useful for discerning whether the limits are inherent to the DDC technique or are due to experimental limitations. ¶ Solid state systems exhibiting long T_2 are typically very specialised systems, such as 29Si dopants in an isotopically pure 28Si and therefore spin free host lattice [16]. These systems rely on on the purity of their environment to achieve long T_2. Despite possessing a long T_2, the spin system remain inherently sensitive to magnetic field fluctuations. In contrast, this work has demonstrated that decoherence times, sufficiently long to rival any solid state system [16], are achievable when the spin of interest is surrounded by a concentrated spin bath. Using the critical point technique results in a hyperfine state that is inherently insensitive to small magnetic field perturbations and therefore more robust for QIP applications.

Laseres de estado sólido que operan en la región espectral de seguridad ocular alrededor de los 2 micrómetros (2µm) son de elevado interés en la actualidad debido a su potencial aplicación en los campos de la medicina, teledetección remota y como fuentes de bombeo en osciladores ópticos paramétricos (OPOs) para conversión en el infrarrojo medio. La transición láser en las 2 µm es posible en los iones de tulio (Tm) ligeramente por debajo de las 2 µm y en iones de holmio (Ho) ligeramente por encima de las 2 µm. La generación láser en iones de Tm es relativamente simple con la utilización de láseres de diodo como fuentes de bombeo, sin embargo, los láseres basados en Ho se han conseguido tradicionalmente en el pasado mediante el codopaje con Tm o mediante bombeo directo del nivel emisor del Ho. Recientemente, diodos láser que operan a 1.9 µm han aparecido en el mercado con buena eficiencia y con alto potencial para el escalado en potencia de los láseres de Ho. Los láseres de Ho son más apropiados que los láseres de Tm especialmente para aplicaciones médicas por dos razones: La longitud de onda láser ligeramente por encima de las 2 µm, donde el agua (mayor componente del cuerpo humano) presenta una ligera menor absorción que la típica longitud de onda láser del Tm, hace que el láser penetre más en el tejido humano. La segunda razón es que los láseres de Ho pueden operar en régimen pulsado generando mayores energías por pulso que los láseres de Tm debido al mayor tiempo de vida del nivel emisor 5I7 y las aplicaciones médicas requieren por lo general régimen pulsado para evitar daño térmico del tejido. Numerosos óxidos y fluoruros cristalinos han demostrado ser adecuadas matrices para Ho, sin embargo, poca atención se ha puesto en los dobles tungstatos cristalinos de fase monoclínica, de fórmula química KRE(WO4)2, brevemente KREW, donde RE = Y, Gd y Lu conocidos por ser matrices láser muy eficientes para la generación láser a potencias intermedias. Estos cristales anisotrópicos presentan una elevada sección eficaz de absorción y emisión cuando son dopados con iones lantánidos y especialmente para ciertas polarizaciones. Considerando el potencial del Ho y las buenas propiedades de KREW, nuestro trabajo se centra en la investigación de las prestaciones láser en cristales de KREW dopados con Ho utilitzando tanto Tm o Yb como iones sensibilizadores y utilizando fuentes de bombeo emitiendo a 1.9 µm que permiten la excitación directa del nivel emisor. En esta tesis, presentamos los resultados basados en el crecimiento cristalino de monocristales de Ho:KREW, codopajes (Ho,Tm) y (Ho,Yb):KLuW a diferentes concentraciones de Ho, su caracterización en términos de estructura, composición y espectroscopia y finalmente la generación láser alrededor de 2.1 µm. / Eye-safe solid-state lasers that operate in the 2µm spectral range are the subject of interest in the present years because of their potential applications in the field of remote sensing, medicine and as a pump source for Optical Parametric Oscillators (OPOs). Laser transitions around 2 µm are possible in the trivalent lanthanide ions Tm3+ (Tm) (slightly below 2 µm) and Ho3+ (Ho) (slightly above 2 µm). Laser generation in Tm ions is easily achieved with comfortable diode pump sources, however, Ho lasers have usually been achieved in the past either by co-doping the active medium with Tm or by direct pumping of the Ho ions with Tm lasers. Recently, relatively cheap diodes emitting around 1.9 µm are in the market to realize Ho lasers with great potential for power scaling. Ho lasers are more suitable than Tm lasers especially for medical applications because of two reasons: The laser wavelength is slightly above 2µm, where water (main component of human tissue) shows slightly less absorption than the typical wavelength of Tm leading to a deeper penetration in human tissue. The second reason is that Ho lasers can operate in pulsed regime delivering higher energies than Tm lasers due to the longer lifetime of the emitting level 5I7 and medical applications are required to be generally in pulsed regime to avoid thermal damage of human tissue. Many oxide and fluoride crystals were shown to be suitable host for Ho, however little attention was paid to the monoclinic potassium rare earth double tungstate crystal, shortly KRE(WO4)2 or KREW, where RE= Y, Gd, Lu known to be very efficient rare earth solid state hosts for generating intermediate power levels. These anisotropic crystals exhibit very high absorption and emission cross sections when doped with lanthanide ions and especially for selected polarizations. Considering the potentialities of Ho and good properties of KREW, our work focuses in the investigation of the laser performances of a Ho doped KREW either by using Tm or Yb as sensitizers and by using in-band pump sources emitting around 1.9 µm, where the development of compact solid state infrared laser emitting at 2.1 µm for intermediate power levels is followed. Here, in this thesis, we present the results based on growth of single doped Ho:KREW, co-doped (Ho,Tm) and (Ho,Yb):KLuW crystals of several doping concentrations, their characterisation in terms of structure, composition and spectroscopy and finally dedicated for the laser generation around 2.1 µm from these materials, which was highly successful.

In this work, alkaline earth aluminate phosphors doped with rare-earth ions and manganese were synthesized using combustion method. Several characterization techniques were used to study the structural and luminescent properties of the as-synthesized phosphors, namely X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray energy Dispersive Spectroscopy (EDS), Ultraviolet-Visible (UV-Vis) Spectroscopy, Photoluminescence (PL), and Thermoluminescence (TL). The structural properties were studied by collecting the XRD patterns of the samples using an X'Pert PRO PANalytical diffractometer with CuKα at λ = 0.15405 nm. The particle morphologies of the as-synthesized powder phosphors were investigated using a JEOL JSM-7500F field-emission scanning electron microscope (FE-SEM). The optical properties of the phosphors were studied using Perkin-Elmer Lambda 750s UV-Vis spectrometer, Jobin Yvon/SPEX FluoroLog spectrofluorometer (Model FL-1040) and Riso TL/OSL reader (Model DA-20). The as-prepared SrAl2O4:Eu 2+ ; SrAl2O4:Dy 3+; SrAl2O4:Mn 2+; phosphors were synthesized at an initiating temperature of 600 oC. The XRD patterns were consistent with the low temperature monoclinic structure of SrAl2O4 for all the as-synthesized phosphor powders. SEM measurements showed nano-rod like particles. The SrAl2O4:Eu 2+ ; SrAl2O4:Dy 3+; SrAl2O4:Mn 2+ samples were excited using a 450 W Xenon light source at 364 nm, 390 nm, and 426 nm respectively. A broad blue emission peak at 500 nm shown by the SrAl2O4:Eu 2+ sample is attributed to the 6 1 7 4f 5d 4f transition of the Eu 2+ ion. Also, the red sharp emission lines due to the 4f-4f transition of the Eu 3+ were observed. SrAl2O4:Dy3+ samples exhibited blue, green, and red emissions which can be atributed to the 4 6 9/2 15/2 F  H ,4 6 9/2 13/2 F  H , and 4 6 9 11 2 2 F  H transitions of Dy 3+ ions respectively. The two broad emissions (green at 513 nm and red at 650 nm) shown by 2+ 0.98 2 4 0.02 Sr Al O :Mn sample can be atributed to the 4 4 6 6 1 1 T ( G)  A ( S) transition of the Mn 2+ ion in the sample. The SrAl2O4:Eu 2+ , Dy 3+ ; SrAl2O4:Eu 2+, Mn 2+ ; SrAl2O4:Dy 3+, Mn 2+; and SrAl2O4:Eu 2+ ,Mn 2+, Dy 3+ phosphors were synthesized by combustion method at an initiating temperature of 600 oC. The blue emissions were observed in all the samples except SrAl2O4:Eu 2+ ,Mn 2+, Dy 3+ sample. The SrAl2O4:Eu 2+ ,Mn 2+, Dy 3+ phosphor showed the longest afterglow intensity. The BaAl2O4 doped with Eu 2+ , Mn 2+ and Dy 3+ phosphors synthesized at an initiating temperature of 600 oC using combustion method. The XRD patterns confirmed the hexagonal structure of BaAl2O4 in all the as-synthesized samples. A broad blue emission of the BaAl2O4:Eu 2+ sample at 490 nm is attributed to the 6 1 7 4f 5d 4f transition of the Eu 2+ ion in the sample. A red emission peak observed at 611 nm is due to the 4f - 4f transition of un-reduced Eu 3+ ions during the combustion reaction. A blue emission at 482 nm, a green emission at 575 nm, and a red emission at 663 nm of the BaAl2O4:Dy 3+ sample can be associated with 4 6 9/2 15/2 F  H ,4 6 9/2 13/2 F  H , and 4 6 9 11 2 2 F  H transitions of the Dy 3+ ions respectively. The green emission peaks exhibited by BaAl2O4:Mn 2+ sample at 512 nm is due to the 4 4 6 6 1 1 T ( G)  A ( S) transitions of the Mn 2+ ions. Barium aluminate phosphors doped with different concentrations of Dy 3+ ion were synthesized by combustion method at an initiating temperature of 600 oC. The XRD patterns confirmed the hexagonal structure of BaAl2O4. The emission peaks observed at 482 nm, 575 nm, and 663 nm are due to4 6 9/2 15/2 F  H ,4 6 9/2 13/2 F  H and 4 6 9 11 2 2 F  H transitions of Dy 3+ ion respectively. The PL measurements also confirmed the quenching of luminescence at higher concentrations of the Dy 3+ ion. The UV-Vis measurements has confirmed the increase in the band-gap of the BaAl2O4 sample followed by a decrease and an increase again as doping concentration of the Dy 3+ increased. The X-ray diffraction patterns of the Ca0.97M0.3Al2O4:Eu 2+ , Dy 3+ (M = Ba, Mg, and Sr) powder samples prepared by combustion method confirms the monoclinic structure of CaAl2O4 in all samples. A broad emission peak at 490 nm for both Ba 2+ and Mg 2+ substituted samples and the one for Sr 2+ substituted sample at 485nm are attributed to the 6 1 7 4f 5d 4f transition of the Eu 2+ . The decay curves confirmed that the Mg 2+ substituted sample has a longer persistence (phosphorescence) than all the other samples. / Physics / M. Sc. (Physics)

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-06T13:50:45Z No. of bitstreams: 1 TeseMM.pdf: 4347312 bytes, checksum: a5a64729ea719b0ac57b31c2cdeeb425 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T16:14:11Z (GMT) No. of bitstreams: 1 TeseMM.pdf: 4347312 bytes, checksum: a5a64729ea719b0ac57b31c2cdeeb425 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T16:14:17Z (GMT) No. of bitstreams: 1 TeseMM.pdf: 4347312 bytes, checksum: a5a64729ea719b0ac57b31c2cdeeb425 (MD5) / Made available in DSpace on 2016-10-20T16:14:23Z (GMT). No. of bitstreams: 1 TeseMM.pdf: 4347312 bytes, checksum: a5a64729ea719b0ac57b31c2cdeeb425 (MD5) Previous issue date: 2016-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / In this study, we present the production and characterization of a novel binary glass system: (100-x)SbPO4-xGeO2 where x = 30, 40, 50, 60, 70, 80 and 90 mol %. The dependence of GeO2 content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV-Visible absorption, infrared transmittance and M-lines techniques. Glass transition temperatures (Tg) shows an almost constant value around 400 °C when GeO2 content was increased. Thermal stability (ΔT = Tx-Tg) increases almost linearly with GeO2 content reaching a maximum value (300 °C). Ions Er3+ and Yb3+ were further incorporated into system SG in different proportions. Infrared and up-conversion emission processes were investigated. The emission spectra in the infrared region showed that the incorporation of Yb3+ ions into the glass composition increases the emission intensity at 1538 nm (4I13/2  4I15/2). The up-conversion processes showed a higher intensity emission at 522 nm and 544 nm (green) and 652 nm (red) regions and the emission mechanism has been the same as proposed in several works in literature. Finally, the glass sample showing the highest emission intensity at 1538 nm was chosen for micromachining using femtosecond laser. The waveguides having the lowest propagation losses were used for the optical internal gain proceeds. The best result obtained for internal gain at 1535 nm was around 1.7 dB/cm and this value is in agreement with other glass systems based on germanium and phosphates glasses present in literature. / Neste estudo, foi realizado a preparação e caracterização do sistema vítreo: (100-x) SbPO4-xGeO2 (SG), onde x varia entre 30 e 90% em mol. A dependência da concentração de GeO2 nas propriedades térmicas, ópticas e estruturais foram estudadas. O comportamento térmico foi investigado através da análise térmica (DSC), enquanto as propriedades estruturais foram estudadas por espectroscopia de espalhamento Raman. As propriedades ópticas foram avaliadas usando as espectroscopias na região do UV-Vis, infravermelho e M-Lines. No sistema SG a temperatura de transição vítrea (Tg) apresenta uma pequena variação e se encontra por volta de 400 °C quando a concentração de GeO2 foi alterada. O parâmetro de estabilidade térmica (ΔT = Tx-Tg) aumenta quase linearmente com o aumento da quantidade de GeO2, alcançando um valor máximo de 300 °C. Para o sistema SG foram incorporados ainda íons Er3+ e Yb3+ em diferentes proporções e as emissões na região do infravermelho e os processos de conversão ascendente de energia (upconversion) foram investigados. Os espectros de emissão na região do infravermelho mostram que a incorporação de íons Yb3+ na composição química do vidro, aumenta a intensidade de emissão em 1538 nm (4I13/2  4I15/2). Os processos de up-conversion mostram emissões de alta intensidade na região do verde (522 e 544 nm) e vermelho (652 nm), e os mecanismos das emissões foram estudados e propostos. Por fim, a amostra com a maior intensidade de emissão em 1538 nm foi escolhida para a realização da microfabricação de guias ópticos, usando lasers de femtossegundo. Os guias de onda que apresentaram as menores perdas por propagação, foram utilizados para as medidas de amplificação óptica.

Recentemente, grande interesse tem sido demonstrado por cerâmicas transparentes dopadas com íons terras raras trivalentes, como meios ativos para lasers na região espectral do infravermelho próximo. Em particular, cerâmicas dopadas com altas concentrações de Nd3+ e Yb3+ são muito estudadas pela possibilidade de gerar emissão laser de alta potência em torno de 1,0 mm. Embora a cerâmica transparente de titanato zirconato de chumbo e lantânio (PLZT), com composição La/ Zr/Ti = 9/65/35, seja originalmente reconhecida por suas propriedades ferroelétricas e eletro-ópticas, a mesma também apresenta características interessantes como matriz hospedeira de íons oticamente ativos. Recentemente, de Camargo et al. realizaram vários estudos espectroscópicos que comprovam a potencialidade laser de amostras dopadas com Yb3+, Er3+, Tm3+ e em especial Nd3+. Apesar de a cerâmica PLZT:Nd ser a mais promissora, se comparada a líder de mercado YAG:Nd (sistema ítrio-alumínio garnet dopado com neodímio), ainda não foi possível obter ação laser da primeira, devido à presença de fases espúrias (imperceptíveis a olho nu), que comprometem a qualidade óptica do material, especialmente para concentrações de dopagem maiores que 1,0% peso de Nd2O3. Uma vez que a qualidade estrutural tem implicação direta na qualidade óptica/espectroscópica de materiais ópticos, faz-se necessário estender os estudos visando otimizar a obtenção de amostras transparentes com mais altos níveis de dopagem. Neste trabalho apresenta-se um método alternativo para a dopagem da matriz PLZT com os íons TR = Nd3+ e Yb3+, e utiliza-se de várias técnicas (DR-X, DTA-TG, FT-IR, Raman, RMN e Luminescência), para caracterizar os compostos precursores e/ou produtos. O novo método baseia-se na obtenção prévia de óxidos precursores dopados, seguida da utilização destes para o preparo das cerâmicas PLZT:TR. As caracterizações foram conduzidas em função da concentração de dopantes (0,1 4,0% peso TR2O3), comparativamente ao método de dopagem convencional utilizado nos trabalhos anteriores. A espectroscopia de ressonância magnética nuclear em sólidos em 207Pb, mostrou-se uma ferramenta bastante útil na elucidação de questões estruturais desses sistemas tão complexos. Como os íons paramagnéticos Nd3+ e Yb3+ não podem ser diretamente acessados por RMN, a estratégia para caracterizar suas distribuições espaciais foi investigar suas respectivas mímicas diamagnéticas Y3+ e Sc3+ (núcleos 45Sc e 89Y). Resultados de DR-X apresentam menor formação de fase secundária nas amostras preparadas via método alternativo, sendo identificado as fases secundárias como (La,Nd)2(Zr,Ti)2O7 (estrutura do tipo pirocloro), ZrO2 em fase parcialmente monoclínica e cúbica e ZrO2 em fase cúbica, das amostras dopadas com Nd3+, Y3+ e Yb3+, respectivamente. De acordo com os resultados de DR-X, experimentos de RMN permitiram melhor avaliação quanto a inserção do íon dopante a medida que há formação de fase secundária e mostraram que a inserção dos íons dopantes é homogênea, bem como resultados de luminescência, com o limite de solubilidade do íon dopante sempre menor do que o necessário para que seja observado supressão da luminescência dos íons emissores. / In recent years, there has been a great interest for rare-earth (RE) doped transparent ceramics as near-infrared laser active media. Particularly, Nd3+ and Yb3+-doped ceramics are of special interest due to the possibility of generating high power emissions at around 1.0 mm. Even though lead lanthanum zirconate titanate (PLZT) ceramics, with composition La/Zr/Ti = 9/65/35, are mostly known by their ferroelectric and electro-optic properties, recent works by de Camargo et al. have also indicated their potentiality as laser active media. In this regard, the most promising system is PLZT:Nd (as compared to YAG:Nd - neodymium-doped yttrium aluminium garnet), however, laser action of the former has not yet been possible, the reason lying in the presence of secondary phases (invisible to the naked eye) that compromise the optical quality of the ceramics, especially for samples with concentration higher than 1.0 wt% Nd2O3. Since the structural quality of samples has a direct implication on their spectroscopic and optical qualities, the goals pursued in this work are to present means to obtain highly transparent samples with higher incorporation of dopants, as well as to understand some fundamental questions regarding the microstructure of PLZT:RE ceramics. Thus, an alternative method, based on the obtainment of RE-doped precursor oxides, is presented for the synthesis of PLZT:RE and several techniques (XRD, DTA-TG, FT-IR, Raman, NMR and Luminescence) are used to characterize the samples, as a function of doping concentration (0,1 4,0 wt% RE2O3). These studies are done in comparison to the conventional method used in previous works. Solid state NMR spectroscopy of 207Pb proved to be a very useful tool for the understanding of these complex systems. Because Nd3+ and Yb3+ are paramagnetic and thus inaccessible by NMR, the strategy used for the characterization of their spatial distribution was to study samples doped with their respective diamagnetic mimics Sc3+ and Y3+ (45Sc and 89Y nuclei). XRD results have shown formation of less secondary phase for samples prepared by alternative method, being identified as secondary phase pyrochlore structure (La,Nd)2(Zr,Ti)2O7, partially monoclinic/cubic ZrO2 and cubic ZrO2 of the samples doped with Nd3+, Y3+ and Yb3+ respectively. NMR measurements allowed to make proposals about dopant ion insertion while secondary phase is formed and showed homogeneous distribution of dopant into the matrix, aswell luminescence measurements with maximum dopant solubility being less than enough to show any suppression of luminescence.

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