Les propriétés structurales et de luminescence de couches minces de TiO2 et Y2O3 dopées terres rares (thulium, terbium et ytterbium) ont été étudiées en vue de les intégrer dans une cellule photovoltaïque comme couche de conversion spectrale du proche UV vers l'infrarouge afin d'en améliorer l'efficacité. Ces couches minces ont été synthétisées par dépôt chimique en phase vapeur à pression atmosphérique à l'aide de précurseurs organo-métalliques et assisté par aérosol (aerosol assisted MOCVD). Les couches minces sont partiellement cristallisées dès la synthèse (400°C pour le TiO2 en phase anatase, 540°C pour Y2O3 en phase cubique). Après traitement thermique la cristallisation est largement améliorée et la luminescence des ions dopant terres rares est obtenue dans les deux matrices oxydes. Le thulium émet dans une large bande située vers 800 nm et l'ytterbium vers 980 nm. Le terbium quand à lui émet dans une gamme située principalement dans le visible. Les spectres d'excitation ont montré que l'absorption des photons se fait via la matrice. En matrice TiO2 une efficacité de transfert d'énergie du Tm3+ vers l'Yb3+ de l'ordre de 20 % a été déterminée pour des teneurs de 0,8 % des deux dopants, ce qui correspond à la limite d'auto-extinction. Le rendement global mesuré est faible, nous avons montré que les causes probables de cette faible valeur sont le manque d'absorption des couches minces pour obtenir l'excitation de l'ion sensibilisateur ainsi que des processus de luminescence et de down conversion pas assez efficaces.

Spontaneous parametric down conversion (SPDC) – incoherent light scattering – is one of the main entangled photons source applied in quantum optics experiments. The tradition to pump SPDC by laser radiation was established from the very first SPDC experiments in 1968. The aim of this thesis was experimentally to investigate the ability to generate an SPDC pumping by both temporal and spatially incoherent radiation - a high-power blue LED. Weak SPDC signals were registered with high sensitivity CCD cameras, photons coincidences were detected with photon counters. The theoretical simulations were performed in parallel with experiments. Therefore, mathematical simulation code was written in order to estimate the SPDC power distribution and simulate photon coincidence experiment changing the properties of pump beam and detection system. Experimental results reveal that incoherent light sources can be good alternative for the laser systems in order to generate average quality biphoton fields especially in those experiments in which low biphoton field coherency would be advantage. The main advantages of the incoherent sources over laser systems are low cost, simple production technology and the huge commercial variety of different wavelength sources. / Parametrinė fluorescencija (PF) – nekoherentinė šviesos sklaida – yra vienas pagrindinių susietųjų fotonų šaltinių taikomų kvantinės optikos eksperimentuose. Nuo pat pirmųjų PF eksperimentinių tyrimų 1968 metais įsigalėjo tradicija šį reiškinį žadinti išimtinai lazerine spinduliuote. Šios disertacijos tikslas – eksperimentiškai ištirti galimybę generuoti PF tiek laikiškai, tiek ir erdviškai nekoherentine spinduliuote – didelės galios šviesos diodu. Atliekant tyrimus didelio jautrio CCD kamera buvo registruojami silpni PF signalai, pavienių fotonų skaitliukais buvo registruojami fotonų sutapimai,. Lygiagrečiai eksperimentiniams tyrimams buvo atliekami teoriniai skaičiavimai. Šiuo tikslu buvo parašytas matematinio modeliavimo programinis kodas, skirtas įvertinti PF erdvinį galios pasiskirstymą bei modeliuoti fotonų sutapimų eksperimentą, keičiant kaupinimo pluošto ir detekcijos sistemos savybes. Šio darbo rezultatai atskleidžia, kad nekoherentiniai šaltiniai gali būti puiki alternatyva lazerinėms sistemoms siekiant žadinti vidutinės kokybės dvyninius laukus, ypatingai tokiose tyrimų srityse, kuriose mažas dvyninio lauko koherentiškumas būtų didžiulis privalumas. Pagrindiniai nekoherentinių šaltinių pranašumai prieš lazerines sistemas: maža kaina, paprasta gamybos technologija ir didžiulė komercinė skirtingo bangos ilgio šaltinių įvairovė.

Parametrinė fluorescencija (PF) – nekoherentinė šviesos sklaida – yra vienas pagrindinių susietųjų fotonų šaltinių taikomų kvantinės optikos eksperimentuose. Nuo pat pirmųjų PF eksperimentinių tyrimų 1968 metais įsigalėjo tradicija šį reiškinį žadinti išimtinai lazerine spinduliuote. Šios disertacijos tikslas – eksperimentiškai ištirti galimybę generuoti PF tiek laikiškai, tiek ir erdviškai nekoherentine spinduliuote – didelės galios šviesos diodu. Atliekant tyrimus didelio jautrio CCD kamera buvo registruojami silpni PF signalai, pavienių fotonų skaitliukais buvo registruojami fotonų sutapimai,. Lygiagrečiai eksperimentiniams tyrimams buvo atliekami teoriniai skaičiavimai. Šiuo tikslu buvo parašytas matematinio modeliavimo programinis kodas, skirtas įvertinti PF erdvinį galios pasiskirstymą bei modeliuoti fotonų sutapimų eksperimentą, keičiant kaupinimo pluošto ir detekcijos sistemos savybes. Šio darbo rezultatai atskleidžia, kad nekoherentiniai šaltiniai gali būti puiki alternatyva lazerinėms sistemoms siekiant žadinti vidutinės kokybės dvyninius laukus, ypatingai tokiose tyrimų srityse, kuriose mažas dvyninio lauko koherentiškumas būtų didžiulis privalumas. Pagrindiniai nekoherentinių šaltinių pranašumai prieš lazerines sistemas: maža kaina, paprasta gamybos technologija ir didžiulė komercinė skirtingo bangos ilgio šaltinių įvairovė. / Spontaneous parametric down conversion (SPDC) – incoherent light scattering – is one of the main entangled photons source applied in quantum optics experiments. The tradition to pump SPDC by laser radiation was established from the very first SPDC experiments in 1968. The aim of this thesis was experimentally to investigate the ability to generate an SPDC pumping by both temporal and spatially incoherent radiation - a high-power blue LED. Weak SPDC signals were registered with high sensitivity CCD cameras, photons coincidences were detected with photon counters. The theoretical simulations were performed in parallel with experiments. Therefore, mathematical simulation code was written in order to estimate the SPDC power distribution and simulate photon coincidence experiment changing the properties of pump beam and detection system. Experimental results reveal that incoherent light sources can be good alternative for the laser systems in order to generate average quality biphoton fields especially in those experiments in which low biphoton field coherency would be advantage. The main advantages of the incoherent sources over laser systems are low cost, simple production technology and the huge commercial variety of different wavelength sources.

One of the current hot topics in physics is quantum information, which, broadly speaking, is concerned with exploring the information-processing and storing tasks that can be performed in quantum mechanical systems. Besides driving forward our experimental control and understanding of quantum systems, the field is also in the early stages of developing revolutionary new technology of far reaching implication. As part of these endeavors, this thesis presents some results in experimental quantum information. Specifically, we develop several new tools for performing quantum information processing in optical quantum systems, and use them to explore a number of applications and novel physical phenomena. A central theme, and one of the most sought after applications of quantum information, is the pursuit of a programmable quantum computer. This thesis is divided into 3 parts. In Part I we develop some new optical quantum logic gates, which are tools for manipulating quantum information and the fundamental building blocks of a quantum computer. We also develop a new technique for simplifying the construction of quantum logic circuits, by exploiting multi-level quantum systems, that has the potential for application in any physical encoding of quantum information. In Part II we use these tools to perform some of the first demonstrations of quantum algorithms. Each of these could, in principle, efficiently solve an important problem that is thought to be fundamentally intractable using conventional `classical' techniques. Firstly we implement a simplified version of the quantum algorithm for factoring numbers, and demonstrate the core processes, coherent control, and resultant entangled states required for a full-scale implementation. Secondly we implement an algorithm for calculating the energy of many-body quantum systems. Specifically, we calculate the energy spectrum of the Hydrogen molecule, in a minimal basis. Finally we demonstrate an algorithm for a novel model of quantum computing that uses mixed states. Here we perform the first characterisation of intrinsically non-classical correlations between fully separable quantum systems, captured by the 'discord'---a measure of quantum correlations in mixed states that goes beyond entanglement. Part III presents a technique that extends experimental control over biphotons---the novel quantum information carriers formed by the polarisation of two photons in the same spatial and temporal mode. We also generate and explore new forms of entanglement: producing the first instance of qubit-qutrit entanglement, by entangling the polarisation of a photon and a biphoton, and developing a technique that enables full control over the level of `W-class' of multi-partite entanglement between the polarisation of three photons.

Submitted by FRANCINE BETTIO COSTA null (franbettiocosta@gmail.com) on 2016-06-24T00:23:52Z No. of bitstreams: 1 Francine Bettio Costa - Tese de Doutorado.pdf: 2483860 bytes, checksum: 50a1ed14dcf31cd79adfc9cd65def751 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-28T14:49:20Z (GMT) No. of bitstreams: 1 costa_fb_dr_ilha.pdf: 2483860 bytes, checksum: 50a1ed14dcf31cd79adfc9cd65def751 (MD5) / Made available in DSpace on 2016-06-28T14:49:20Z (GMT). No. of bitstreams: 1 costa_fb_dr_ilha.pdf: 2483860 bytes, checksum: 50a1ed14dcf31cd79adfc9cd65def751 (MD5) Previous issue date: 2016-03-22 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Pró-Reitoria de Pós-Graduação (PROPG UNESP) / A busca por novas fontes renováveis de energia tem se tornado de grande apelo devido à necessidade de se reduzir os impactos ambientais. Esse interesse tem motivado a pesquisa e o desenvolvimento de células fotovoltaicas (CFs) mais eficientes e baratas. Assim, a energia solar fotovoltaica tem sido uma opção para se complementar e ampliar a geração de eletricidade. Entretanto, as células de silício cristalino (Si-c) disponíveis no mercado apresentam baixa eficiência de conversão da radiação luminosa em energia elétrica devida, principalmente, às perdas por incompatibilidade espectral entre as regiões de máxima emissão solar (região do visível - Vis) e de máxima eficiência fotovoltaica da célula de Si-c (região do infravermelho - IV). Para minimizar essas perdas e, consequentemente, melhorar a eficiência da CF, conversores descendentes de energia compostos por íons terras-raras são usados na conversão de fótons de alta energia (Vis) em fótons de menor energia (IV). Nesse ínterim, no presente trabalho foram estudadas as propriedades espectroscópicas dos íons neodímio (Nd3+) e itérbio (Yb3+) incorporados, como dopantes, no vidro telurito-tungstênio (TW). Tais propriedades foram obtidas a partir de medidas de difração de raios-X, densidade de massa, espectroscopia de infravermelho por transformada de Fourier, Raman, absorção óptica, luminescência, excitação, evolução temporal da luminescência e lente térmica. Este estudo foi dividido em duas etapas. Primeiramente, vidros TW dopados com Nd3+ foram preparados em diferentes atmosferas, i.e., uma atmosfera ambiente e outra rica em O2, para investigação da influência dos grupos hidroxilas (OH) nas propriedades espectroscópicas de amostras com diferentes concentrações de Nd3+. A dependência com a concentração indicou que a transferência de energia do íon Nd3+ para o grupo OH foi desprezível e que a eficiência quântica luminescente do nível 4F3/2 diminuiu com o aumento da concentração de Nd3+. Posteriormente, vidros TW co-dopados com Nd3+ e Yb3+ foram preparados em atmosfera ambiente para investigação da correlação entre os íons Yb3+ e os mecanismos de conversão descendente de energia (CDE). Os resultados mostraram que a luminescência, oriunda do nível 4F3/2, diminuiu com o aumento da concentração de íons Yb3+. Simultaneamente, observou-se um aumento correspondente na emissão do Yb3+ e uma redução no calor gerado pela amostra. A transferência de energia Nd3+ → Yb3+ foi observada qualitativamente e a eficiência dessa transferência foi avaliada quantitativamente por valores do tempo de vida. Esses resultados indicam que o vidro TW co-dopado com íons Nd3+ e Yb3+ é um sistema com potencial para ser usado como material conversor descendente de energia aplicado sobre as células fotovoltaicas de Si-c. / The demand for new and renewable energy sources has been of great appeal due to the reduction of environmental impacts. This interest has motivated the research and the development of more efficient and less expensive photovoltaic (PV) cells. Thus, the photovoltaic solar energy has been an option to complement and expand the generation of electricity. However, commercialized crystalline silicon cells present low conversion efficiency of the light irradiation energy into electric energy, mainly due to the spectral mismatch between the regions of maximum solar emission (visible spectrum) and of maximum PV cell efficiency, which is in infrared region. To minimize such losses and, consequently, improve the efficiency of PV cell, down-converters with rare-earth ions in their structure are used to convert the high energy photons (at the visible - Vis) into low energy photons (at the infrared - IR). Meanwhile, in the present work we study the spectroscopic properties of neodymium (Nd3+) and ytterbium (Yb3+) ions incorporated as dopants in a tellurite-tungsten (TW) glass matrix. The characterization of the samples were obtained from measurements of X-ray diffraction, mass density, Fourier transform infrared spectroscopy, Raman spectroscopy, optical absorption, luminescence, excitation, temporal evolution of the luminescence and thermal lens. This study was divided into two stages. Primarily, Nd3+-doped TW glasses were prepared in different atmospheres, i.e., an ambient atmosphere and in another rich in O2 to investigate the influence of the hydroxyl (OH) groups in the spectroscopic properties of samples with different concentrations of Nd3+. The results showed that the energy transfer from Nd3+ ion to the OH group was negligible. The concentration dependency indicated that the energy transference from the Nd3+ ion to the OH group was negligible. In addition, the luminescent quantum efficiency of 4F3/2 level decreased with increasing of Nd3+ concentration. Subsequently, Nd3+ and Yb3+ co-doped TW glasses were prepared in ambient atmosphere to investigate the correlation between Yb3+ ions and down-conversion (DC) mechanisms. The results showed that the luminescence of the 4F3/2 decreased as the concentration of Yb3+ was increased. Simultaneously, it was observed a corresponding increase in the emission of the Yb3+ and a reduction in the generated heat by the sample. The Nd3+ → Yb3+ energy transfer was observed qualitatively and the efficiency of such transfer was quantitatively evaluated by lifetime values. The results indicate that the co-doped TW glasses by Nd3+ and Yb3+ are systems with potential to be used as down-converter material applied to the c-Si photovoltaics cells.

Orientador: João Carlos Silos Moraes / Abstract: The demand for new and renewable energy sources has been of great appeal due to the reduction of environmental impacts. This interest has motivated the research and the development of more efficient and less expensive photovoltaic (PV) cells. Thus, the photovoltaic solar energy has been an option to complement and expand the generation of electricity. However, commercialized crystalline silicon cells present low conversion efficiency of the light irradiation energy into electric energy, mainly due to the spectral mismatch between the regions of maximum solar emission (visible spectrum) and of maximum PV cell efficiency, which is in infrared region. To minimize such losses and, consequently, improve the efficiency of PV cell, down-converters with rare-earth ions in their structure are used to convert the high energy photons (at the visible - Vis) into low energy photons (at the infrared - IR). Meanwhile, in the present work we study the spectroscopic properties of neodymium (Nd3+) and ytterbium (Yb3+) ions incorporated as dopants in a tellurite-tungsten (TW) glass matrix. The characterization of the samples were obtained from measurements of X-ray diffraction, mass density, Fourier transform infrared spectroscopy, Raman spectroscopy, optical absorption, luminescence, excitation, temporal evolution of the luminescence and thermal lens. This study was divided into two stages. Primarily, Nd3+-doped TW glasses were prepared in different atmospheres, i.e., an ambient atmosphere and... (Complete abstract click electronic access below) / Resumo: A busca por novas fontes renováveis de energia tem se tornado de grande apelo devido à necessidade de se reduzir os impactos ambientais. Esse interesse tem motivado a pesquisa e o desenvolvimento de células fotovoltaicas (CFs) mais eficientes e baratas. Assim, a energia solar fotovoltaica tem sido uma opção para se complementar e ampliar a geração de eletricidade. Entretanto, as células de silício cristalino (Si-c) disponíveis no mercado apresentam baixa eficiência de conversão da radiação luminosa em energia elétrica devida, principalmente, às perdas por incompatibilidade espectral entre as regiões de máxima emissão solar (região do visível - Vis) e de máxima eficiência fotovoltaica da célula de Si-c (região do infravermelho - IV). Para minimizar essas perdas e, consequentemente, melhorar a eficiência da CF, conversores descendentes de energia compostos por íons terras-raras são usados na conversão de fótons de alta energia (Vis) em fótons de menor energia (IV). Nesse ínterim, no presente trabalho foram estudadas as propriedades espectroscópicas dos íons neodímio (Nd3+) e itérbio (Yb3+) incorporados, como dopantes, no vidro telurito-tungstênio (TW). Tais propriedades foram obtidas a partir de medidas de difração de raios-X, densidade de massa, espectroscopia de infravermelho por transformada de Fourier, Raman, absorção óptica, luminescência, excitação, evolução temporal da luminescência e lente térmica. Este estudo foi dividido em duas etapas. Primeiramente, vidros TW dopado... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

The FCC allocated the spectrum of 402-405 MHz for MICS (Medical Implant Communication Services) applications in 1999. The regulations for MICS band apply to devices that support the diagnostic and/or therapeutic functions associated with implanted medical electronics. The implanted devices aid organs and control body functions of patients to support specific treatments, and monitor patients continuously so that necessary action can be taken in advance to avoid serious conditions. To enable to use MICS applications, several requirements must be satisfied. An implanted wireless device should have a small size, consume ultra-low power, and achieve the date rate of at least 200 kbps within 2 m distance. The major challenge is to realize ultra-low power devices. Thus the low-power design of the RF circuit is crucial for MICS applications as the power consumption of the wireless devices is mostly contributed by RF circuits. This thesis investigates low-power design of an LNA and a down-conversion mixer of a receiver for MICS applications. The key idea is to stack an LNA and a mixer, while the LNA operates in the normal super-threshold region and the mixer in the sub-threshold region. In addition, a gm-boosting technique with a capacitor cross-coupled at the LNA input stage is also adopted to achieve a low noise figure (NF) and high linearity, which is critical to the overall performance of the receiver. The mixer operating in the sub-threshold region significantly reduces power dissipation and relaxes the voltage headroom without sacrificing the LNA performance. The relaxed voltage headroom enables stack of the LNA and the mixer with a low supply voltage of 1.2 V. The proposed circuit is designed in 0.18 μm RF CMOS technology. The merged LNA and mixer consumes only 1.83 mW, and achieves 21.6 dB power gain. The NF of the block is 3.55 dB at 1 MHz IF, and the IIP3 is -6.08 dBm. / Master of Science

Die Nutzung von Quanteneigenschaften für die Informationsverarbeitung, die sogenannte Quanteninformationsverarbeitung (QIP), ist ein seit zwei Jahrzehnten zunehmend populäres Forschungsfeld. Es hat sich gezeigt, dass Einzelphotonen die am besten geeigneten Träger für den Transport von Quanteninformation über weite Strecken sind. Obwohl viele Methoden zur Erzeugung von Einzelphotonen existieren, wurde bisher nur wenig Forschungsarbeit an schmalbandigen Einzelphotonen, d.h. mit spektralen Breiten im MHz-Bereich geleistet. Allerdings sind solche Einzelphotonen besonders wichtig, wenn Kopplungen zwischen Einzelphotonen und atomaren Systemen, die oft als Verarbeitungseinheiten in der QIP genutzt werden, realisiert werden sollen. Diese Doktorarbeit befasst sich mit mehreren Forschungsaspekten zu schmalbandigen Einzelphotonen, die von Bedeutung sind, wenn solche Photonen als Informationsträger genutzt werden sollen. Zunächst wird eine Quelle von schmalbandigen Einzelphotonen vorgestellt, die auf dem Konzept der parametrischen Fluoreszenz innerhalb eines optischen Resonators basiert und die einen konstanten Strom von Photonenpaaren emittiert. Eine statistische Beschreibung dieser Photonenpaare wird vorgestellt und erstmals direkt gemessen. Um Emission in nur eine einzelne Mode zu erreichen, wurde der Photonenstrom mit Hilfe eines speziell entwickelten Mehrpass-Fabry-Perot-Etalons mit geringem Durchlassbereich und sehr hohem Kontrast gefiltert. Photon-Atom-Wechselwirkungen werden im zweiten Teil der Arbeit gezeigt. Der Effekt der elektromagnetisch induzierten Transparenz (EIT) wird vorgestellt und experimentell demonstriert. Die ersten EIT Experimente in Cäsiumgaszellen bei Raumtemperatur mit Probepulsen, die nur ein einzelnes Photon enthalten, werden demonstriert. Schließlich zeigt ein umfassender Ausblick wie die entwickelten experimentellen Bausteine erweitert werden können, um Einzelphotonenspeicherung zu erlauben und die Technologie für Quantenrepeater zu demonstrieren. / The use of quantum mechanical properties for information processing, so-called quantum information processing (QIP) has become an increasingly popular research field in the last two decades. It turned out that single photons are the most reliable long distance carriers of quantum information, e.g., tools to connect different processing nodes in QIP. While several methods exist to produce single photons, only little research has been performed so far on narrow-band single photons with spectral bandwidths in the MHz regime. Such photons are, however, of particular importance when coupling of single photons to atomic systems, which are often used in QIP as processing nodes, shall be realized. This thesis covers several research aspects on narrow-band single photons, all of which are important if such photons should be used as quantum information carriers. At first, a source for narrow-band single photons is introduced. This source is based on the concept of parametric down-conversion inside an optical resonator. It emits a constant stream of photon pairs. One of the two photons from the pair can be detected heralding the presence of the other photon. A statistical description of these photon pairs is introduced and for the first time also directly measured. In order to reach single-mode single-photon emission, the stream of photons was filtered with a specifically developed multi-pass Fabry-Perot etalon. This filter has a passband FWHM of only 165 MHz and particularly high contrast.

Le projet s'inscrit dans le développement de sources lasers RGB miniaturisées pour l'affichage et la vidéoprojection, la conversion de fréquence dans les cellules solaires.Les verres fluorés ZLAG (ZrF4-LaF3-AlF3-GaF3) codopés terres rares ont été considérés. Ce verre possède une faible énergie de phonon, une forte solubilité des terres rares et peut être fabriqué en couche mince par la technique PVD. Il est de plus le précurseur de vitrocéramiques transparentes. On a observé dans les verres massifs et les guides d'onde des émissions bleue, orange et rouge avec un codopage Pr3+-Yb3+, bleue et rouge avec un co-dopage Tm3+-Yb3+. L'émission RGB dans les verres tri-dopés Tm3+-Er3+-Yb3+ semble prometteuse. Par ailleurs, la vitro-céramisation a permis d'augmenter de plus de 30% les sections efficaces d'absorption des ions Pr3+ et Yb3+.Une efficacité de transfert de 92% a été obtenue dans les verres co-dopés 0,5Pr3+-10Yb3+ pour le processus de conversion d'un photon bleu en deux photons IR.

This thesis describes the specification, design and implementation of a software-defined radio system on a two-channel 14-bit digitizer/generator. The multi-stage interpolations and decimations which are required to operate two analog-to-digital converters at 800 megasamples per second (MSps) and two digital-to-analog converters at 1600 MSps from a 25 MSps software-side interface, were designed and implemented. Quadrature processing was used throughout the system, and a combination of fine-tunable low-rate mixers and coarse high-rate mixers were implemented to allow frequency translation across the entire first Nyquist band of the converters. Various reconstruction filter designs for the transmitter side were investigated and a cheap implementation was done through the use of programmable base-band filters and polynomial approximation.