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1
Karamlou, Amir H. "Towards quantum information processing with diamond color centers." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119749.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 59-63).
The DiVincenco requirements summarize the key properties that quantum systems should have to be useful for quantum computing. The work in this thesis focuses on one of the leading solid-state quantum systems, the nitrogen vacancy (NV) center in diamond. The NV has emerged as an excellent quantum sensor, in which quantum logic techniques can significantly improve performance. However, a remaining problem concerns the rate and fidelity of NV spin measurement. To address this problem in this thesis we first propose and theoretically demonstrate a scheme for spatially robust state-selective transitions with over 99.9% fidelity between different spin states in zero-field splitting. Furthermore, another central challenge tackled in this work is the efficient collection of the emitter's fluorescence. Optical antennas are appealing as they offer directional emission together with spontaneous emission rate enhancement across a broad emitter spectrum. We introduce and optimize metal-dielectric nano-antenna designs recessed into a diamond substrate and aligned with quantum emitters. We analyze trade-offs between external quantum efficiency, collection efficiency, Purcell factor, and overall collected photon rate. This analysis shows that an optimized metal-dielectric hybrid structure can increase the collected photon rate from a nitrogen vacancy center by over two orders of magnitude compared to a bare emitter. As a result, these metal-dielectric antennas should enable single-shot electron spin measurements of NV centers at room temperature.
by Amir H. Karamlou.
M. Eng.
2
Nahra, Mackrine. "Color Centers in Nanodiamonds for Quantum Optics Applications." Electronic Thesis or Diss., Troyes, 2021. http://www.theses.fr/2021TROY0017.
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L’intérêt de trouver un émetteur quantique émettant des photons uniques à la demande devient de plus en plus important dans le domaine de l'optique quantique. Les centres colorés dans les nanodiamants (NDs) se révèlent être des candidats prometteurs. Cependant, la production de NDs ayant des centres colorés brillants et émettant des photons indiscernables reste un défi. Dans cette thèse, nous étudions les centres colorés du groupe IV, en particulier le SiV- et le GeV-, synthétisés par la méthode haute pression haute température (HPHT). Nous étudions l'effet des différents paramètres de croissance sur les propriétés optiques du SiV- et rapportons la largeur de raie la plus étroite de 6 GHz pour un ensemble de SiV- sous excitation hors résonante. En raison de la faible probabilité de trouver un SiV- unique, nous avons dirigé notre attention vers les GeV- où la probabilité de trouver un photon unique était significativement plus élevée. Ces GeV- possèdent des propriétés spectrales remarquables à température ambiante, y compris une raie à zéro phonon (ZPL) stable et brillante. Nous étudions la dynamique de leur population dans le cadre d'un modèle à trois niveaux. Nous rapportons un taux maximal de comptage d'émission de photons de 1,6 Mcps à saturation et une visibilité en polarisation de 92% de la lumière de fluorescence. Outre la ZPL, nous observons d'autres transitions électroniques situées dans la bande latérale des phonons du GeV-. Nous démontrons que la méthode HPHT produit des SiV- et GeV- dans les NDs ayant des propriétés optiques supérieures pour des applications en optique quantiqueThe emerging field of quantum optics has attracted the interest of finding an accessible solid-state quantum emitter generating single photons on-demand. Color centers in nanodiamonds (NDs) have shown to be promising candidates. However, producing NDs hosting bright and indistinguishable photons from color centers remains challenging. In this thesis, we study group IV color centers, particularly silicon vacancy (SiV-) and germanium vacancy (GeV-), synthesized by the high pressure high temperature (HPHT) method. We study the effect of the different growth parameters on the optical properties of the SiV- at room and low temperature (T) and report the narrowest linewidth of 6 GHz for an SiV- ensemble using off resonant excitation. Due to the low probability of finding a single SiV- center, we turn our attention to GeV- color centers where the probability of finding a single photon source was found to be significantly higher. Single GeV- in NDs with size ranging from 10 to 50 nm showed remarkable spectral properties at room T including a stable and a bright zero-phonon line (ZPL). We study their internal population dynamics in the framework of a three level model with intensity dependent de-shelving. We find a maximum photon emission count rate of 1.6 Mcps at saturation. We also report a polarization visibility of 92 % from the fluorescence light. Besides the ZPL, we analyze the origin of other transitions lying within the phonon sideband. We demonstrate that the HPHT method can produce SiV- and GeV- in NDs with superior optical properties required for quantum optics applications
3
PEIRO, GREGORIO P. "Operacao C.W. e sintonia por um par de prismas de um laser de cor KCL:TLsup0 (1)." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10367.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Fisica, Universidade de Sao Paulo - IF/USP
4
Felgen, Nina [Verfasser]. "Investigation of diamond nanostructures with incorporated color centers / Nina Felgen." Kassel : Universitätsbibliothek Kassel, 2019. http://d-nb.info/1182471285/34.
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Pham, Linh My. "Magnetic Field Sensing with Nitrogen-Vacancy Color Centers in Diamond." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10993.
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In recent years, the nitrogen-vacancy (NV) center has emerged as a promising magnetic sensor capable of measuring magnetic fields with high sensitivity and spatial resolution under ambient conditions. This combination of characteristics allows NV magnetometers to probe magnetic structures and systems that were previously inaccessible with alternative magnetic sensing technologies. This dissertation presents and discusses a number of the initial efforts to demonstrate and improve NV magnetometry. In particular, a wide-field CCD based NV magnetic field imager capable of micron-scale spatial resolution is demonstrated; and magnetic field alignment, preferential NV orientation, and multipulse dynamical decoupling techniques are explored for enhancing magnetic sensitivity. The further application of dynamical decoupling control sequences as a spectral probe to extract information about the dynamics of the NV spin environment is also discussed; such information may be useful for determining optimal diamond sample parameters for different applications. Finally, several proposed and recently demonstrated applications which take advantage of NV magnetometers' sensitivity and spatial resolution at room temperature are presented, with particular focus on bio-magnetic field imaging.Engineering and Applied Sciences
6
Balasubramanian, Priyadharshini [Verfasser]. "Towards quantum technologies with color centers in diamond / Priyadharshini Balasubramanian." Ulm : Universität Ulm, 2021. http://d-nb.info/1237750776/34.
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Babinec, Thomas Michael. "Topics in Nanophotonic Devices for Nitrogen-Vacancy Color Centers in Diamond." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10461.
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Recently, developments in novel and high-purity materials allow for the presence of a single, solitary crystalline defect to define the electronic, magnetic, and optical functionality of a device. The discrete nature of the active dopant, whose properties are defined by a quantum mechanical description of its structure, enables radically new quantum investigations and applications in these arenas. Finally,there has been significant development in large-scale device engineering due to mature semiconductor manufacturing techniques. The diverse set of photonic device architectures offering light confinement, guiding, and extraction is a prime example. These three paradigms – solitary dopant photonics and optoelectronics (solotronics), quantum science and technology, and device engineering – merge in the development of novel quantum photonic devices for the next generation of information processing systems. We present in this thesis a series of investigations of optical nanostructures for single optically active spins in single crystal diamond. Chapter 1 introduces the Nitrogen-Vacancy (NV) color center, summarizes its applications, and motivates the need for their integration into photonic structures. Chapter 2 describes two prototype nanobeam photonic crystal cavities for generating strong light-matter interactions with NV centers. The first device consists of a silicon nitride photonic crystal nanobeam cavity with high quality factor \(Q \sim 10^5\) and small mode volume \(V \sim 0.5*(\lambda/n)^3\). The second device consists of a monolithic diamond nanobeam cavity fabricated with the focused ion beam (FIB) directly in a single crystal diamond sample. Chapter 3 presents a high-efficiency source of single photons consisting of a single NV center in a photonic diamond nanowire. Early FIB prototypes are described, as is the first successful realization of the device achieved via reactive ion etching nanowires in a single crystal diamond containing NV centers, and finally a variation of this approach based on incorporation of NV centers in pure diamond via ion implantation. In chapter 4 we consider the optimal design of photonic devices offering both collection efficiency and cavity-enhancements and extend the model of the NV center to include photonic effects. In chapter 5 we briefly introduce a novel optically active spin discovered in a diamond nanowire. Finally, in chapter 6 we conclude with several proposals to extend this research program.Engineering and Applied Sciences
8
Fernandez-Acebal, Pelayo [Verfasser]. "Hyperpolarization and sensing with color centers in diamond / Pelayo Fernandez-Acebal." Ulm : Universität Ulm, 2020. http://d-nb.info/1203211619/34.
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DeLong, Kenneth Wayne. "Two-photon absorption and color centers: Effects on all-optical switching." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185023.
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This dissertation explores the effects of two-photon absorption and color center induced absorption on all-optical switching devices. The amount of allowable two-photon absorption was quantified by the parameter T = 2βλ/n₂, where λ is the operating wavelength, β is the two-photon absorption coefficient, and n₂ is the nonlinear refractive index coefficient, the latter two being measured at λ. If the value of T exceeds unity, the operation of all-optical switching devices is in general degraded beyond usable regimes. This result was demonstrated by numerical experiments on systems of equations modelling a nonlinear directional coupler, a prototypical all-optical switching device. The value of T was measured in two fibers, one made of lead silicate glass, and one made of TiO₂-doped silica. We find the value of T to be greater than unity at a wavelength of 1.06 μm in both fibers. Significant color center formation was seen in the lead glass fiber. These color centers were created through two-photon absorption and destroyed through one-photon absorption. Color center induced absorption was seen to mimic two-photon absorption in certain regimes. The nonlinear optical response of semiconductor-doped glasses, an example of a one-photon resonant nonlinearity, was studied. A relaxation time which is dependent on the carrier density was found to be important when modelling the response of these glasses.
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UDO, PAULO T. "Desenvolvimento de um laser de centros de cor-centros F2 em LiF." reponame:Repositório Institucional do IPEN, 1986. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9865.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
11
Wang, Chunlang. "A Solid-State Single Photon Source Based on Color Centers in Diamond." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-72761.
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Lesik, Margarita. "Engineering of NV color centers in diamond for their applications in quantum information and magnetometry." Thesis, Cachan, Ecole normale supérieure, 2015. http://www.theses.fr/2015DENS0008/document.
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Le centre coloré NV, constitué d’un atome d’azote et d’une lacune, est un défaut ponctuel du diamant qui se comporte comme un atome artificiel piégé dans cette matrice. Grâce aux propriétés de son spin électronique, qui peut être lu et manipulé comme un système quantique élémentaire, le centre NV as de nombreuses applications comme qubit pour l’information quantique ou comme sonde de champ magnétique. Cependant, ces applications nécessitent de contrôler les propriétés des centres NV ainsi que leur position dans le cristal. Cette thèse examine des méthodes pour atteindre ces objectifs en combinant des techniques d’implantation d’atomes et de croissance assistée par plasma (CVD) de diamant.Le mémoire est divisé en six chapitres. Le premier chapitre résume les propriétés des centres NV, ce qui permet de définir les objectifs principaux dans la fabrication des centres NV. Le chapitre deux montre qu’il est possible de créer un réseau de centres NV par implantation au moyen d’une colonne d’ions focalisés. Cette technique est adaptée à la création de centres NV dans des nanostructures comme des cristaux photoniques ou des pointes de type AFM. Cependant la faible énergie cinétique des ions, nécessaire pour atteindre une résolution meilleure que 10 nm en diamètre de spot, conduit à une implantation proche de la surface ce qui affecte fortement les propriétés des centres NV. Le troisième chapitre examine comment la recroissance d’une couche de diamant sur des centres NV implantés permet de réduire l’impact négatif de la surface. Les quatrième et cinquième chapitres décrivent des méthodes pour la fabrication des centres NV en contrôlant les paramètres de la croissance CVD. Des couches minces fortement dopées avec les centres NV peuvent être créées, et un contrôle quasi parfait de l’orientation de l’axe du centre NV peut être obtenu. Dans l’objectif d’optimiser les propriétés du temps de cohérence du spin, le sixième chapitre étudie comment le spin électronique du centre NV peut être protégé contre les effets de décohérence induits par les spins non-polarisés dans la matrice du diamantThe Nitrogen-Vacancy (NV) color center is a defect of diamond which behaves as an artificial atom hosted in a solid-state matrix. Due to its electron spin properties which can be read-out and manipulated as an elementary quantum system, the NV center has found a wide panel of applications as a qubit for quantum information and as a magnetic field sensor. However these applications require to control the properties of the NV centers and their localization. This doctoral thesis investigates methods allowing us to tailor the properties of NV centers by combining techniques for the implantation of nitrogen atoms and the plasma-assisted (CVD) synthesis of diamond.The manuscript is divided into six chapters. The first chapter summarizes the properties of the NV center which will set our objectives for the NV engineering. The second chapter will describe how arrays of NV centers can be created using Focused Ion Beam implantation. The results open a wide range of applications for the targeted creation of NV centers in diamond structures such as photonic crystals and tips. However the low kinetic energy which is required for achieving implantation within a spot of 10-nm diameter leads to shallow defects which properties are strongly affected by the sample surface. The third chapter investigates how the overgrowth of a diamond layer over implanted NV centers can remove the detrimental influence of the surface. The fourth and fifth chapters describe effective methods for NV center fabrication through the control of the CVD growth conditions of the hosting crystal. Thin layers with high NV doping can be grown and almost perfect control of the orientation of the NV axis can be achieved. With the goal to optimize the spin coherence properties, the sixth chapter investigates how the electron spin of the NV center can be protected from decoherence effects induced by magnetic noise due to the unpolarized spins in the diamond lattice
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FREITAS, ANDERSON Z. de. "Operacao do laser KCl:Tlsup(0)(1) no regime de travamento de modos por bombeamento sincrono." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10659.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:94/04083-5
14
Martins, Evely. "Medidas de transições ópticas em candidatos a meio laser ativo: aplicação a centros de cor." Universidade de São Paulo, 1990. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-16052014-102017/.
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Centros de cor e íons de metal de transição em cristais iônicos tem mostrado um grande potencial como candidatos a meios laser ativos sintonizáveis. Para determinar se tais materiais são apropriados ou não para operar como meios laser, seus parâmetros espectroscópicos fundamentais tem de ser conhecidos. No presente trabalho, nos descrevemos um metodo espectroscópico que permite determinar o diagrama de níveis de energia da espécie investigada, o tempo de decaimento, a eficiência quântica e a secção de choque de emissão. O tempo de decaimento foi medido usando-se um bombeamento senoidal de excitação e detecção sensível a fase; obtendo-se 1,6ms para o kcl:TL POT.0 (1), 17ns para o LIf:F IND.2, 28ns para o LIf:F2 POT.+ E 4ns para o LIf:F3 POT.+. Usando-se uma técnica de absorção rotulada foi possível determinar absorções do estado fundamental e do primeiro estado excitado da espécie investigada mesmo com a interferência de outros centros. Técnica utilizada em kcl:tl onde níveis de energia do centro de cor de TL POT.0 (1) foram identificados vários outros agregados de tl devido a preparação do cristal, que perturbam o centro TL POT.0 (1) também foram identificados. Vários outros agregados de T1, devido a preparação do cristal, que perturbam o centro TL POT.0 (1), também foram observados.Color centers and transition metal ions in ionic crystals have shown a qreat potential as candidates for tunable laser sources. In order to determine whether or not such materials are suitable to operate as laser media, their fundamental spectroscopic parameters have to be known. In the present work we describe a spectroscopic method that can determine the energy level diagram of the species under investigation, the decay time, quantum efficiency and emission cross section. Firstly, the decay time was measured by using a sinosoidal pumping excitation and phase sensitive detection. Using a specially home designed cryostat we were able to measure the decay time in the temperature range of 77K to 310K, and therefore, the temperature dependence of the quantum efficiency. This technique was applied to the T1°(1):KCl, F2:LiF, F+3:LiF and F+2:LiF, where decay times of 1.6s, 17ns, 4ns and 28ns were measure, respectively. Secondly, by using a pump-probe technique we were able to determine the excited-state absorption of the studied species, even under the interference of other centers. This is particularly important in color centers due to the presence of several other species during the centers formation. Besides, this technique can identify excited state absorptions that can eliminate laser medium candidates. This technique was used in KCl:T1 crystals where laser active Tl° (1) color center energy levels were identified. Besides, several other Tl aggregates due to the crystal preparation that perturb the Tl° (1) center were also observed.
15
Müller, Tina. "Novel colour centres in diamond : silicon-vacancy and chromium centres as candidates for quantum information applications." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608164.
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Dong, Wenzheng. "Quantum Information Processing with Color Center Qubits: Theory of Initialization and Robust Control." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103438.
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Quantum information technologies include secure quantum communications and ultra precise quantum sensing that are significantly more efficient than their classical counterparts. To enable such technologies, we need a scalable quantum platform in which qubits are con trollable. Color centers provide controllable optically-active spin qubits within the coherence time limit. Moreover, the nearby nuclear spins have long coherence times suitable for quantum memories. In this thesis, I present a theoretical understanding of and control protocols for various color centers. Using group theory, I explore the wave functions and laser pumping-induced dynamics of VSi color centers in silicon carbide. I also provide dynamical decoupling-based high-fidelity control of nuclear spins around the color center. I also present a control technique that combines holonomic control and dynamically corrected control to tolerate simultaneous errors from various sources. The work described here includes a theoretical understanding and control techniques of color center spin qubits and nuclear spin quantum memories, as well as a new platform-independent control formalism towards robust qubit control.Doctor of Philosophy
Quantum information technologies promise to offer efficient computations of certain algorithms and secure communications beyond the reach of their classical counterparts. To achieve such technologies, we must find a suitable quantum platform to manipulate the quantum information units (qubits). Color centers host spin qubits that can enable such technologies. However, it is challenging due to our incomplete understanding of their physical properties and, more importantly, the controllability and scalability of such spin qubits. In this thesis, I present a theoretical understanding of and control protocols for various color centers. By using group theory that describes the symmetry of color centers, I give a phenomenological model of spin qubit dynamics under optical control of VSi color centers in silicon carbide. I also provide an improved technique for controlling nuclear spin qubits with higher precision. Moreover, I propose a new qubit control technique that combines two methods - holonomic control and dynamical corrected control - to provide further robust qubit control in the presence of multiple noise sources. The works in this thesis provide knowledge of color center spin qubits and concrete control methods towards quantum information technologies with color center spin qubits.
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Schmidt, Alexander [Verfasser]. "Fabrication and characterization of diamond nanopillars, waveguides and AFM tips with incorporated color centers / Alexander Schmidt." Kassel : Universitätsbibliothek Kassel, 2020. http://d-nb.info/123242756X/34.
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Andrade, Luis Humberto da Cunha. "Criação e caracterização óptica em cristais de KI." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-06052008-084549/.
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No presente trabalho apresentamos um outro método para criação de centros de cor, em matrizes de KI puro, através da absorção de dois fótons. Este processo possui uma característica útil: a coloração é realizada a baixa temperatura, ao contrário de outros métodos, que necessitam aquecer o cristal até próximo a ponto de fusão, fazendo com que as impurezas adicionadas durante o crescimento migrem para a superfície do cristal. Com este método, colorimos alguns cristais de KI puro, a fim de demonstrar a eficiência do processo, e algumas aplicações deste como em cristais de KI: \'Cu POT.+\', onde foi realizada a tentativa de criação de centros de cor do tipo \'F IND.A\', e cristais de KI:\'Yb POT.2+\', nos quais foram identificados centros de cor do tipo Z, com a possibilidade de formação de novos centros. Outras propriedades interessantes, como a suposta formação de \'Yb POT.3+\' nessas matrizes a partir da criação de centros de cor, abrem espaço para mais um amplo estudo desse processo, que ainda deverá ser investigado.In this work we present an other method to produce color centers in pure KI lattice by two photon absorption. This process has a useful feature: coloring is achieved at low temperature as opposed to other methods that require heating of crystal up to near fusion temperature in such a way that impurities added during growing migrate to the surface of crystal. By this method we colored some pure KI crystals to demonstrate the efficiency and some applications of the process to some crystals such as KI: \'Cu POT.+\' crystals trying to create FA centers and KI:\'Yb POT.2+\' crystals where we identified Z centers with possibilities of formation of other centers. Other interesting properties as the supposed formation of \'Yb POT.3+\' in these lattices through color center creation widen the study of the process to be yet investigated.
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PRADO, LUCIA. "Estudos espectroscopicos de centros de defeitos potencialmente laser ativos: o centro Pbsup+<1> em cristais fluorados." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10644.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
20
BUSTAMANTE, ANDREA N. P. "Crescimento de cristais de KCL:TL para aplicacoes laser." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10371.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Fisica, Universidade de Sao Paulo - IF/USP
21
NARDI, DANIELA T. "Estudo da formacao de cor em polimeros irradiados com feixe de eletrons." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11148.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
22
VIEIRA, JUNIOR NILSON D. "Estudo dos defeitos TLsup(0)(1) e INsup(0)(1) em aletos alcalinos: protótipo de um centro de cor como meio laser ativo." reponame:Repositório Institucional do IPEN, 1986. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11626.
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Tese (Doutoramento)
IEA/T
Instituto de Fisica, Universidade de Sao Paulo - IF/USP
23
Glebov, Boris L. "Ionizing-Radiation-Induced Color Centers in YAG, Nd:YAG, and Cr:Nd:YAG: Developing and Analyzing a Radiation-Hard Laser Gain Medium." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195883.
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This report presents results from a series of experiments in which YAG samples (undoped, as well as doped with Nd and Cr3+) were exposed to ionizing radiation (gamma rays and UV). These experiments were performed for the purpose of investigating the various phtodarkening processes taking place in these materials in response to the ionizing radiation. The purpose of this investigation was to establish whether and how co-doping YAG with Cr3+ improves the material's resistance to photodarkening due to the ionizing radiation. The experiments tracked time-resolved transmittance of the samples at 1064 nm in immediate response a pulsed exposure to the ionizing radiation, as well as steady-state spectrally-resolved changed in the samples' optical absorption after the irradiation. The investigation revealed a number of photodarkening processes occurring in the samples in response to the ionizing radiation, both transient and permanent. It was further revealed that inclusion of Cr3+ ions in YAG significantly reduces these photodarkening processes, improving the material's radiation resistance. It was observed that materials containing at least 0.5 at% Cr3+ are essentially radiation-hardened, resisting both transient and steady-state changes in transmittance observed in the materials not containing Cr3+.
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ROSA, LUIZ A. R. da. "Termoluminescencia do LiF: Mg, Ti entre 66 e 315 K." reponame:Repositório Institucional do IPEN, 1989. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10259.
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Tese (Doutoramento)
IPEN/T
Instituto de Fisica, Universidade de Sao Paulo - IF/USP
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Assis, Luiz Santiago de. "Estudo do comportamento temporal do lasr C.W. de ND:YAG usando cristais com centros de cor como absorvedores saturáveis." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-27022014-113956/.
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Existe uma família de centros de cor e cristais dopados com íons metálicos que absorvem na região de emissão do laser de neodímio. Dentre estes, os que são laser ativos são normalmente bombeados em um esquema de cavidades colineares. Eles podem também ser usados como absorvedores saturáveis para o chaveamento Q passivo, C.W. Porém, neste caso a absorção máxima intracavidade que pode ser introduzida é limitada de forma a permitir que a ação laser ocorra. Assim, no caso de ser simultaneamente utilizado como absorvedor e meio ativo existe uma limitação do ganho máximo que o meio ativamente bombeado pode alcançar. Usando-se um esquema de cavidades acopladas, estudamos o desempenho dos centros de cor KCl:T1° (1) e LiF: F POT - IND 2 , para gerar chaveamento Q c.w. passivo (Q- switching) e o travamento de modos (mode-locking) com o esquema de cavidades acima mencionada, na região espectral do infravermelho. Em particular estudamos a ação laser simultânea dos centros KCl: Tl° (1) e do laser de Nd:YAG com o esquema de cavidades acopladas citado, onde o centro de cor tinha o papel dual de absorvedor saturável e meio de ganho. Obteve-se uma alta extração do laser de KCl:Tl° (1), atingindo o limite teórico de 40%, no regime Q-switched c.w.pois a única fonte de perdas do laser de bombeio é o absorvedor saturável. Devido ao baixo ganho dos materiais mencionados e a alta intensidade de saturação foram exploradas as propriedades da cavidade com compensação astigmática, que permite uma grande focalização do feixe sobre o cristal, num regime de cavidades acopladas. Além deste esquema, usamos também um método de bombeamento colinear para a obtenção do travamento de modos ativo-passivo no regime C. W. do laser de Nd: YAG 1 usando o LiF: F POT IND 2 como elemento de modulação passiva dos pulsos. Como um absorvedor saturável lento este necessita de cavidades longas para a obtenção deste regime de operação. Os pulsos modulados (ativamente) sofrem um processo de modulação passiva, o que é dado pela mudança do seu perfil de intensidade de gaussiano para exponencial simétrica, caracterizando a mudança do travamento de modos ativo para passivo.In general, tunable lasers are colinearlly pumped by other powerfull lasers. In the particular case of color centers, that cover the near infrared spectral region, there is a shortcoming due to the difficulty of creating high densities of centers to efficiently extract output energy. One possible way to circumvent this problem is to use intracavity pumping, but there is a limiting factor that is the maximum available gain of the pumping laser, that limits the maximum absortion that can be introduced in the pump laser cavity. A coupled cavities scheme is a solution to solve this problem. In this sense, this scheme was studied using a simple theoretical model. Two sets of experiments were performed, using LiF:F2 and KCl:T1°(1) color centers. In the first case, in which the LiF: F-2 centers were used only as saturable absorber, it was demonstrated that the coupled cavity is responsable for the temporal behavior of the main laser, and operation in the Q-switched mode was obtained, wi th pulses of 1 SJ..S duration. In the second case, KCl:Tl° (1) color centers are also laser active and simultaneous laser operation were achieved, in the Q-switched regime. The remarkable fact was that the pumping efficiency was close to the maximum theoretically allowed and the pulse duration was also totally dependent on the control cavi ty. In both cases, the pulse time duration was in good agreement with the theoretical predictions. The mode-locking regime in these scheme was also studied, using LiF: F-2 color centers, that has a decay time much longer than the cavity round trip time. By the reducing gain a partial modulation in the couple cavity scheme, we only observed a partial modulation of the laser power, indicating that other effects prevent the full modulation. In these case, the effective absortion used was 0,6 % .In order to explore the role of the saturable absorbers in the mode-locking regime, a active modulator was used to start and sustain the regime, besides the presence of the crystal inside the cavity. We clearly observed a change in the shape of the pulses from gaussian to hyperbolic secant squared that is a characteristic of the passivily mode-locked system. In the optimum case the pulse duration was reduced by a factor of 2,4.
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Riedrich-Möller, Janine Simone [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Deterministic coupling of single color centers to monolithic photonic crystal cavities in single crystal diamond / Janine Simone Riedrich-Möller. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1064305814/34.
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COURROL, LILIA C. "Estudo do processo de estabilizacao dos centros Fsup(+)sub(2) em cristais de LIF:OHsup(-) irradiados e espectroscopia dos produtos de dissociacao." reponame:Repositório Institucional do IPEN, 1990. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10223.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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GOMES, LAERCIO. "Estudo compreensivo da fotodissociacao do ion OHsub(-) nos haletos alcalinos e sua interacao com centros de cor." reponame:Repositório Institucional do IPEN, 1985. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9850.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Logan, Joshua Warren-Louis Britnell Richard E. "Guidelines for the proper application of color and light in the health and fitness industry for the purpose of improving user experience and performance." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/master's/LOGAN_JOSHUA_19.pdf.
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Evans, Geraint Andrew. "Characterisation of point defects in SiC by microscopic optical spectroscopy." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391196.
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Aizatsky, N. I., N. P. Dikiy, A. N. Dovbnya, I. D. Fedorets, V. A. Kushnir, Yu V. Lyashko, D. V. Medvedev, et al. "Properties of Zirconia Nanoceramics under High-Energy Electrons Irradiation." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35622.
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Formation of radioactive isotopes is investigated under irradiation by relativistic electrons with energy
up to 100 MeV. Radioactive isotopes 87,88Y, 88,89,95Zr, 95Nb, 175Hf are registered after irradiation by
relativistic electrons with energy 47.2 MeV. The present data are necessary for the choice of a material for
a dielectric wakefield accelerator. The greatest danger at operation of accelerators represents 88Y.
Formation of radiation defects in nanoceramics is investigated. The various types of radiation defects are
found out at an irradiation by relativistic electrons with energy 47 MeV and 86 MeV. In UV VIS spectra
the absorption lines of radiation are registered at 402.2 nm and 635 nm, which correspond to the F and F'
centers of monocline lattices of zirconia. It is revealed, that krypton atoms are the centers of segregation of
point defects.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35622
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Neu, Elke Katja [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Silicon vacancy color centers in chemical vapor deposition diamond : new insights into promising solid state single photon sources / Elke Katja Neu. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2012. http://d-nb.info/1052338593/34.
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Neu-Ruffing, Elke [Verfasser], and Christoph [Akademischer Betreuer] Becher. "Silicon vacancy color centers in chemical vapor deposition diamond : new insights into promising solid state single photon sources / Elke Katja Neu. Betreuer: Christoph Becher." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2012. http://d-nb.info/1052338593/34.
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Nicolas, Louis. "Spectroscopie haute résolution d’ensembles de centres colorés du diamant pour des expériences d’optique quantique." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE066.
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Le travail décrit dans ce manuscrit porte sur l’élaboration d’une interface atome-champ originale pour un émetteur de la matière condensée : un système de demi-cavité composé d’un miroir et d’une lentille à forte ouverture numérique. Ce système permet de contrôler et en particulier d’augmenter le temps de vie d’un dipôle niché au sein d’un cristal situé au point focal de la lentille alors même que la distance entre l’atome et le miroir est très grande devant la longueur d’onde. Utiliser un tel système permet aussi d’obtenir une interaction forte entre un champ résonant fortement focalisé et l’atome. Pour cet objectif, les centres colorés du diamant sont des atomes artificiels de choix car ils présentent des propriétés de photoluminescence exceptionnelles. Une grande partie du travail effectué durant cette thèse a été dédiée à l’élaboration d’une plateforme expérimentale permettant d’étudier les propriétés de photoluminescence dans le domaine visible de systèmes de la matière condensée à température cryogénique afin de trouver les émetteurs adéquats pour réaliser cette interface. Nous avons caractérisé de nouveaux échantillons dans le cadre de collaborations avec des laboratoires spécialisés dans la croissance du diamant, en particulier des nanodiamants contenant des centres SiV- et GeV- aux propriétés optiques prometteuses. La photoluminescence de pointes en diamant nanométriques contenant des centres SiV- a été particulièrement étudiée. Un effet de photochromisme a été observé et nous a permis de mesurer la largeur de raie homogène d’un ensemble de centres SiV- élargi inhomogènement. Cette largeur se rapproche de la limite radiative. Nous donnons une explication de ce phénomène de photochromisme corroborée par différentes mesures. Enfin, des expériences préliminaires ont été réalisées en demi-cavité. Nous montrons comment la modification du temps de vie peut être mesurée en présence d’élargissement inhomogène en utilisant un second interféromètre en aval de la demi-cavitéThis dissertation presents the elaboration of an original atom-light interface in the solid-state: a half-cavity made out of a mirror and a high numerical aperture lens that allows control and more specifically enhancement of the lifetime of a dipole located at the focus of the lens. Such a system also allows strong interaction between the dipole and a highly focused field given that the field can be totally reflected by the dipole. Diamond colored centers are suitable artificial atoms as they exhibit outstanding optical properties. The major part of the work realized during this PhD was dedicated to the elaboration of an experimental platform to study photoluminescence properties of condensed matter systems in the visible domain at cryogenic temperatures and to find suitable emitters for an efficient atom-field interface. This set up allows us to characterize new samples as part of collaborations with teams specialized in diamond synthesis, in particular, SiV- and GeV- embedded in nanodiamonds synthesized by chemical vapor deposition. They exhibit sub-GHz linewidths which is very promising for quantum electrodynamics experiments. Optical properties of SiV- centers embedded in diamond nanopyramids have been extensively studied. Photochromism has been observed and allows us to measure the homogeneous linewidth of inhomogeneously broadened SiV- center ensembles. This linewidth is close to be lifetime limited.We try to explain this photochromism effect with different hypotheses corroborated by measurements. Finally, preliminary results have been obtained using a half-cavity. We show how the modification of the lifetime is measured when inhomogeneous broadening is present, by using another interferometer in addition to the half-cavity
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Enokihara, Cyro Teiti. "Estudo do quartzo verde de origem hidrotermal tratado com radiação Gama." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-18022014-133514/.
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Uma variedade específica de quartzo de cor verde, seja natural ou induzida pela radiação é muito rara. Trata-se de um mecanismo de formação de cor completamente diferente daqueles conhecidos e amplamente discutidos na literatura, que são responsáveis pela formação do quartzo fumê, do citrino e da ametista, incluindo a prasiolita produzida pelo aquecimento da ametista de Montezuma (MG). Somente duas ocorrências, conhecidas até o momento, tem o quartzo incolor, uma no pequeno distrito em Thunder Bay Amethist Mine, no Canadá e a outra na Bacia do Paraná ( Brasil) , ao longo de uma faixa de 600 km, com ocorrências dispersas de geodos, que se estende da região de Quaraí (RS) até a localidade de Uberlândia (MG). Estas duas ocorrências foram formadas sob fortes atividades hidrotermais, a de Thunder Bay é devido ao tectonismo e a da Bacia do Paraná está relacionada às atividades da água meteórica e hidrotermal do Aquífero Guarani. Estes cristais de quartzo hidrotermal apresentam um histórico de crescimento muito rápido, permitindo a formação dos defeitos de crescimento como as geminações, o crescimento em mosaico, as formações com pequenos ângulos inclinados e as estrias que facilitam a absorção da água na forma de água molecular, silanol (Si-OH), hidroxila (OH) e como micro inclusões. Este tipo de quartzo pode ser considerado como quartzo hidratado (wet quartz) semelhante ao quartzo sintético. O teor em água, com até 3200 ppm em massa, é superior à concentração das impurezas estruturais como o Fe, Al e Li. Não existe uma correlação entre o conteúdo da água e a quantidade de impurezas, como ocorre em outras variedades de cor do quartzo. No quartzo hidrotermal de geodos são formados complexos de silanol que quando são irradiados geram os centros de cor NBOHC (Centro de cor do oxigênio com elétron desemparelhado que não participa da ligação) que apresenta absorção no intervalo de 590 nm a 620 nm e formando uma janela de transmissão a 550 nm aproximadamente, responsável pela cor verde. Várias técnicas de análises químicas e de espectroscopia foram empregadas para caracterizar estas amostras de quartzo verde. A determinação do teor de água por meio dos espectros de infravermelho FTIR mostraram menos água (até 2300 ppm em massa), em comparação com os resultados das análises de aquecimento (3200 ppm) decorrente provavelmente, ao complexo silanol remanescente. Para documentar a influência da água na formação da cor verde foram realizadas análises por espectroscopia de infravermelho FTIR em amostras de quartzo de 3 diferentes grupos de ambientes geológicos, o quartzo pegmatítico com Al e Li formado à alta temperatura da região de Santana do Araguaia, o quartzo de veios hidrotermais com Al, mas sem água originado à média temperatura, da região de Curvelo e a ametista com muito Fe, pouco Al e pouco silanol da região de Brejinho e o quartzo de geodos hidrotermais formado a baixa temperatura com alto conteúdo de água molecular e silanol, e com muito Fe e pouco Al. As análises e as comparações permitiram diferenciar e determinar a formação do centro de cor NBOHC (Centro de cor do oxigênio com elétrons desemparelhados que não participam da ligação) para o quartzo hidrotermal de geodos da Bacia do Paraná. Assim, somente cristais de quartzo com alta concentração de água molecular e silanol são apropriados para desenvolver a cor verde por meio da radiação gama. Pode-se mencionar que no mesmo geodo podem coexistir cristais de quartzo com diferentes teores de água. Cabe ressaltar também que o quartzo verde tratado com radiação gama é sensível à radiação ultravioleta e ao aquecimento, levando à perda parcial ou total da cor verde.A specific variety of quartz showing a green color in nature or induced artificially by radiation is quite rare. This can be explained by the fact that the mechanism of formation of this color is very different from the ones widely discussed in the literature and responsible for the formation of the fumée, citrine and amethyst types of quartz, including the prasiolite (leak green quartz) formed by heating amethyst from Montezuma, Brazil. Only two occurrences are known today, where this type of quartz can be found: Canada, at the Thunder Bay Amethyst Mine, Ontario, a small district, and Brazil, at widely scattered geode occurrences along a 600 km stretch from Quaraí at Brazils southernmost tip to Uberlandia in Minas Gerais. These two occurrences have been formed by strong hydrothermal activities, at Thunder Bay due to tectonics and in Brazil by meteoric and hydrothermal waters of the Guarani aquifer. That way much quartz crystals showed a very fast growth history facilitating the formation of growth defects (twinning, small angle tilting, mosaic growth, striations) and the uptake of water in form of micro inclusions, molecular water, silanol (Si-OH) and OH. This type of quartz can be considered ¨wet quartz¨, similar to synthetic quartz. The water content with up to 3200 ppm by weight exceeds the amount of charge balancing cations (Fe, Al, Li). There is no correlation between water content and cations as in other color varieties. Instead, silanol complexes are formed, which by radiation due to gamma rays form the color center NBOHC (non-bonding oxygen hole defect), showing absorption between 590 to 620 nm and leaving a transmission window at about 550nm, responsible for the green color. To characterize samples which will be colored green by gamma rays analyses by ICP, NAA, Electron microscopy, water loss techniques and UV-VIS and NIR-FTIR spectroscopic have been made. The spectroscopic water determination showed less water (up to 2300 ppm by weight) compared with heating techniques (3200 ppm), probably due to remaining silanol complexes.To trace the influence of water on color formation, samples from 3 different geological settings (high temperature pegmatitic quartz with Al and Li, from Santana de Araguaia; intermediate temperature vein quartz with Al but without water from Curvelo; amethyst with more Fe, less Al and small silanol content from Brejinho, and low temperature regimes from geodes, high silanol and high molecular water, cations similar to the above mentioned) have been analised by NIR spectroscopy.The former will not show green color, only the latter one. It may be mentioned that even in geodes one has crystals with high and intermediate water content coexisting. The crystals with high silanol and molecular water are the ones to treat by radiation. The radiation induced color is heat and UV sensible with bleaching by longer exposure to these factors.
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Dickens, Emily. "Color Your Plate: A Pilot Nutrition Education Intervention to Increase Fruit and Vegetable Intake Among Older Adults Participating in the Congregate Meal Site Program in Kentucky Senior Centers." UKnowledge, 2016. http://uknowledge.uky.edu/foodsci_etds/44.
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The purpose of this study was to determine if the amount and variety of fruit and vegetable intake increased among community-dwelling older adults participating in Kentucky’s congregate meal site program following a series of educational nutrition lessons. A convenience sample (n=35) of community-dwelling older adults at two intervention (n=19) and two control (n=16) senior centers in central Kentucky participated in this quasi-experimental pre-post pilot study. Following the intervention there was a trend towards increased self-reported intake in the variety of fruit and vegetables among the intervention group (range:0.03±3.31 to 1.32±2.75 servings per week); a significant increase in the number of days participants incorporated at least 4.5 servings of fruits and vegetables per day intake; significant increases in the incorporation of fruits and vegetables in evening meal, and all meals (p≤0.05); and phytochemical knowledge (p≤0.05). Actual fruit and vegetable intake at the congregate meal increased post-intervention among the intervention group only (p≤0.05) as measured by plate waste. The mean Phytochemical Index score was 25.4, with participants consuming 79% of the phytochemical- rich component to their meal. These results indicate that theory-based educational nutrition lessons among older adults is linked to favorable trends towards increased fruit and vegetable consumption and phytochemical knowledge.
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TEIXEIRA, MARIA I. "Propriedades dosimetricas de vidros comerciais e de areia para doses altas." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11177.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
38
Fedin, Igor. "Peculiarities of the Thermo-Optic Coefficient at High Temperatures in Fibers Containing Bragg Gratings." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1309207081.
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ROSSI, WAGNER de. "Construcao e operacao de lasers de neodimio: estudo do comportamento temporal." reponame:Repositório Institucional do IPEN, 1995. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10435.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
40
Tjörnhammar, Staffan. "Properties of Volume Bragg Gratings and Nonlinear Crystals for Laser Engineering." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173868.
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This thesis focuses on two topics: thermal limitations of volume Bragg gratings (VBGs) employed as laser-cavity mirrors and formation of color centers in KTiOPO4 and its isomorphs. To explore the mechanisms of the thermal limitations of VBGs in high power lasers, I designed and constructed a diode-pumped, solid‑state laser with a VBG as cavity mirror that had a significantly higher absorption than what is typical. Thereby I could study the limiting thermal effects by using only moderate intra-cavity power. Additionally, I designed a computer model to numerically investigate the thermal effects in VBGs. Both the experiments and the simulations showed that the laser became successively more unstable when the power was increased. Absorption of the reflected laser beam causes broadening of the grating spectrum accompanied by decreasing diffraction efficiency. The reduced reflectivity leads to a leakage of the radiation through the grating. Moreover, the simulations showed that this increased instability was due to a reshaping of the intensity distribution profile inside the grating, which, in turn, leads to a sharp reduction of the diffraction efficiency. High-intensity visible radiation induces color centers in KTiOPO4, which can lead to severe decrease in the performance of the crystal and can cause catastrophic breakdown. The formation of color centers was investigated by measuring picosecond, blue-light induced infrared absorption (BLIIRA) in periodically-poled KTiOPO4, Rb:KTiOPO4, RbTiOPO4, KTiOAsO4 and RbTiOAsO4 through thermal lens spectroscopy using a common-path interferometer. This setup is capable of measuring absorption as low as 10-5 cm-1. The dependence of the BLIIRA signal on blue light average power and intensity as well as on the crystal temperature was studied. The results show the presence of at least two different types of color centers. A higher level of remnant absorption was observed in the phosphates compared to that of the arsenates. The largest portion of the induced absorption is attributed to photo-generated electrons and holes being self-trapped in the proximity to the Ti4+ and O2- ions, respectively, forming polaron color centers. Stabilization of these centers is aided by the presence of mobile alkali metal vacancies in the crystal.Denna avhandling fokuserar på både volymbraggitters (VBGs) termiska begränsningar, i tillämpning som speglar i laserkaviteter, och på bildandet av färgcentra i KTiOPO4 och isomorfa kristaller. För att undersöka de termiska effekterna i VBGer som medför begränsningar på högeffektlasrar utfördes både experiment och simuleringar. För experimenten konstruerades en diod-pumpad Yb:KYW laser med ett VBG som har betydligt högre absorption än vad som är typiskt. Därmed kunde de termiska effekterna studeras vid måttliga intrakavitetseffekter. Simuleringarna bestod av två delmodeller; gitterstrukturen modelerades med överföringsmatriser och värmeflödet med en tredimensionell modell baserad på finita elementmetoden. Både experimenten och simuleringarna visade att en laser blir successivt mer instabil när den optiska effekten ökar. Absorptionen av laserstrålen i VBGt förändrade dess spektrala egenskaper, vilket i sin tur påverkade laserns stabilitet och prestanda. De huvudsakliga effekterna var en breddning av gittrets spektrum med en minskad reflektans. Simuleringarna visade även att den ökade instabiliteten berodde på en förändring av strålningens intensitetsfördelning inuti gittret, vilket accelererade reduktionen av gittrets reflekterande förmåga. I termer av den effekt som faller in mot gittret, har lasern en tydlig övre effektgräns. När den gränsen har uppnåtts leder vidare ökning av pumpeffekten i huvudsak till ökat läckage genom volymbraggittret, i stället för till ökad uteffekt hos laserstrålen. Kortvågigt synlig ljus av hög intensitet inducerar färgcentra i KTiOPO4, vilket kan leda till kraftigt reducerad transparens och kan orsaka permanent skada i kristallen. För att undersöka skapandet av dessa färgcentra mättes den termiska lins som uppstår vid blå-ljus-inducerad infraröd absorption (Eng: blue-light induced infrared absorption = BLIIRA) inducerad av blåa laserpulser vid en våglängd av 398 nm och vid pulslängder i storlek av pikosekunder i periodiskt‑polad KTiOPO4, Rb:KTiOPO4, RbTiOPO4, KTiOAsO4 och RbTiOAsO4. Den termiska linsen mättes med en metod kallad gemensam-vägsträcka-interferometer (Eng: common-path interferometer), en metod känslig nog för att mäta absorption så låg som 10-5 cm-1. Dessutom undersöktes hur nivån av BLIIRA beror på medeleffekten och intensiteten hos den blåa laserstrålen samt på kristalltemperaturen. Resultaten visar att det bildas minst två typer av färgcentra med olika livslängder. Vidare observerades en högre grad av långsamt avklingande absorption i fosfaterna jämfört med arsenaterna. Den största delen av den inducerade absorptionen tillskrivs fotogenererade elektroner och hål som ”självfångas” i närheten av Ti4+ respektive O2- joner, och bildar färgcentra av polaron karaktär. Stabilisering av dessa centra underlättas av lättrörliga alkalivakanser i kristallerna.
QC 20150922
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Dardaillon, Rémi. "Fibres optiques passives et actives sous irradiation : application à l'amplification et à la dosimétrie en environnement spatial." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS052/document.
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Les fibres dopées erbium couvrent de nombreuses applications, particulièrement dans le domaine des télécommunications terrestres et sous marines, avec les amplificateurs optiques. Aujourd’hui, il existe un réel intérêt pour l’industrie spatiale d’utiliser ces fibres dans les satellites. Cependant, pour utiliser leur potentiel, une qualification en milieu radiatif doit être effectuée, c'est justement l'objet principal de ce travail de thèse. Grâce au partenariat industriel avec Draka-Prysmian, nous avons accès à une grande diversité de fibres en termes de compositions chimiques : ceci nous permet d’étudier leur sensibilité aux radiations, et de comprendre le rôle essentiel des dopants et des codopants dans cette sensibilité. Une étude de celle-ci en temps réel, associée à une caractérisation pré et post-irradiation des fibres optiques, rend possible l'identification fine des défauts induits sous irradiation, et la compréhension de leur mécanisme de formation, en fonction de la composition de ces fibres. Cette étude permet ainsi de proposer un modèle physique de leur dégradation, et aussi de leur guérison, complété par un modèle d'amplificateur. Il permet de prédire, en fonction de la composition des fibres, le comportement quantitatif des amplificateurs optiques associés, en termes de gain et et de bande passante, versus un dépôt de dose typique d'une mission spatiale ; il répond ainsi aux attentes des principaux acteurs du domaine. En outre, le bénéfice de ce travail ouvre des portes dans le domaine de la dosimétrie par fibre optique active, dans différents environnements radiatifs autres que le domaine spatial, tels que le milieu médical ou l'environnement nucléaireErbium-doped optical fibers open up many applications, especially in the field of terrestrial and underwater telecommunications, with optical amplifiers. Nowadays, there is a real interest for the space industry to use these fibers in satellites. However, in order to use their full potential, qualification in radiative environments is to be carried out, this is the main focus of this PhD work. Thanks to the partnership with Draka-Prysmian group, we have a full access to a large diversity of specialty fibers, in terms of chemical compositions : this allows us to study their sensitivity to radiations, and to determine the important role of dopants and co-dopants in this sensitivity. A real-time study of it, associated with a qualification of pristine and irradiated optical samples, enables the detection of radiation-induced defects, and the understanding of their creation process, as a function of the fiber structure. This study provides a physical model describing the degradation and the recovery of these fibers, enhanced with an amplifier modeling. It allows the prediction of the quantitative behavior of specialty fiber-based amplifiers, in terms of gain and bandwidth, versus the chemical composition of the fibers used, for a typical space mission dose ; thus this modeling meets the needs of the spatial market key actors. Furthermore, the benefit of this work opens up another avenues for some larger opportunities, in various radiative environments, such as the medical field or the areas of nuclear facilities
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Chiamenti, Ismael. "Produção e caracterização de guias de ondas óticos em fluoreto de lítio." Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/392.
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CNPq, Capes e FINEPEste trabalho descreve a produção e caracterização de guias de onda óticos em cristal de fluoreto de lítio (LiF) produzidos expondo o cristal a um feixe focalizado de um laser de femtosegundo, com o deslocamento do cristal na direção perpendicular ao eixo de propagação do feixe. A medida da emissão, sob iluminação específica, demonstra a presença de centros de cor dos tipos F2 e F3+ nas regiões do cristal expostas ao feixe focalizado do laser. As estruturas produzidas possuem incremento do índice de refração em relação ao índice de refração do cristal. Tais estruturas são caracterizadas em termos da sua morfologia usando microscopia convencional e confocal. A capacidade de guiamento de luz é investigada acoplando fontes laser com diferentes comprimentos de ondas. Os modos suportados são também analisados, bem como as perdas na propagação. A produção de guias de ondas de Bragg é testada acoplando uma fonte de luz branca e comparando seu espectro com o espectro que passa somente pelo cristal. A capacidade de guiamento das estruturas produzidas é confirmada pela análise dos perfis de campo próximo. Os guias suportam poucos modos e os incrementos de índices obtidos são da ordem de 10^-4.
This work describes the production and characterization of optical waveguides in lithium fluoride crystal (LiF) produced by exposing the crystal to a focused femtosecond laser beam, with the crystal displacement perpendicular to the beam. The measured emissions, with specific illumination, demonstrate the presence of color centers of types F2 and F+3 at the crystal regions exposed to the focused laser beam. The produced structures have increased refractive index relative to the crystal refraction index. Such structures are characterized in terms of their morphology using conventional and confocal microscopy. Their ability to guide light is investigated through coupling different laser light. The propagation modes supported by the guides are also estimated, as well as the propagation losses. The production of a Bragg grating waveguide is locked for by coupling a white light in the guides and comparing its spectrum with that passing only through the crystal. The guiding capacity of the structural changes produced is confirmed by the near-field profile analysis. The guides support few propagation modes and the obtained changes in the refractive index are in the order of 10^-4.
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Holz, Laura Isabel Vilas. "Yttria-stabilized Zirconia with beige colour." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21874.
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Mestrado em Engenharia de MateriaisA Zircónia é um cerâmico avançado que se tem destacado como um material versátil e promissor, apresentando uma combinação interessante de propriedades térmicas, elétricas, óticas e mecânicas, pouco comuns nos materiais cerâmicos, sendo por isso utilizada em diversas aplicações. A empresa INNOVNANO produz pós de Zircónia com diferentes características e atualmente tem clientes interessados em cerâmicos à base de Zircónia estabilizada com ítria de coloração bege com propriedades mecânicas específicas. Assim, o trabalho realizado neste estágio pretendeu desenvolver um material que cumpra os requisitos solicitados, tendo como referência uma amostra cedida por um cliente da INNOVNANO cuja cor se pretendia reproduzir, mas cuja composição e processamento eram desconhecidos. Deste modo, o trabalho teve início com a caracterização da amostra de referência através de Microscopia Eletrónica de Varrimento, Difração de raios X, espectroscopia de Raman, Fotoluminescência e Refletância Difusa de modo a permitir compreender o mecanismo de coloração, o qual mostrou ser baseado em defeitos estruturais, desenvolvidos em condições redutoras. A introdução de defeitos extrínsecos pela dopagem com óxido de ferro (Fe2O3) na matriz da Zircónia estabilizada com 2 mol % de ítria (2YSZ) foi a alternativa selecionada para a reprodução da cor solicitada. As amostras foram estudadas do ponto de vista microestrutural, estrutural e ótico. A dopagem com óxido de ferro revelou ser um mecanismo de coloração adequado, reprodutível e irreversível, permitindo o desenvolvimento de um material cromaticamente estável no que concerne à sua utilização em diferentes condições de processamento, tais como diferentes atmosferas e intervalos de temperatura. A estabilidade da cor foi confirmada com tratamentos térmicos em atmosferas oxidantes e redutoras. O efeito da adição do dopante nas propriedades mecânicas da Zircónia foi estudado, avaliando-se a tenacidade à fratura (KIC), a dureza de Vickers (HV10) e a resistência à flexão (σflexural) em amostras com elevado teor de Zircónia tetragonal ( >92 %) e com elevada densidade relativa ( >96%). Os materiais desenvolvidos preenchem os requisitos previamente definidos pela INNOVNANO, tendo-se observado, contudo, um ligeiro decréscimo da tenacidade à fratura com a adição de dopante. Já a dureza Vickers e a resistência à flexão não foram significativamente afetadas pela adição de Fe2O3.
Zirconia is a very versatile advanced ceramic that offers an interesting combination of thermal, chemical, electrical, mechanical and optical properties which are uncommon to find in ceramic materials and therefore is used in several applications. INNOVNANO is one of the main Zirconia powders suppliers in the market with potential clients for beige YSZ ceramics with specific mechanical properties. Thus, the work performed during this internship aimed to develop a material that meets the requested requirements, having as reference a sample provided by an INNOVNANO’s client which colour was intended to be reproduced but which composition and processing were unknown. In this way, the work began with reference material characterization through Scanning Electron Microscopy, X-ray Diffraction, Raman Spectroscopy, Photoluminescence and Diffuse Reflectance in order to understand the colouring mechanism, which was shown to be based on structural defects developed under reducing conditions. The introduction of extrinsic defects by doping with iron oxide (Fe2O3) in the matrix of 2 mol % yttria-stabilized Zirconia (2YSZ) was the alternative selected for the reproduction of the requested colour. The samples were studied from the microstructural, structural and optical point of view. Doping with iron oxide has proved to be a suitable, reproducible and irreversible colouring mechanism allowing the development of a chromatically stable material with respect to its use in different processing conditions such as different atmospheres and temperature ranges. Colour stability was proved by thermal treatments in oxidizing and reducing atmospheres. The effect of dopant addition on the mechanical properties of Zirconia was studied by evaluating the fracture toughness (KIC), Vickers hardness (HV10) and flexural strength (σflexural) in samples with high tetragonal Zirconia content (> 92%) and high relative density (> 96%). The developed material fulfils the requirements previously defined by INNOVNANO, but a slight decrease of the fracture toughness with the addition of dopant was observed while Vickers hardness and flexural strength were not significantly affected by the addition of Fe2O3.
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Dale, Matthew W. "Colour centres on demand in diamond." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/80044/.
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This thesis reports research on point defects in single crystal synthetic diamond. A number of techniques have been used including electron paramagnetic resonance (EPR), infrared (IR) absorption, ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectroscopies. The effect of perturbations by uniaxial stress on defect formation and migration have been investigated. Photo- and thermo-chromic effects have been investigated in irradiated and annealed type-IaA diamond. Charge transfer between nitrogen and di-nitrogen vacancy defects together with quantification in their negative charge states has allowed their calibration constants to be determined. Improvements have been made in the 13C hyperfine parameters for N2V− and its observation in diamond of natural isotopic abundance has allowed its 14N quadrupole parameters to be determined. Defects in neutron irradiated diamond have been studied by annealing isochronally up to 1600 XC. The majority of nitrogen could be accounted for through all annealing stages in a variety of defects including a maximum of 72(7) ppm of NV−. The annealing behaviour strongly supports the involvement of interstitials in interstitial mediated nitrogen aggregation in addition to vacancy assisted nitrogen aggregation. A model of the mechanisms has been proposed and simulated with chemical kinetics, the result of which agrees well with experiment. The effect of applying up to 3.0 GPa (0 0 1) uniaxial stresses to type-IIa samples during electron irradiation has been investigated. The treatment caused very little preferential orientation of the single interstitial and nearest neighbour di-interstitial, however it caused significant preferential orientation of 3H, believed to be the next nearest neighbour di-interstitial. The production rate of both di-interstitials was also increased by stress. Irradiated samples have been annealed under [0 0 1] uniaxial stresses. The annealing successfully created preferentially oriented populations of the (0 0 1)-split self interstitial with up to 93(1)% efficiency. Preferentially oriented interstitials have been annealed in situ in an EPR spectrometer allowing the site populations to be determined throughout the anneal.
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Cherman, Aleksey, Srimoyee Sen, Mithat Ünsal, Michael L. Wagman, and Laurence G. Yaffe. "Order Parameters and Color-Flavor Center Symmetry in QCD." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/626283.
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Common lore suggests that N-color QCD with massive quarks has no useful order parameters that can be nontrivial at zero baryon density. However, such order parameters do exist when there are n(f) quark flavors with a common mass and d equivalent to gcd(n(f), N) > 1. These theories have a Z(d) color-flavor center symmetry arising from intertwined color center transformations and cyclic flavor permutations. The symmetry realization depends on the temperature, baryon chemical potential, and value of n(f)/N, with implications for conformal window studies and dense quark matter.
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Fournier, Clarisse. "Centres colorés contrôlés en position dans le nitrure de bore hexagonal pour l'émission de photons uniques cohérents." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST165.
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Le traitement optique de l'information quantique nécessite des émetteurs de photons uniques indiscernables. Dans ce cadre, des émetteurs quantiques récemment découverts dans les matériaux 2D offrent de nouvelles perspectives en termes de dispositifs photoniques intégrés. Ainsi, dans le nitrure de bore hexagonal (hBN), une nouvelle famille de centres colorés a l'avantage de posséder une faible dispersion en longueur d'onde. Ces centres émettant dans le bleu (λ ≈ 435 nm) peuvent également être positionnés de manière déterministe. Ces deux qualités sont rares parmi les émetteurs quantiques dans l'état solide et s'ajoutent en outre à des propriétés photophysiques avantageuses. Cette famille d'émetteurs constitue l'objet d'étude principal de cette thèse.Dans un premier temps, nous détaillons les principales figures de mérite d'un émetteur de photons uniques : brillance, pureté, cohérence temporelle et indiscernabilité. Nous évoquerons également les principaux systèmes physiques émettant des photons uniques, afin de contextualiser la caractérisation à suivre des centres colorés bleus dans hBN.Nous décrivons, dans une deuxième partie, les méthodes expérimentales génériques employées au cours de la thèse en commençant par l'exfoliation mécanique permettant d'obtenir des cristaux de hBN et l'irradiation électronique pour la création des centres colorés. Ceux-ci sont ensuite caractérisés optiquement à l'échelle individuelle au moyen de techniques combinant microscopie confocale, cryogénie, comptage de photons et spectroscopie. Nous détaillons également le traitement des données utilisé pour calculer la fonction d'autocorrélation d'intensité. Le troisième chapitre est consacré aux mesures de différentes propriétés photophysiques des centres bleus à l'échelle de l'émetteur individuel, telles que le temps de vie, la pureté, la polarisation et la photostabilité. Nous nous intéressons également au processus de création des centres colorés bleus, en effectuant des mesures de cathodoluminescence in situ, complétées par des mesures optiques. La nature microscopique de cette famille de centres colorés est également évoquée.Nous traitons ensuite de l'excitation laser résonante d'un centre bleu. L'étude des corrélations de photons permet d'observer des oscillations de Rabi, et d'en extraire le temps de cohérence de l'émetteur. En outre, ces corrélations donnent accès à la dynamique de la diffusion spectrale prenant place à une échelle de temps de l'ordre de la dizaine de microsecondes. Enfin, nous étudions l'indiscernabilité des photons émis par un centre bleu en mesurant les corrélations de photons dans un interféromètre de Hong, Ou et Mandel. Nous mettons en évidence le phénomène d'interférence à deux photons témoignant de l'indiscernabilité partielle des photons émis par le centre coloré. Ce résultat prometteur pourra être améliorée grâce à l'intégration des émetteurs dans des structures photoniques visant à augmenter la collection et diminuer l'impact du déphasage.Les résultats détaillés dans cette thèse démontrent le potentiel de ces centres colorés bleus dans hBN pour des applications dans le domaine de l'information quantique. De futur développements permettront une meilleure compréhension et un meilleur contrôle de leur dynamique d'émission ainsi que leur intégration dans des dispositifs optoélectroniques. Ces travaux ouvrent de nouvelles perspectives en termes de photonique quantique avec des matériaux 2DOptical quantum information processing requires single and indistinguishable photon emitters. In this context, recently discovered quantum emitters in 2D materials offer new perspectives in terms of integrated photonic devices. In hexagonal boron nitride (hBN), a new family of color centers has the advantage of a low wavelength dispersion. These blue-emitting color centers (λ ≈ 435 nm) can also be positioned deterministically. These two qualities are rare among solid-state quantum emitters, and add up to advantageous photophysical properties. This family of emitters is the main focus of this thesis.First, we detail the main figures of merit of a single-photon emitter: brightness, purity, temporal coherence and indistinguishability. We also discuss the main physical systems emitting single photons, in order to contextualize the following characterization of blue color centers in hBN.In the second part, we describe the generic experimental methods used during the thesis: mechanical exfoliation to obtain hBN crystals and electron irradiation to create the color centers. The latter are then optically characterized on an individual scale using techniques combining confocal microscopy, cryogenics, photon counting and spectroscopy. Finally, we describe the data processing methods used to calculate the intensity autocorrelation function.The third chapter is devoted to measurements of various photophysical properties of blue centers at the scale of individual emitters, such as lifetime, purity, polarization and photostability. We also focus on the creation process of blue color centers, by carrying out in-situ cathodoluminescence measurements, complemented by optical measurements. The microscopic nature of this family of color centers is also discussed.We then address the resonant laser excitation of a blue center. The study of photon correlations allows us to observe Rabi oscillations, and to extract the coherence time of the emitter. In addition, these correlations give access to the dynamics of the spectral diffusion taking place on a time scale of a few tenths of microseconds. Finally, we study the indistinguishability of photons emitted by a blue center by measuring photon correlations in a Hong-Ou-Mandel interferometer. We demonstrate two-photon interference, indicating partial indistinguishability of photons emitted by the color center. This promising result could be improved by integrating the emitters into photonic structures designed to increase collection and reduce the impact of dephasing.The results detailed in this thesis show the potential of this family of blue color centers in hBN as quantum emitters for quantum information applications. With future developments aiming to understand and control their dynamics, as well as to integrate them into optoelectronic devices, our work opens new perspectives for optical quantum information with 2D materials
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McAllister, Michael Joseph. "Photoacoustic spectroscopy of colour centres in crystals." Thesis, Queen's University Belfast, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356943.
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Zheng, Dingwei. "Study and manipulation of photoluminescent NV color center in diamond." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00595302.
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Le contrôle des propriétés et la maîtrise du couplage cohérent d'objets quantiques individuels dans une matrice solide sont un enjeu essentiel pour le développement de l'information quantique. Les centres colorés dans le diamant, équivalent aux molécules artificielles, présentent des caractéristiques qui sont très prometteuses pour la réalisation d'une telle application. Parmi les centres colorés, le centre NV (azote-lacune) est le plus intéressant, dû en particulier à sa grande photostabilité à température ambiante. Le travail de cette thèse est consacré à l'étude des propriétés optiques et électroniques des centres colorés NV à température ambiante.
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Chen, Yu-Chen. "Laser writing of coherent colour centres in diamond." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:1b9fc247-3e35-457e-bfa5-d4ca474ac1ff.
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Optical active point defects in crystals have gained widespread attention as photonic systems that could be applied in quantum information technologies[1, 2]. However, challenges remain in the placing of individual defects at desired locations, an essential element of device fabrication. Here we report the controlled generation of single negatively charged nitrogen-vacancy (NV-) centres in diamond using laser writing[3]. Aberration correction in the writing optics allows precise positioning of the vacancies within the diamond crystal and subsequent annealing produces single NV- centres with a probability of success of up to 45%, located within about 200nm of the desired position in the transverse plane. A simple model was established to understand the mechanism of vacancies generation and estimate the success probability of NV- centres generation. Selected NV- centres display stable, coherent optical transitions at cryogenic temperatures, a prerequisite for the creation of distributed quantum networks of solid-state qubits. Strain measurement results of selected NV- centres show that the broadening of NV- optical transitions is due to local strain. The results illustrate the potential of laser writing as a tool for defect engineering in quantum technologies and extend laser processing to the single-defect domain.
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Osterkamp, Christian [Verfasser]. "Engineering colour centres in tailored diamond / Christian Osterkamp." Ulm : Universität Ulm, 2021. http://d-nb.info/1224969391/34.
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