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Dissertations / Theses on the topic 'Magneto-optical traps; Cold atom traps'
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1
Cooper, Catherine J. "Laser cooling and trapping of atoms." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308685.
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Ivanov, Vladyslav Victorovych. "Cold atoms modified radiative properties and evaporative cooling from optical traps /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/47332.
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Bruce, Graham D. "Alternative techniques for the production and manipulation of ultracold atoms." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2617.
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This Thesis contains details of the construction and characterisation of a compact apparatus for the cooling of ultracold atoms to quantum degeneracy, and their manipulation in flexible holographic optical traps. We have designed and built two iterations of this apparatus. The first version consists of a stainless steel single-cell vacuum chamber, in which we confine ⁸⁷Rb and ⁶Li or ⁷Li in a Magneto-Optical Trap. We characterise the alternative methods of pulsed atomic dispenser and Light Induced Atomic Desorption (LIAD) to rapidly vary the background pressure in the vacuum chamber with the view to enabling efficient evaporative cooling in the single chamber, loading MOTs of up to 10⁸ atoms using pulsed dispensers. The LIAD is found to be ineffective in loading large MOTs in this setup, while the pulsed dispensers method gradually increases the background pressure in the chamber over time. Based on the results of this first iteration, we designed and built a second single-chamber apparatus for cooling of ⁸⁷Rb to quantum degeneracy. The LIAD technique was used to successfully load MOTs containing 8x10⁷ atoms in this single pyrex cell with a rapidly-varying background pressure. The lifetime of an atomic cloud loaded from the MOT into a magnetic trap increased by a factor of 6 when LIAD was used. The holographic optical traps for cold atoms are generated using a Spatial Light Modulator, and we present our novel method for improving the quality of holographic light patterns to the point where they are suitable for trapping ultracold atoms using a feedback algorithm. As demonstrations of this new capability, we show power-law optical traps which provide an efficient, reversible route to Bose-Einstein Condensation and a dynamic ring trap for the investigation of superfluidity in cold atoms.
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Clements, Ethan Robert. "CHARACTERIZATION OF OPTICAL LATTICES USING PUMP-PROBESPECTROSCOPY AND FLUORESCENCE IMAGING." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470323164.
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Pollock, Samuel. "Integrated magneto-optical traps for atom chips." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/11271.
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Muckley, Eric S. "Constructing a magneto-optical trap for cold atom trapping /." Click here to view, 2009. http://digitalcommons.calpoly.edu/physsp/2.
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Thesis (B.S.)--California Polytechnic State University, 2009.<br>Project advisor: Katharina Gillen. Title from PDF title page; viewed on Jan. 14, 2010. Includes bibliographical references. Also available on microfiche.
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Van, Dongen Janelle. "Simultaneous cooling and trapping of 6Li and 85/87Rb." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/351.
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This thesis provides a summary of the laser system constructed in the Quantum Degenerate Gases Laboratory for laser cooling and trapping of 85/87Rband 6Li as well as of experiments that have been pursued in our lab to date. The first chapter provides an overview of the experimental focus of the QDG lab. The second and third chapters provide the fundamental theory behind laser cooling and trapping. The fourth chapter provides details of the laser system. The fifth chapter describes an experiment performed on the subject of dual-injection, performed in collaboration with Dr. James Booth of the British Columbia Institute of Technology (BCIT) involving the dual-injection of a single slave amplifier. The last chapter describes the progress made on the experimental setup needed for the study of Feshbach resonances between 85/87Rb and 6Li and the photoassociative formation of molecules.
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Ladouceur, Keith. "Experimental advances toward a compact dual-species laser cooling apparatus." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2508.
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This thesis describes the advances made towards a dual-species magneto-optical trap (MOT) of Li and Rb for use in photoassociation spectroscopy, Feshbach resonance studies, and, as long-term aspirations, the formation of ultracold heteronuclear polar molecules. The initial discussion will focus on a brief theoretical overview of laser cooling and trapping and the production of ultracold molecules from a cold atom source. Subsequently, details of the experimental system, including those pertaining to the required laser light, the vacuum chamber, and the computer control system will be presented. Finally, preliminary optimization and characterization measurements showing the performance of a single species Li MOT are introduced. These measurements demonstrated the loading of over 8 x 107 Li atoms directly into a MOT without the need for a Zeeman slower.
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Morsch, Oliver. "Optical lattices for ultra-cold atoms." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301174.
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Deb, Amita. "Theoretical and experimental studies on ultra-cold atoms in optical traps." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600174.
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This thesis describes a number of theoretical and experimental studies on the production, manipulation and detection of ultra-cold atoms in arrays of optical traps, i. e. optical lattices for applications such as direct quantum simulation of many-body systems and quantum information processing. A method of deterministically preparing a single atom in each site of an optical lattice is explored and the parameter regime that would be required to implement this protocol in experiments is investigated. A novel method of state-selective spatial transfer of atoms between neighbouring sites of a lattice using an intermediate trap is reported and the experimental parameters worked out. The theory of off-resonant light scattering from atoms in an optical lattice is explored. The possibility of using the far- field intensity distribution and t he frequency spectrum of the light scattered from atoms in an optical lattice for performing thermometry of atoms and for identifying quantum fluctuations in the system are investigated for cases of non-interacting fermions and weakly-interacting bosons. A spatial filtering method for detecting a small number of classical defects in an optical lattice is investigated. Experiments on trapping and manipulating Bose-Einstein condensates (BEC) of 8 1Rb atoms in dynamically configurable t raps created using spatial light modulators are discussed. The construction of a new magnetic trap for trapping and magnetically transporting atoms and the experimental stages subsequently leading to the production of BECs are reported.
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Milori, Debora Marcondes Bastos Pereira. "Caracterização de uma armadilha magneto-optica para átomos de sódio em célula de vapor." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-30042009-090336/.
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Dentro as técnicas de controle do movimento atômico utilizando pressão de radiação, aprisionamento tem merecido maior destaque por produzir amostras de átomos mais frios (temperaturas da ordem de μK), com altas densidades e confinadas em pequenas regiões do espaço. Devido a essas motivações, tem sido grande o esforço para desenvolver e caracterizar estas armadilhas atômicas. Uma das mais eficientes armadilhas de átomos neutros construídas até agora é a armadilha magneto-óptica. O átomo uma vez capturado por este tipo de armadilha passa por um intenso processo de desaceleração via efeito Doppler e acaba por ficar confinado no poço de potencial gerado pela interação com o campo magnético. O número e a densidade de átomos aprisionados, o tamanho da nuvem e o processo de carga possuem forte dependência com os parâmetros da armadilha, tais como: Este trabalho trata da caracterização de uma armadilha deste tipo para átomos de sódio através de um estudo sistemático para descobrir as condições de sua melhor performance. Paralelamente a este estudo, desenvolvemos modelos teóricos para entender em detalhe os processos de produção dessas nuvens de átomos aprisionados e as forças envolvidas neste tipo de material que é esse gás super resfriado.<br>Among the various atomic motion control techniques using radiation pressure magneto-optic trapping has been looked at with great enthusiasm because it produces samples of cold atoms (temperatures about μK), with high densities and confined in small regions of space. Due to these motivations the efforts for developing and characterizing these atoms traps has been high. Once the atom is captured by the magneto-optic trap, it goes through an intense process of desacceleration via Doppler Effect and ends up confined in the potential well genered by the interaction with the magnetically Field. The number and the density of the trapped atoms, the size of the cloud and the loading process are strongly related to trap parameters, such as: magnetic Field gradient, laser beam intensity and background vapor temperature. This work deals with the characterization of a trap of this kind for sodium atoms through a systematic study, in order to discover the conditions for a better performance. At the same time theoretical models are developed in order to understand in depth the atomic forces involved in the production of a new kind of material which is this highly refrigerated gas.
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Souther, Nathan Jon. "Light Shift Measurements of Cold Rubidium Atoms using Raman Pump-Probe Spectroscopy." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1250622906.
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Lytle, Christian, and Christian Lytle. "Spectroscopy of Neutral Mercury in a Magneto-Optical Trap Based on a Novel Ytterbium Fiber-Amplified Cooling Laser Source." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621471.
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In this dissertation I present experimental results obtained on the mercury optical clock project in the research group of Jason Jones at the University of Arizona. The project began in 2008 with the purpose of investigating the feasibility of neutral mercury as an optical clock species. The first series of investigations involved building the essential apparatus and scanning the doppler-broadened 6¹S₀ - 6³P₀ clock transition in ¹⁹⁹Hg. Here I present significant modifications to the cooling and trapping laser, improvements to the spectroscopy laser linewidth, and attempts to measure the 2-photon transition in ¹⁹⁹Hg. After previously demonstrating spectroscopy of the mercury clock transition using an optically-pumped semiconductor laser for the cooling and trapping source (OPSL), we replaced the OPSL with a a fiber-amplified ECLD system. We custom built a fiber amplifier to provide gain at 1015 nm, demonstrating the system can yield up to 5 W of signal power with excellent suppression of the ASE power. We find that the ASE is well suppressed by using a two-stage configuration and short sections of gain fiber. The linewidth of our original spectroscopy laser was over 10 kHz, which is unsuitable to resolve of sub-Doppler features. To enhance the performance of our spectroscopy system, we integrated faster feedback bandwidth using AOMs, and incorporated derivative gain into the system. This resulted in a feedback bandwidth for our spectroscopy laser of over 200 kHz. With this system, we demonstrate anactively stabilized linewidth of 525 Hz for our spectroscopy system. Using the upgraded cooling and spectroscopy laser systems, we demonstrate spectroscopy of the clock system and confirm temperature measurements derived from the transition linewidth. We also describe attempts to detect the recoil shift and 2-photon transition in neutral mercury.
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Salas, Andres David Rodriguez. "Geração de uma armadilha magneto-óptica de estrôncio 88." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-05112012-155605/.
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Neste trabalho é apresentada a construção da montagem de um sistema experimental para resfriar átomos de estrôncio. A construção do sistema está focada no estudo do espalhamento coletivo em nuvens atômicas frias e ultrafrias por meio da teoria de Mie. O estrôncio é um elemento que conta com dois estágios de resfriamento, o primeiro utilizando a transição forte entre estados singletos ¹S₀-¹P ₁ de Γ = (2 π)32 MHz, e o segundo com uma transição fraca entre estados singleto e tripleto ¹S₀-³P₁ de Γ = (2 π)7,5 MHz. O objetivo deste trabalho é a construção do sistema para resfriar átomos de estrôncio utilizando a primeira transição. A construção do sistema se apresenta em várias partes, primeiro a construção do um forno como fonte de vapor de estrôncio, onde o estrôncio metálico é aquecido até uma temperatura T = 600°C. O forno conta com um sistema de microtubos encarregados de colimar o feixe atômico, estes microtubos tem um diâmetro interno D ≈ 180µm e um comprimento de 8mm. Depois da implementação do forno e do sistema de microtubos foi medido o perfil de velocidades transversais e a divergência do feixe atômico que sai do forno. A largura tem um valor wr = (2π)108 MHze a divergência do feixe de α ≈4,12. A segunda parte do sistema conta com a construção do desacelerador Zeeman, responsável por desacelerar os átomos do feixe atômico utilizando um feixe laser contrapropagante de λ=461 nm, circularmente polarizado e com uma dessintonização utilizada, após a caracterização do sistema, de Δ=(-2π)580MHz. Os átomos sentiram os efeitos da força de pressão radiativa dentro de um tubo de comprimento de 0,28m. Para compensar o efeito Doppler causado pelo movimento dos átomos foi utilizado um arranjo de bobinas em configuração spin flip para gerar o campo. A terceira e principal parte do sistema foi a construção da armadilha magnetoóptica (AMO). Onde os átomos que saem do desacelerador Zeeman são confinados e resfriados pela combinação de seis feixes contrapropagantes, dos quais três são retrorefletidos utilizando a transição Γ=(2π)32MHz. A dessintonia dos feixes após da caracterização do sistema foi de Δ=(-2π)39MHz. Depois da construção do sistema foi feita a primeira caracterição da armadilha magneto-óptica de átomos de estrôncio 88 em nosso grupo, onde obtivemos a temperatura dos átomos na armadilha para o eixo vertical da expansão foi de Tv=4.7mK e para o eixo horizontal de TH=4mK. Também foi medido o tempo de carga dos átomos na armadilha tcarga=0.15s como bombeamento óptico de estado ³P₂-³D₂. O tempo de vida foi de 0.3s e 0.03s com e sem bombeamento óptico, respectivamente.<br>This work presents the construction of the assembly of an experimental system for cooling strontium atoms. The construction of the system is focused on the collective scattering in atomic cold cloud and ultra cold using the Mie theory. The strontium is an element that permits two stage of cooling, the first using the strong transition between singlet states ¹S₀-¹P₁ of Γ=(2π) 32 MHz, and a second stages is the weak transition between singlet and triplet states ¹S₀-³P₁ de Γ=(2π) 7.5MHz. The objective of this work is building the system for cooling strontium atoms using the first transition. The construction of the system is presented in several parts. First is described the construction of oven as vapor source strontium, where the strontium metal is heated to Temperature Range T = 600°C. The oven has a microtubule system responsible for collimating the atomic beam, these microtubules has an internal diameter of D ≈ 180µm and a length of 8mm. After implementation of the oven system and the microtubes were measured transverse velocity profile and the divergence of the atomic beam that leaves the oven, the width value was f wr=(2π)108MHzand beam divergence value was α ≈ 4,12. The second part of the system relies on the construction of the Zeeman slower responsible for decelerating the atoms of the atomic beam using a laser beam antipropagating of λ = 461 nm nm with a circularly polarized , the detuning used after of the characterization of the system was Δ = (2π)580 MHz. Atoms felt the effects of pressure force radiative within a tube length of 0.28m to compensate the Doppler shift due to motion a of atoms used an arrangement of coils in configuration \"spin flip\" to generate the magnetic field to compensate this effect. The third and main part of the system was the construction of magneto-optical trap (MOT), the atoms coming out of the Zeeman decelerator are confined and cooled by a combination of six counterpropagating beams, three of which are retro reflected using the transition Γ = (2π)32MHz, the detuning of the beam after the characterization of the system was Δ = (-2π) 39 MHz and the opposite polarization for each pair of beam in the same direction. After the construction of the system was made the first magneto-optical trap of strontium atoms 88, the temperature of the trap was atoms to the vertical he expansion was Tv = 4.7mK and the horizontal axis TH = 4 mK 4, also was measured loading time of the atoms in the trap tcharge = 0.15s as optical pumping state ³P₂- ³D₂. The lifetime with and without optical pumping was tlife = 0.3s and tlife = 0.03s respectively.
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Silva, Ilde Guedes da. "Estruturas espaciais de átomos de Na em armadilha magneto-óptica." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-21022014-101849/.
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Neste trabalho demonstramos o confinamento de átomos de sódio usando a armadilha magneto-óptica, onde os átomos foram capturados diretamente a partir da distribuição inicial do vapor atômico a uma temperatura ambiente, contido em uma célula fechada. Observamos além da nuvem de átomos aprisionados, estruturas circulares em forma de anek, que surgem devido ao desalinhamento introduzido nos feixes de aprisionamento. Estudamos o comportamento do raio do anel em função de vários parâmetros utilizados na armadilha magneto-óptica como por exemplo: gradiente de campo magnético, intensidade do laser, dessintonia e desalinhamento. Os experimentos foram realizados no regime de baixa densidade (N<10s) onde o raio do anel é independente do número de átomos aprisionados. Assim, os resultados obtidos podem ser explicados utilizando um modelo simples que leva em conta a força de vórtice dependente da coordenada radial (ou macroscópica) e as forças usuais presentes na armadilha magneto-óptica<br>In this work we demonstrate the confinement of neutral sodium atoms using the magneto-optical trap, where the atoms were captured directly from the low velocity tail of the room-temperature atomic vapor contained in the closed vacuum cell. We observed besides the cloud shaped, circular structures like a ring of trapped atoms that apeears when we introduce a misalignment among the trapping beams. We studied the behavior of ring radius with respect to several trapping parameters as: magnetic-field gradient, laser intensity, detuning, and misalignment. The experiments were performed in the low density regime (N<10s), so the ring radius is independent of the number of trapped atoms. Hence, the results obtained can be explained using a simple model that takes into account a radial coordinate dependent (or macroscopic) vortex force and the usual magneto-optical trap forces
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Pereira, Andrea Antunes. "Estudo de colisões inelásticas heteronucleares no sistema rubídio(Rb)/césio(Cs) em regimes de baixas temperaturas." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-09092008-123340/.
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Armadilhamento duplo de átomos neutros constitui um dos avanços mais recentes no estudo de colisões frias. Obtivemos experimentalmente as taxas de perda devido a interação de espécies alcalinas mistas (Cs/Rb). Utilizamos uma armadilha magneto-óptica mista operando com feixes de alta intensidade permitindo o resfriamento e confinamento das amostras com sucesso. Esse trabalho apresenta-se de forma relevante pois corresponde a primeira etapa para o estudo do processo de formação de moléculas frias heteronucleares. Uma comparação entre duas técnicas de monitoramento dos processos de carga de átomos foi realizada. Os resultados tanto qualitativamente como quantitativamente foram satisfatórios. Determinamos as taxas de perda, de interesse e analisamos essas taxas considerando a proporção entre as massas dos átomos envolvidos e enfocando o efeito causado pela diferença de massa entre eles concluindo assim o objetivo principal dessa dissertação.<br>Double trapping of neutral atoms is one of the most recent advances in the study of collisions cold. Experimentally obtained the rates of loss due to the interaction of species alkaline mixed (Cs / Rb). We use a magneto-optical trap mixed operating with beams of high intensity allowing the cooling and containment of the samples successfully. This work is so important because it represents the first step to study the process of formation of molecules heteronucleares cold. A comparison between two techniques of monitoring procedures for cargo of atoms was performed. The results both qualitatively and quantitatively were satisfactory. And the rates of loss of interest and analyze the rates considering the ratio between the masses of atoms involved and focusing on the effect caused by the difference of mass between them thus completing the main objective of this dissertation.
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Peñafiel, Edwin Eduardo Pedrozo. "Absorção cooperativa de dois fótons em átomos frios." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-04102011-155751/.
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Neste trabalho estudamos a absorção cooperativa de dois fótons em processos de colisão entre átomos frios de sódio aprisionados. Efeitos não-lineares exigem amostras de alta densidade para ser observados. Redesenhamos nosso sistema experimental para conseguir amostras de 1012 átomos/cm3. As principais alterações foram a construção de um desacelerador Zeeman em configuração spin-flip, a implementação de bombeamento diferencial entre o forno e a câmara principal, assim como redesenhar o forno. A fim de compreender e melhorar os processos de medição utilizamos a técnica de fotoionização nos estados 32P1/2 e 32P3/2. Com esses dados conseguimos calcular a seção transversal de ionização para cada um desses estados, que está de acordo com valores reportados na literatura. Estes resultados mostram que o novo desenho do sistema permite um grande ponto de partida para a medição da absorção de dois fótons. Uma tentativa de medir a absorção de dois fótons foi feita. Um pequeno aumento no número de íons produzidos por unidade de tempo foi observada em uma região deslocada para o vermelho de cerca de 4,5 GHz de onde inicialmente se esperava ocorrer a transição. Isto motiva a aprofundar o estudo da absorção de dois fótons, já que provavelmente essa medida seja um indício da ocorrência desse fenômeno. Assim, tanto a medição da seção de choque dos estados 32P1/2 e 32P3/2 e a tentativa de medir a absorção de dois fótons, fornecem uma base sólida para conhecer qual é a melhor maneira de obter resultados mais decisivos no que diz respeito à absorção cooperativa de dois fótons, e as vantagens do nosso sistema em futuros experimentos.<br>In this work we study the cooperative two-photon absorption in collisional processes between cold trapped sodium atoms. Nonlinear effects require high density samples to be observed. We redesign our experimental system to achieve samples up to 1012 atoms/ cm3 .The key changes were building a spin-flip Zeeman slower, implementing differential pumping between the oven and the chamber and changing the oven´s design. In order to understand and improve the measurement processes we did photoionization from the states 32P1/2 e 32P3/2. With this data we could calculate the ionization cross section for each of these states, which is in agreement with values reported in the literature. These results show that the new design of the system allows a great starting point for measuring of two-photon absorption. An attempt to measure the absorption of two-photon was made. A small increase in the number of ions produced per unit time was observed in a region shifted to the red of about 4.5 GHz from where we initially expected the transition to occur. This probably indicates two-photon absorption. Thus, both the measurement of cross section of states and the attempt to measure the absorption of two photons, provide a solid foundation for understanding what is the best way to obtain more decisive results with regard to cooperative absorption, and the advantages of performance of our system in future experiments.
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Magalhães, Kilvia Mayre Farias. "Medida do tempo de vida de estados de Rydberg em átomos frios de 85 Rb." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-21112007-100629/.
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Neste trabalho apresentamos os primeiros resultados sobre medida do tempo de vida de estados de Rydberg utilizando átomos frios confinados em uma armadilha magneto-optica de 85Rb. Medidas de tempo de vida de estados altamente excitados são importantes para o teste de teorias modernas sobre interação átomo-vácuo; desta forma medidas precisas são necessárias. A utilização de átomos frios apresenta várias vantagens quando comparadas com técnicas convencionais. Entre elas podemos citar a possibilidade de observação do sistema atômico por longos períodos (>100 µs), e o controle da densidade de forma eficiente para evitar a manifestação de efeitos indesejáveis (colisões, superradiância) que limitam a precisão da medida. Apresentamos a medida do tempo de vida do estado 27D e 38S e comparamos os resultados experimentais com previsões teóricas de diferentes modelos. Algumas discrepâncias são observadas, o que reforça a necessidade da obtenção de um conjunto maior de medidas incluindo outros níveis para indicar qual modelo teórico é mais próximo da realidade.<br>In this work we present our first results on lifetime measurement of Rydberg states using cold atoms held in a magneto-optical trap of 85Rb. Lifetime measurements of highly excited states are important for testing modern theories on atom-vaccum interaction, therefore precise measurements are required. The use of cold atoms presents some advantage when compared with conventional techniques. Among them we cam point out the possibility of atomic observation for long periods of time (<100 µs), the atomic density control in order to avoid undesired effects (such collisions and superradiance) which can limit the measurement precision. We present the lifetime measurement of 27D and 38S states and compared the experimental results with theoretical prediction using different models. Some discrepancies are observed, which indicates the need of a large set of measurement for other states in order to indicate the best model.
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Fritsch, Amilson Rogelso. "Montagem e caracterização de uma armadilha magneto-óptica de rubídio." Universidade do Estado de Santa Catarina, 2011. http://tede.udesc.br/handle/handle/2008.
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Previous issue date: 2011-07-20<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>In this work we present the building and characterization of a Magneto-Optical Trap (from now on named MOT) for Rubidium atoms. We perform experiments for studying the e¤ect of a broadband light over trapped atoms. In order to carry out this study we used a incandescent lamp which is broad in the wavelength spectrum. We observed in a MOT, with a number of 109 trapped atoms, that the broadband light increases the emitted .uorescence by the cloud of atoms. This could indicate an e¤ective enlargement in the trap e¢ciency. However, we cannot distinguish, based on our experiments, if this di¤erence is due to an increasing in the number of the trapped atoms or if it is just scattered light caused by the increasing in the intensity of the incident light over the
cloud. Thus, we did an analysis in the answer of the laser beam versus the variation in the intensity of lasers used for trapping. In a second step, we perform this study but with a lower number of trapped atoms, 108 atoms, and we verify that the heating of the lamps implies in the increasing of the loss of atoms in the trap, diminishing the number of trapped atoms. Hence, this lead us to make a study on the collisions dynamics that are in the trap, in order to understand the in.uence of the temperature on the trap e¢ciency. We observe that a small uniform increasing in the chamber temperature would lead to a great loss in the trap , but the increasing in the temperature caused by the lamps is a local increasing and generates a degassing of the chamber, increasing the quantity of the background vapour.<br>Neste trabalho apresentamos a construção e caracterização de uma armadilha magneto-óptica, a qual utilizamos para aprisionamento de átomos de Rb. Após a construção da armadilha e sua caracterização, fizemos experimentos para estudar os efeitos da luz de banda larga sobre os átomos aprisionados. Para esse estudo, utilizamos lâmpadas incandescentes que possuem um espectro largo de comprimentos de onda. Verificamos que em uma armadilha com 109 átomos aprisionados, a luz de banda larga aumenta a fluorescência emitida pela nuvem de átomos, tendo fortes indícios que isto representa efetivamente um aumento na eficiência da armadilha. No entanto, com os experimentos que fizemos, não podemos distinguir se essa diferença é referente a um aumento de átomos aprisionados ou apenas espalhamento de luz causado pelo aumento da intensidade de luz incidida sobre a nuvem. Fizemos então uma comparação da resposta dos átomos, frente a variações na intensidade dos feixes de laser utilizados para o aprisionamento. Por motivos que serão discutidos neste trabalho, refizemos esse estudo com um número menor de átomos aprisionados, 108 átomos, e verificamos que o aquecimento das lâmpadas reflete no aumento das perdas na armadilha, diminuindo então o número de átomos aprisionados. Isto nos levou a fazer um estudo sobre a dinâmica das colisões presentes na armadilha, para entendermos a influência da temperatura na eficiência da armadilha. Verificamos que um pequeno aumento uniforme na temperatura da câmara levaria a grandes perdas na armadilha, mas o aumento da temperatura causado pelas lâmpadas é um aumento local, e gera um processo de desgaseificação da câmara, aumentando a quantidade de átomos, "diferentes de Rb", presentes no vapor de fundo.
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Magalhães, Kilvia Mayre Farias. "Obtenção da degenerescência quântica em sódio aprisionado." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-24012008-083710/.
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Usando a técnica de resfriamento evaporativo para átomos comprimidos numa armadilha magnética tipo QUIC, implementamos experimentos para observar Condensação de Bose-Einstein de átomos de sódio. Nessa armadilha magnética temos átomos advindos de uma armadilha magneto-óptica, a qual é carregada por um feixe desacelerado como etapa de pré-resfriamento. Nossas medidas foram baseadas em imagens de absorção fora de ressonância de um feixe de prova pela amostra atômica. Essas imagens foram feitas in situ, ou seja, na presença do campo da armadilha magnética, pelo fato do número de átomos ser baixo e a técnica de tempo de vôo não ser adequada a essa situação. Baseado no perfil de densidade e na temperatura medidos, calculamos a densidade de pico no espaço de fase D, a qual é seguida nas várias etapas de evaporação. Nossos resultados mostram que para uma freqüência final de evaporação de 1,65 MHz nós superamos o valor esperado para D (2,612) alcançar o ponto crítico, no centro da amostra, para obter a condensação. Devido ao baixo número de átomos restantes no potencial, a interação não produz efeitos consideráveis e dessa forma um modelo de gás ideal permite justificar essa observação.<br>Using a system composed of a QUIC trap loaded from a slowed atomic beam, we have performed experiments to observe the Bose-Einstein Condensation of Na atoms. In order to obtain the atomic distribution in the trap, we use an in situ out of resonance absorption image of a probe beam to determine the temperature and the density, which are use to calculate the phase space D. We have followed D as a function of the final evaporation frequency. The results show that at 1.65 MHz we crossed the critical value for D which corresponds to the point to start Bose-Condensation of the sample. Due to the low number of atoms remaining in the trap at the critical point, the interaction produce minor effects and therefore an ideal gas model explains well the observations.
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Kim, Soo Y. "Cold single atoms for cavity QED experiments." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26581.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009.<br>Committee Chair: Chapman, Michael; Committee Member: Citrin, David; Committee Member: Kennedy, T. A. Brian; Committee Member: Kuzmich, Alexander; Committee Member: Raman, Chandra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Corrêa, Thiago Reginaldo. "Implicações do uso de campos magnéticos oscilantes em um mot de rubídio." Universidade do Estado de Santa Catarina, 2012. http://tede.udesc.br/handle/handle/1969.
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Previous issue date: 2012-03-08<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>This work presents a study about infuences that a quadripolar magnetic field periodically time dependent, can promote in a magneto-optical trap (MOT). The intention reflects the interest in finding an oscillating field configuration that enables the capture and provide benefits if compared to the typical process of trapping. In many papers that will be cited here, a MOT uses a magnetic field that promotes a linear steady magnetic field gradient from the center of the trap. Applying experimental results involving magnetic field oscillations, which will be quoted in detail throughout this text, came the initiative to mathematically model the problem and seek a form of oscillation that may result in a more efficient trapping. Numerical results in a one-dimensional model suggests that the number of atoms is strongly aflected by fuctuations, but we have not found, for the modulations suggests in this work, an oscillation model that could provide an increase of the trap atoms. It was noted that the oscillation frequency of the atom is subjected, aflect the amplitude of the oscillations in the number of trapped atoms.<br>Neste trabalho apresentamos um estudo sobre as influências que um campo quadripolar magnético, periodicamente dependente do tempo, pode promover em uma armadilha
magnético-óptica (Magneto Optical Trap - MOT). O objetivo deste trabalho reflete o interesse em encontrar uma configuração de campo oscilante que possibilite o aprisionamento e forneça vantagens em relação ao processo típico de armadilhamento. Em muitos dos trabalhos que serão citados aqui, um MOT utiliza um campo magnético quadripolar estacionário que promove um gradiente de campo magnético linear à partir do centro da armadilha. Usando resultados experimentais envolvendo oscilações no campo magnético, que serão citados mais detalhadamente no decorrer deste texto, surgiu a iniciativa de modelar o problema matematicamente e buscar uma forma de oscilação que possa resultar em um aprisionamento mais eficiente. Resultados numéricos concebidos em um modelo unidimensional sugerem que o número de átomos é fortemente afetado pelas oscilações, mas não foi possível encontrar, para as modulações sugeridas neste trabalho, uma modulação que pudesse fornecer aumento expressivo no número de átomos armadilhados. Foi possível constatar que a freqüência da oscilação a que o átomo é submetido, afetará a amplitude das oscilações no número de átomos armadilhados.
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Erickson, Christopher Joseph. "Development of a Strontium-87 Ion Interferometer." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2750.
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I present the construction of a low-velocity intense source (LVIS) of laser-cooled neutral strontium using permanent ring magnets. The LVIS consists of a magneto-optical trap from which cold strontium is extracted in a well-collimated beam. I also present the development and implementation of a full suite of low-noise, high-bandwidth laser control electronics including a microcontroller unit. This microcontroller remotely controls and monitors the current driver, temperature controller, and PID lock circuit for each diode laser simultaneously. The current driver output is accurate to within 2 micro-amps and repeatable to with a few nano-amps. The noise spectral density of the current driver hits a floor of 10^(-10) amps per root Hz at ~50 Hz and has a modulation bandwidth of ~50 MHz. The PID lock-circuit includes a scan-balancing option that we have used to scan an AR coated laser diode ~30 GHz mode-hop free. I describe the construction of an 80 mW frequency doubled 461 nm laser system using PPKTP for cooling and trapping neutral strontium in the LVIS. The LVIS, the electronics systems, and the 461 nm laser system represent major milestones on the way to producing a matter-wave interferometer using Sr-87 ions. The interferometer is based on an optical Raman transition between the hyperfine ground states of the Sr-87 ion. The ions will be produced by exciting the strontium LVIS beam to an auto-ionizing state in the continuum. In the interferometer two half-pi pulses of light and one pi pulse will be delivered to the ions to split and recombine their wave functions. I present calculations of the predicted sensitivity and a discussion of the possible applications. I present a method for locking a 407.8 nm laser to the 5s doublet S J=1/2 to 5p doublet P J=3/2 strontium ion transition in a neutral vapor. I present calculations for the necessary vacuum levels for the experiment and describe the preparation and assembly of the vacuum apparatus. The major vacuum system consists of two connected elastomer sealed chambers: one at 10^(-7) Torr and the other at 10^(-10) Torr separated by a region of low conductance. I present a Sr vapor cell constructed from standard CF fittings that allows the strontium to be heated to ~730 C, which can also be run as a thermal beam. I present a method for protecting the viewports on small-form alkali-earth vapor cells using lead or indium foil during the evaporation of oxide layers. Finally, I report on the current status of the experiment as well as detail future work on the apparatus.
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Kondo, Jorge Douglas Massayuki. "Ressonâncias moleculares em estados nP de átomos de Rydberg frios." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18112010-145903/.
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Neste trabalho estudamos a interação entre átomos de Rydberg no estado nP e sua dependência com o campo elétrico dc. Estes estados apresentam ressonâncias Föster para um número quântico principal n menor que 37. Nestes processos de ressonância um par atômico no estado nP muda para um par nS+(n+1)S. Realizamos dois experimentos de evolução temporal para 32≤n≤36. No primeiro investigamos a dependência da taxa de transferência de população NnS em função do número quântico principal n. E no segundo estudamos a transferência de população para um estado fixo de n=33 em função do campo elétrico. Além disso, estudamos a dependência da população no estado 33S em função da densidade de átomos de Rydberg no estado 33P. Estes resultados nos permitem observar duas contribuições distintas, uma linear relacionada a radiação de corpo negro e uma quadrática ligada a interação de dois corpos. Estes resultados confirmam o modelo de taxa para o efeito da radiação de corpo negro.<br>In this work we studied the role of Rydberg atoms interactions in the nP state and the dc electric field dependency of this process. The nP state shows Föster resonances for principal quantum number less than 37. In this resonance process, an atomic pair in nP state changes to a pair nS+(n+1)S. We have performed two time evolution experiments for 32≤n≤36. In the first one we have investigated the NnS population transfer rate for a variable principal quantum number n. In the second we have study the population transfer for a fixed n=33, by varying an electric field. Moreover, we observed the density dependency of the population in the 33S state by varying the nP state atomic density. The results allow us to observe two distinct contributions, a linear contribution related with the black body radiation and a quadratic one connected with two body process. The results agree well with the rate model used to treat the black body radiation.
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Alloschery, Olivier. "Manipulation d’atomes froids par des puces atomiques optiques." Toulouse 3, 2007. http://www.theses.fr/2007TOU30052.
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Ce mémoire présente le confinement d'atomes froids dans des pièges dipolaires mis en forme par des micro-structures gravées à la surface d'un miroir, à la manière de lentilles de Fresnel. Dans la première partie, nous détaillons le dispositif expérimental que nous avons mis en place pour former un piège magnéto-optique à miroir, et donnons ses caractéristiques. Dans la deuxième partie, nous décrivons les moyens théoriques, numériques et expérimentaux que nous avons utilisés pour dessiner et caractériser différents motifs de lentilles. Nous étudions alors le chargement, la température et la durée de vie des atomes de Césium capturés. Plusieurs géométries sont présentées : lentilles simples (cylindriques ou circulaires), lentille à focale variable, réseaux de lentilles. Un adressage dynamique de ces derniers est démontré. Quelques perspectives sont finalement dégagées, en particulier au sujet des lentilles à focales variables et d'une possibilité d'adressage magnétique des pièges<br>This thesis presents the confinement of cold atoms in dipolar traps formed by Fresnel microstructures fabricated on the surface of a metallic mirror. The thesis consists of two parts. In the first part we undertake a detailed description of the experimental setup realized for a mirror-magneto-optic trap (MMOT) and discuss the characteristics of this trap. In the second part we discuss the theoretical, numerical and experimental tools that we have used for the design and characterization of various Fresnel microlens types. We then study the loading, temperature and lifetime of cesium atoms captured into dipole traps formed from these microstructured Fresnel lenses. Several different geometries are presented: simple lenses (cylindrical and circular), variable-focus lenses and lens arrays. Dynamical addressing of each member of the lens array is demonstrated. Perspectives for future development are finally discussed, in particular concerning the variable-focus lenses and the possibility of magnetic-field addressing of each member of a lens array
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Hoendervanger, Lynn. "A New Metastable Helium Machine : An Investigation into the Attributes of Trapping, Cooling and Detecting Metastable Helium." Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0006/document.
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Cette thèse décrit le travail accompli au cours des trois dernières années sur la nouvelle expérience d’Hélium métastable de l'Institut d'Optique à Palaiseau.Le premier chapitre décrit une étude visant à améliorer à la fois l'efficacité et la précision du système de détection par galettes à micro-canaux (MCP). Nous avons fait des mesures avec des galettes recouvertes d'une couche d'or sur la face avant, obtenant un accroissement de l'efficacité de détection mais également une réduction de la précision. L'ajout d'une tension intermédiaires entre les deux galettes empilées a au contraire améliorer à la fois l'efficacité et la précision des MCP, en l’absence d’une couche d’or.Le deuxième chapitre est consacré à la construction de l'appareil expérimental pour le refroidissement et le piégeage d’atomes. L’excitation de l'état fondamental de l’Hélium à l'état métastable est décrite, ainsi que la collimation et le refroidissement ultérieur par Zeeman lent du faisceau atomique chaud résultant. Le faisceau ralenti est alors capturé dans un piège magnéto-optique (PMO), dans lequel nous avons capturé 8x108 atomes.Dans le troisième chapitre une étude originale du refroidissement Doppler tridimensionnel dans un PMO et une mélasse désaccordée vers le rouge de la transition atomique est discutée. L’atome d’Hélium métastable est unique et ses propriétés ont permis une telle étude. En effet, les faibles densités atomiques impliquent qu’il n'y a pas de diffusion multiple de photons d’une part, et la faible masse et la faible largeur de la transition 23S1 -> 23P2 rend inefficace les processus de refroidissement sous la limite Doppler. Ces conditions nous ont permis d’observer pour la première fois à trois dimensions un gaz refroidit dans le régime Doppler.Le quatrième chapitre présente une étude sur les collisions dans un piège magnéto-optique d’Hélium métastable. Les collisions Penning induites par la lumière, en particulier à des intensités élevées et à des fréquences proches de la fréquence de transition, sont responsables de pertes élevées d’atomes piégés. Nous mesurons le coefficient de taux associé à ces pertes, Ksp = 2,8 ± 0,4 x 10-7cm3/ s<br>This thesis describes the work done over the past three and a half years on the new metastable helium experiment at the Institut d'Optique in Palaiseau. In the first chapter it describes a study to improve both the efficiency and the accuracy of the Microchannel Plate (MCP) detection system. We have experimented with adding a gold layer on the top of the input plate, something that we have found increases the efficiency but also decreases the accuracy. The addition of a voltage between the two stacked plates has been shown to both raise the efficiency and improve the accuracy in non-coated MCPs.The second chapter is devoted to the construction of the experimental apparatus. Here the excitation of ground state helium to its metastable state is described, as well as the subsequent collimation and cooling by Zeeman slower of the resulting hot atomic beam. The slowed beam is then captured in a Magneto-Optical Trap, in which we have captured 8x108 atoms.In the third chapter an original study on three-dimensional Doppler cooling in a red-detuned molasses and in the Magneto-Optical trap is presented. The metastable helium system is unique as there is no multiple scattering of photons and there are no sub-Doppler effects. This allows for a never before seen experimental realisation of pure Doppler cooling theory. The fourth chapter describes a study on collisions in a magneto-optical trap of metastable helium. Light-induced Penning collisions are responsible for high trap losses at high intensities and at frequencies close to the transition frequency. We measure the constant rate coefficient to Ksp = 2.8 ± 0.4 x 10-7cm3/s
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Khalili, Guyve. "Réalisation d'une source d'électrons par ionisation d'un jet d'atomes de césium refroidis par laser." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112103/document.
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Les faisceaux d’électrons et d’ions sont au cœur de nombreuses techniques instrumentales servant à explorer, analyser et agir sur des matériaux à l’échelle du micromètre au nanomètre (Microscopie électronique, spectrométrie d’électrons, techniques de « FIB »). Les limites de résolution spatiale et énergétique de ces techniques dépendent en grande partie des propriétés des sources qu’elles utilisent et en particulier de leur température de fonctionnement. De fait, depuis plus de 10 ans, le potentiel des atomes froids ionisés comme nouveau type de source d’électrons ou d’ions est intensivement exploré.Le projet expérimental réalisé au LAC et décrit dans cette thèse utilise un jet d’atomes de césium issu d’un piège magnéto-optique à deux dimensions. La température transverse du jet est de l’ordre de 100 µK. Malgré cela, le jet est encore trop divergent après la sortie de la zone de refroidissement pour notre expérience. Afin guider le jet d’atomes jusqu’à la zone d’ionisation, nous avons étudié une méthode particulière de guidage dipolaire. L’utilisation d’un seul laser convenablement réglé nous a permis de guider et pousser les atomes du jet en même temps tout en limitant le chauffage. Nous avons ainsi pu compresser avec ce laser pousseur-guideur le jet d’atomes sur un diamètre de 400 µm à 60 cm de la zone de refroidissement du PMO-2D.Le jet est ensuite ionisé par la méthode d’ionisation en champ électrique statique d’atomes de Rydberg. Les atomes sont tout d’abord excités par laser sur un état de Rydberg (n~30) en présence d’un champ électrique uniforme et homogène. Les atomes du jet ainsi excités voyagent vers une zone présentant un fort gradient de champ où ils vont alors s’ioniser autour de la même valeur de potentiel, réduisant ainsi la taille de la zone d’ionisation et donc de la dispersion en énergie potentielle initiale du faisceau d’électron. La probabilité d’ionisation des atomes dans le champ dépend grandement de l’état de Rydberg préalablement excité. Le choix de l’état de Rydberg optimal, i.e. qui a une probabilité d’ionisation la plus grande possible, nécessite une étude de l’ionisation des états de Rydberg du césium. Un modèle à deux niveaux est présenté dans cette thèse qui permet de retrouver le comportement d’ionisation d’état de Rydberg observé expérimentalement. Ce modèle simple nous a permis de comprendre quel type d’état nous devions exciter. Enfin une étude expérimentale est également présentée<br>Electron and Ion beams are at the base of many instrumental techniques used to explore, to analyse and to modify materials from the micrometer to the manometer scale (Electronic Microscopy, Electron Spectrometry, Focused Ion beams techniques…). Spatial and Energetic resolutions of these techniques are strongly dependent on its source‘s properties and particularly their working temperature. In fact, for more than ten years, the potential of ionised cold atoms have been intensively studied. Our experiment at LAC, described in this thesis, uses a 2 dimensional magneto-optical trap (2D-MOT) to create a caesium atomic beam. The transverse temperature of the beam is around 100 µK. Despite this, the beam is still too divergent after exiting the cooling area. To guide the atomic beam up to the ionisation area, we have studied and implemented a particular method of dipolar guiding. The use of a unique laser properly set allowed us to push and guide altogether the atoms of the beam while limiting the heating effect. Thus, we have managed to compress the atomic beam’s size to 400 µm at 60 cm from the output of the MOT.Afterward, the atomic beam is ionised by the method of Rydberg (static) field ionisation. The atoms are firstly excited by laser on a Rydberg state (n~30) as a static homogeneous and uniform electric field is applied. The excited atoms of beam travel therefore to a high-gradient field area where they ionise around the same electric potential value, therefore reducing the ionisation area’s size and the initial potential energy spread of the electron beam. The ionisation probability of the atoms in the field depends greatly on the excited Rydberg state. The choice of an optimal Rydberg state , i.e. with the highest probability of ionisation, needs better knowledge of the ionisation of cesium Rydberg states. A two levels model us to describe the ionisation behaviour of some Ryberg. This simple models helps to understand what kind of states we want to excite in order to optimise the ionisation area‘s size. An experimental study of cesium Rydberg states is also presented
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Braga, Helena Carolina. "O operador de Wigner aplicado a colisões de mudança de estrutura fina entre átomos alcalinos no regime frio." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-09042008-091650/.
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Neste trabalho abordamos os processos de perdas colisionais por mudança de estrutura fina e por escape radiativo. Estes processos são importantes por serem os principais fatores limitantes da densidade e da permanência de átomos confinados em armadilhas magneto-ópticas. A utilização do formalismo de Wigner nos possibilitou tratar a dinâmica dos graus de liberdade internos do sistema de forma puramente quântica, enquanto tratamos os graus de liberdade translacionais de maneira semiclássica. Com este formalismo deduzimos equações inéditas para uma colisão unidimensional e desenvolvemos um algoritmo, também inédito, para a resolução numérica de tais equações.<br>In this work we study the collision loss processes caused by fine-structure change and radiative escape. These processes are important because they limit the density and the confinement time of atoms in magneto-optical traps. The use of the Wigner-function formalism allows us to treat the internal degrees of freedom purely quantum mechanically, while treating the dynamics of the external degrees of freedom quasi-classically. This dissertation employs this formalism to derive for the first time, quasi-classical equations describing one-dimensional cold collisions, including dissipation due to spontaneous emission, and an algorithm, also for the first time, to solve numerically the mentioned set of coupled equations.
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Raskop, Jérémy. "Quantum optics with single collective excitations of nanofiber-trapped arrays of atoms." Thesis, Sorbonne université, 2020. http://www.theses.fr/2020SORUS005.
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Cette thèse traite des interactions entre des photons guidés par une nanofibre optique et des réseaux d'atomes piégés. Notre montage expérimental consiste en un piège dipolaire bicolore compensé, généré dans le champ évanescent d'une nanofibre et permettent de piéger des atomes de césium de part et d'autre de la fibre. Une épaisseur optique de plus de 130 est obtenue avec quelques milliers d'atomes seulement. Nous démontrons la capacité de préparer les atomes piégés dans un sous-niveau Zeeman unique, bien qu'avec une efficacité limitée. Cette étape est importante pour la réalisation de mémoires quantiques avec de longs temps de vie avec notre plateforme fibrée. Le résultat principal que nous présentons est la réalisation d'une excitation collective unique dans l'ensemble d'atomes. L'excitation est annoncée par la détection d'un photon émis dans le mode guidé. Nous sommes alors capables de lire l'état atomique et récupérer un photon unique dans le mode guidé avec une efficacité jusqu'à 25%. Ce résultat consiste en une première démonstration d'un état atomique intriqué, couplé préférentiellement à un guide d'onde, une étape importante dans le contexte de l’électrodynamique quantique avec des guides d'ondes<br>This thesis focuses on the study of interactions between photons guided by an optical nanofiber and arrays of trapped atoms. Our experimental setup consists in a two-color compensated dipole trap located in the evanescent field of an optical nanofiber in a ultra-high vacuum chamber. Cold cesium atoms are trapped in two 1D arrays above and below the nanofiber. An optical depth of over 130 is achieved with only a few thousand atoms. We demonstrate the ability to prepare the trapped atoms in a single Zeeman sub-level, albeit with limited efficiency. This is an important step towards the realization of a long-lived quantum memory with our fibered platform. The main result of this thesis concerns the initialization of a single collective excitation coupled to the nano-waveguide. The excitation is heralded by the detection of a Raman scattered photon in the nanofiber. We are then able to readout the atomic state and retrieve a single photon in the guided mode with an efficiency of up to 25%. This result is the first demonstration of an atomic entangled state preferentially coupled to a waveguide. It is a milestone in the context of the emerging waveguide-QED approach, with applications to quantum networking, quantum non-linear optics and quantum many-body physics
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Métivier, David. "Modèles cinétiques, de Kuramoto à Vlasov : bifurcations et analyse expérimentale d'un piège magnéto-optique." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4074/document.
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Les systèmes en interaction à longue portée sont connus pour avoir des propriétés statistiques et dynamiques particulières. Pour décrire leur évolution dynamique, on utilise des équations cinétiques décrivant leur densité dans l'espace des phases. Ce manuscrit est divisé en deux parties indépendantes. La première traite de notre collaboration avec une équipe expérimentale sur un Piège Magnéto-Optique. Ce dispositif à grand nombre d'atomes présente des interactions coulombiennes effectives provenant de la rediffusion des photons. Nous avons proposé des tests expérimentaux pour mettre en évidence l'analogue d'une longueur de Debye, et son influence sur la réponse du système. Les expériences réalisées ne permettent pour l'instant pas de conclure de façon définitive. Dans la deuxième partie, nous avons analysé les modèles cinétiques de Vlasov et de Kuramoto. Pour étudier leur dynamique de dimension infinie, nous avons examiné les bifurcations autour des états stationnaires instables, l'objectif étant d'obtenir des équations réduites décrivant la dynamique de ces états. Nous avons réalisé des développements en variété instable sur cinq systèmes différents. Ces réductions sont parsemées de singularités, mais prédisent correctement la nature de la bifurcation, que nous avons testée numériquement. Nous avons conjecturé une réduction exacte (obtenue via la forme normale Triple Zero) autour des états inhomogènes de l'équation de Vlasov. Ces résultats génériques pourraient être pertinents dans un contexte astrophysique. Les autres résultats s'appliquent aux phénomènes de synchronisation du modèle de Kuramoto pour les oscillateurs avec inertie et/ou interactions retardées<br>Long-range interacting systems are known to display particular statistical and dynamical properties.To describe their dynamical evolution, we can use kinetic equations describing their density in the phase space. This PhD thesis is divided into two distinct parts. The first part concerns our collaboration with an experimental team on a Magneto-Optical Trap. The physics of this widely-used device, operating with a large number of atoms, is supposed to display effective Coulomb interactions coming from photon rescattering. We have proposed experimental tests to highlight the analog of a Debye length, and its influence on the system response. The experimental realizations do not allow yet a definitive conclusion. In the second part, we analyzed the Vlasov and Kuramoto kinetic models. To study their infinite dimensional dynamics, we looked at bifurcations around unstable steady states. The goal was to obtain reduced equations describing the dynamical evolution. We performed unstable manifold expansions on five different kinetic systems. These reductions are in general not exact and plagued by singularities, yet they predict correctly the nature and scaling of the bifurcation, which we tested numerically. We conjectured an exact dimensional reduction (obtained using the Triple Zero normal form) around the inhomogeneous states of the Vlasov equation. These results are expected to be very generic and could be relevant in an astrophysical context. Other results apply to synchronization phenomena through the Kuramoto model for oscillators with inertia and/or delayed interactions
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Xiao, Yanyang. "Magneto-optical trap and its application to ultra-cold atom collision studies." Thesis, 1994. http://hdl.handle.net/1911/13918.
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We have successfully trapped $\sp7$Li in a vapor cell magneto-optical trap (MOT). The trap is studied in detail and the parameters are measured from the experiment. The trapping mechanism has been understood in terms of the radiation force and a simple one dimensional model is used in interpreting and predicting the experimental results. The cold-cold atom collision rate coefficient is measured in a beam MOT. The two collision mechanisms, fine structure changing and radiative escape, are discussed in a molecular picture. One of the channels, the fine structure changing channel, can be turned on and off by the experimental conditions, namely the laser intensity in this experiment. The rate coefficient for each mechanism has been determined from the experiment.
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Chen-HungRen and 陳宏任. "Electromagnetically Induced Transparency of the Cold Cesium Atoms in a Magneto-Optical Trap." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/29784995468297834580.
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碩士<br>國立成功大學<br>物理學系碩博士班<br>101<br>We construct the cold cesium atoms, which number is 5.62×108 atoms and density is 3.03×1011 atoms/cm3, by magneto-optical trap (MOT). The loading time is 761.81 ms. We applied the ladder-type electromagnetically induced transparency (EIT) in the cold cesium atoms. The three-level system is coupled by the probe field coupling the states｜62S1/2,F=4＞ and ｜62P3/2,F'=5＞ , and the coupling field coupling the states｜62P3/2,F'=5＞ and ｜82S1/2,F=4＞ .In our experiment, we lock the probe laser frequency from｜62S1/2,F=4＞ to ｜62P3/2,F'=5＞ and scan the coupling laser frequency to receive the background free EIT spectrum when coupling laser frequency is on two-photon resonance.
We observe the EIT window by the methods of suppression and recovery and directly detecting transmission of probe field, respectively. Suppression and recovery apply a probe laser to disperse cold atoms but it will be more residual cold atoms which mean higher fluorescence signal due to EIT. It will be suitable to strong probe laser because probe laser is enough powerful to disperse all of cold atoms in MOT. however, it will be better in low probe regime that I detect the transmission of probe laser directly. Probe laser is too strong that it exists a background signal in EIT spectrum because the absorption is less than part of unabsorption by cold atoms.The results with better signal-to-noise ratio and narrower EIT window are observed by directly detecting the transmission of probe field in lower coupling Rabi frequency. In ladder-type EIT, if the coupling Rabi frequency is lowered to 2.15 MHz, the linewidth of EIT window is narrowed to 1.72 MHz. We still find the smaller EIT linewidth is observed while EIT is applied in cold atoms, in comparison of that in room temperature cell, with the same lower coupling Rabi frequency.
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Lee, Yi-Chi, and 李益志. "Study of the Transportation of Cold Atoms between the Double Magneto-Optical Trap." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/54604193473640416134.
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碩士<br>國立清華大學<br>物理學系<br>93<br>To realize Bose-Einstein condensation (BEC) ,we decide to build up a new system called “ Double Magneto-Optical Trap”(DMOT)in our lab. This is different from the old system (single Magneto-Optical Trap).
In DMOT system, we use a chamber as the first MOT, and second MOT is a cell made with Pyrex .We trap the atoms in the first MOT，the number of atoms is 1.3 x109.After trapping the atoms, a laser beam named
”Push beam” pushes atoms from first MOT to second MOT. The frequency of the push beam is on resonance(|5S1/2,F=2>�逖5P3/2,F’=3>).The second MOT is collecting the atoms from first MOT. We trap 5.77 x10^7 atoms in second MOT per push time. The efficiency is 4.4 %.We need enough atoms in evaporative cooling which is an important step before the birth of BEC. In my thesis, we have succeeded in building the DMOT system ,and also transported the atoms from first MOT to second MOT .To realize BEC, we still have some works to do in the future. This is the beginning ,I believe we can see the beautiful phenomenon of BEC in this new system .
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Xiao, Hau-Yl, and 蕭豪毅. "Trapping Cold Atoms with an Optical Dipole Trap." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/14163296521974752188.
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Lin, Li-Chieh, and 林豊傑. "Optical Dipole Trap of Ultra-Cold Rubidium Atoms." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/26400870264276979758.
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Hung, Weilun, and 洪偉倫. "Studies of loading and storage of cold atoms in an optical dipole trap." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80470018929241589603.
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博士<br>國立清華大學<br>物理系<br>102<br>This thesis focuses on transferring cold atoms into an optical dipole trap (ODT). Optical density as well as number density of the cold atoms confined in the ODT can be achieved to a sufficiently high level that is suitable for single-photon nonlinear optics experiments. We studied the processes of loading cold atoms into the ODT from a temporal dark magnetic-optical trap (MOT), a spatial dark MOT, and a time-averaged orbiting potential (TOP) magnetic trap.
We further investigated how to prolong the storage time of the atoms captured in the ODT. A rapid loss of the atoms distributed among all the Zeeman states of the hyperfine level |F=2>is due to the hyperfine-changing collision. To increase the storage time, we optically pumped the atoms either to the hyperfine level |F=1> or to a single Zeeman state of |F=2, m=2>or |F=2, m=2>. In the latter case, a uniform magnetic field larger than 4.3 G was applied.
We were able to load 5.6106 87Rb atoms with a temperature of 57μK into the ODT with a trap depth of 850 μK from the TOP magnetic trap. Under this condition, the peak number density of the atoms can be as high as 61013 cm-3, i.e. 120 atoms within the volume of 3 where is the wavelength of light.
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Rathod, Ketan D. "Continuous Beam of Laser-Cooled Ytterbium Atoms for Precision Measurements." Thesis, 2014. http://hdl.handle.net/2005/2781.
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What if an elementary particle such as an electron had an intrinsic electric dipole moment (EDM)? Existence of such an EDM would be an indication of time-reversal symmetry
violation in the laws of Physics. The Standard model of Physics is considered incomplete, and theories that go beyond the standard model predict existence of such EDM’s within experimental reach. Experiments that search for their existence serve as a test bed for these theories. Use of laser-cooled Yb atoms launched in a fountain for EDM search has been proposed earlier.
This thesis describes the main experimental work on generating a continuous cold
beam of Yb atoms using laser cooling. Such cold beams are ideal for performing EDM
experiments and have several advantages over the more common pulsed fountain. We
demonstrate two ways to achieve this (i) extracting the beam from atoms trapped in 2-
dimensions and (ii) deflecting the atomic beam using 1D-optical molasses. We find that
the latter method gives a longitudinal temperature of 41 mK, which is a factor of 3 better than the former one. We also demonstrate the implementation of Ramsey’s separated oscillatory field technique in a thermal beam to measure the larmor precession frequency with high precision. This serves as a first step towards implementation with cold beam.
Extending the work reported here, we suggest future experiment for measuring an EDM.
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Wu, Feng-chuan, and 吳豐全. "Effect of the Two-Photon Raman Transition on the Storage Time of Cold Atoms in an Optical Dipole Trap." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/tc85cv.
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Huang, Pan-Pan, and 黃盼盼. "Characterization of cold atoms captured in an optical dipole trap and study of their interaction with a probe laser." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/85772064979083502470.
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碩士<br>國立交通大學<br>光電工程研究所<br>101<br>To maximize the optical density (OD) of cold 87Rb atoms in an optical dipole trap (ODT) for future single-photon experiments, we investigated the methods of loading the atoms into the ODT from a time-averaged orbiting potential (TOP) and from a dark magnetic-optical trap with and without the magnetic compression (abbreviated as dark-CMOT and dark-MOT, respectively). The atomic temperature and density in the TOP 3A (the current through the TOP coils) were 57.5 K and 1.2×1012 cm-3; those in the dark-CMOT or dark-MOT were 300 K and 3.8×1010 cm-3. The ODT was realized by a 1064 nm fiber laser with a maximum power of 10 W. The e-2 full width of the focused laser beam was approximately 54 μm, giving the ODT trap depth of about 850 K.
We studied the temperature, number, and life time of the atoms captured in the ODT. ODs of the atoms were measured by the absorption of a weak probe laser beam tuned to the D2 transition of 87Rb and propagating along the major axis of the ODT. The alignment of the probe beam is critical to the absorption measurement and was studied by imaging the atom cloud under the radiation pressure from the high-intensity probe field driving the cycling transition from |F=2 to |F’=3 resonantly.
With the loading from the TOP 3A, there were about 1.6×106 atoms with a temperature of 61 μK in the ODT with a power of 10.7 W. The OD along the central axis estimated by the atom number and the dimension of the cigar-shaped cloud of 82×82×3000 μm3 (e-2 full widths) is 170. However, the transmission of the probe field with the e-2 full width of 45 μm driving the non-cycling transition from |F=2 to |F’=2 resonantly and propagating through the major axis of the atom cloud is about 20%, showing that the OD along the central axis of the cloud is only 11.
With the loading from the dark-CMOT, there were about 2.7×106 atoms with a temperature of 350 μK and a life time of 0.43 s in the ODT with a power of 10.7 W. The life time was measured under the captured atoms being placed in the |F=2 ground state. The OD along the central axis estimated by the atom number and the dimension of the cigar-shaped cloud of 160×160×2800 μm3 (e-2 full widths) is 72.
With the loading from the dark-MOT, there were about 4.4×106 atoms with a temperature of 350 μK in the ODT with a power of 10.7 W. The OD along the central axis estimated by the atom number and the dimension of the cigar-shaped cloud of 170×170×2500 μm3 (e-2 full widths) is 120. When the captured atoms were placed in the |F=1 ground state, their lifetime of 0.84 and 11 s were observed in the 10.7-W and 1.6-W ODT, respectively. We will further cool down the atoms to make the simpler dark-MOT loading method outperform the more complicate TOP loading method.