This thesis reports an optical dipole trap for atomic calcium. The dipole trap is loaded from a magneto-optical trap (MOT) of calcium atoms cooled near the Doppler limit (~1 mK). The dipole trap is formed by a large-frame argon ion laser focused to 20 microns into the center of the MOT. This laser runs single-line at 488 nm with a maximum power of 10.6 watts. These parameters result in a trap of 125 mK for calcium atoms in the 4s3d 1D2 state. The 488 nm light also photo-ionizes the trapped atoms due to a near-resonant transition to the 4s4f 1F3 level. These ions leave the trap and are detected to determine the trap decay rate. By measuring this decay rate as a function of 488 nm intensity, we determine the 1F3 photo-ionization cross section at this wavelength to be approximately 230 Mb.

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.

This thesis describes the design, construction and optimisation of two compact setups to produce ⁸⁷Rb Bose-Einstein condensates and dual ⁷Li-⁸⁷Rb Magneto- Optical Traps (MOTs). The motivation for compact systems is to have simplified systems to cool the atoms. The first experimental setup is based on a single pyrex glass cell without the need for atom chips. Fast evaporation will be achieved in a hybrid trap comprising of a magnetic quadrupole trap and an optical dipole trap created by a Nd:YVO4 laser and with future plans of using a Spatial Light Modulator (SLM). To enhance an efficient and rapid evaporation, we have investigated Light-Induced Atomic Desorption (LIAD) to modulate the Rb partial pressure during the cooling and trapping stage. With this technique, a ⁸⁷Rb MOT of 7 x 10⁷ atoms was loaded by shining violet light from a LED source into the glass cell, whose walls are coated with rubidium atoms. The atoms were then cooled by optical molasses and then loaded into a magnetic trap where lifetime measurements demonstrated that LIAD improves on magnetically-trapped atoms loaded from constant background pressure by a factor of six. This is quite encouraging and opens the possibility to do a rapid evaporation. In a second experiment, we have designed a compact system based on a stainless steel chamber to trap either ⁷Li or ⁶Li atoms in a MOT loaded from alkali-metal dispensers without the need of conventional oven-Zeeman slower. This setup can also load ⁸⁷Rb atoms, allowing future projects to simultaneously produce degenerate quantum gases of bosonic ⁸⁷Rb and fermionic ⁶Li atoms.

Uma análise dos processos colisionais homonucleares e heteronucleares, responsáveis por perdas em uma armadilha magneto-óptica, foi realizada neste trabalho. Resultados experimentais inéditos para as taxas de perdas, no sistema Rb-Cs, foram obtidos. Os dados experimentais em conjunto com os resultados do modelo sugerem que o processo de escape radiativo é dominante. O modelo utilizado é muito sensível à profundidade da armadilha, a qual depende de outros parâmetros (intensidade, dessintonia, gradiente de campo magnético, etc.). A colaboração com pesquisadores italianos possibilitou uma análise mais detalhada das taxas de perdas heteronucleares em outras regiões de intensidade. Estudamos a dependência das taxas heteronucleares com a razão das massas do par atômico, e uma razoável concordância foi observada. O estudo de processos colisionais em armadilhas magneto-ópticas é importante na obtenção do condensado de BoseEinstein com duas espécies atômicas distintas, e também em experiências de espectroscopia fotoassociativa. / In this work, we had investigated the heteronuclear trap loss rate in a two-species Rb-Cs magneto-optical trap. The experimental results suggest that radiative escape is the main collisional process responsible for heteronuclear losses. An addapted Gallagher - Pritchard model is compared with the data. The model is very sensitive to the trap depth, which depends on the trap parameters (intensity, detuning, magnetic - field gradient, etc.) This observation is also supported by experimental results from a Pisa\' group. We have compared experimental of heteronuclear rates as a function of the masses ratio of the atomic pair with the model, and a reasonable agreement is observed. These studies are relevant for high resolution atomic / molecular spectroscopy, and for the production of mixed - species Bose-Einstein condensates.

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. / 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.

Neste trabalho estudamos o processo de foto-ionização associativa(PAI) em uma amostra fria de átomos de sódio com o objetivo entender os efeitos dos estados repulsivos e dimensão da colisão. Realizamos experimentos de PAI com duas cores em uma armadilha magneto-óptica adicionando um feixe de prova com intensidade, frequências e polarização ajustáveis. O formato dos átomos aprisionados também foi uma das variáveis no estudo da PAI. Para os átomos em formação esférica, observamos uma mudança marcante no comportamento da constante de taxa de formação da foto-ionização associativa(K) para um determinado domínio de frequências, e essa mudança no comportamento pode ser atribuída a participação de estados moleculares repulsivos na PAI e a formação de um possível cruzamento evitado entre os níveis moleculares. No atomotron ,armadilha atômica em forma de anel, variamos a polarização do laser de prova e constatamos que a razão entre K das polarizações paralela e perpendicular ao movimento dos átomos é igual a 4. Uma comparação entre K do atomotron e o da armadilha esférica em função da intensidade do feixe de prova, nos mostrou uma diferença no comportamento e no valor da constante de taxa. / Photoassociative ionization (PAI) in a cold sample of sodium atoms was the main subject of our studies as a way to understand the effects of repulsive states and collision dimensions. Two-color PAI experiment were preformed in a magneto-optical trap (MOT) trough the addition of a probe laser beam, the intensity, polarization and frequency of that probe laser were tunable. The shape of the trapped atoms also could be changed. In a spherical shape MOT, we observed a marked change in the PAI rate constant (K) for a definite frequency range, and that change can be attributed to the influence of repulsive molecular states and the a possible formation of an avoided crossing between molecular levels. In atomotron, ring shaped mot, we changed the polarization of the probe beam, and saw that the ratio between K for a polarization parallel to the atoms motion and a perpendicular one is 4. Comparing the K as a function of the intensity between a spherical shaped mot and atomotron showed us a difference in the behavior and the value of the rate constant.

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. / 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.

Este trabalho relata o desenvolvimento de todo o aparato experimental para a realização de aprisionamento de césio através de uma armadilha magneto-óptica. As fontes de luz neste processo foram os lasers de diodo e todo seu sistema para operação, estabilização e redução da largura de linha foi construído. As medidas das constantes de mola e amortecimento foram realizadas como função dos parâmetros característicos das armadilhas de césio e de sódio. Também realizamos outros experimentos com átomos aprisionados de sódio na presença de duas freqüências, linha D1 e D2. A primeira medida constitui na obtenção da taxa de colisões entre átomos aprisionados na linha D1 e depois foi realizado observações de uma nova estrutura operando neste regime. / This thesis describes the development of a complete experimental setup for trapping cesium by a magneto-optical trap (MOT). In this work we have employed diode lasers as light sources and built the entire system for their operation, stabilization and linewidth reduction. We have measured the MOT spring and damping constants as functions of the characteristic parameters of the cesium and sodium traps. We have also carried out two other experiments on trapped sodium atoms operating in the simultaneous presence of the D1 and D2 line frequencies. The first experiment has established the collision rate of trapped atoms in the D1 line MOT and the second has allowed us to observe a new structure operating in this two-frequency regime.

Neste trabalho apresentamos a produção de moléculas frias heteronucleares em uma armadilha magneto-óptica mista de 39K e 85Rb e detectadas no estado fundamental. A técnica de detecção consiste na fotoionização pulsada das moléculas que, após terem sido fotoassociadas, decaem através de emissão espontânea para estados ligados do potencial do estado molecular fundamental. A partir dos resultados da produção de moléculas frias KRb, estudamos-as com relação ao tipo de colisões que as originam, e à temperatura associada ao seu movimento translacional. Experimentos foram também realizados para comprovar que as moléculas detectadas são provenientes do estado fundamental. Finalmente, também estudamos neste trabalho, a taxa segundo a qual são formadas. Concomitantemente à produção de KRb, moléculas frias homonucleares 39K2 e 85Rb2 são também formadas, detectadas e caracterizadas. São apresentados também, os primeiros passos dados em direção à realização de espectroscopia fotoassociativa dos estados ligados das moléculas heteronucleares obtidas. / In this work, cold ground-state KRb molecules were produced by photoassociation in a two species magneto-optical trap (MOT) containing 39K and 85Rb. The KRb molecules are produced through photoassociation and detected in the ground state by multiphoton pulsed ionization. We have characterized their translational temperature and measured their formation rate constant. Homonuclear cold molecules 39K2 and 85Rb2 detected in their ground state were also formed in our trap and characterized as well. It is also reported our first efforts towards the realization of photoassociation spectroscopy of the heteronuclear molecules produced in our trap.

Ce manuscrit présente le rayonnement de second harmonique provenant de plusieurs milieux diélectriques allant de la réponse interfaciale à la réponse volumique. Ce travail de thèse constitue une première étape dans le but d'étudier une bulle de savon dans un piège optique par génération de second harmonique. Deux axes de recherche sont ainsi explorés : d'une part l'étude de la génération de second harmonique sur deux tensioactifs le TTAB et le SDS, constituants de base d'une bulle de savon, et de l'autre l'élaboration d'un nouveau dispositif expérimental permettant d'allier un piège optique à une excitation de second harmonique par un laser femtoseconde. Dans un premier temps, on explicite le montage optique reposant sur le principe d'un microscope confocal inversé et les mesures associées de la réponse harmonique d'interface air/verre et air/eau. Dans un second temps, on s'intéresse comme objet modèle, en lieu et place de la bulle, à une microparticule de silice. Ainsi, on commence par analyser sa réponse harmonique en microscopie non linéaire quand celle-ci se trouve déposée sur une matrice de verre. L'étude de cet objet met en avant l'interdépendance entre les aspects d'optique linéaire mesurés à la longueur d'onde fondamentale et l'intensité harmonique mesurée. Par la suite, cette microsphère est placée au sein du piège optique réalisé par un second faisceau. Malgré la faible taille et la symétrie de la particule diélectrique, on parvient à mettre en évidence la réponse harmonique d'une particule unique piégée. Enfin, dans une dernière partie, on s'intéresse à caractériser la génération de second harmonique pour des solutions savonneuses, première étape dans la réalisation d'une bulle. Les mesures de diffusion de second harmonique en volume pour des solutions de TTAB et SDS de diverses concentrations montrent un comportement similaire et une singularité lors du passage de la concentration micellaire critique. Lors de l'étude du signal de second harmonique à l'interface air/eau savonneuse en revanche, on mesure des comportements différents pour des tensioactifs anioniques et cationiques, provenant de la charge de surface et de l'orientation de l'eau sous-jacente / This thesis reports an experimental study of harmonic radiation from various dielectric media. We both study second harmonic generation on interfaces and hyper Rayleigh scattering in solutions. We present the first step for the realization of the following project : the study of the second harmonic generation on an optically trapped soapy bubble. To do so, two main axis of investigation are developped. Firstly, we study the harmonic response of two commonly used surfactants such as TTAB, a cationic one and SDS carrying a negative charge. This study consits of understanding the main component of a soapy bubble. We investigate how harmonic intensity is modified with an increase of soap concentration. These experiements are carried both in volume and at the air/water interface. The harmonic scattered intensity shows similar features for SDS and TTAB, as a sudden drop appearing at the critical micelar concentration. However, on the surface, the two oppositely charged surfactants give a radically different evolution of second harmonic signal versus their concentration. Indeed, the water molecules of the surroundings behaves in an opposite manner with negative or positive charged surfactants. The second axis of research that we work on in this thesis, is on a novel experimental development. We combine an optical tweezer to trap microsized particles with a femtosecond laser probe to generate the second harmonic. This is a first step in order to trap a bubble and study it with second harmonic generation. This non linear inverted confocal microscope is used to study harmonic profil of an silica bead stuck on a sample. This study gives a glance of the complexity of the correlation between linear optics effects on the laser probe beam and the created harmonic intensity. We also perform experiments on a trapped particle and we measure the harmonic response of an unique particle