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<p> A quantum particle moving in a periodic potential, with periodicity d, when acted by an external constant force F undergoes the dynamical phenomenon of Bloch-Zener oscillations (BZO). We investigate BZO of a neutral cold atom in an optical cavity pumped by a laser. We find that the single mode electromagnetic field of the optical cavity is affected by the atomic dynamics and propose the idea that a measurement of the electromagnetic field leaking out of the cavity will reflect the BZO frequency WB = Fd/h, and can be used for a precision measurement of F. The motivation for such a study comes from the fact that if the force F is gravity, then one can probe gravitational forces on sub-millimeter scales since the size of these systems are generally a few hundreds of microns. Such a study can be used to detect deviations from Newtonian gravity at short range proposed by some theories beyond the standard model of particle physics. </p> / Thesis / Master of Science (MSc)

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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Ce mémoire présente la conception et réalisation d'un montage expérimental pour le développement d'un interféromètre à atomes froids de 87Rb guidés sur un microcircuit à atomes, l'objectif final étant la réalisation d'un capteur inertiel de rotations. Nous avons ainsi étudié théoriquement le confinement magnétique des atomes dans un guide circulaire. Une telle étude nous a permis d'identifier les principales problématiques liées à la propagation sur une orbite stable d'un paquet d'onde atomique dans un guide magnétique, à savoir: la rugosité du potentiel de guidage, les défauts du potentiel associés au motif de micro fils employés pour créer ce potentiel, et les pertes par effet Majorana. Dans cette thèse nous proposons des solutions originales à ces problèmes basés sur des études précédentes et sur les résultats de nos calculs. Du point de vue expérimental, nous avons monté une nouvelle expérience d'atomes froids dont la principale caractéristique est d'être compacte et donc transportable pour des mesures locales de vitesses de rotations. Nous avons donc, au cours de ce travail, assemblé un système à ultra vide efficace, développé un banc optique très compacte comprenant des sources laser pour le refroidissement et piégeage des atomes, un laser de Bragg pour la réalisation de l'interféromètre atomique, ainsi que toute l'électronique de contrôle de cette expérience. / This manuscript present the design and realization of an experimental setup for the development of a cold atom interferometer using 87Rb atoms guided on an atom chip, the final goal being the realization of an inertial sensor for rotation measurements. We have therefore study theoretically the magnetic confinement of these atoms in a circular guide. Such a study allowed us to identify the main challenges linked to the atomic wave packet propagation along a stable circular orbit in a magnetic guide, namely: the roughness of the guiding potential, the magnetic potential defects associated to the pattern of the micro wires used to produce this potential, and the Majorana losses. In this thesis we propose original solutions to these questions based on preliminary studies and on the results of our calculations. From the experimental point of view, we have assembled a new cold atom experiment with the main feature of being compact and therefore transportable for in situ measurement of rotations. We have along this work put together an efficient ultra high vacuum system, developed a compact optical bench containing the laser sources for cooling and trapping, a Bragg laser for the atom interferometer, as well as all the needed electronics to control the experiment.

Nuage d'atomes de rubidium refroidi par laser. Ces mesures fournissent des informations sur la sourceet sur le milieu de propagation. Je considère une configuration particulière en transmission, le laserse propageant au travers du nuage atomique. Cette géométrie est pertinente pour étudier différentespropriétés, comme le mouvement des atomes. Cependant, le bruit intrinsèque du laser a unecontribution importante sur les spectres de bruit. Ce bruit technique peut alors devenir gênant pourextraire le signal étudié et une bonne compréhension du phénomène est donc essentielle.Expérimentalement, les spectres de bruit en intensité montrent un comportement différent auxfréquences basses et hautes. Alors que l'on observe la conversion "standard" du bruit de fréquence enbruit d'intensité pour les fréquences basses, la résonance atomique correspondant à un discriminateurde fréquence, des différences apparaissent à hautes fréquences. Nous montrons qu'une approche dechamp moyen, en associant une susceptibilité électrique au nuage atomique, est suffisante pourexpliquer les observations. Partant de ce modèle, les spectres permettent d'extraire des informationsquantitatives sur le laser et sur le nuage atomique. Ceci est connu sous le nom de spectroscopie debruit.La perspective est d'utiliser ces mesures de bruit afin d'obtenir une signature claire du laser aléatoireà atomes froids en étudiant la cohérence temporelle de la lumière émise. Cette thèse expose unerevue du phénomène de laser aléatoire, en particulier sur le laser à atomes froids et ses propriétés decohérence / In this thesis, I present some measurements of fluctuations of light after interaction with a cloud oflaser-cooled rubidium atoms. These measurements can provide useful information on the sourceitself as well as on the medium in which light propagates. I address a particular configuration inwhich intensity noise are measured on a laser beam transmitted through the atomic cloud. Thisgeometry is relevant to investigate different properties, such as the atomic motion. However, in ourexperiment the intrinsic noise of the incident laser has an important contribution to the detected noisespectrum. This technical noise may be hard to distinguish from the signal under study and a goodunderstanding of this process is thus essential.Experimentally, the intensity noise spectra show a different behavior for low and high Fourierfrequencies. Whereas one recovers the "standard" frequency to intensity conversion at lowfrequencies, due to the atomic resonance as a frequency discriminator, some differences appear athigh frequencies. We show that a mean-field approach, which corresponds to describing the atomiccloud by a dielectric susceptibility, is sufficient to explain the observations. Using this model, thenoise spectra allow to extract some quantitative information on the laser noise as well as on theatomic sample. This is known as noise spectroscopy.The perspective of this thesis aims at applying noise measurement to obtain complementarysignatures of the cold-atom random laser by studying the temporal coherence of the emitted light.The manuscript therefore outlines a review on random laser phenomena with a focus on cold-atomrandom lasers and its coherence properties

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19476号 / 理博第4136号 / 新制||理||1595(附属図書館) / 32512 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川上 則雄, 教授 石田 憲二, 教授 高橋 義朗 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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