A pair of high-stability optical frequency references has been developed. The devices are based on room temperature Fabry-Perot cavities with mirrors spaced apart by a hollow single-crystal sapphire element. The sapphire element delivers mechanical sti ness that provides improved immunity to vibrational perturbations compared with the more common spacers made from ultra-low expansion glass. The system is housed in an vacuum chamber designed to provide isolation from environmental perturbations through the use of an active thermal control system, suspension legs and a unique beam alignment system. The dimensional stability of the Fabry-Perot was translated into a highly stable laser frequency by frequency locking a 1064nm Nd:YAG laser to the centre of a mode of the cavity. This frequency lock was implemented by the Pound-Drever-Hall scheme. By careful design, this control system was able to hold the frequency of the laser to within parts in 1016 of the frequency of the fundamental cavity mode. The minimum fractional frequency stability of the laser frequency was measured at 2.1x10[-]14 for integration times of 0.8 s, limited by the residual instability of the Fabry-Perot cavity. The experimental methods used to measure the performance of the system have also been considered in depth. For example, the most common way of characterizing the frequency stability of a frequency standard is the Allan variance. It is demonstrated that, without care, data taken with modern frequency counters can produce erroneous and distorted results when their output is supplied to this algorithm. The method to avoid or account for these errors is also presented. The Fabry-Perot cavity performance is limited on long timescales by residual temperature uctuations, which can be ameliorated in future by enhancing the design of the thermal control system. At short timescales, the system is limited by vibration-induced uctuations together with a white noise source, that is yet to be identi ed, but may relate to fundamental thermodynamic temperature uctuations of the sapphire spacer. This system was used to measure the stability of an optical signal synthesised from a cryogenic microwave sapphire oscillator using an wide-band optical frequency comb. This was the rst demonstration of a multiplication of an ultra-stable signal from the microwave frequency domain into the optical frequency domain, without loss of delity at the level of 2x10[-]14.

The 87Rb 49s->48s Rydberg state transition was rendered insensitive to electric field fluctuations about a 1V/cm dc electric field. This was accomplished by applying a non-resonant 38.445GHz microwave field to modify the electric dipole moment difference between the two states involved. This effect can be used to preserve the coherence of Rydberg state qubits in the presence of varying electric fields.

The 87Rb 49s->48s Rydberg state transition was rendered insensitive to electric field fluctuations about a 1V/cm dc electric field. This was accomplished by applying a non-resonant 38.445GHz microwave field to modify the electric dipole moment difference between the two states involved. This effect can be used to preserve the coherence of Rydberg state qubits in the presence of varying electric fields.

This dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be measured. Experimental results begin with an exploration of the consequences on the timing and amplitude jitter of the phase noise of an RF source used for mode-locking. These results lead to an ultralow timing jitter source, with 30 fs of timing jitter (1 Hz to 5 GHz, extrapolated). The focus of the work then shifts to generating a stabilized optical frequency comb. The first technique to generating the frequency comb is through optical injection. It is shown that not only can injection locking stabilize a mode-locked laser to the injection seed, but linewidth narrowing, timing jitter reduction and suppression of superfluous optical supermodes of a harmonically mode-locked laser also result. A scheme by which optical injection locking can be maintained long term is also proposed. Results on using an intracavity etalon for supermode suppression and optical frequency stabilization then follow. An etalon-based actively mode-locked laser is shown to have a timing jitter of only 20 fs (1Hz-5 GHz, extrapolated), optical linewidths below 10 kHz and optical frequency instabilities less than 400 kHz. By adding dispersion compensating fiber, the optical spectrum was broadened to 2 THz and 800 fs duration pulses were obtained. By using the etalon-based actively mode-locked laser as a basis, a completely self-contained frequency stabilized coupled optoelectronic oscillator was built and characterized. By simultaneously stabilizing the optical frequencies and the pulse repetition rate to the etalon, a 10 GHz comb source centered at 1550 nm was realized. This system maintains the high quality performance of the actively mode-locked laser while significantly reducing the size weight and power consumption of the system. This system also has the potential for outperforming the actively mode-locked laser by increasing the finesse and stability of the intracavity etalon. The final chapter of this dissertation outlines the future work on the etalon-based coupled optoelectronic oscillator, including the incorporation of a higher finesse, more stable etalon and active phase noise suppression of the RF signal. Two appendices give details on phase noise measurements that incorporate carrier suppression and the noise model for the coupled optoelectronic oscillator.

Dans cette thèse, nous décrivons une approche jusqu’à maintenant inexplorée dans le développement des interféromètres atomiques; la rétroaction des états atomiques au cours de leur évolution. Le long de cet objectif, nous présentons des nouvelles techniques expérimentales, comme la condensation de Bose-Einstein tout-optique d’atomes de rubidium-87 à l’aide d’une cavité optique, une nouvelle technique de stabilisation de laser décalage de fréquence serrodyne et le développement de la spectroscopie par modulation de fréquence comme un outil non-destructif pour mesurer des différences de population atomique. Cette détection non destructive est combinée à la rétroaction, soit directement sur les atomes avec un rayonnement micro-onde soit sur l’oscillateur à micro-ondes. De cette manière, nous montrons que les états quantiques atomiques peuvent être protégés contre la décohérence d’un bruit collectif. Grâce à cette méthode, nous développons des protocoles de rétroaction dédiés pour améliorer les interféromètres atomiques, et démontrons expérimentalement l’un d’entre eux dans le cas d’une horloge atomique. Nous montrons que le temps d’interrogation dans les interféromètres atomiques peut être prolongé, ce qui est prometteur pour augmenter la sensibilité des senseurs atomiques. / In this thesis, we describe an until now unexplored approach in the operation of atomic interferometers; the feedback control of the atomic states during their evolution. Towards this goal, we present several novel experimental techniques, such as the all-optical Bose-Einstein condensation of rubidium-87 in a cavity enhanced dipole trap, a new laser stabilization technique based on serrodyne frequency shifting and the development of frequency modulation spectroscopy as a minimal destructive tool for the measurement of atomic population differences. This nondestructive detection is combined with feedback, either directly on the atoms with microwave radiation or on the microwave oscillator. In this way, we show that atomic quantum states can be protected against decoherence from collective noise. We develop dedicated feedback protocols to use this method to improve atomic interferometers, and experimentally demonstrate one such protocol in an atomic clock. We show that the interrogation time in atomic interferometers can be prolonged, which holds promise for increasing the sensitivity of atomic sensors.

Made available in DSpace on 2015-05-14T12:14:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2614177 bytes, checksum: 64cd8eee6f69230497da81e691be96a2 (MD5) Previous issue date: 2005-11-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Interactions with surfaces modify internal and external liberty degrees of atoms next to these surfaces. The dominant long range interaction (which extends itselfs to about an atomic transition wavelength is the van der Waals interaction, usually attractive. Firstly, this thesis treats C3 coefficient, which is characteristic of this interaction and depends on the type of surface and temperature. Other theme is determination of this coefficient using a spectroscopic technique (Selective Reflection) in the atomic cesium system (6S1=2 - 8P3=2 transition) on a dielectric surface. This interaction allows the long range excitation transfer (Förster effect) from atom to the dispersive dielectric surface. Considering small distances (atomic dimensions), interaction becomes repulsive because of electronic orbital overlap between the atom and surface components. The sum of these two kinds of interaction (far and close range) results in a potential well, with discrete energy levels. Next, are presented results of simulations on optic transfer from free atoms to atom-surface bounded states. The radiation sources used on the experiments to evidence atom-surface effects described in the first part of this thesis are resonant diode lasers, with spectral characteristics that must be modified on the laboratory to became useful tools to perform high resolution experiments. The Part II treats diode lasers, beginning from stabilization techniques description and going to a new technique developed on the laboratory during doctoral work, where the laser frequency is controlled by an coupled optical orthogonal feedback with atomic transition to diode. Other effects related to this stabilization technique, as the bi-stability phenomena, are described and interpreted on the last chapter. / Interações dos átomos com superfícies modificam os graus de liberdade internos e externos desses átomos quando próximos a elas. A interação dominante de longo alcance (até a ordem do comprimento de onda das transições atômicas) é a interação de van derWaals, geralmente atrativa. Nesta tese é abordado o coeficiente C3, característico dessa interação e dependente da superfície e temperatura, determinado através do uso de uma técnica espectroscópica (Reflexão Seletiva). Trata-se também da transferência de excitação de longo alcance (efeito Förster) do átomo para a superfície. A curtas distâncias (dimensões atômicas), a interação torna-se repulsiva, devido à sobreposição dos orbitais eletrônicos do átomo incidente e dos constituintes da superfície. A soma das contribuições de curto e de longo alcance resulta em um poço de potencial com níveis discretos de energia que são simulados em uma transferência ótica para esses estados ligados. As fontes de radiação utilizadas nas experiências da primeira parte desta tese são lasers de diodo ressonantes, cujas características espectrais precisam ser modificadas no laboratório para eles se tornarem ferramentas adequadas para a realização de tais experiências de espectroscopia de alta resolução. A Parte II da tese trata de diodos lasers, iniciando com a descrição de técnicas de estabilização e chegando a uma nova técnica desenvolvida no laboratório durante este trabalho de doutorado, onde a freqüência do laser é controlada através de um retorno ótico com polarização ortogonal no diodo acoplado à transição atômica. Outros efeitos relacionados a essa técnica de estabilização, como o fenômeno de bi-estabilidade, são descritos e interpretados no último capítulo desta tese.

Les gaz quantiques dégénérés des atomes neutres sont d’excellentssystèmes avec les applications importantes dans les études de la physique à plusieurs corps, de la matière condensée, de la mesure de haute précision et de l'information quantique. Dans cette thèse, nous démontrons la production des condensats de Bose-Einstein de 87Rb dans les différents modes transverses de la cavité qui a une configuration en papillon (bow-tie cavity). La cavité est résonante à deux longueurs d'onde, 1560 nm et 780 nm. Nous utilisons la radiation à 1560 nm, une longueur d'onde accessible dans la télécommunication (bande C) pour obtenir le condensat de Bose-Einstein dans un piège dipolaire intra-cavité. La cavité optique permet de réaliser un piège dipolaire profond à partir d'une source optique à puissance modérée (3W), grâce à l'amplification de la puissance au sein du résonateur. Les modes non dégénérés du résonateur permettent d'obtenir de multiples condensats dans les modes transverses supérieurs. Comme exemples représentatifs, nous avons réalisé le condensat de Bose-Einstein dans le mode fondamental et le mode TEM01 de la cavité. L'utilisation de ces modes nous permet d'avoir un et deux puits de potentiels pour le piégeage où l'échantillon atomique ultra-froid est couplé au mode du résonateur. En contrôlant la puissance relative entre le mode fondamental et les modes transverses supérieurs (TEM01, TEM10), nous arrivons à réaliser la division et la recombinaison d’un 'ensemble atomique ultra-froid. De plus, dans ce manuscrit nous présentons le développementd'un système d'asservissement autour de la cavité optique qui nous permet d'obtenir les deux radiations asservies sur le résonateur ainsi que la stabilisation de la longueur de la cavité sur les atomes de rubidium. La deuxième longueur d'onde provient du faisceau à 1560 nm après le doublage de fréquence. Par la suite, les deux longueurs d'onde sont asservies sur la cavité par la technique de Pound-Drever-Hall. Une partie du composant doublé en fréquence est comparée en fréquence avec un laser à 780 nm asservi sur les atomes de rubidium par la technique de battement optique. Ensuite, le signal de battement est converti par un synthétiseur de fréquence et est envoyé vers le contrôleur de transducteur piézo-électrique de la cavité via un régulateur PI pour éviter la dérive à long terme liée aux fluctuations de la température. La résonance à 780 nm sera utilisée comme faisceau de sonde intra-cavité. Cela nous permettra de réaliser une mesure quantique non-destructive et de générer des états comprimés de spins induits par cette mesure / Quantum degenerate gases of neutral atoms are excellent systems with important applications in the study of many body quantum physics, condensed matter physics, precision measurements, and quantum information processing. In this thesis we demonstrate the creation of 87Rb Bose-Einstein condensates (BECs) in different transverse modes of a bow-tie cavity. The cavity resonant at two wavelengths, 1560 and 780 nm. We are using the radiation 1560 nm accessible in telecom (C band) to create BEC in the cavity enhanced optical dipole trap with only 3 W of optical power from the source. The non-degenerate cavity modes enable the creation of arrays of BECs in the higher transverse modes. As representative examples we realize the BEC in the fundamental TEM00 and the TEM01 mode of the cavity which are the single well and double well trapping configuration with ultra-cold atomic simple well coupled to the cavity modes. By controlling the relative power between the fundamental and the higher transverses cavity modes (TEM01, TEM10), splitting and merging of ultra-cold atomic ensemble is shown. Moreover, in this manuscript we present the development of a lock system around the optical cavity which allows us to obtain both radiations locked to the cavity as well as the lengthe of the optical resonator is referenced on the rubidium atoms. The second wavelength is derived from 1560 nm beam by frequency doubling and then both radiations are locked to the cavity by Pound-Drever-Hall technique. One part of the frequency doubled 780 nm is referenced to an independent 780 nm laser locked on the rubidium atoms. The beat signal between these two lasers is frequency synthesized and through the PI controller is sent to the piezo-electric transducer driver to avoid long-term drifts of the cavity due to temperature fluctuations. The cavity resonance at 780 nm will be used as a probe beam for cavity aided quantum non-demolition measurements to generate measurement induced spin squeezed states.