By shining a precisely tuned laser through an atomic vapor, we can determine local mag- netic field strength in scalar form and in a way that is not affected by temperature changes. This technology has been used in space many times before on missions flown by NASA and ESA, such as SWARM, Øersted, and CHAMP to calibrate accompanying vector mag- netometers which are subject to offsets caused by temperature changes. The device we constructed is a small, low-cost application of this scientific principle and opens up new areas of scientific possibility for cubesats and the ability to define geomagnetic field struc- tures on a small (<10km) scale as part of the ANDESITE cubesat mission being developed at Boston University. Previously, magnetic sensors in orbit have been flown individually on a single spacecraft or in very small groups such as the International Sun-Earth Exporers (ISEE) and SWARM which each used three separate spacecraft. This method of analyzing the geomagnetic field cannot provide a spatial or time resolution smaller than that of the separation between magnetic field readings. This project has focused on producing a tabletop demonstra- tion of a compact sensor head which could enable measurements on unprecedented small scales. Toward this end we have accomplished the construction and preliminary testing of a compact sensor head which contains all necessary elements to function as a scalar atomic magnetometer.

An J=1→J=1 atomic system in Samarium with incident laser resonant radiation has been investigated. A linearly polarized laser at 686nm excites atoms from the level 4ƒ[superscript]66s[superscript]2 [superscript]7F[subscript]1 to a excited level 4ƒ[superscript]66s6p [superscript]9F[subscript]1 via the process of optical pumping. When an external magnetic field is applied to the atom-laser interaction and the decay fluorescence collected, a level-crossing profile appears. Theoretical predictions of the level-crossing profile can be made using spherically irreducible tensors to describe the density matrix which take advantage of the symmetry of the atomic system. By comparing theory with experimental data, a discussion is made of the various parameters and external factors that can affect this system, which show that Doppler broadening is the major influence. An additional investigation is made into the evolution of the J=1→J=1 atomic system with increasing laser exposure. Comparisons of the experimental data with theoretical predictions are made by analyzing the FWHM of the overall level-crossing profile, the FWHM of the dip about B = 0 and the relative depth of the dip. By charting the progress of these parameters with increasing laser exposure, it can be seen that the theory and experimental data agree qualitatively. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320338 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2008

Coherent nonlinear effects such as Electromagnetically Induced Transparency (EIT), Coherent Population Trapping (CPT), and Slow light are studied in thermal Rb vapor by both continuous and pulsed laser fields. This work primarily includes three parts: (I) mode-locked rubidium laser and its applications (II) enhanced coupling between optical and sound waves in the forward direction via ultra-slow light (III) optical steering via ultra-slow light in rubidium vapor. In part(I), I describe the construction and study of a mode-locked rubidium laser operating at the Rb D1 line using an active mode-locking technique inside the laser cavity. The mode-locked laser field is used to observe coherent effects in a dense rubidium gas. In part(II), I experimentally demonstrate enhanced acoustic-optic coupling that occurs when the velocity of sound is close to the group velocity of light. Dragging of the light by effective motion of the gas in a Rb cell is the origin of enhanced coupling. Good agreement between theory and experiment is found. In part(III), I experimentally demonstrate optical beam deflection in coherently driven rubidium vapor due to the steep refraction index profile in the region of EIT.

In this work, interference and coherence phenomena, appearing in atomic and molecular ensembles interacting with coherent light sources, as electromagnetically induced transparency (EIT), coherent population trapping (CPT), and slow group velocity of light are investigated. The goal of the project is to make the steps towards various applications of these phenomena, first, by studying them in solid media (which are the most advantageous for applications), second, by suggesting some novel applications such as CPT-based plasma diagnostics, and realization of new types of solid-state lasers (based on suppression of excited-state absorption via EIT). The third goal of the project is extension of coherence and interference effects well-known in optics to the gamma-ray range of frequencies and, correspondingly, from atomic to nuclear transitions. A particular technique of chirped pulse compression applied to M??ossbauer transitions is considered and the possibility of compression of M??ossbauer radiation into ultrashort gamma-ray pulses is analyzed. The theoretical treatment of the interference and coherence effects is based on the semiclassical description of atom-light interaction, which is sufficient for correct analysis of the phenomena considered here. Coherent media are considered in two-, three-, and four-level approximations while their interaction with light is studied both analytically and numerically using the Maxwell-Bloch set of equations.

Experimental and theoretical progress has been made toward the production and manipulation of novel atomic and molecular states. The design, construction and characterization of a driver for an acousto-optic modulator is presented which achieves a maximum diffraction efficiency of 54 % at 200 MHz, using a commercial modulator. A novel design is presented for a highly sensitive optical spectrum analyzer for displaying laser mode structure in real time. Utilizing programmable microcontrollers to read data from a CMOS image sensor illuminated by the diffraction pattern from a Fabry-Perot interferometer, this device can operate with beam powers as low as 3.3 micro-watts, at a fraction of the cost of equivalent products. Computational results are presented analyzing the behaviour of a model quantum system in the vicinity of an avoided crossing. The results are compared with calculations based on the Landau-Zener formula, with discussion of its limitations. Further computational work is focused on simulating expected conditions in the implementation of the STIRAP technique for coherent control of atoms and molecules in the beam experiment. The work presented provides tools to further the aim of producing large, mono-energetic populations of heavy Rydberg systems. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-10-03 17:17:56.841

Ce mémoire porte sur l’étude de la stabilité de fréquence d’une horloge atomique à piégeage cohérent de population. Le cadre de cette étude est d’une part d’approfondir la connaissance du piégeage cohérent de population en cellule de vapeur et d’autre part de construire un prototype d’horloge démontrant une stabilité de fréquence à l’état de l’art des meilleures horloges compactes de laboratoire. Grâce à une interrogation impulsionnelle et un schéma d’excitation en polarisations linéaires et orthogonales, cette horloge présenterait une stabilité de fréquence relative nettement inférieure à 10^-13 à 1 s si elle était limitée par un bruit fondamental tel que le bruit de photon. Après une présentation du montage expérimental, la première partie de ce mémoire est consacrée à l’étude des différentes sources de bruit limitant la stabilité de fréquence court-terme. Le soin particulier donné à la modélisation, à la caractérisation expérimentale et à la réduction des transferts de bruit de fréquence de l’oscillateur local (effet Dick) et du bruit d’intensité du laser en bruit de fréquence de l’horloge, a permis de mesurer une stabilité de fréquence au niveau de 3.2x10^-13 à 1 s. Dans un deuxième temps une étude théorique et expérimentale du déplacement de fréquence micro-onde en fonction de la puissance laser est présentée. Au-delà de la mise en évidence du caractère clé de la déformation de la raie dans l’explication de ce déplacement, elle a posé les bases de la dernière partie de ce mémoire qui propose une méthode d’insensibilisation du déplacement de fréquence aux fluctuations de puissance. / This report refers to the frequency stability study of a compact clock using coherent population trapping. The frame of such a study is firstly to deal in depth with the understanding of the systematic effects affecting the frequency of a coherent population trapping resonance. A second goal is to build a state-of-the-art compact atomic clock. Because of a pulsed interrogation and laser beams linearly and orthogonally polarized, our prototype would present a fractional frequency stability distinctly below 10^-13 at 1 s integration if it was shot-noise limited. Further to a setup description, the first part of this report is devoted to study the noise sources which limit the short-term stability of the clock. A special attention has been paid to model, experiment and reduce the transfer of local oscillator frequency noise and of laser intensity noise to microwave frequency noise. It led to measure an interesting stability measurement at the level of 3.2x10^-13 at 1 s. An experimental and theoretical study of the frequency shift due to laser intensity fluctuation is then presented. Beyond the influence on this shift of dark resonance overlapping that has been enlighted, this study gives the basics to understand the insensibilization method of the frequency to power fluctuations presented in the last chapter.

La combinaison du phénomène physique de piégeage cohérent de population (CPT), les techniques de micro-fabrication et les diodes laser à semi-conducteur permet le développement de micro-horloges atomiques présentant une stabilité relative de fréquence journalière 2 ordres de grandeur meilleure que celle des oscillateurs à quartz massivement utilisés pour un volume et une puissance de consommation similaires. Ces micro-horloges atomiques reposent sur l’interaction entre un module physique et une carte électronique pilotant l’horloge.Ce travail de thèse, co-encadré par le laboratoire FEMTO-ST et l’industriel Tronics Microsystems, soutenue activement par la DGA dans le cadre des projets DGA HABAC puis DGA EDAM, a eu pour but la conception, simulation thermique et magnétique, réalisation et caractérisation métrologique en horloge de modules physiques hautement miniaturisés, répondant aux contraintes et spécifications d’une micro-horloge industrielle pour applications stratégiques. Deux concepts de modules physiques ont été proposés, la différence essentielle étant le chemin lumineux.Le module physique intègre une diode laser VCSEL (vertical-cavity surface emitting laser), des éléments optiques pour le routage et la polarisation du faisceau lumineux, une microcellule à vapeur de césium diluée par une pression de gaz tampon (développée à FEMTO-ST et transférée industriellement à Tronics Microsystems), un photodétecteur et divers capteurs/actuateurs pour stabiliser la température d’éléments-clés. L’ensemble est inséré dans un cube de dimensions extérieures 15*15*13 cm3, lui-même entouré d’un solénoide pour appliquer un champ magnétique directeur et un blindage magnétique mu-métal. La consommation de ces modules physiques en régime permanent est de l’ordre de 250 mW à température ambiante.Ces modules physiques ont été testés à l’aide d’une électronique de laboratoire non intégrée. Des performances de stabilité relative de fréquence proches de l’état de l’art mondial, de l’ordre de 2,5.10-11 à 1 s et meilleures que 2 10-11 à 105 s, ont été démontrées en environnement calme. Pour l’aboutissement des performances ultimes sur la stabilité de fréquence d’horloge moyen et long terme (temps d’intégration supérieurs à 100-1000s) ont été mises en œuvre des techniques avancées, par le biais de deux boucles d’asservissement supplémentaires, visant à réduire drastiquement les effets de déplacement lumineux, eux-mêmes largement dépendants de la température extérieure et du bloc optique. Ces études ont aussi été associées à l’étude de la stabilité de l’atmosphère interne de microcellules, potentiellement limitée par des phénomènes de perméation de gaz tampon à travers le verre de la cellule. En ce sens, des tests de « vieillissement » préliminaires, menées sur 15-21 jours, ont été menés sur plusieurs microcellules, adoptant soit des verres de type borofloat, soit des verres de type alumino-sicilicaté (ASG). Dans le cas de microcellules Cs-Ne, ce phénomène de fuite est estimé pouvoir limiter la stabilité des micro-horloges atomiques à un niveau proche de 10-11 à 1 jour. Des tests, menés sur des cellules Cs-He, démontrent une réduction significative de presque 2 ordres de grandeur de ces phénomènes de fuite avec l’utilisation de verres alumino-silicatés (ASG). / The combination of coherent population trapping (CPT) physics, microfabrication techniques and semi-conductor diode lasers has allowed the development of miniature atomic clocks exhibiting a fractional frequency stability at 1 day averaging time up to 2 orders of magnitude better than massively-used quartz-crystal oscillators for a similar volume and power consumption. These miniature atomic clocks associate a fully-miniaturized physics package and an electronics card that drives the clock.This thesis, supervised by FEMTO-ST and Tronics Microsystems and actively supported by DGA in the frame of projects DGA HABAC and DGA EDAM, targeted to the design, thermal and magnetic simulation, development and metrological characterization in clock operation of fully-miniaturized physics packages. These physics packages have to respond to constraints and specifications of an industrial miniature atomic clock for strategic applications. Two designs of physics package have been proposed, the main difference between them being the optical path.The physics package integrates a VCSEL (vertical-cavity surface emitting laser) diode laser, optical components to route and polarize the laser beam, a buffer-gas filled Cs vapor microfabricated cell (developed in FEMTO-ST and industrially transferred to Tronics Microsystems), a photodetector and several sensors/actuators to stabilize the temperature of key elements. The ensemble is inserted into a 15*15*13 mm3 « cube », surrounded by a solenoid to apply a static magnetic field and a mu-metal magnetic shielding. The power consumption of the physics package is about 250 mW in the steady-state at room temperature.Physics packages have been tested in clock operation with a non-integrated laboratory-prototype electronics support. State-of-the-art clock fractional frequency stability performances at the level of 2.5 10-11 and 2 10-11 at 1 and 105 s averaging time respectively have been demonstrated in a quiet environment. In order to demonstrate best mid-term stability performances, advanced techniques have been implemented through two additional servo loops, aiming to reduce dramatically temperature-induced light-shift effects. Studies targeting to evaluate the stability of the microcell inner atmosphere, possibly limited by gas permeation effects through the cell windows, have been also performed. In that sense, preliminary “aging” tests, performed over 15-21 days measurements, have been investigated with different microcells, adopting borofloat glass or alumino-silicate glass (ASG). In the case of Cs-Ne microcells, this phenomenon is measured and estimated to limit the clock fractional frequency stability at a level o about 10-11 at 1 day. Other tests, led with Cs-He cells, have demonstrated a significant reduction by almost 2 orders of magnitude of these leakage phenomena using ASG wafers.

Ce travail de thèse effectué dans le cadre d’un contrat CIFRE-Défense porte sur l’étude des sources d’instabilité de fréquence d’une horloge atomique basée sur le piégeage cohérent de population. L’objectif est de démontrer une stabilité de fréquence d’horloge de l’ordre de 10-13 tau-1/2 jusque 10 000 s. Une cellule de vapeur de césium est utilisée avec un schéma d’excitation à fort contraste en utilisant des polarisations linéaires croisées et avec une interrogation impulsionnelle de type Ramsey. Un chapitre d’abord consacré aux sources de bruit à court terme présente les travaux réalisés pour réduire le bruit de phase et le bruit de puissance laser, limitant tous deux les performances de l’horloge à 1 s d’intégration. L’optimisation de la chaine micro-onde avec un nouvel oscillateur local, et la réalisation d’un asservissement de puissance performant ont permis d’améliorer la stabilité de fréquence à 2,3x10-13 à 1 s. L’analyse des fluctuations des paramètres de fonctionnement (puissance laser, champ magnétique, température, etc.) et la mesure de la fréquence d’horloge montrent que les variations de fréquence à moyen terme sont majoritairement limitées par les variations de puissance laser et celles du champ magnétique à 2x10-14 à 2 000 s. Ces analyses démontrent aussi que les fluctuations de puissance laser, malgré l’asservissement, sont liées aux fluctuations de polarisation via les fluctuations de température de l’expérience. Pour finir, les études d’un laser bifréquence et bipolarisation pour une horloge CPT compacte sont présentées, ouvrant la voie vers l’industrialisation en réduisant le banc optique. / This thesis work has been granted by a CIFRE-Défense contract to study the frequency stabilities of an atomic clock based on coherent population trapping. The objective is to demonstrate a frequency stability in the range of 10-13 tau-1/2 up to 10 000 s. A caesium vapour cell is used with a high-contrast excitation scheme using cross linear polarisations and a Ramsey interrogation. The short-term frequency stability is presented with the reduction of the phase and the laser power noise, both limiting clock performance at 1 s integration time. The optimisation of the microwave chain with a new local oscillator, and the implementation of a very low noise power lock loop have improved the frequency stability down to 2,3x10-13 at 1 s integration time. The fluctuations analysis of the operating parameters (laser intensity, magnetic field, temperature, etc.) and the measurement of the clock frequency show that the medium-term frequency instability is mostly limited by laser power and magnetic field fluctuations at the level of 2x10-14 at 2 000 s integration time. These analyses also show that laser power fluctuations, despite servo loop control, are related to polarisation fluctuations through temperature fluctuations inside the experiment isolation box. Finally, the studies of a dual-frequency and dual-polarisation laser for a compact CPT clock are presented, paving the way to industrialisation by reducing the optical bench.

Ce mémoire présente l'étude du déplacement collisionnel de la fréquence d'horloge du césium en présence du gaz tampon hélium ou xénon. L'introduction d'un gaz tampon dans les cellules à vapeur alcaline est nécessaire pour diminuer la largeur de raie de la résonance CPT par effet Dicke. Cependant, la présence de gaz tampon induit un déplacement quadratique de la fréquence d'horloge en fonction de la température de la cellule. Il est possible d'annuler la dépendance thermique du déplacement collisionnel en se plaçant à une température, dite d'inversion, déterminée par le ratio de gaz tampons introduits dans la cellule. Cette température est un point de fonctionnement de choix pour l'opération d'horloges atomiques miniatures et nécessite d'être de l'ordre de 90 voire 100 °C pour les applications à contraintes environnementales sévères. Nous avons mesuré les valeurs des coefficients de déplacement collisionnel de la fréquence d’horloge du césium en présence d’hélium et déterminé pour la première fois la valeur du coefficient quadratique en température. Concernant le xénon, les mesures des valeurs des coefficients de déplacement collisionnel sont incertaines en raison du caractère cubique non-attendu du déplacement collisionnel de la fréquence d’horloge du césium en présence de xénon. Ce comportement serait attribué à des interactions avec les molécules transitoires de van der Waals. Nous avons également établi qu'un mélange de gaz tampon néon-hélium permet d'obtenir des températures d'inversion supérieures à 80 °C. Des mesures dans des micro-cellules ont révélé des températures de l'ordre de 89 à 94 °C pour des mélanges à quelques pourcents d'hélium. / This thesis presents a study on collisional shift of cesium clock frequency in the presence of helium or xenon buffer gas. Introduction of buffer gas in alkaline vapour cells is necessary to narrow the CPT line-width by Dicke effect. Nevertheless, buffer gas induces a quadratic shift of the clock frequency versus temperature cell. Cancellation of collisional shift temperature dependence is possible at a so-called inversion temperature depending on the buffer gas ratio. This inversion temperature is great working point for micro atomic clocks. This temperature is required to be 90 or even 100 °C, especially to work in harsh environmental constraints. We measured collisional shift coefficients of cesium clock frequency in presence of helium buffer gas and we determined for the first time the value of the quadratic coefficient. About xenon buffer gas, the measurement of collisional shift coefficients is more difficult because of non-expected cubic behavior of collisional clock frequency shift which could be linked to the interaction with van der Waals molecules. We established that a neon-helium buffer gas mixture could allow an inversion temperature superior to more than 80 °C. Inversion temperatures from 89 to 94 °C are measured in cesium vapor microcells filled with a mixture containing a few percent of helium.

Submitted by Murilo Oliveira (murilo.oliveira@df.ufscar.br) on 2018-05-28T14:03:10Z No. of bitstreams: 1 MuriloOliveira_dissertacao.pdf: 3213764 bytes, checksum: eaf61f839f12dceed4b235ef7970e674 (MD5) / Rejected by Ronildo Prado (ri.bco@ufscar.br), reason: Oi Murilo, Faltou enviar a Carta comprovante assinada pelo orientador. Solicite o modelo em sua Secretaria de Pós-graduação, preencha e colete a assinatura com o orientador e acesse novamente o sistema para fazer o Upload. Fico no aguardo para finalizarmos o processo. Abraços Ronildo on 2018-06-04T17:58:14Z (GMT) / Submitted by Murilo Oliveira (murilo.oliveira@df.ufscar.br) on 2018-06-04T18:39:43Z No. of bitstreams: 2 MuriloOliveira_dissertacao.pdf: 3213764 bytes, checksum: eaf61f839f12dceed4b235ef7970e674 (MD5) IMG_20180604_0001.pdf: 522878 bytes, checksum: b7fa478fbcdf1b45955f8a02f8403af0 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-06-06T17:29:19Z (GMT) No. of bitstreams: 2 MuriloOliveira_dissertacao.pdf: 3213764 bytes, checksum: eaf61f839f12dceed4b235ef7970e674 (MD5) IMG_20180604_0001.pdf: 522878 bytes, checksum: b7fa478fbcdf1b45955f8a02f8403af0 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-06-06T17:32:09Z (GMT) No. of bitstreams: 2 MuriloOliveira_dissertacao.pdf: 3213764 bytes, checksum: eaf61f839f12dceed4b235ef7970e674 (MD5) IMG_20180604_0001.pdf: 522878 bytes, checksum: b7fa478fbcdf1b45955f8a02f8403af0 (MD5) / Made available in DSpace on 2018-06-06T17:32:18Z (GMT). No. of bitstreams: 2 MuriloOliveira_dissertacao.pdf: 3213764 bytes, checksum: eaf61f839f12dceed4b235ef7970e674 (MD5) IMG_20180604_0001.pdf: 522878 bytes, checksum: b7fa478fbcdf1b45955f8a02f8403af0 (MD5) Previous issue date: 2018-02-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / The aim of this work is to study the electromagnetically induced transparency (EIT) and the coherent population trapping (CPT) phenomena in three-level systems, such as atoms and quantum dot molecules (QDM). The present work can be basically divided into two parts. The first one focus on comparing and explaining the differences between the optical reponses of systems composed by atoms and QDM and on proposing a possible application in cavity linewidth narrowing. In the second part, we turn our attention to the study of controlable optical bistability in three-level systems in the regime of CPT, bringing new perspectives to the study of these bistable systems and some practical applications as well. / O presente trabalho de mestrado tem como objetivo estudar o fenômeno da transparência eletromagneticamente induzida (EIT) e do aprisionamento coerente de populações (CPT) em sistemas de três níveis, como átomos e moléculas de ponto quântico (QDM). Essa dissertação pode ser dividida basicamente em duas partes. A primeira se encarrega de comparar e explicar a origem das diferenças observadas na resposta óptica de sistemas compostos por átomos e sistemas compostos por QDM, bem como propor uma possível aplicação para o sistema de QDM no estreitamento da largura de linha de cavidades. Já a segunda parte consiste de um estudo da biestabilidade óptica controlável em sistemas de 3 de níveis no regime de CPT, trazendo novas perspectivas de estudo desses sistemas biestáveis e aplicações como sensores de pequenas flutuações de frequência ou de amplitudes de campos eletromagnéticos. / CNPq: 131392/2016-6