Thesis (Ph.D.) - University of St Andrews, June 2007.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2005. / Includes bibliographical references (leaves 20-24).

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 114-119). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018. / This research investigates the absorption spectra of rubidium and the feedback control of an external cavity diode laser. This research is a necessary prerequisite for laser (Doppler) cooling and trapping of rubidium atoms. Cooling rubidium atoms down to such low temperatures can be achieved using the Doppler cooling technique. Here a laser is tuned to remain resonant with a speci c atomic transition. To do this, the absorption spectra of rubidium must therefore be observed. All of the above require a reasonable knowledge about topics such as atomic physics, laser cooling and trapping, feedback control systems, and absorption spectroscopy. A discussion of these topics is provided. We have utilised an experimental setup which allowed for measurements of the Doppler broadened and Doppler free absorption spectra of rubidium, as well the analysis of the Zeeman e ect on the Doppler free spectra. The setup consisted of a saturated absorption spectrometer for high resolution spectroscopy and a Michelson interferometer for calibrating our measurements. In analysing the Zeeman e ect we added a set of Helmholtz coils to the saturated absorption spectroscopy arrangement to measure the splitting of the hyper ne energy levels. / French South African Institute of Technology (F'SATI) National Research Foundation

No description available.

Thesis (MSc (Physics))--University of Stellenbosch, 2009. / In the presented study a diode laser was characterised and used for spec- troscopy, measuring the resonance lines of atomic rubidium. The characteristics of diode lasers and external cavity diode lasers (ECDL) for the purposes of ab- sorption spectroscopy were investigated and an experimental setup for tunable diode laser spectroscopy using an ECDL was developed. In external cavity diode lasers, the advantages of low cost, small size and e ciency of a diode laser is combined with tunability and a narrow frequency bandwidth. The ECDL was applied in experimental setups for absorption spectroscopy and saturated ab- sorption spectroscopy. Measurement of the absorption of atomic rubidium's D2 line near 780 nm is discussed. The Doppler broadened, as well as the Doppler free spectrum of the ne and hyper ne structure of the D2 line were measured and is discussed. Finer control of the ECDL's stability and frequency, using a servo circuit, were investigated and tested. An overview is given of laser cool- ing and trapping of neutral rubidium atoms, which is the main application the ECDL were developed for.

Thesis (MSc)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: A Magneto Optical Trap (MOT) is a configuration formed by three orthogonal pairs of counterpropagating circularly polarized laser beams and a magnetic field gradient. A MOT is used to cool, capture and trap large numbers of atoms in vacuum at very low temperature in K range. In this thesis the development of an experimental setup for realising a MOT of 87Rb atoms is presented. The atomic structure of Rb and the theoretical background of laser cooling and magneto optical trapping was reviewed. The influence of rubidium background pressure in the vacuum system, the laser beam size and the power and frequency on the number of the trapped atoms were studied in literature. The trapping and repumping lasers were characterised experimentally. Six circularly polarised trapping beams with equal power were formed and properly aligned to intersect at the center of the trapping cell. Two optical setups were designed and exploited to investigate and optimise the trapping beam polarisation. The repumping laser beam was successfully aligned and colinearly combined into all the trapping beams. Three different experimental setups for saturated absorption spectroscopy were developed. Saturated absorption spectra showing the hyperfine structure of both 85Rb and 87Rb isotopes were measured and are discussed. Using two saturated absorption spectroscopy setups, the frequencies of both lasers were successfully locked to the trapping and repumping transitions of 87Rb respectively. A rectangular trapping cell was designed and attached to the vacuum system. A pressure of about 10­¯7 mbar was achieved. The magnetic field coils were characterised and affixed on both sides of the cell in an anti-Helmholtz configuration. Setups for imaging and quantification of the 87Rb atoms in the MOT were designed. Finally, the procedures for demonstrating a MOT are presented. In conclusion, the current status of the project is reported, with recommendations for the future work. / AFRIKAANSE OPSOMMING: ’n Magneto optiese val (Magneto Optical Trap, MOT) is ’n konfigurasie wat gevorm word deur drie ortogonale laserbundelpare, wat elk uit twee sirkelvormig gepolariseerde bundels met teenoorgestelde voortplantingsrigtings bestaan, en ’n magneetveld gradient. ’n MOT word gebruik om ’n groot aantal atome af te koel, te vang en vas te hou in vakuum by ’n baie lae temperatuur in die K bereik. In hierdie tesis word die ontwikkeling van ’n eksperimentele optelling vir die realisering van ’n MOT van 87Rb atome voorgelê. Die atoomstruktuur van Rb en die teoretiese agtergrond van laser afkoeling en ’n magneto optiese val is hersien. Die invloed van die rubidium agtergronddruk in die vakuumstelsel, die grootte van die laserbundels en die laser drywing en frekwensie op die aantal gevangde atome is bestudeer uit die literatuur. Die MOT-laser en die optiese pomplaser is eksperimenteel gekarakteriseer. Ses sirkelvormig gepolariseerde MOT-laserbundels met gelyke drywings is gevorm en behoorlik belyn om in die middel van die MOT-sel te kruis. Twee optiese opstellings is ontwerp en gebruik om die polarisasie van die MOT-laserbundels te ondersoek en te optimeer. Die optiese pomplaserbundel is suksesvol belyn en ko-liniêr ekombineer met al die MOT-laserbundels. Drie verskillende eksperimentele opstellings vir versadigde absorpsie spektroskopie is ontwikkel. Versadigde absorpsie spektra wat die hiperfyn struktuur van beide die 85Rb en 87Rb isotope toon is gemeet en bespreek. Deur twee versadigde absorpsie spektroskopie opstellings te gebruik is die frekwensies van beide lasers suksesvol gestabiliseer op die MOT- en optiese pomp-oorgange van 87Rb onderskeidelik. ’n Reghoekige MOT-sel is ontwerp en aangesluit by die vakuumstelsel. ’n Druk van ongeveer 10­¯7 mbar is bereik. Die magneetveld spoele is gekarakteriseer en weerskante van die sel gemonteer in ’n anti-Helmholtz konfigurasie. Ten einde word die prosedures vir die demonstrasie van ’n MOT voorgelê. In die gevolgtrekking word daar verslag gedoen oor die status van die projek, met aanbevelings vir toekomstige werk.

In this thesis I describe experimental work and present data on the guiding of Rubidium atoms along free-space propagating light beams as well as within hollow core glass fibres, namely photonic crystal fibres. I describe experiments, laser systems and vacuum trap assemblies designed to facilitate this guiding. These experiments are intended to aid progression within the field of cold atom guidance wherein narrow diameter, long distance hollow-fibre guides are a current goal. Realisation of these guides could lead to promising applications such as atom interferometers and spatially accurate, multi-source, atom depositors. Herein, guided fluxes are observed in free-space guiding experiments for distances up to 50mm and up to 10GHz red-detuning from resonance. Additionally hollow-core, Kagome structured, quasi- and true-photonic crystal fibres are characterised. Finally a number of detailed fibre-guiding magneto-optic traps are developed. Both cold atomic-beams and cold atomic clouds are reliably positioned above fibre entrance facets in conjunction with a guiding laser beam coupled into the fibre core. Issues regarding optical flux detection outwith fibre confinement appear to have hindered observation of guided atoms. A far more sensitive detection system has been developed for use in current, ongoing fibre-guide experiments.

Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.

We present a novel method of in situ magnetic field mapping related to the Hanle effect. This method uses the change in spatial radiation pattern of scattered light, which we call a 'directional Hanle effect,' rather than the loss of polarization more commonly associated with the Hanle effect. It is particularly well suited for fields in a magneto-optical trap (MOT), requiring only the addition of a narrow slit and a camera to typical MOT components. The use of this method is demonstrated by measuring the gradient through, and location of, the zero-point of the field in our strontium MOT.