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This thesis describes the development of a laser-cooling experiment aimed at efficient transfer of cold atoms over a short distance, for loading into a conservative atom trap. We detail the construction of a 3D magneto-optical trap (MOT) and perform characterisation measurements to optimise the number and temperature of the cold atoms. The atoms are launched vertically in a fountain from the MOT using a 'moving molasses' technique and a red-detuned far-off-resonant laser beam is used to guide them into an UHV chamber. Loading into the guiding beam is optimised with respect to the beam and MOT parameters. We demonstrate a maximum loading of 20% and guiding over a distance of more than 10 cm without loss of atoms. The atoms are delivered to the UHV chamber in a cloud with a transverse dimension of order 200 µm. We discuss the extension to continuous operation of the guided atomic fountain. The 3D MOT is replaced by a funnel with 2D trapping and 3D cooling which continuously extracts the cold atoms using moving molasses. A comparison between the flux of guided atoms obtained in a pulsed fashion from the 3D MOT and continuously from the funnel indicate that the pulsed case is a factor of ten more efficient. The difference is due to inferior loading from the funnel. The optically guided fountain is used to load an optical dipole trap in the UHV chamber, using an 'optical trap door'. No additional cooling is required. The dynamics of the atoms in the optical dipole trap are studied. We discuss multiple loading of a conservative trap with the view of accumulating more atoms than can be obtained in a MOT.

Nestes últimos anos, tivemos um aumento no interesse na monitoração dos efeitos da atividade humana sobre a atmosfera e o clima no planeta. O uso de técnicas de sensoriamento remoto têm sido utilizados em diversos estudos, inclusive em estudos relacionados à mudanças globais. Um sistema LIDAR de espalhamento, primeiro deste tipo no Brasil, tem sido usado para fornecer o perfil vertical do coeficiente de retroespalhamento de aerossóis em 532 nm para altitudes de 4 a 6 km acima do nível do mar. Neste estudo, foram utilizados dados coletados no ano de 2005. Estes dados foram correlacionados com dados do fotômetro solar CIMEL e também com dados meteorológicos. Os principais resultados indicaram existir um padrão no comportamento destes dados meteorológicos e a distribuição vertical do coeficiente de extinção obtido através do LIDAR. Em períodos desfavoráveis de dispersão atmosférica, ou seja, elevação da temperatura do ar associado a queda de umidade relativa, aumento da pressão atmosférica e baixa taxa de ventilação, foi possível determinar com boa precisão a altura da Camada Limite Planetária, tanto através do perfil vertical do coeficiente de extinção quanto através da técnica da temperatura potencial. A técnica LIDAR mostrou ser um importante aliado na determinação da estrutura termodinâmica da atmosfera, auxiliando a caracterizar a evolução da CLP ao longo do dia, devido a sua boa resolução espacial e temporal. / In these last years, we had an increase in the interest in the monitoring of the effect of the human activity being on the atmosphere and the climate in the planet. The remote sensing techniques has been used in many studies, also related the global changes. A backscattering lidar system, the first of this kind in Brazil, has been used to provide the vertical profile of the aerosol backscatter coefficient at 532 nm up to an altitude of 4-6 km above sea level. In this study, data has was collected in the year of 2005. These data had been correlated with data of solar photometer CIMEL and also with meteorological data. The main results had indicated to exist a standard in the behavior of these meteorological data and the vertical distribution of the extinction coefficient gotten through LIDAR. In favorable periods of atmospheric dispersion, that is, rise of the temperature of associated air the fall of relative humidity, increase of the atmospheric pressure and low ventilation tax, was possible to determine with good precision the height of the Planetary Boundary Layer, as much through the vertical profile of the extinction coefficient how much through the technique of the vertical profile of the potential temperature. The technique LIDAR showed to be an important tool in the determination of the thermodynamic structure of the atmosphere, assisting to characterize the evolution of the CLP throughout the day, which had its good space and secular resolution.

In the current PhD thesis a thorough study is performed on the design, fabrication and analysis of microstructures created by use of laser methods. The work comprises the design and fabrication of organic, inorganic and hybrid microstructures for use in photonics applications. In addition, several techniques are applied for the fabrication and replication of photonic diffractive microstructures. Fabricated structures are tested as potential functional photonic sensors for humidity, ammonia and temperature detection. Furthermore, a detailed study on polymer-based microstructures creation by laser radiation forces is attempted both theoretically and experimentally. The created 2D and 3D free-standing micro/nanostructures are optically characterized. / Στην παρούσα διδακτορική διατριβή παρουσιάζεται μια ενδελεχής μελέτη στην σχεδίαση, κατασκευή και ανάλυση μικροδομών που δημιουργούνται με τη χρήση δέσμης λέιζερ. Η εργασία περιλαμβάνει τον σχεδιασμό και την κατασκευή οργανικών, ανόργανων και υβριδικών μικροδομών για χρήση τους σε εφαρμογές φωτονικής. Επιπρόσθετα, εφαρμόζονται διάφορες τεχνικές για την κατασκευή και αναπαραγωγή φωτονικών περιθλαστικών μικροδομών. Οι δομές ελέγχονται ως λειτουργικοί φωτονικοί αισθητήρες για την ανίχνευση υγρασίας, αμμωνίας και θερμοκρασίας. Ακόμα, πραγματοποιείται μια λεπτομερής μελέτη πάνω στη δημιουργία μικροδομών βασισμένων σε πολυμερή με χρήση δυνάμεων ακτινοβολίας λέιζερ τόσο σε θεωρητικό όσο και σε πειραματικό επίπεδο. Οι δημιουργούμενες δισδιάστατες και τρισδιάστατες μικρο/νανοδομές ελεύθερου χώρου χαρακτηρίζονται οπτικά.

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Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) is a powerful analytical technique for the direct elemental analysis of solid samples, with spatial resolution down to a few microns However, calibration remains the limiting factor in obtaining quantitative analysis by LA-ICP-MS for a wide range of sample types. No universal method exists as yet and the ones that are currently used tend to employ matrix-matched solid standards Matrix-matched solid standards are not available for many types of sample, such as polymers, biological materials, fluid inclusions, etc The need for a universal method of calibration that involves standards that are easy to prepare and suitable for any type of sample is required. Additional to matrix-matching, internal standards are widely used in LA-ICP-MS for quantitative analyses The internal standard compensates for the different ablation yields from the sample and the standard and for the laser shot to shot variation. Given that the use of an internal standard is required to obtain reliable results, the need for matrix-matching might be regarded as questionable This project has focused on the development and application of a new method of calibration for LA-ICP-MS. It involves the use of aqueous standards whose absorption characteristics are modified by the addition of a chromophore to the solution. Additives were selected for ablation with KrF excimer, and Nd.YAG lasers The influence of the additive concentration on the ablation yield was investigated for different laser energies. Response curves were obtained showing that as the additive concentration was increased, less energy was required to ablate the modified standard solutions efficiently. A general procedure was then defined for the preparation and use of the modified standard solutions for a given sample. The new method of calibration was used for the quantitative analysis of different sample types· low density polyethylene (LDPE), polyketone (PK), polyethylene thin film as well as gels contained in the thin film, and stainless steel. Investigations were carried out on the mechanism of ablation of the modified standard solutions. It appeared that the ablation proceeded by a three-step process leading ultimately to nebulisation of the bulk liquid.