LASERS

Author: RESTREPO MONTOYA JOSE WILLIAM.
Year: 2005.
University: BARCELONA [www.ub.es].
Place of defense: UNIVERSITAT DE BARCELONA.
Place of preparation: UNIVERSITAT DE BARCELONA.

Summary: This paper aims at studying the procedures set by vitrification ceramic tiles and enamel color on white tiles, through irradiation with a laser Nd: YAG, with the goal of obtaining sustainable patterns with a noticeable visual quality. In addition, it seeks to understand the mechanisms involved in these processes and learn how to influence the parameters marked on the characteristics of the patterns obtained. The lines and the areas marked with laser ceramic stoneware are comprised of a phase vitreous green is the result of the merger and subsequent consolidation of ceramic components. The tone green lines increases with the hematite content of the ceramics. Precalentando ceramics to 350C is achieved marked lines and areas of good visual quality. The study dimensional lines marked reveals that the volume per unit length of vitrified material is controlled by the energy density, but the width and depth of the lines depends on each particular combination of power and speed dial. The low visual contrast of the lines marked in ceramics cream can be improved by providing hematite to the surface before making markings. In the process of enamel, the enamel surface of the tiles were coated with a layer colored varnish before making marking laser. The sharp lines are formed by a vibriado created by the merger and subsequent solidification of varnish deposited and enamel substrate. The coatings colored with pigment blue, black and green presents a good response to radiation from laser Nd: YAG (= 1064nm), which enables the realization of graphics enamel laser patterns in these colors. It is possible to get different shades of these colors by varying the parameters of laser technology and / or varying the composition and thickness of coatings deposited. With yellow and red pigments only get dial lines with soft colors, because of their low absorption of the laser radiation and / or during the decomposition process.

Author: RAMIREZ HERRERO MARIA DE LA O.
Year: 2005.
University: AUTÓNOMA DE MADRID [www.uam.es].
Place of defense: UNIVERSIDAD AUTONOMA DE MADRID.
Place of preparation: DPTO. FISICA DE MATERIALES, FACULTAD DE CIENCIAS, UNIVERSIDAD AUTONOAMADE MADRID.

Summary: This work includes the study of two systems ferroeléctricos: Niobato Lithium (LiNbO3) and Niobato of Barium and Strontium (SrxBa1-xNb2O6) doped with different ions best assets, both from the point of view as essential from the point sight applied, in order to extend their potential applications such as optical devices multifunctional profit. The first part of the report is devoted to system Yb3 +: LiNbO3. From the fundamental point of view, have addressed the following points: the origin of the transitions intraconfiguracionales 4f 13 (which include the transition laser), the presence of biestabilidad optics inherent in the stimulated emission ion Yb3 + in LiNbO3 and determining the intrinsic quantum efficiency throughout the range of concentrations laser. Given the importance of radiative mechanisms energizing the state 2F5 / 2 ion Yb3 + in laser applications, we have made use of the technique under high pressure spectroscopy to analyze the probability of energizing radiative transitions intraconfiguracionales 4f - 4f ion Yb3 + in LiNbO3. Moreover, it has been demonstrated for the first time and simultaneously, the presence of biestabilidad optics inherent in the stimulated emission of ions Yb3 + in LiNbO3 in the visible and infrared regions of the spectrum. Finally, we analyzed the different rates of warming on a spontaneous and stimulated as well as the influence of reabsorption, to conclude that blocking the luminescence in our system, it is not active in the concentration range laser. From the point of view more applied, it has demonstrated the ability to get action under pumping with efficient laser diode laser in the visible and infrared regions of the electromagnetic spectrum to achieving efficiencies laser more than 70%. In addition, radiation was tuned obtained both in the infrared region (56 nm) and in the visible region (20 nm). The second part of the report is devoted to Niobato of Barium and Strontium (SrxBa1-xNb2O6), commonly known as SBN. From the fundamental point of view, this system has a lot of interest due mainly to its low temperature transition and thermal hysteresis presented during the transition. These intrinsic properties of the matrix enabled us to follow the evolution of a structural transition phase through the use of optical probes. Likewise, since the thermal hysteresis of the material was studied the presence of biestabilidad optics both in the issuance of doping ions in the second harmonic generation. The results were analyzed considering the redistribution respect to the plane of symmetry of the various network sites during the transition ferro-paraeléctrica. From the point of view more applied, it has demonstrated the ability to generate laser action and autodoblado frequency of a stable before, during and after the transition phase ferro-paraeléctrica in SBN. In addition, the high structural disorder which presents the matrix together with the appropriate design of a cavity laser sintonizable allowed to obtain laser radiation multifrequency sintonizable under diode pumping with the system Nd3 +: SBN, revealing for the first time the possibility to tune the infrared radiation and visible in a range exceptionally high for an ion laser as the Nd3 + (43 nm in the infrared region, 20 nm in the region green and 7 nm in the blue region). In short, this paper has demonstrated the ability of systems SBN and LiNbO3 to act as a multifunctional optical devices, since both can be generated in a single 8 emento l 366 as functions: i) Generating action under laser pumping with diode ii) Process conversion frequencies iii) Sintonizabilidad of coherent radiation in various spectral ranges iv) Biestabilidad Optics

Author: POLO QUEROL VICTOR.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: AULA 116-EDIFICI D-5.CN.
Place of preparation: D3 111 Nord.

Author: REBOLLAR GONZÁLEZ ESTHER.
Year: 2005.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS QUÍMICAS.
Place of preparation: INSTITUTO DE QUÍMICA FÍSICA ROCASOLANO.

Summary: The influence of molecular weight (PM) in the mechanisms operating in the laser ablation of polymers has rarely been seen despite the fact that this parameter determines many of the properties of these substrates such as transition temperature, viscosity or the mechanical properties . This paper presents the results of a study to elucidate the effect of the size of the polymer chain in the laser ablation of excímero to 248 nm of two polymers, polimetilmetacrilato, PMMA (1.9, 2.5, 120 and 996 kDa) and polystyrene , PS (15.1, 280 and 532 kDa) doped with compounds photochemistry well known yodonaftaleno (Napl) and yodofenantreno (Phenl). For this purpose were discussed processes induced in the substrate after ablation and properties of the pen ablation of the films mentioned polymers doped using a set of techniques espectroscópias and analytical. For monitoring of the processes induced in the film after ablation was used and an outline of pumping test in which detects the formation of fotoproductos using laser-induced fluorescence (IBF). The chemical changes induced in the substrate were also studied by spectroscopy micro-Raman. The morphological changes induced by laser irradiation were examined by optical microscopy. Para investigar la escala de tiempos en la que ocurren estos cambios, se midió en tiempo real la transmisión por el substrato y por la pluma de ablación de un láser de prueba continuo de HeNe. The distribution of translational product ArH in the pen ablation was measured in vacuum through FIL using the fourth harmonic of a laser Nd: YAG laser as evidence. The results illustrate the profound effect of PM and the absorption coefficient of polymer on the ablation process. The polymer is obtained greater PM higher performance and speed of formation of the product ArH and higher yields training product type Ar2. The kinetic studies show that the difference in the formation of products is linked to the evolution of temperature on the substrate. The results can be explained by a model fototérmico volume (Bulk Photothermal model) according to which the ejection of material occurs when fragments a number of critical links. The study of the various PM allows examine the involvement of an explosive boiling process (Explosive Boiling); such participation is higher for the polymer PM higher. It also considered ablation of polymers doped with a laser hybrid excímero-colorante operating at 248 nm with pulse duration of 500fs. The results, following the observation of the substrate after irradiation by FIL spectroscopy micro-Raman and optical microscopy, showed no influence of polymer PM. In addition to the above studies on the processes and mechanisms of ablation UV polymer, in this thesis deals with an application of the laser ablation doped polymer. Manufacturing has been studied by pulsed laser deposition (PLD) of thin layers of materials polímerocos for the development of environmental sensors. For these experiments polymers are doparon with fluorescent probes that can act as sensors presence in the environment of harmful pollutants (volatile organic acids). The probes are employed aromatic amino species and dendrímeros derived from these compounds, which have proven to be sensitive to changes in solution pH, viscosity and polarity, increasing its emission of fluorescence and / or changing the position of its maximum band emission. The characteristics of deposits (morphological and chemical composition) are heavily dependent on the wavelength and pulse duration of the laser used in the irradiation of whites and gracious composition thereof. The analysis revealed the transfer to the polymer substrate and the probe.

Author: BLASCO LOPEZ ANTONIO JOSE.
Year: 2005.
University: SALAMANCA [www.usal.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This thesis deals with the study of the interaction of a very intense laser (intensities higher than the atomic unit) with a plasma. The study was conducted using the numerical simulation using the CIP (Particle in Cell) as a basic tool. This code consists of group electrons in a convenient and make them behave as if they were a single particle. The code consists of three parts: the integration of the Maxwell equations, movement of charged particles and calculation of the flow. Another important point is the debate about whether the PIC code performs well in a conventional scenario. To check this point were simulations were compared with the theoretical case. A further chapter deals with the case of a charged particle in interaction with a laser paying special attention to the radiation from such interaction, in particular the temporary forms of radiation in the directions of maximum emission is observed. It analyzes the pulses are obtained and that provides an explanation for its shape and origin. It also deals with the study of the influence of the ultra phase of a pulse on the interaction of that pulse with a sheet plasma. It uses a one-dimensional simulation and concluded that the phase plays an important role in this interaction. It is also advised what type of pulse should be used for a variety of harmonics sharper. The latest chapter includes the study of the interaction of a pair of laser beams cross on a sheet of plasma in a two-dimensional scene. Such interaction appears to be stationary wave that creates a force on the surface of the plasma electrons that attracts points towards stable balance. It discusses various cases under different intensities and is a study of the temporal evolution of the structures obtained.