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A two channel system is used to study, simultaneously in two directions, the scattering of ruby laser light from a plasma jet. The experimental scattering spectrums compare well with theoretical predictions for scattering from an infinite homogeneous thermal plasma. The fluctuations in the integrated spectrums for the two directions are shown to be positively correlated, as well as to be too large to be accounted for by known sources of fluctuation. Changes in the plasma parameters, electron density and temperature, are ruled out as the source of the extra fluctuations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A transverse gas flow TEA C0₂ laser has been constructed and the use of a perforated hollow rod to serve simultaneously as the cathode of the discharge and the gas inlet vessel was successfully demonstrated. The electrical efficiency of the laser is typically 3% with peak powers of 40 kw being emitted on the P(20), P(18) and P(16) lines of the C0₂ spectrum. A parametric study of peak power, gas pressure, gas composition, time delay of the laser pulse and the interdependence of these quantities was undertaken. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The scattering of laser light by laboratory plasmas has been observed. When the scattering was from a plasma formed in a θ-pinch, with scattering angle of 90° , a nearly Gaussian profile of the scattered intensity as a function of wavelengths was observed, corresponding to scattering by non-interacting electrons. When the scattering was from a plasma jet, with scattering angle of 45° from the forward direction distinct satellite peaks were observed on both sides of a narrow central peak at the laser frequency as predicted by theory, 1,2,3,4 indicating a strong collective scattering effect between the electrons and the ions. The widths of the satellite lines were greater than the values predicted by theory. The discrepancy is ascribed to spatial variations in the electron density in the volume of the observed plasma. The intensities and frequencies at-which they occur these peaks also vary with the current of the plasma jet in a manner consistent with theory. The scattered intensity of the central peak was measured approximately and it agrees with theoretical prediction. Some indication of perturbation of the plasma by the incident laser light has also been observed. 1. E.E; Salpeter, Phys. Rev. 120, 1528(1960). 2. J.A. Fejer, Can. J. Phys. 38, 1114(1960). 3. J.P, Dougherty and D.T. Farley, Pro. Roy. Soc. (London) A259, 79(1960). 4. M.N. Rosenbluth and N. Rostoker, Phys. Fluids 5., 776(1962). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The enhancement of the scattered light signal due to the mixing of two optical beams in a plasma has been observed. The two beams are produced in a dual-cavity organic dye laser pumped by a Q-switched ruby laser. The plasma is generated by a Helium plasma jet. In normal scattering a distinct satellite is observed on either side of the incident ruby wavelength 6943Å. The presence of enhanced oscillations is demonstrated by a significant increase in the intensity of one of these satellites when the dye lasers are tuned such that the difference in their frequencies is equal to the normally-observed resonant frequency of the plasma. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Based upon the results reported by Balykin, V. S.r Letokhov, V. S., Mishen, V. I., and Semchishen, V. A., Chem. Phys., 17, 111 (1976), an attempt was made to shift the ortho-iodine to para-iodine ratio by (1) selectively predissociating the ortho-iodine molecules with the 5145 A argon ion laser line and (2) by reacting the selectively excited ortho molecules with the scavengers, 2-hexene, acetylene, nitric oxide, nitrosyl chloride, and ethyl iodide. In both cases the ortho to para ratio was monitored via the fluorescence induced by a scanning dye laser beam. Neither tactic prooved effective, in contradiction with the aforementionned authors. In the case of systems containing low pressures ' of iodine' vapour alone, time dependent differential quenching of the vibrational [mathematical formula omitted] transitions was observed attributed to outgasing of the test cells over the course of the experiment and may be the cause of the apparant shift claimed by Letokhov et al. In mixtures of iodine and scavenger, the null result was probably due to the formation of radical chains during the photo-induced reactions capable of rapidly relaxing any shift that had occurred. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The output from a ruby laser was homogenized, and used to laser anneal the active layer of GaA1As double heterostructure wafers in an attempt to improve the radiative efficiency of the active layer. At anneal energies exceeding the estimated threshold for melting of the active layer, the radiative efficiency was reduced by a factor of two. Subsequently, semiconductor laser diodes fabricated from laser annealed heterostructures performed much worse than those fabricated from unannealed heterostructures. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A Z-pinch plasma, suitable for the study of C0₂ laser-plasma interaction mechanisims, is thoroughly diagnosed using a number of non-perturbing, optical probe techniques. Simple streak and shadow methods give an important preliminary view of the spatial distribution and radial dynamics of plasma during the high compression phase. The electron density and temperature are determined as a function of time by spectrally resolving the ion feature of Thomson scattered ruby laser light. Peak electron densities well in excess of 1 x 10¹⁹ cm⁻³ and temperatures near 50 eV are observed. Complementing the scattering results, holographic interferometry is performed to examine both the temporal and spatial variation of electron density. The diagnostics used are well suited to the examination of moderately dense, hot plasma and have been developed specifically for application in our laser-plasma interaction studies. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Orientador: Mauro Antonio de Arruda Nobilo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-03T16:12:59Z (GMT). No. of bitstreams: 1 Silva_TatianaBernardon_M.pdf: 793567 bytes, checksum: 4eee295ab77444b217d4ff56677aa193 (MD5) Previous issue date: 2003 / Mestrado