Browsing by Subject "Laser spectroscopy"
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Item Laser/microstructure interaction and ultrafast heat transfer(2006) Heltzel, Alexander John; Howell, John R.The industrial demand for smaller structures required for the manufacture of quantum devices, high-density recording media, etc., have resulted in the need for fabrication technology at the nanometer scale. However, most lithography and milling techniques are limited either by their inability for large-area fabrication or by the diffraction limit and in most cases the high manufacturing costs. To overcome the diffraction limit and to spatially-control matter on a nanometer scale, near-field optics techniques have been employed. It has been shown that laser/microstructure interaction can create surface modifications below the diffraction limit in both localized and parallel fashions. This dissertation investigates laser/microstructure interaction using both numerical and analytical tools for computation. Two fundamental problems required for predictive optical nanolithography are addressed: the electrodynamic response of the laser energy in the vicinity of micro/nanostructures, and the resulting energy transport through the target material. The dissertation first concentrates on the interaction between lasers and dielectric microspheres. Analytical solutions provided by near-field Mie theory and numerical solutions to Maxwell’s equations are obtained. Three-dimensional electromagnetic fields are resolved in the near-field of these spheres and functional dependencies on several experimental parameters are uncovered. Energy transport through the substrate is modeled numerically in both two and three dimensions using conventional conduction formulae and ultrafast electron density evolution for the case of femtosecond pulse irradiation. The combined electrodynamic/heat transfer solutions generate final lithographic predictions which are compared to experimental characterizations. The final segment of this dissertation investigates the interaction between lasers and gold, silver, and carbon nanotube structures for the purposes of optical lithography and photonic signal propagation. Fundamentals of surface plasmons, coupled electron/photon waves at conductor/dielectric interfaces, are explored computationally. Practical lithographic and photonic applications are optimized theoretically in an effort to advance knowledge in this area.Item Methane detection by He-Ne laser for oil and natural gas prospecting(Texas Tech University, 1984-05) Jordan, Kevin JamesSurface geochemistry studies are valuable methods of petroleum prospecting. Atmospheric methane surveys can outline those areas where detailed geochemical studies need to be conducted. This report describes a field device capable of measuring small changes in methane concentration in the near surface atmosphere. Methane concentration is determined by measuring the attenuation of the 3.3922y He-Ne line in a pressurized gas flow cell due to absorption by methane. A second He-Ne laser line at 3.3912 p, which is only weakly absorbed by methane, is used as a reference signal to compensate for laser intensity fluctuations and scattering by water and dust. This system s fast, allowing measurements to be made from a moving vehicle- Also, the system allows for continuous sampling of the changing methane concentration as opposed to point measurements.Item Nonlinear optical spectroscopy of silicon-boron and other silicon-adsorbate systems(2001-08) Lim, Daeyoung; Downer, Michael CoffinItem Precision absolute frequency laser spectroscopy of argon II in parallel and antiparallel geometry using a frequency comb for calibration(2010-01-14) Lioubimov, VladimirA collinear fast ion beam laser apparatus was constructed and tested. It will be used on-line to the SLOW RI radioactive beam facility in RIKEN (Japan) and as in the present experiment for precision absolute frequency measurements of astrophysically important reference lines. In the current work we conducted absolute measurements of spectral lines of Ar ions using parallel and antiparallel geometries. To provide a reference for the laser wavelength iodine saturation spectroscopy was used. The precision of this reference was enhanced by simultaneously observing the beat node between the spectroscopy laser and the corresponding mode of a femtosecond laser frequency comb. When performing collinear and anticollinear measurements simultaneously for the laser induced fluorescence, the exact relativistic formula for the transition frequency v0 = pvcoll ? vanticoll can be applied. In this geometry ion source instabilities due to pressure and anode voltage fluctuation are minimized. The procedure of fluorescence lineshapes fitting is discussed and the errors in the measurements are estimated. The result is v0 = 485, 573, 619.7 ? 0.3MHz corresponding to (delta v)/v = 6 ? 10?10 and is an improvement of two orders of magnitude over the NIST published value.Item Time resolved fluorescence spectroscopy with a fast analog technique: applications to microscopic specimens(Texas Tech University, 1987-05) Pleil, Matthias W.Not available