 Announcing the Final Examination of Mr. Robert Bernath for the degree of Doctor of Philosophy in Electrical EngineeringDate: Nov 9, 2007 A detailed study of laser-induced effects generated at distance using self-channeled femtosecond laser pulses was made both experimentally and with novel modeling techniques. Peak laser pulse powers above 3 GW allow beam propagation without divergence up to several kilometers. Using this process, experiments were performed at 30 meters from the laser system in a custom propagation and target range, utilizing the Laser Plasma Laboratory’s Terawatt laser system. Experiments included investigations of laser ablation; electromagnetic pulsed (EMP) radiation generation over the 1-18 GHz region; shockwave formation in air and solid media; optical coupling of channeled pulses into transparent media; and, conservation of energy in these interactions. The use of bursts of femtosecond pulses was found to increase the ablation rate significantly over single-pulse ablation in both air and vacuum. EMP generation from near-field focused and distance-propagated pulses was investigated. Field strengths upwards of 400 V/m/λ for vacuum focusing and 25 V/m/λ for self-channeled pulses were observed. The total field strengths over 1-18 GHz measured at distance surpassed 12 kV/m. Shockwaves generated in transparent media at 30 meters were observed as a function of time. Due to the processes involved in self-channeling, significant portions of the laser pulse were able to couple into the target materials, resulting in internal optical and exit-surface damage. Basic estimations on the conservation of energy in the interaction are presented. The results of the experiments are supported by hydrodynamic plasma physics code and acoustic modeling. The interaction characteristics and effects for self-channeled femtosecond laser pulses were proposed and observed for the first time in this research. Major: Electrical Engineering Educational Career: Committee in Charge: Approved for distribution by Martin Richardson, Committee Chair, on October 29, 2007. The public is welcome to attend.
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