laser, femtosecond, ultra-fast, shockwaves, self-channeling, filamentation, EMP, ablation
To our knowledge this is the first comprehensive study of laser-induced effects generated at intermediate distances using self-channeled femtosecond laser pulses. Studies performed were made both experimentally and theoretically with the use of novel modeling techniques. Peak laser pulse powers above 3 GW allow beam propagation without divergence for up to several kilometers. In this regime, 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/[Lambda] for vacuum focusing and 25 V/m/[Lambda] 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. It was found that the interaction conditions control the formation and propagation of the shock fronts into the medium. Due to the processes involved in self-channeling, significant fractions of the laser pulse were coupled 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.
Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical Engineering and Computer Science
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Bernath, Robert Thomas, "High-intensity Ultra-fast Laser Interaction Technologies" (2007). Electronic Theses and Dissertations. 3084.