26 May 2006 Shock-wave generation in transparent media from ultra-fast lasers
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Laser interactions with bulk transparent media have long been investigated for material processing applications involving ablation and shock wave generation in both the nanosecond and femtosecond pulse width regimes1. Shock waves have been studied in fused silica and other optical glasses but previously have been characterized by the morphology of the concurrent ablation. We perform ablation at distances of 30 meters using the non-linear self-channeling effect. Using silicon wafers as targets because of their clearly defined ablation zones, we examine the effect that the filament has on the thin SiO2 layer coating the wafer's surface. It is observed that the surface layer experiences a shock wave resulting from the explosive forces produced by the plasma. The use of several laser pulses in burst mode operation leads to the observation of multiple shock fronts in the material, and the possibility of shock wave addition for higher damage. Optical interferometry will be used to characterize the shock wave dynamics, using both traditional means of focusing in the near field and at 30 meters using propagating self-channeled femtosecond pulses. The novelty of using self-channeling laser pulses for shock wave generation has many implications for military applications. These experiments are to be performed in our secure test range using intensities of 1014W/cm2 and higher incident on various transparent media. Interferometry is performed using a harmonic of the pump laser frequency. Experiments also include burst-mode operation, where a train of ultra-fast pulses, closely spaced in time, and novel new beam distributions, strike the sample.
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R. Bernath, R. Bernath, C. G. Brown, C. G. Brown, J. Aspiotis, J. Aspiotis, M. Fisher, M. Fisher, M. Richardson, M. Richardson, } "Shock-wave generation in transparent media from ultra-fast lasers", Proc. SPIE 6219, Enabling Technologies and Design of Nonlethal Weapons, 62190A (26 May 2006); doi: 10.1117/12.663818; https://doi.org/10.1117/12.663818

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