14 July 2015 Time-resolved shadowgraphy of optical breakdown in fused silica
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Abstract
Dynamics of a laser-induced optical breakdown in the bulk of fused silica initiated by a sub-nanosecond laser pulse of an energy fluence as high as 8.7 kJ/cm2 was investigated by using femtosecond time-resolved shadowgraphy. Plasma ignition, growth of the damaged region and accompanying hydrodynamic motion were recorded from the moment directly before the arrival of the driving laser pulse, in the time steps adapted to the rate of the occurring processes. The growth rate of the plasma channel, curvature radii and velocities of the wave fronts were extracted from the shadowgrams. It was found that the plasma channel develops with a supersonic velocity and the first observed shock front tends to transform itself from the initial bowl-like shape to the final spherical one characterising an acoustic wave. Appearance of multiple fronts accompanying the main shock front was registered and used in more detailed analysis of the optical breakdown dynamics in the transparent dielectrics.
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K. A. Tran, K. A. Tran, Y. V. Grigorov, Y. V. Grigorov, V. H. Nguyen, V. H. Nguyen, Z. U. Rehman, Z. U. Rehman, N. T. Le, N. T. Le, K. A. Janulewicz, K. A. Janulewicz, } "Time-resolved shadowgraphy of optical breakdown in fused silica", Proc. SPIE 9532, Pacific Rim Laser Damage 2015: Optical Materials for High-Power Lasers, 953205 (14 July 2015); doi: 10.1117/12.2185910; https://doi.org/10.1117/12.2185910
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