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Proceedings Paper

Unified model of plasma formation, bubble generation and shock wave emission in water for fs to ns laser pulses (Conference Presentation)

Paper Abstract

We developed modeling tools for optical breakdown events in water that span various phases reaching from breakdown initiation via solvated electron generation, through laser induced-plasma formation and temperature evolution in the focal spot to the later phases of cavitation bubble dynamics and shock wave emission and applied them to a large parameter space of pulse durations, wavelengths, and pulse energies.

The rate equation model considers the interplay of linear absorption, photoionization, avalanche ionization and recombination, traces thermalization and temperature evolution during the laser pulse, and portrays the role of thermal ionization that becomes relevant for T > 3000 K. Modeling of free-electron generation includes recent insights on breakdown initiation in water via multiphoton excitation of valence band electrons into a solvated state at Eini = 6.6 eV followed by up-conversion into the conduction band level that is located at 9.5 eV.

The ability of tracing the temperature evolution enabled us to link the model of laser-induced plasma formation with a hydrodynamic model of plasma-induced pressure evolution and phase transitions that, in turn, traces bubble generation and dynamics as well as shock wave emission. This way, the amount of nonlinear energy deposition in transparent dielectrics and the resulting material modifications can be assessed as a function of incident laser energy. The unified model of plasma formation and bubble dynamics yields an excellent agreement with experimental results over the entire range of investigated pulse durations (femtosecond to nanosecond), wavelengths (UV to IR) and pulse energies.

Paper Details

Date Published: 21 April 2017
PDF: 1 pages
Proc. SPIE 10094, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XVII, 1009408 (21 April 2017); doi: 10.1117/12.2250884
Show Author Affiliations
Xiao-Xuan Liang, Univ. zu Lübeck (Germany)
Xi’an Jiaotong Univ. (China)
Sebastian Freidank, Univ. zu Lübeck (Germany)
Norbert Linz, Univ. zu Lübeck (Germany)
Günther Paltauf, Karl-Franzens-Univ. Graz (Austria)
Zhenxi Zhang, Xi'an Jiaotong Univ. (China)
Alfred Vogel, Univ. zu Lübeck (Germany)

Published in SPIE Proceedings Vol. 10094:
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XVII
Alexander Heisterkamp; Peter R. Herman; Michel Meunier; Roberto Osellame, Editor(s)

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