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Roles of Tunneling, Multiphoton Ionization, and Cascade Ionization for Femtosecond Optical Breakdown in Aqueous Media
Final rept. 27 Dec 2004-7 Jan 2010
LUBECK MEDICAL UNIV (GERMANY) MEDICAL LASER CENTER
Pagination or Media Count:
The interplay of the various ionization mechanisms reveals itself through the dependence of breakdown events on laser parameters such as pulse duration, wavelength, and pulse energy. In the past, the dependence of the breakdown threshold on pulse duration has attracted most attention because of the lowering of the energy threshold with decreasing pulse duration that enables precise material processing. In the present study, these aspects are included because we use pulse durations ranging from approximately equal to 300 fs to approximately equal to 10 ns. However, we go far beyond by presenting a detailed analysis of the wavelength dependence of the breakdown thresholds for nanosecond and femtosecond breakdown, and of the dependence of energy deposition on laser pulse energy. These studies are performed with unprecedented wavelength and energy resolution. They reveal previously unknown features of the optical breakdown process, and enable to assess the possibilities of controlled nonlinear energy deposition in the entire wavelength-pulse duration parameter space.
APPROVED FOR PUBLIC RELEASE