Author: Kaushik Subramanian
Requested Type: Either Oral or Poster
Submitted: 2015-04-30 10:33:55
Co-authors: S. Haering, C. Martin, A. Ben-Yakar
University of Texas at Austin
204 E. Dean Keeton Street Sto
Austin, Texas 78712-1
The high peak intensities of ultrafast laser pulses result in photo-ionization and plasma formation locally within the laser focal volume when focused in water. This hot plasma expands to form transient bubbles that grow and collapse with each pulse. At breakdown threshold energies, these bubbles are smaller than the diffraction limited focal spot size and are detected using scattering techniques like the pump-probe method. However, for nanoparticle –water suspensions, the uncertainty of particle position within the laser focal volume renders the pump probe technique ineffective in relating bubble radius to their corresponding breakdown fluences. Here, we present two new approaches to determine nanoparticle mediated bubble formation enhancements in liquid media. The first method uses kinetic theory to provide spatial information on where the smallest bubbles are formed within the laser focal volume. The radial information is calculated from the collision frequency of the nanoparticles in solution. The second method compares observed probability distributions for bubbles formed at nanoparticle sites with a theoretical distribution for particle location within the ultrafast laser focal volume to establish a relationship between bubble radii and associated laser Intensity.