Optical Probes for Laser Induced Shocks
Final rept. 15 Mar 1990-14 Mar 1992
MASSACHUSETTS GENERAL HOSPITAL BOSTON WELLMAN LABS OF PHOTOMEDICINE
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The support provided by grant AFOSR-90-0210 resulted in the publication of four papers and three conference proceedings. This research covered three topics. First we studied shock waves generated by dielectric breakdown of nano- and picosecond pulses at 1.06 micron wavelength in water. We described a noninvasive optical technique to measure the propagation velocity of shock waves in water and showed that during spherical expansion in water the pressure of a shock wave scales as the inverse of the square of the propagation distance and drops to acoustic values within a few hundred microns. Second, we investigated the pressure transients generated during the ablation of sheet polyimide by nanosecond excimer-laser pulses. We observed the formation of multi-kbar shock waves. The pressures generated during ablation were shown to result from the violent expansion of the rapidly heated gaseous ablation products. Third, in addition, work initiated prior to the AFOSR grant by the ADZ at the University of Berne, Switzerland, was completed. That research was concerned with the ablation of tissue and tissue-like targets by pulsed laser radiation in the infrared. A model that explains the ablation process as a combination of evaporation and ejection of liquefied material was developed.
- Lasers and Masers
- Electrooptical and Optoelectronic Devices