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Proceedings Paper

Transient photoacoustic effects induced in liquids by pulsed erbium lasers
Author(s): Martin Frenz; Hans Surya Pratisto; Michael Ith; Thomas Asshauer; Klaus Rink; Guy P. Delacretaz; Valerio Romano; Rene-Paul Salathe; Heinz P. Weber
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Paper Abstract

The intense interest in the investigation of erbium laser radiation in medicine is due to the fact that radiation at 3 micrometers is very strongly absorbed by water, which is present in all biological tissue. As a consequence of this high absorption the interaction of pulsed radiation is characterized by an explosive process with a low ablation threshold and a thin coagulation zone along the laser incisions. Erbium lasers, therefore, have a wide field of potential medical applications which become even more attractive with the availability of reliable delivery systems. An interesting situation arises in orthopaedics and angioplasty, where a precise cutting instrument is needed in a liquid environment. For this reason, we experimentally investigated the interaction mechanism of fiber transmitted, pulsed, free-running and Q- switched Erbium:YSGG ((lambda) equals 2.79 micrometers ) and Erbium:YAG ((lambda) equals 2.94 micrometers ) laser radiation with liquid water. The dynamics of the bubble formation and the propagation of shockwaves in water was studied and visualized by flash photography. Acoustic transients of a few hundreds of bars accompanying the ablation process were measured with a needle hydrophone. A clear correlation between the spikes of the laser pulse and those of the pressure signal was observed. Additionally, strong pressure transients were measured after the end of the laser pulse, which could be associated with the collapse of the vapor bubble and further collapses after multiple rebounds. The influence of pulse energy, fiber size and pulse duration on the formation and the amplitude of the pressure waves is demonstrated.

Paper Details

Date Published: 17 August 1994
PDF: 10 pages
Proc. SPIE 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, (17 August 1994); doi: 10.1117/12.182959
Show Author Affiliations
Martin Frenz, Univ. Bern (United States)
Hans Surya Pratisto, Univ. Bern (United States)
Michael Ith, Univ. Bern (Switzerland)
Thomas Asshauer, Swiss Federal Institute of Technology (Swaziland)
Klaus Rink, Swiss Federal Institute of Technology (Switzerland)
Guy P. Delacretaz, Swiss Federal Institute of Technology (Switzerland)
Valerio Romano, Univ. Bern (Switzerland)
Rene-Paul Salathe, Swiss Federal Institute of Technology (Switzerland)
Heinz P. Weber, Univ. Bern (Switzerland)

Published in SPIE Proceedings Vol. 2134:
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards
Steven L. Jacques; David H. Sliney; Michael Belkin, Editor(s)

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