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Proceedings Paper

Effect of reduction of laser pulse width from 100 ps to 20 fs on the plasma-mediated ablation of hard and soft tissue
Author(s): Frieder H. Loesel; An-Chun Tien; Sterling John Backus; Henry C. Kapteyn; Margaret M. Murnane; Ron M. Kurtz M.D.; Samir I. Sayegh M.D.; Tibor Juhasz
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Paper Abstract

As ultrafast laser technology advances, it is of importance to evaluate the potential of sub-100-fs laser pulses for laser surgery. We have extended the investigation of laser- induced optical breakdown on hard and soft tissues down to laser pulse widths of 20 fs. Powerful 20-fs to 100-ps pulses from a single Ti:sapphire oscillator/amplifier laser source at 800 nm were focused in vitro onto the surface of fresh human corneas and human enamel to a spot of 60 - 70 micron in diameter. The threshold for ablation was determined by increasing the pulse energy while monitoring scattered probe light at ejected ablation particles. Our experiments show a slower decrease of the threshold fluence in dependence of the pulse width in the femtosecond regime than in the picosecond regime. Unlike previously suggested, no saturation behavior could be observed at the shortest available pulse widths. For the shortest pulses with 20 fs width, we measured a threshold of 0.38 J/cm2 and 0.42 J/cm2 for cornea and enamel, respectively. For the longest pulses at 100 ps, the threshold fluence was 4.3 J/cm2 and 2.06 J/cm2, respectively. Comparison to theoretical models and to previous data determines the contribution of multi-photon and avalanche processes. Our results suggest an optimum laser pulse width of several hundred femtoseconds for most applications in ultrashort pulse laser surgery.

Paper Details

Date Published: 4 January 1999
PDF: 8 pages
Proc. SPIE 3565, Thermal Therapy, Laser Welding, and Tissue Interaction, (4 January 1999); doi: 10.1117/12.335791
Show Author Affiliations
Frieder H. Loesel, Univ. of Heidelberg and Univ. of Michigan (Germany)
An-Chun Tien, Univ. of Michigan (United States)
Sterling John Backus, Univ. of Michigan (United States)
Henry C. Kapteyn, Univ. of Michigan (United States)
Margaret M. Murnane, Univ. of Michigan (United States)
Ron M. Kurtz M.D., Univ. of Michigan and Kellogg Eye Ctr./Univ. of Michigan (United States)
Samir I. Sayegh M.D., Univ. of Michigan and Kellogg Eye Ctr./Univ. of Michigan (United States)
Tibor Juhasz, Univ. of Michigan and Kellogg Eye Ctr./Univ. of Michigan (United States)

Published in SPIE Proceedings Vol. 3565:
Thermal Therapy, Laser Welding, and Tissue Interaction
Stephen G. Bown; Guy P. Delacretaz; Guilhem Godlewski M.D.; Gerhard J. Mueller; Roberto Pini; Hans-Dieter Reidenbach; Rudolf W. Steiner; Lars Othar Svaasand; Karl-Goran Tranberg, Editor(s)

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