4 January 1999 Effect of reduction of laser pulse width from 100 ps to 20 fs on the plasma-mediated ablation of hard and soft tissue
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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.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Frieder H. Loesel, Frieder H. Loesel, An-Chun Tien, An-Chun Tien, Sterling John Backus, Sterling John Backus, Henry C. Kapteyn, Henry C. Kapteyn, Margaret M. Murnane, Margaret M. Murnane, Ron M. Kurtz, Ron M. Kurtz, Samir I. Sayegh, Samir I. Sayegh, Tibor Juhasz, Tibor Juhasz, } "Effect of reduction of laser pulse width from 100 ps to 20 fs on the plasma-mediated ablation of hard and soft tissue", Proc. SPIE 3565, Thermal Therapy, Laser Welding, and Tissue Interaction, (4 January 1999); doi: 10.1117/12.335791; https://doi.org/10.1117/12.335791

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