Role of desiccation in pulsed laser ablation at the 2.94 μm wavelength: Experiments and modeling

L. R. Jones, S. L. Jacques

Research output: Contribution to journalConference article

Abstract

A difficulty with using an OPO laser to reshape the cornea by ablation is the tendency for ablation to stop prematurely. We report on using an OPO laser (2.94 um wavelength, 5 ns pulse duration, 7 mJ pulse energy, approx. 0.5-mm 1/e2-radius Gaussian beam) to ablate a 20% acrylamide gel as a model for the cornea. Experiments demonstrated that ablation proceeds at an average rate of ablation of 3-4 μm/pulse then stops at about 1 mm depth. A computer model was developed to simulate the ablation and desiccation processes. Using a range of operating parameters, the model could achieve ablation rates of 2.8-3.5 μm/pulse and cessation of ablation after 0.25-2.1 mm. A key factor is the absorption coefficient of desiccated gel which was measured experimentally to be about 1700 cm-1. In conclusion, desiccation from residual heat after an ablative pulse creates a dried layer that attenuates subsequent pulses. If the threshold energy density required for ablation is too high, then too much residual energy remains after each pulse and the consequent dried layer halts the ablation process.

Original languageEnglish (US)
Pages (from-to)317-328
Number of pages12
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume4257
DOIs
StatePublished - Jan 1 2001
EventLaser-Tissue Interaction XII: Photochemical, Photothermal, and Photomechanical - San Jose, CA, United States
Duration: Jan 21 2001Jan 24 2001

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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