PHOTOMECHANICAL BASIS OF LASER-ABLATION OF BIOLOGICAL TISSUE

The photomechanical model of laser ablation of biological tissue asser ts that ablation is initiated when the laser-induced tensile stress ex ceeds the ultimate tensile strength of the target. We show that, unlik e the one-dimensional thermoelastic model of laser-induced stress gene ration that has appeared in the literature, the full three-dimensional solution predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to occ ur. An interferometric technique has been developed to measure the tim e-dependent thermoelastic expansion, and the results for subthreshold laser fluences are in precise agreement with the predictions of the th ree-dimensional model.