EVAPORATIVE REMOVAL OF GELATIN BY ND-YAG LASER

Abstract

Simulation of laser removal of biological tissue has been performed using gelatin and an Nd:YAG laser. A gelatin disc was exposed to a focused beam of a continuous Nd:YAG laser with multimode operation and the process was observed using a high-speed video camera. The absorbed laser power raises the temperature of the gelatin and explosive evaporation takes place just below the surface after some time. The delay time until the abrupt evaporation is shorter when the beam diameter is smaller and the laser power is greater. The experimental results have been rearranged to find the dependence of the dimensionless explosion time (Fourier number) on the ratio of the conduction loss to the laser power absorption in the gelatin. This conduction to laser power parameter has been found to be an important dimensionless number to describe the needed exposure time. An analysis based on an unsteady heat transfer model for a one-dimensional system has been presented. Fair agreement has been found between the experimental results and the analytical predictions of the explosion time.