EVAPORATIVE REMOVAL OF GELATIN BY Nd: YAG LASER

Simulation of laser removal of biological tissue has been made using gelatin and a Nd: YAG laser. A gelatin disc was exposed to focused beam of 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 gelatin and explosive evaporation takes place just below the surface after some time. The evaporative removal occurs earlier 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 on unsteady heating for an one-dimensional system has been presented. A series solution for the temperature change at the center has been obtained. Fair agreement has been found between the experimental results and the analytical predictions of the explosion time. The conduction-to-laser power parameter need be smaller than 0.1 for effective removal.