Optimization of surface engraving quality with ultrafast lasers

Large area engraving is achieved by moving a focused femtosecond beam on the sample surface. Of course, the process parameters are the moving speed (moving beam or moving sample or both) and the laser repetition rate. Surface engraving is obtained by multiple linear pass shifted along the y-axis perpendicular to the moving x-axis. The resulting surface shape is thus highly dependent on the deviation Δy between two successive shifted passes. Being able to predict and optimize the process in terms of the depth and surface quality is a key advantage. In this work, we show that experimentally engraved surface shapes can be numerically estimated using a simple ablation model. Only two parameters are needed to have a satisfactory description of the laser matter interaction for a given material. We combine the description of the engraving process with the laser matter interaction model to calculate the surface shape after laser scanning.