A time based method for predicting the workpiece surface micro-topography under pulsed laser ablation

The generation of micro-features in a predictable and repeatable manner by use of pulsed laser ablation requires an understanding of the temporal and energetic distributions of the laser beam upon the workpiece surface. Modelling the response of the material to known energetic and kinematic parameters of the pulsed laser ablation process can be carried out in a discretised time-based approach, allowing the workpiece topography to be simulated mathematically to reflect a real-life process. Considerations of the antecedent workpiece surface texture such as increases in irradiated area due to the surface gradient, and increases in laser spot size due to beam divergence throughout the elevation of the workpiece are used to predict energy densities and hence the resultant ablated depth and texture of the targeted surfaces. A fully calibrated Yb:YAG pulsed fibre laser (SPI G3.0 RM) was used to validate the model on three materials, highlighting the models strengths for different material types. It was found that Ni based workpieces presented redeposition phenomena under these laser ablation conditions. To analyse the model without redeposition, validations trials on materials that do not present such side effects, e.g. diamond, were carried out and differences were found to be up to 9.39%.