Suited simulations for optimal ultrafast laser processing of metals

摘要

Due to a large material removal rate and a minimal collateral damage, subpicosecond laser pulse offers many advantages for material processing. Post-experimental examination of ultrashort laser material ablation shows that the heated surface of the bulk does not exhibit thermal damage. A lot of complicated physical processes follow intense laser irradiation and have often been modeled in over-simplified way to explain experimental results. Because a more complete understanding of the damage mechanisms would be very interesting and would open new applications in the scientific research community and industry. A detailed model of the ultrashort response to reproduce ablation process is presented, describing dynamical electronic properties such as temperature, pressure and energy. To simulate the interaction between the laser and the metallic target, these theoretical models are inserted inside a 1D Lagrangian hydrodynamic code. It is still a very challenging task to disentangle the cumulative/competitive effects of all physical processes if included at once in numerical simulations. Adding the different processes into numerical simulations on a one by one basis allow to assess their contributions to the quantity of ejected matter on a large range of laser intensity. Experimental results related to the influence of multi-pulses or tailored pulses for ablation efficiency with ultrafast pulses (pulse duration up to 5 ps) has been obtained. A significant improvement of the micro structuring quality in metals is demonstrated, and the theoretical approach presented allow to manage the optimal temporal shape of pulses. An efficient process control can be reached and the industrial applications will be evidenced.