Simulation of evaporation ablation dynamics of materials by nanosecond pulse laser of Gaussian beam and flat-top beam

Abstract

Based on the established two-dimensional asymmetric model of the interaction between a nanosecond pulse laser and metallic aluminum, the effect of beam shaping on the evaporation ablation dynamics during the ablation of metallic aluminum by a nanosecond pulse laser was simulated. The results show that plasma shielding, which has a significant influence on the ablation properties of the target, occurs mainly in the middle and late phases of the pulse. Among the three laser profiles, the Gaussian beam has the strongest shielding effect. As the diameter of the reshaped flat-top beam increases, the shielding effect gradually weakens. The two-dimensional spatial distribution of target temperature is relatively different between ablated by a Gaussian beam and a flat-top beam. For the Gaussian beam, the center of the target is heated first, and then the temperature spreads in radial and axial directions. For the flat-top beam, due to the uniform energy distribution, the target is heated within a certain radial range simultaneously. Beam shaping has a great influence on the evaporation ablation dynamics of the target. For the Gaussian beam, the center of the target is ablated first, followed by radial ablation. For the flat-top beam, the evaporation time of the target surface is delayed due to the lower energy density after beam shaping. In addition, the target evaporates simultaneously within a certain radial range due to the more uniform distribution of laser energy. For the three laser profiles, the evaporation morphology of the target resembles the intensity distribution of the laser beam. The crater produced by the Gaussian beam is deep in the center and shallow on both sides, while it becomes relatively flat by the flat-top beam.