Modeling pulsed laser ablation of aluminum with finite element analysis considering material moving front

During the pulsed laser ablation (PLA) of solid materials, the surface of the target material progressively recedes which in turn necessitates to account for the moving front boundary in the formulation of the laser heat conduction problem. Hence, developing an accurate predictive simulation model that captures the material moving front and updates simultaneously the laser source boundary conditions is an important and yet challenging task. In this paper, the PLA of aluminum is formulated and modeled with finite element analysis (FEA) that considers the instant material removal during the ablation process. Here, the implementation of such an FEA enables a strong coupling between the progressive surface recession (i.e., the shape change of the target material) and the laser heat conduction. Moreover, the proposed numerical simulation model not only predicts the progressive surface recession due to the material evaporation in the low laser fluence regime, but it also captures the ablation depth due to the material phase explosion in the high laser fluence regime. In addition, the temperature-dependent material and optical properties of the aluminum target are considered in the simulation. With nanosecond Nd:YAG 266 and 193 nm laser pulses, simulations are performed for the PLA of aluminum under various laser fluence. The predicted ablation depths under low laser fluence clearly show better agreement with experimental data, when compared to other predictions based on the hydrodynamics simulation model. Furthermore, the predicted threshold of the material phase transition in the high laser fluence regime also shows a good degree of consistency with experimental data.