Ultra-short pulsed (USP) laser ablation has become a key enabling technology for high-precision micro material processing. Beam shaping has recently gained increasing attention to tailor energy deposition and thereby control ablation efficiency, surface morphology, and feature geometry. However, the fundamental mechanisms governing the interaction between different beam intensity distributions and the resulting ablation dynamics remain insufficiently understood.

In this study, a 3D multiphysics simulation framework is applied to investigate USP laser ablation of copper using different beam shapes, including Gaussian, donut-shaped, and top-hat intensity profiles. The simulations are based on a fully compressible mass-of-fluid formulation capable of resolving the coupled dynamics of solid, liquid, and vapor phases. Energy deposition in the metal is modeled using a two-temperature model describing electron–lattice nonequilibrium, while laser absorption is described through an electron-temperature-dependent Drude model. The framework further incorporates coupled phase change models for melting, evaporation, condensation, and resolidification, enabling description of transient melt pool and vapor plume dynamics.

The simulations allow analysis of the evolution of ablation mechanisms, including melt expulsion, recoil-pressure-driven flow, and phase-explosion-like behavior under high fluence conditions. Particular attention is given to the formation of crater geometries and surface structures as a function of beam shape and pulse energy. By systematically comparing Gaussian, donut, and top-hat beams, the study provides insights into how spatial energy deposition influences melt dynamics and material removal.

The results contribute to a deeper mechanistic understanding of beam-shape-dependent USP ablation and provide guidance for the design of tailored beam profiles in precision laser micromachining.