Multiphysics modeling of femtosecond laser-copper interaction: from electron dynamics to plasma eruption

The femtosecond laser ablation of metals is a complex and violent non-equilibrium process, and numerous studies seek to reveal the evolution of a single physical phenomenon, such as laser-induced periodical surface micro-nano structures or plasma eruptions. By taking the multi-physics scenarios of energy and heat transfer, structural mechanics, hydrodynamics and nucleation dynamics into account, a femto-nanosecond and nano-micrometre multiscale framework combining electron-phonon-coupled heat transfer, lattice deformation, phase transition and plasma eruption are constructed to describe the heat and mass transfer mechanism of the femtosecond laser-copper interaction. A multiphysics model was proposed in the research to simulate the ablation process with different laser fluence. Ablation takes place at low near-threshold fluences primarily via a combination of the thermal phase transition process of melting and thermoplastic deformation coupled with the nonthermal phase transition process of hot electrons explosion. Marangoni convection and ununiform nucleation at the solid-liquid interface create micro-nano structures on the surface of the ablation crater. In high laser fluence, plasma plumes are emitted via gasification and eruption, as the material is heated to decrease its density, the surface is broken into a micro-columns structure, and then the micro-columns fracture and erupt to form the micro-nano structures and plasma plumes. The numerical results offer a better understanding of the surface topography modifications and plasma plume evolution and promote the application of femtosecond laser precision fabrication in the field of aviation, mechanics, electronics and materials engineering.