Stress waves in laser-material interaction: From atomistic understanding to nanoscale characterization

Abstract

During pulsed laser-assisted manufacturing, the extremely high-temperature gradient in space will lead to very high-stress waves that play a critical role in structuring. Both shear and normal stress waves emerge in space. This work provides a review and perspective based on our past work spanning theoretical analysis, 1D molecular dynamics (MD) modeling, 3D MD modeling, and experimental characterization. Discussions are given on the non-Fourier effect during ultrafast laser-material interaction, stress-induced structural defects in recrystallization, and ablation confinement by ambient gas and nanotip during nanotip-assisted near-field nanomanufacturing. The presence of stress waves in space could cause permanent and temporary damages, and these damages are more caused by the shear stresses than the normal ones where the compressive component usually is much stronger than the tensile part. Due to the fact of very fast stress waves propagation and slow cooling and solidification, it is very challenging to conduct MD modeling of the entire domain even using stage-of-the-art parallel computation. Hybrid modeling that combines MD and macroscale modelings provides a better choice to tackle this problem. Time-resolved ultrafast temperature and stress characterization are still highly needed to provide deep physics understanding of laser-material interaction toward process control and optimization.