Efficiency enhancement by transient electron dynamic control in shaped femtosecond laser fabrication of metals

Ultrafast laser pulse train processing has been widely used to improve the efficiency and quality of nonmetallic material processing. However, it is commonly believed that the split of one pulse into sub-pulses for metallic material will suppress the ablation with near-threshold laser fluence. In this article, a high-efficiency metal processing by femtosecond laser double pulses train with different energy ratio is performed in the aspects of theory simulation and experiment. In theory, a Femto-picosecond and Nano-micrometre multiscale framework combining photoelectric effect and electron-phonon-coupled heat transfer proved that the pulse train can effectively control the electron properties, so as to enhance processing efficiency. Theory-guided experiments indicate that the ablation crater reaches maximum ablation depth with a sub-pulse energy ratio optimized pulse train, which is 40%–100% deeper than that of single pulse processing. This method can be used for femtosecond laser processing of various metal materials with high efficiency and high quality, and is helpful to solve the manufacturing bottleneck challenges in the fields of aviation, mechanics, electronics and materials engineering.