Improvement of Cu Ablation Efficiency Using GHz-Burst Femtosecond Laser at 515 nm Wavelength

In recent years, gigahertz (GHz)-burst-mode femtosecond lasers have revolutionized laser processing by significantly improving processing efficiency and quality. However, the underlying mechanisms are still unclear and experimentally optimizing the processing parameters is difficult due to their huge number. This study implements a theoretical approach based on simulations to investigate the underlying mechanisms of the Cu ablation efficiency enhancement by GHz-burst mode. The simulation results obtained using a two-temperature model suggest that the ablation efficiency is improved due to the interaction of subsequent intra-pulses in a GHz burst with Cu melted by the preceding intra-pulses. It is demonstrated that for GHz-burst mode, a 515 nm wavelength achieves higher Cu ablation performance than when using the infrared wavelength and demonstrates 2.8 times higher ablation efficiency than the single-pulse mode. The simulation results well agree with the experimental results. The approach used here represents a major advance not only in understanding the underlying mechanisms but also in determining the optimal processing conditions for practical applications.