Recently, major laser manufacturers have introduced MHz- and GHz-burst mode capabilities, where each primary laser pulse is subdivided into a series of lower peak power pulses that collectively sum to the same energy as a single pulse. While experimental studies suggest that burst mode can improve ablation efficiency for select materials—particularly those with reduced free-electron density—there is limited evidence for its efficacy for metal machining.

This work systematically benchmarks MHz-burst mode against single pulse mode in 5-axis ultrafast laser micromachining, specifically evaluating its impact on blind hole drilling in stainless steel. Recent findings demonstrate that a position-based pulse control mechanism, wherein the number of pulses emitted per spatial location is precisely controlled, significantly enhances ablation efficiency. By allowing a predefined number of pulses at each position-based firing event, material removal rates can be optimized while maintaining high-quality hole characteristics, including controlled sidewall taper, minimal surface charring and smooth bottom surface finish. This controlled approach is functionally analogous to burst mode, where pulse packets enable deeper penetration and faster material removal without increasing the average power.

By directly comparing burst mode with single pulse mode under identical machining conditions, this study quantifies tradeoffs between processing speed and feature quality. Blind holes serve as an ideal test case, allowing detailed examination of entrance edge integrity, sidewall formation and floor smoothness as key quality metrics. While previous studies primarily report either efficiency or quality, this work seeks to establish a comprehensive understanding of their interplay in a controlled 5-axis micromachining environment.