Investigating anisotropic effects and optimizing parameters in ultra-short pulsed (USP) laser machining of single crystalline diamond (SCD)

This research investigates the anisotropic behavior of single crystalline diamonds (SCD) during ultra-short pulse (USP) laser machining. The ablation behavior of SCD synthesized by high-pressure high-temperature (HPHT) and chemical vapor deposition (CVD) methods is studied on their primary crystallographic planes: {100}, {110}, and {111}. The results show different ablation thresholds for each plane, with the {100} plane having the highest threshold for both SCD types. CVD diamonds exhibit higher ablation thresholds than HPHT diamonds, indicating synthesis methods influence USP laser machining. The anisotropy of material removal, breakouts, and cracks, dependent on the in-plane machining angle, is investigated by machining grooves on the {100}, {110}, and {111} planes. Each plane shows unique characteristics, with varying anisotropic behavior at different in-plane angles. The material removal rate (MRR) differs between planes and even between grooves at different in-plane angles on the same plane. Distinct cracking behaviors are also observed, emphasizing the relationship between the crystallographic plane and the in-plane angle. The ideal in-plane angle for stable and clean ablation on each plane is determined. Temporal beam shaping, with MHz burst pulses, effectively minimizes detrimental effects such as cracks during SCD processing, enhancing machining quality and expanding USP laser machining applicability. • SCDs show anisotropic ablation with USP lasers, varying in ablation thresholds, removal rates, and defect formation. • Anisotropy in SCD laser ablation depends on crystallographic planes, angles, and machining direction. • Soft directions good for mechanical machining aren't ideal for lasers; hard directions give cleaner ablation. • MHz burst pulses with lower energy per pulse reduce anisotropy and match the material removal rate of 100 kHz pulses. • Multiple crystallographic orientations of SCD can be machined simultaneously using MHz bursts without cracks or breakouts.