Ultrashort 30 fs Laser Photoablation for High-Precision and Damage-Free Diamond Machining

Abstract

A 30 fs, 800 nm, 1 kHz femtosecond was used to photoablate diamond across radiant energy doses of 1–500 kJ/cm², with fluences of 10–50 J/cm² and pulse counts from 100 to 10,000. The objective was to maximize material removal while minimizing surface roughness (R_a) by operating above the photoablation threshold. Results demonstrate that 30 fs laser photoablation achieves R_a < 0.1 μm, meeting both high- and ultrahigh-precision machining standards, while maintaining surface integrity and preventing heat-affected zone (HAZ) damage. At 1 kJ/cm² (10 J/cm² fluence, 100 pulses), an R_a of 0.09 μm was achieved, satisfying ultrahigh-precision criteria (R_a < 0.1 μm). Additionally, doses below 10 kJ/cm² consistently met high-precision machining requirements (R_a < 0.2 μm). Photoablation efficiency peaked below 50 kJ/cm², after which material removal diminished, indicating nonlinear process limitations. The sp³ diamond phase remained intact, as confirmed by the unchanged T_2g Raman mode at 1332 cm^–1, with no detectable Raman G or D modes, confirming the absence of sp²-related graphitization, structural disorder, or nitrogen vacancy (NV) center annealing. These findings establish 30 fs laser processing as a high-precision, damage-free approach for diamond machining, with promising applications in NV center-containing quantum materials and advanced tooling.