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Mechanism of surface quality enhancement in MHz burst femtosecond laser machining of single-crystal diamond revealed by in-situ observation.

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Title: Mechanism of surface quality enhancement in MHz burst femtosecond laser machining of single-crystal diamond revealed by in-situ observation.
Authors: Teshima, Yuta1 (AUTHOR), Yoshizaki, Reina1 (AUTHOR) r.yoshizaki@mfg.t.u-tokyo.ac.jp, Kuroda, Yuya1 (AUTHOR), Sugita, Naohiko1 (AUTHOR)
Source: Applied Physics A: Materials Science & Processing. May2026, Vol. 132 Issue 5, p1-14. 14p.
Subjects: Diamond crystals, Laser machining, Femtosecond lasers, Scientific observation, Surface texture, Ultrashort laser pulses, Material erosion
Abstract: Diamonds are expected to have widespread applicability across various fields; however, owing to their extreme hardness, precise processing using conventional methods remains challenging. Among the different approaches, laser processing has attracted considerable attention owing to its non-contact nature, which enables machining without inducing subsurface damage, and its flexibility in creating complex, non-planar geometries. Burst pulse laser irradiation has been reported to improve surface quality; however, the underlying physical mechanisms remain unclear. In this study, the machining process of single-crystal diamond {100} surfaces was investigated through in-situ high-speed imaging combined with post-processing microscopic evaluation, to elucidate these mechanisms. The experimental results revealed that increasing the number of sub-pulses per burst generally enhanced the surface quality, particularly under low-energy irradiation, which may be associated with reduced air ionization as the energy delivered by each sub-pulse decreases. In the near-threshold regime, however, the surface quality exhibited a non-monotonic dependence, indicating an optimal processing window; an excessively large sub-pulse count per burst can destabilize material removal. In addition, the amount of optically visible scattered particles decreased and the deposited debris became finer with increasing number of sub-pulses per burst. This tendency may be associated with burst-induced plume interaction, including possible gas-phase cluster nucleation driven by subsequent sub-pulses within each burst. These tendencies are particularly pronounced under low-energy irradiation. The insights obtained from this study significantly advance the understanding of the material removal mechanisms involved in the ultrashort pulse laser machining of single-crystal diamonds. Ultimately, these findings can contribute to establishing robust and precise laser-based processing methods for highly brittle and difficult-to-machine materials. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Diamonds are expected to have widespread applicability across various fields; however, owing to their extreme hardness, precise processing using conventional methods remains challenging. Among the different approaches, laser processing has attracted considerable attention owing to its non-contact nature, which enables machining without inducing subsurface damage, and its flexibility in creating complex, non-planar geometries. Burst pulse laser irradiation has been reported to improve surface quality; however, the underlying physical mechanisms remain unclear. In this study, the machining process of single-crystal diamond {100} surfaces was investigated through in-situ high-speed imaging combined with post-processing microscopic evaluation, to elucidate these mechanisms. The experimental results revealed that increasing the number of sub-pulses per burst generally enhanced the surface quality, particularly under low-energy irradiation, which may be associated with reduced air ionization as the energy delivered by each sub-pulse decreases. In the near-threshold regime, however, the surface quality exhibited a non-monotonic dependence, indicating an optimal processing window; an excessively large sub-pulse count per burst can destabilize material removal. In addition, the amount of optically visible scattered particles decreased and the deposited debris became finer with increasing number of sub-pulses per burst. This tendency may be associated with burst-induced plume interaction, including possible gas-phase cluster nucleation driven by subsequent sub-pulses within each burst. These tendencies are particularly pronounced under low-energy irradiation. The insights obtained from this study significantly advance the understanding of the material removal mechanisms involved in the ultrashort pulse laser machining of single-crystal diamonds. Ultimately, these findings can contribute to establishing robust and precise laser-based processing methods for highly brittle and difficult-to-machine materials. [ABSTRACT FROM AUTHOR]
ISSN:09478396
DOI:10.1007/s00339-026-09581-4