Near-THz bursts of pulses : governing surface ablation mechanisms for laser material processing

Mur, Jaka (author), Petkovšek, Rok (author)

Laser operation in bursts of pulses has recently attracted a lot of attention, as high average powers and pulse energies have become available. Bursts of pulses have become a mean to achieve different laser-matter interaction regimes with a single laser source. We have used an ultra-short pulse laser source in combination with an external array of birefringent crystals to generate near-THz bursts of single-picosecond pulses. Variability of the setup and high single pulse energy were exploited to generate bursts of up to 16 pulses at different delays between consecutive pulses. The experimental setup was applied for surface processing of different industrially relevant materials, including metals, ceramics, and polyimides. The goal of this study was to find out if the reduced ablation thresholds using near-THz bursts of pulses as reported in previous studies of other group could be utilized for increased ablation efficiency. Our findings show that near-THz bursts of pulses interact with materials in a similar fashion as a single, albeit longer, pulse would. We observed a clear trend on all the tested materials, showing a declining ablation efficiency with increasing total burst duration at a fixed pulse repetition frequency. Findings contradict the results of other groups concluding on an improved efficiency of laser to material energy transfer using bursts at near-THz intra-burst repetition rates. A simple model describing ablation efficiency decline with pulse prolongation was used to compare the experimental data with theoretical predictions. Detailed analysis of surface ablation effects on metallic materials also revealed a presence of melting processes typically associated with laser pulses above 10 ps in duration as opposed to original 1.5 ps pulses.

• Language: English
• Keywords: bursts of pulses, ultra-short laser processing, surface effects, ablation efficiency
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Submitted for review: 18.12.2018
• Article acceptance date: 21.01.2019
• Publication date: 01.06.2019
• Year: 2019
• Number of pages: Str. 355-360
• Numbering: Vol. 478
• PID: 20.500.12556/RUL-127043
• UDC: 535:621.7.08+681.7.069.24(045)
• ISSN on article: 0169-4332
• DOI: 10.1016/j.apsusc.2019.01.182
• COBISS.SI-ID: 16467995
• Publication date in RUL: 14.05.2021

Record is a part of a journal

• Title: Applied surface science
• Shortened title: Appl. surf. sci.
• Publisher: Elsevier
• ISSN: 0169-4332
• COBISS.SI-ID: 3283215

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
• Licensing start date: 01.06.2019

Secondary language

• Language: Slovenian
• Keywords: paketi pulzov, laserska obdelava z ultra-kratkimi pulzi, površinski pojavi, učinkovitost ablacije