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1Investigation of microrelief formation features under multi-pulse nanosecond laser irradiation of metal surface under increased
pulse repetition rate
Yu. Karlagina1*, V. Veiko1, D. Polyakov1, G. Romanova1
1-Institute of Laser Technologies, ITMO University, 14-16 Birzhevaya Line, Saint Petersburg, Russia, 199034
This study investigates the influence of laser pulse repetition rate (in the kilohertz range) on the characteristics of the microrelief formed on the surface of a metal during its laser nanosecond ablation.
Previously, it was assumed that during laser ablation of metal surfaces with short pulses (from units to hundreds of nanoseconds), the main role in the formation of microrelief (depressions or craters, holes, etc.) is played by such parameters of laser radiation as pulse duration, pulse energy density, and irradiation multiplicity (number of pulses). However, with the growing popularity of industrial fiber laser systems, which have high average power and a wide-range adjustable pulse repetition rate, the issue of high-frequency microprocessing for various applications, such as creating functional coatings, forming microchannels, wetting gradients, etc., has become particularly relevant.
The purpose of this study is to investigate the role of heat accumulation during multi-pulse laser processing with a scanning beam in near-threshold ablation regimes, developed ablation regimes (above the ablation threshold), and under conditions of formation of radiation-absorbing plasma by using different energy density Q. In the experiments, the same effective exposure time t to the surface area was ensured at a variable frequency f in the range from 1.6 kHz to 100 kHz. A theoretical calculation was carried out to investigate the influence of the laser pulse repetition rate on the cumulative heating of titanium using a thermal model of laser ablation.
Fig. 1. Optical microscopy - Two limiting cases a) fj=1.6 kHz and b) f2=45 kHz (Q=const, t=const) demonstrating the significant role of heat accumulation effects in the target on the formation of microrelief during multi-pulse laser processing.
Regularities and ranges of effective laser ablation regimes were established to control the dynamics of melting by varying the pulse repetition rate, and the mechanisms of surface microgeometry formation were described.
This research was supported by Priority 2030 Federal Academic Leadership Program (financial support for the conduct of the research).
