Fundamentals of the interaction of high-frequency bursts of ultrashort laser pulses with dielectric materials of various energy band gaps

• Applicant: Professor Dr. Steffen Weißmantel
• Subject Area: Theoretical Condensed Matter Physics ; Experimental Condensed Matter Physics ; Glass, Ceramics and Derived Composites ; Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518776750

The general goal of the project is the quantitative understanding of the physical processes that occur during the interaction of fast pulse trains (bursts) of ultrashort laser pulses with dielectrics, in order to describe the changes in the ablation process compared to ablation with laser pulses in single-pulse mode in dependence of the burst parameters. The repetition rates within the bursts will be in the gigahertz to megahertz range. Based on the knowledge gained in the planned project and the developed general ablation model for dielectrics, defined burst parameters with specific material removal are then to be transferred to other dielectrics that have not been investigated. Likewise, the determination of optimal parameters for the efficient production of high-quality optically active structures with fast pulse sequences of ultra-short pulsed laser radiation should be made possible in subsequent projects. For this purpose, the observed effects resulting from the use of laser pulses in bursts already described in the state of research and our own preliminary work, such as the changed ablation thresholds due to the accumulation of free electrons and residual heat, the interaction of the laser radiation of a subsequent pulse with the plasma or the ablation cloud generated by the previous pulse and the material surface changed by incubation after the irradiation with each pulse or burst will be examined and the physical relationships and dependencies determined. The investigations will be made complementary, i.e. experimentally with a predefined variation of the material parameters (dielectrics with different band gaps) and the process parameters (fluence, pulse duration, number of laser pulses in the burst, temporal pulse spacing in the nanosecond and picosecond range, number of bursts, wavelength of laser radiation) and theoretically by simulating the laser-matter interaction, taking into account the time-dependent generation of free electrons through accumulated, non-linear ionization and heat accumulation. In order to achieve the general goal of quantitatively explaining the interaction of ultrashort laser pulses in bursts with dielectrics, the project is divided into three work packages WP 1 (single pulse), WP 2 (single burst) and WP 3 (multi-burst), each with increasing complexity and progressive knowledge gain.

• DFG Programme: Research Grants