An overview on femtosecond laser pulse shaping techniques applied to control of the initial photo-physical steps involved in materials processing is presented. First, pulse shaping methodology in frequency domain is introduced and examples of shaped pulses relevant to laser microfabrication are discussed. Then, the use of tailored femtosecond pulses to control the initial steps of laser processing of high band gap materials is demonstrated. In particular, control on basic ionization processes acting as the initial photo-physical step of the ablation dynamics is exerted by highly asymmetric femtosecond laser pulse shapes generated by Third Order Dispersion (TOD).

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Ultra-short laser pulses are frequently used for material removal (ablation) in science, technology and medicine. However, the laser energy is often used inefficiently, thus, leading to low ablation rates. For the efficient ablation of a rectangular shaped cavity, the numerous process parameters such as scanning speed, distance between scanned lines, and spot size on the sample, have to be optimized. Therefore, finding the optimal set of process parameters is always a time-demanding and challenging task. Clear theoretical understanding of the influence of the process parameters on the material removal rate can improve the efficiency of laser energy utilization and enhance the ablation rate. In this work, a new model of rectangular cavity ablation is introduced. The model takes into account the decrease in ablation threshold, as well as saturation of the ablation depth with increasing number of pulses per spot. Scanning electron microscopy and the stylus profilometry were employed to characterize the ablated depth and evaluate the material removal rate. The numerical modelling showed a good agreement with the experimental results. High speed mimicking of bio-inspired functional surfaces by laser irradiation has been demonstrated.

Here, to the best of our knowledge, for the first time we report the in-depth study of extremely high ultrafast laser ablation efficiency for processing of copper and steel with single-pulses, MHz-, GHz-and burst in the burst (biburst) regime. The comparison of burst, biburst and single-pulse ablation efficiencies was performed for beam-size-optimised regimes, showing the real advantages and disadvantages of milling and drilling processing approaches. Highly-efficient ultrashort pulse laser processing was achieved for ~1 µm wavelength: 8.8 µm 3 /µJ for copper drilling, 5.6 µm 3 /µJ for copper milling, and 6.9 µm 3 /µJ for steel milling.We believe that the huge experimental data collected in this study will serve well for the better understanding of laser burst-matter interaction and theoretical modelling.

The LMTB has designed and implemented a novel optical concept for the development of a versatile trepanning system, enabling the adjustment of the displacement and the inclination angle during circular rotation at up to 20000 r.p.m. The presented trepanning systems are able to laser machine through-holes diameters of 100 µm with a negative taper of up to 5°. Starting from an early stage of implementation, the novel trepanning system has been customized for different applications and industrial partners. The conference paper outlines the development steps and advanced performance, accenting laser micro machining results utilizing the novel LMTB trepanning system in operation at different laser parameters.