ABSTRACT
Surface patterning is one of the most important applications of ultrashort laser pulses used in micromachining. The transition from bulk machining to surface patterning will be described in more detail. In particular, absorption, reflection, and heat conduction will be analyzed with respect to ablation regimes. Characteristic effects such as beam filamentation and plasma interaction specific for ultrashort laser pulses will be explained. Surface patterning has become an emerging technology in the field of selective ablation of thin-film layers, which are used in modern industries such as flat-panel displays and integrated solar cell manufacturing. Therefore, part of this chapter focuses on the wavelength-and intensity-dependent deposition of the laser energy in a small surface layer without influencing the underlying substrate. Also the optical setup plays an important role not only in the accuracy but also in throughput. Differences between focusing optics and image or mask projection will lead to different results. Bulk machining can be used,
on the other hand, to generate more complex three-dimensional structures. Finally, some details about the beam guiding and forming will be provided, which are specific for pico-and femtosecond laser pulse ablation. In the second part, more information on the laser drilling process will be provided. Here, the different drilling strategies will be compared with respect to their specific application fields. For drilling with high aspect ratios, an effect of the polarization can be observed. It will be shown how this effect can be used to drill perfect circular or shaped holes. This technology requires a special optical setup that is given in more detail here. Although laser cutting is regarded quite important it can be described as an extension of the through-hole drilling process. Basically, some additional parameters will be taken into account, such as the support by a process gas. The characterization is focused on the edge roughness and the heataffected zone.
