Abstract

The study of interaction mechanisms of ultrashort laser pulses with covalent semiconductors such as silicon and germanium is of key importance for optimizing a range of micromachining applications. Ultrafast phase transitions have been observed in Si [1,2] and Ge [3] using pump-and-probe experiments and the appearance of solid or liquid phase overheating phenomena upon strong ultrafast excitation have received considerable attention. In such situations, nucleation of vapour bubbles from the superheated liquid may give rise to a process known as phase explosion (explosive boiling) [4]. The use of imaging techniques, such as femtosecond pump-probe microscopy, for these studies additionally yields the spatial information of the monitored process. Using these techniques it was possible to identify and spatially discriminate narrow fluence windows in which interesting ablation mechanisms take place, both in Si [5] and Ge [6].

© 2009 IEEE