Machining of metals with ultrashort laser pulses: fundamental aspects and their consequences

The recipe to increase the quality of material removal processes by reducing the pulse duration to the femtosecond range has turned out to be less curative than expected. Fundamental investigations revealed three sources for remaining flaws: (1) strong deformation of laser beam near focus, (2) essentially thermal nature of ablation process even in femtosecond range, (3) deflection radiation at hole wall.