Femtosecond laser micromachining

Ultrashort laser pulses with durations in the femtosecond range up to a few picoseconds provide a unique method for the structuring of practically all materials with high precision and minimal thermal and mechanical influence of the surrounding. Due to the high intensities obtained in the focal volume even at moderate pulse energies not only surface structuring becomes possible but also the precise three-dimensional structuring within the bulk of transparent samples due to efficient nonlinear absorption processes. However, to exploit the full potential, a detailed knowledge of the interaction process of these intense pulses with matter is indispensable. Thus, this chapter describes the fundamentals of ultrashort pulse micromachining, including the absorption in transparent and absorbing materials, the energy relaxation processes, the resulting material modifications (ablation and bulk damage/modification), and some experimental considerations. Finally, various applications are highlighted, including surface structuring, hole drilling, optical data storage, fabrication of embedded waveguides and microfluidic channels, cutting of biological tissues as well as nonlinear photopolymerisation