Investigation of laser-induced ablation processes and production of microstructures by picosecond laser pulses
Material ablation induced by picosecond laser radiation was investigated. The first 20 nanoseconds of the ablation process were analysed by high-speed photography and pump and probe, measurements with a time resolution of 40 picoseconds. The measurements allow a detailed characterization of the melting, vaporization and solidification processes. Shock waves in the ambient atmosphere were detected and from their expansion the energy in the shock wave was determined to be 5-20% of the available ablation pulse energy. Picosecond laser pulses were used for microstructuring metals, ceramics and diamond. Using 40 ps laser pulses line patterns with a minimum line width of 7 mu m were formed in diamond without destroying the crystallinity. In Si3N4-ceramics holes were drilled with diameters <6 mu m. Ultrathin Cu and Au films of 1 mu m thickness were removed from fused silica and Si (100) without influencing the substrates.