Ultra-fast Diagnostics of Laser-induced Melting of Matter in ns to μs Time-scales

The interaction of laser radiation with dielectrics and metals is detected with femtosecond resolution by pump&probe techniques (t = 80 fs or 3 ps, λ = 810 nm). Even with femtosecond laser radiation melt ejection dynamics can be observed by irradiating metals like copper or aluminium using time-resolved shadowgraphy. Laser-induced melt ejection has been observed in the time range of 100 ns to 1.04 μs after the initial laser-metal interaction. Depending on metal-specific parameters, rosette-like surface structures of the ablated regions are observed. The modification of BK7 glass by femtosecond or picosecond laser radiation is observed by timeresolved Nomarski-Photography using ultra-short pulsed white-light continuum as probe beam. The pump beam is focussed by a microscope objective into the glass. After partial absorption of the optical energy the glass is heated and depending on the focus diameter (2ω0 ≈ 1 μm) cracking is induced. For BK7 glass using picosecond laser radiation modification and cracking are induced. By decreasing the intensity of the laser radiation glass can be melted inside and on the surface without cracking.