Investigations on ultrafast welding of glass-glass and glass-silicon

Using ultrafast laser radiation glass substrates are welded with glass and silicon plates. The pump beam is focused by a microscope objective with large NA=0.4 (beam diameter 4 mu m) into the glass. After partial absorption of the optical energy, the glass is heated and melted. Procedures for high-quality welding of glass-glass and glass-silicon substrates with high-repetition ultra-fast laser radiation have been derived at the repetition rate 700 kHz. The dependencies of the dimension and geometry of the welding seam on scan velocity, repetition rate and pulse energy have been investigated defining a process window. Adding a noninterferometric technique for quantitative phase detection with the welding setup, the interaction zone of the welding seam for the welding partners glass-glass is detected. A change in refractive index is induced by heating and compression of the glass and has been detected by phase detection up to 2 mu s after irradiation with 100 fs time resolution.