Investigations on Melting and Welding of Glass by Ultra-short Laser Radiation

The interaction of laser radiation with pulse duration at 80 fs and wavelength lambda = 800 nm with BK7 glass is detected by pump&probe techniques. No melt ejection dynamics can be observed in the time-range of 100 ns to 1.6 mu s by irradiating with a single pulse a glass on the surface using time-resolved shadowgraphy. Using ultra-short pulsed laser radiation glass plates are welded together. The pump beam is focussed by a microscope objective (2 omega(0) approximate to 4 mu m) into the glass. After partial absorption of the optical energy the glass is heated. Due to the large intensities in the focus using high NA objectives multi-photon absorption gets the dominant process and due to large repetition rates heat is accumulated and meting of the glass is induced. By setting the intensity of the laser radiation below the ablation threshold glass can be melted inside and on the surface without cracking which makes welding of glass possible. The modification of a technical glass (D263 Schott) induced by ultra-short pulsed laser radiation with large repetition rates up to 1 MHz is observed during welding by time-resolved quantitative phase microscopy. The change in refractive index induced is detected.