Micro-welding of glass by fs-laser irradiation and process observation using fs-pump-probe white light interference microscopy

The miniaturization of optical components claims for new methods for assembling e.g. micro lenses on integrated optical circuits or sealing of OLEDs in order to improve productivity and quality. Welding of glass for micro-technological application is still a field of research, because scaling-down the welding seam into the micrometer scale implicates also sub-micrometer heat-affected zones [1]. The localized melting in the volume and the welding of borosilicate and quarz glasses by ultrafast laser radiation (λ = 1045 nm, IMRA, µJewel D-1000) with femtosecond pulse durations has been investigated. A wide range of further applications like the writing of waveguides [2] and the micro-structuring by material modification and subsequent etching [3] is based on the same initial processes. The non-linear absorption of the fs-laser radiation, localized melting and the fast cooling of the material are the basic processes for all these techniques. Compression and expansion of material lead to refractive index changes as well as local differences in the temperature.