Industrial ultrashort pulsed laser welding of copper and titanium to quartz and glass components for optical applications

Ultrashort pulsed laser welding of dissimilar materials is becoming an attractive alternative technique to currently used adhesive bonding for metal-glass components in the manufacture of optical and laser systems. This laser welding process relies on the very high peak intensity from a laser beam that is tightly focused through the top of the transmissive optical component (glass) to provide a focal spot in the vicinity of the metal-glass interface. Non-linear multi-photon absorption results in the generation of free electrons in a highly localised focal volume, leading to plasma formation. For a successful weld, the laser pulse repetition rate must be sufficiently high to also provide thermal accumulation, resulting in a localised melt volume (heat affected zone (HAZ)) surrounding the small plasma. The size of this HAZ depends on the laser parameters used and can be modified to be smaller than 100 µm. As the laser spot translates across the material, this highly localized melt zone solidifies behind the beam and forms a strong bond (micro weld) between the two surfaces.
We present our recent findings on the influence of laser process parameters such as; pulse duration and the use of burst mode; and the effect of material properties such as surface texture. We will also present results quantifying the effect of mismatch in coefficients of thermal expansion on the residual stress of optical components (quartz or glass) welded to structural (metal) components using the ultrashort pulse laser welding technique. The technique is based on the use of an ultrashort (260fs-5ps) pulsed Amplitude laser operating at 1030nm and 500 kHz.
The results from the shear strength tests and accelerated lifetime tests of ultrashort laser pulse welded components will also be presented.