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Ultrashort pulsed laser welding of dissimilar materials has become an attractive alternative technique to commonly used adhesive bonding for joining optics to metal mounts / assemblies in the manufacturing of optical and laser systems. The laser welding process relies on very high peak intensities from an ultrashort (ps/fs) pulsed laser beam which is tightly focused through a transmissive optical component, providing a focal spot in the vicinity of the optic-metal interface. Nonlinear multi photon absorption in the optic and linear absorption in the metal results in a highly confined plasma, surrounded by a localised melt zone that rapidly cools to form a bond. For successful welding, the laser pulse repetition rate must be sufficiently high to provide thermal accumulation, to ensure a localised melt volume (the heat-affected zone, HAZ) surrounding the small plasma. The size of this HAZ is dependent on the laser processing parameters and material combinations used during the process and is typically on the ~100μm scale. As the laser spot translates across the material, this highly localised melt/plasma zone rapidly solidifies behind the beam and forms a strong bond (micro weld) between the two surfaces.
We present our recent results from the ultrashort pulsed laser welding of Er,Yb:Phosphate laser glass and Nd:YAG laser crystals to copper for a combination of mechanical mounting and thermal management (heatsinking) applications in laser systems. Er,Yb:Phosphate glass is a well-known and commonly used active medium for lasers emitting in the ‘eye-safe’ spectral range from 1.5-1.6μm. Nd:YAG is the most popular lasing media for solid state lasers typically emitting light in the 1.064μm spectral range. We investigate the influence of laser processing parameters such as pulse duration and repetition rate on the resultant welds. Analysis of welded parts includes shear strength and accelerated lifetime tests.
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