The Nd laser has proved almost perfect for metal working and has been used to great advantage in the Philips Company. Experience over seven years shows increasing complexity in beam handling and the use of increasing higher powered lasers. Because of thermal lensing of the laser rod as a function of output power beam parameters as divergence angle and beam waist are seen to vary with output power. Above - 100 W one has to give due attention to this phenomenon and one has to use the proper laser resonator and focusing optics. In order to obtain the maximum benifit from laser welding one has to design products for this joining technique. Both weld geometry and the proper alloys should be chosen for reliable welding.
C. J. Nonhof,
G.J. A. M. Notenboom,
"Spot Welding With Nd Lasers", Proc. SPIE 0611, Laser Processing of Semiconductors & Hybrids, (7 July 1986); doi: 10.1117/12.956409; https://doi.org/10.1117/12.956409