Advantages of beam shaping in quasi-simultaneous fiber laser welding of polymers

Single mode fiber lasers offer a competitive solution for laser welding of polymers. In most laser applications the highly Gaussian nature of the fiber laser out put beam is known to be beneficial but in the case of polymer joining this may not always be true. The strength of the weld is largely defined by the effective joint width, increasing weld width by increasing the number of scans or increasing the laser power can in some cases lead to degradation of the polymer near the center line of the weld. To avoid these problems, beam shapers can be used which convert the characteristic spatial profile of the beam into a more rectangular top hat shape. To investigate these possible improvements to the polymer welding process, polycarbonate samples have been welded with fiber laser quasi-simultaneously by using Gaussian and top hat beam profiles. Beam shaping was performed using a refractive optic module to a Galilean design. Limiting values for input energies were established by varying the laser power and the number of scans. Advantages of beam shaping are discussed based on these results.