Influence of the laser-plume interaction on the beam profile during deep-penetration welding with coherent beam shaping.

A high-power laser beam profiling system was set up to investigate the influence of the interaction between the laser beam and the process emissions during welding with a shaped beam profile. A positional instability of the beam on the workpiece in the order of magnitude of tens of µm and noticeable distortions of the beam shape were observed when no cross jet was used. Both perturbations were reduced when a cross jet was applied to remove the process emissions from the beam path and minimized when the cross jet was positioned closest to the workpiece.

Dynamic of cold-atom tips in anharmonic potentials.

Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion. Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time.