Welding and cutting of copper with high brightness lasers

When using a fiber laser for the processing of copper or other high reflecting materials, we have to take care of the back reflection. If we used a polarized laser with wave lengths in the range of 1 micro m, it would be relatively easy to build up an optical diode to block optical feedbacks by using the Faraday isolator (rotator) or the l/4 window. That system can also be used in order to increase the beam power and power d. at the workpiece. The presentation will show the effect of optical feedbacks during cutting and welding with the fiber laser, how those feedbacks could be reduced and how they have to be used to optimize the cutting or welding process. On the other hand the presentation will show the influence of the Brewster effect for applications with the fiber laser. Those effects will be explained from the phys. basics to industrial applications.