The performance achievable in laser material processing depends not only on the optical power of the source but also onthe quality (for example in terms of the beam-parameter-product) of the beam incident on the workpiece. Therefore, tooptimize the production yield, flexible laser machines must have the possibility to change the beam quality depending onthe specific process in which they are used. A typical example is sheet metal cutting with fiber lasers, as thin and thicksheets require two different beam quality values. The paper reports on a new device that allows continuously anddynamically changing the beam quality of laser beams in the kilowatt range to optimize the performance of laser cuttingof sheet metals of different thicknesses. When the device is used with 100 μm input and output fibers, the beamparameter product can be tuned from about 4 mm?mrad to 7.5 mm?mrad with coupling efficiency always larger than95%. An even broader beam parameter product range up to 9 mm?mrad can be achieved when using 50 μm input and100 μm output fibers, respectively.
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