Scientists from the Laserzentrum Fachhochschule Münster in Steinfurt, Germany, and the Technische Universitat Chemnitz reported that they seam welded stainless steel foil with a joint smaller than 70 µm. They employed a fiber laser that was produced in cooperation with SDL Inc. of San Jose, Calif., and AMS Optotech GmbH of Munich, Germany. The device, which emits 9 W of continuous-wave power, comprises 25 m of Yb-doped quartz fiber and a diode laser pump. For this study, a 50-mm focusing lens collimated the TEM00 beam to a 30-µm spot. The group predicted that advances in focusing optics will allow seam widths of less than 10 µm. It expects applications to be found in micromachining.