Josef Feldhaus is a graduated physicist.
From 2005 to 2007 Feldhaus was head of the FLASH-Group at the German Electron Synchrotron DESY in Hamburg. He was responsible for the operation and further development of the world‘s first free electron laser in the X-ray range, with which scientists from all over world experimented.
He was, inter alia, member of the Scientific Advisory Council of the Helmholtz-Centrum Berlin (HZB) and of the Facility Advisory Committee of the X-ray laser project LCLD in Stanford, USA. Currently he is a member of the Photon Science Advisory Committee of the Paul-Scherrer-Institute (PSI), Villingen, Switzerland.