Soft and Hard X-ray SASE Free Electron Lasers

Abstract

In the last couple of years, free electron lasers (FELs) have been a remarkable success as fourth generation light sources all over the world. Operating in the SASE mode, they produce laser-like radiation in a broad wavelength range. Especially in the soft and hard X-ray ranges, these light sources open unique and completely new fields in physics and allow a vast range of applications in most scientific fields. This article gives an overview of the principles of FELs and the SASE process, discusses technological challenges and solutions, and presents an outlook for future developments.