Abstract: The invention relates to a method for generating electromagnetic radiation (preferably UV, VUV, XUV, or X-rays), to an optical short-period undulator (10) and to a free-electron laser comprising the latter. To accomplish the method, a high-energy electrically charged particle beam (5) is provided, and high-intensity electromagnetic pulses (7, 7a, 7b) are generated, and by interfering said pulses with one another an electromagnetic standing wave is created, wherein said standing wave has an electric field strength of a pre-determined peak value. The particle beam is directed through the non-steady electromagnetic field of the standing wave in or in the vicinity of a plane spanned by nodes with maximal electric field strength of said electromagnetic standing wave.

Abstract: The invention relates to a method for generating electromagnetic radiation (preferably UV, VUV, XUV, or X-rays), to an optical short-period undulator (10) and to a free-electron laser comprising the latter. To accomplish the method, a high-energy electrically charged particle beam (5) is provided, and high-intensity electromagnetic pulses (7, 7a, 7b) are generated, and by interfering said pulses with one another an electromagnetic standing wave is created, wherein said standing wave has an electric field strength of a pre-determined peak value. The particle beam is directed through the non-steady electromagnetic field of the standing wave in or in the vicinity of a plane spanned by nodes with maximal electric field strength of said electromagnetic standing wave.