The free-electron laser at DESY produces ultraviolet laser light with wavelengths between 80 and 180 nanometers (one millionth of a millimeter). These are the shortest wavelengths ever produced by an FEL. The maximum light amplification ("saturation") was obtained with a wavelength of 98 nanometers. Hence research is now presented with a new, extremely powerful light source. Moreover this demonstration is an important milestone towards the X-ray laser which is being developed and planned in international cooperation at the research center DESY in Hamburg in the context of the TESLA project.

The spectacular results were produced using a free-electron laser in the test facility for TESLA presently in operation at DESY. There the intensive laser light is produced using a new principle: electrons are brought to high energies in a superconducting accelerator, traverse thereafter on a slalom-like course a special arrangement of magnets and emit thereby laser-like bundles of radiation. The trick to amplification is that the electrons and the emitted radiation influence each other as they traverse the 15 m long magnet structure. In the process, tiny bunches of electrons become more and more dense and radiate even more intensely – a self amplifying effect. The process repeats itself until all the electrons oscillate in unison. The light emitted by the electrons overlaps and produces extremely intense flashes of laser light. This is the principle of SASE – "self-amplified spontaneous emission". A remarkable feature of the SASE principle is that, unlike traditional lasers, it is not limited to specific wavelengths. The electron acceleration may simply be selected accordingly. At the SASE free-electron laser at DESY, it has been shown for the first time that the self amplifying effect indeed does lead to the theoretically calculated amplification by a factor of ten million in the ultraviolet regime. Similar amplification factors have been demonstrated last year at institutes in the USA in the regime of visible light, while the DESY FEL now offers considerably shorter wavelengths. At DESY the first groups of scientists are embarking on research applying this new, unrivaled light source. DESY director of research, Prof. Jochen Schneider: "Compared to the best synchrotron light sources where we presently carry out our research, our free-electron laser is a million times better."

In about one year, the existing test facility will be upgraded to a 300 meter long free-electron laser with wavelengths smaller than six nanometers. This is the regime of "soft" X-rays. This unprecedented light source would then present unique opportunities to scientists from all around the world. At the same time, the facility will serve as a test bed for the future project TESLA at which the new SASE technology will be applied to produce ever shorter wavelengths.

TESLA stands for TeV-Energy Superconducting Linear Accelerator where TeV denotes Tera-electron-Volts. Implied is a 33 km long linear accelerator, which is being developed in international collaboration, within which electrons are brought into collision with their antiparticles, the positrons. The special feature of the new facility is that the accelerator allows collisions between particles of highest energies while simultaneously serves as a source for intense and extremely short x-ray pulses with laser-like properties. The TESLA X-ray lasers will offer new perspectives for research in may different disciplines including physics, chemistry, biology, material science, and medicine. A decision regarding the TESLA project is expected after the summer of 2002. TESLA would be founded and operated as an international center. After its approval and the completion of the planning procedure, TESLA could begin operation after an eight year construction period at the start of the next decade.