Electron laser achieves world first

17 Jun 2002

German researchers' electron laser amplifies ultraviolet light by a factor of 10 million.

Researchers at the German research center DESY have built the world's most powerful ultraviolet free electron laser. Reaching the theoretical maximum amplification of 10 million, the laser brings researchers closer to their ultimate goal of an X-ray laser.

The laser's intensive light is fuelled by DESY's superconducting linear accelerator TESLA, which accelerates bunches of electrons to velocities approaching the speed of light. At the end of the accelerator the electrons travel through an undulator. This comprises a sequence of north- and south-pole magnets to guide the electrons along a zigzag path.

As each electron changes direction it emits radiation which interacts with other electrons in its bunch, forcing some to speed up and others to slow down. After a complex series of interactions, each bunch of electrons becomes tightly packed until eventually, all electrons in every bunch oscillate in phase and emit intense flashes of light.

Researchers can tweak this self-amplifying effect to take place at any wavelength by altering the acceleration of the electrons. They have successfully amplified ultraviolet wavelengths between 80 and 180 nm and achieved maximum amplification with a wavelength of 98 nm.

"Compared with the best synchrotron light sources where we presently carry out our research, the free electron laser is a million times better," said Jochen Schneider, DESY's director of research.

The researchers expect an X-ray laser to have a range of uses in medicine, chemistry, physics and biology, including studying living cells, molecules and materials at the atomic level.