Storage‐ring free‐electron laser operates in the visible

The successful generation of a 6500‐Å free‐electron laser beam this summer at the French electron storage ring ACO represents a number of firsts. This culmination of a three‐year effort by an Orsay–Stanford collaboration at Orsay's LURE (Laboratoire pour l'Utilisation du Rayonnement Electromagnetique) synchrotron‐light laboratory is the first operation of a free‐electron laser oscillator at a visible‐light wavelength. It is, furthermore, the first operation of a free‐electron laser oscillator at any wavelength using the circulating electron beam of a storage ring. The Orsay–Stanford FEL is also the first device to achieve laser oscillation with an “optical klystron”—a modified wiggler design suggested by N. A. Vinokurov and Alexander Skrinsky at Novosibirsk (in 1977) for enhancing the gain of free‐electron lasers.