Update on free‐electron lasers an applications

Lasers whose operating frequencies are not determined by energy levels in atoms or molecules have long been a goal of researchers in the field. Stimulated scattering by free electrons passing through spatially varying magnetic fields promises to meet that goal. Two years ago, a group at Stanford reported laser action from stimulated bremsstrahlung, and a collaborative effort of the Columbia University Plasma Lab and the Naval Research Lab has produced a laser based on stimulated Raman scattering by free electrons. These results have encouraged many other laboratories to investigate the construction and potential uses of free‐electron lasers. Active research is now going on at Bell Labs, Los Alamos, The University of Trento, Frascati, Brookhaven, and the Lawrence Livermore Labs, among others. Much of the excitement is due to these lasers' promise of exceedingly high power levels at a low enough cost to make them useful suppliers of industrial process energy.