Free electron lasers: scientific challenge for military and civilian development

Both classified and unclassified experiments throughout the world, most recently at France's Orsay Laboratory for the Utilization of Electromagnetic Radiation, show that the en­ ergy of high-quality electron beams can be directly converted to laser radiation. Theoretical and computer studies based on these experi­ ments indicate that this conversion of "free electron" energy into laser beam energy can be scaled to high power levels and readily tuned to a wide variety of wavelengths with extremely high efficiencies compared to conventional lasers. This free electron laser (FEL) promises to be a most versatile tool for laser applications-such as optical communications, isotope separation, metal cutting and finishing, photochemistry, anti­ missile beam weapons and inertial confinement fusion-and for making feasible entirely new ones such as intercontinental transport of power and laser beam propulsion of satellites. Thus, the FEL promises to be the "electric motor" of the emerging laser industrial revolution. As announced in the June 24 Le Monde, scientists at the Orsay Laboratory for the Utilization of Electromagnetic Ra­ diation reported that on June 22 that they were able to extend the operation of their FEL, which is based on an electron beam storage ring, to the shorter "red" wavelength-about 0.6328 micrometers-at low beam power levels of about 50 microwatts. The previous short wavelength record for an FEL was held by Stanford University which achieved outputs in the multimicrometer infrared range. The French team which is led by Dr. Yves Petroff who has been collaborating with Stanford's Dr. John Maddy, the inventor of the FEL con­ cept, for the last several years. This most recent FEL break­ through demonstrates the increasing progress of FEL tech­ nology in general and will have immediate applications in the full range of laser photochemistry and spectroscopy research.