Optical Gain Results Of The Los Alamos Free-Electron Laser Amplifier Experiment

Optical gain has been detected at 10.6 μm during the recent tapered-wiggler free-electron laser amplifier experiment at Los Alamos. In addition, it was possible to measure separately the coherent spontaneous emission at the fundamental and at the second-hand third-harmonic wavelengths. Separation of the stimulated gain and coherent spontaneous emission from each other and from the high-power (gigawatt) CO2 laser radiation was possible by use of polarization analysis and passive frequency filtering in hot CO2 gas. The magnitude of the optical gain signals near resonance was consistent with the theoretically predicted gain of about 1%. Optical measurements as a function of several parameters of the electron beam (energy and current) and the CO2 laser (power) provided further supporting evidence for our identifications.