Amplified-spontaneous-emission power oscillation in a beam-wave interaction.
We present in this paper compelling evidence supporting the three-wave traveling-wave theory developed by Pierce fifty years ago. The transition in a Smith-Purcell free-electron laser from low, through moderate amplified spontaneous emission, to strong gain conditions was carefully controlled. Below threshold, the emitted far-infrared power exhibits oscillations with a cubic dependence on the electron beam current. Both characteristics are expected in a three-wave interaction yet, to date, have not been observed.
Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755-3528, USA.
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Bakhtyari
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Walsh
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Brownell