Xj. Shu, COUPLING BETWEEN 2 RESONANT WAVES IN A WAVE-GUIDE FREE-ELECTRON LASER, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 55(3), 1997, pp. 3489-3492
The coupling between two resonant branches of a waveguide free-electro
n laser is studied. It is shown that the induced electron energy sprea
d, which is produced along with the bunching by the radiation, strongl
y influences this coupling. In a low-gain oscillator, the growth of a
lower frequency branch results in large induced energy spread, which s
tops the development of the upper frequency branch. On the other hand,
in a high-gain amplifier, a strong signal can be obtained at high fre
quency by injecting a signal at low frequency that bunches the electro
n beam without large induced energy spread. In this way, the contradic
tion about the nonlinear interaction of two resonant waves in a wavegu
ide free-electron laser is explained.