The physical mechanism in the free-electron laser depends upon the propagation of an electron beam through a periodic magnetic field. Both incoherent and coherent radiation results from the undulatory motion of the electron beam in the external fields which permits a wave-particle coupling to the output radiation. Coherent radiation depends upon the stimulated emission due to the ponderomotive wave formed by the beating of the radiation and wiggler fields. The wiggler field itself may be either magnetostatic or electromagnetic in nature. Although the bulk of experiments as of this time have relied upon magnetostatic wigglers with either helical or planar polarizations, the fundamental principle has also been demonstrated in the laboratory using a large-amplitude electromagnetic wave to induce the requisite undulatory motion in the electron beam. In this chapter, we discuss the fundamental theory of free-electron lasers with electromagnetic-wave wigglers.
KeywordsElectromagnetic-wave wiggler Single-particle trajectories Small-signal gain Efficiency enhancement
- 7.H.R. Hiddleston, S.B. Segall, G.C. Catella, Gain-enhanced free-electron laser with an electromagnetic pump field, in Physics of Quantum Electronics: Free-Electron Generators of Coherent Radiation, ed. by S.F. Jacobs, G.T. Moore, H.S. Pilloff, M. Sargent, M.O. Scully, R. Spitzer, vol. 9 (Addison-Wesley, Reading, 1982), p. 849Google Scholar