摘要
In recent years, much attention has been paid to the free-electron laser (FEL). Especially, Madey provided an important theorem, the first part of which expresses the stimulated emission as the derivative of the spontaneous emission, and the second part gives an expression for the spontaneous emission in terms of the firstorder perturbation to the energy of the electron expressed in powers of the optical field. Subsequently, Kroll Morton et al. and Groven et al. rewrote the Madey theorem as the following form:
