Computer simulation of FEL sidebands in a strongly dispersive waveguide

A set of coupled equations suitable for the study of the radiation spectrum of an FEL (free-electron laser) is described. These equations include all the effects of waveguide dispersion. A computer simulation that numerically integrates these equations is used to study sideband growth and saturation in the regime of strong dispersion. The computer simulations seem to confirm that the sideband instability is a process similar to stimulated scattering. Simulations performed in highly dispersive waveguides show that dispersion can have a large effect on the location and gain of FEL sidebands. In the case where the electron velocity and the radiation group velocity become equal, the sideband instability is completely suppressed.<>