In this paper we discuss the spectroscopic details of the two-frequency undulator, a recently proposed device to suppress the sideband instability in free-electron lasers. We present an analytic and numerical approach to the problem and discuss the intrinsic differences between the brightnesses of one- and two-frequency undulators. We study the dependence of the emission on various physical parameters including the electron-beam qualities.

• Received 14 September 1992

DOI:https://doi.org/10.1103/PhysRevE.47.2061