Spectral properties of a far-infrared free-electron laser oscillator based on a two-frequency wiggler

The spectral properties and the nonlinear interactions between an electron beam and the emitted radiation field were studied in a far-infrared free-electron laser oscillator. A two-frequency wiggler was used to obtain a high efficiency and a narrow spectrum, and a multi-particle simulation code was developed using a modified free-electron laser model based on the two-frequency wiggler. Numerical simulations were performed to obtain the optimal condition for the two-frequency wiggler, and the emitted field amplitude and the spectral properties were found to be improved when the two-frequency ratio parameter of the wiggler was optimized.