Enhanced harmonic generation at terahertz frequencies with a two-frequency wiggler

It is known that a strong harmonic radiation from free electron laser (FEL) devices could lead to a significant reduction in the minimum electron energy required to generate radiation at a given frequency. However practical application of this technique to terahertz FELs has been hampered by the very weak strength of FEL radiation at high harmonics. In this paper, a two-frequency wiggler configuration is considered as a means to enhance the strength of FEL emission at high harmonics. It is shown that by adjusting the nonlinear interference between the two constituent components of the two-frequency wiggler the emission strength around the 10th harmonic can be increased considerably by two orders of magnitude. This characteristic can then be used to reduce the electron energy needed for terahertz radiation from 2.5 MeV to below 500 keV, thus reducing significantly size and cost of the eventual terahertz FEL system