MISCONCEPTIONS REGARDING SECOND HARMONIC GENERATION IN X-RAY FREE-ELECTRON LASERS

Nonlinear generation of coherent harmonic radiation is an important option in the operation of a X-ray FreeElectron Laser facility (XFEL) since it broadens the spectral range of the facility itself, thus allowing for a wider scope of experimentalapplications. We find that up-to-date theoretical understandingof second harmonicgeneration is not correct. Derivation of correct radiation characteristics will follow our criticism. A more detailed report of our study is given in [1].