Abstract

The bunching phenomenon is the basic process occurring in a free-electron generator of coherent generation such as the Klystron in the mm-wave- length range or the free-electron laser (FEL) in the optical region. During interaction with the incident electromagnetic wave the electrons are progressively gathered into small packets separated by a length equal to its wavelength λ_L. Once the electrons are bunched there is a given phase relationship between them and the field of any wave which wavelength is an harmonic of λ_L. This is the source of the gain (electrons decelerated by the field) or of the absorption (electrons accelerated by the laser) mechanisms.¹

© 1986 Optical Society of America