Free-electron laser exploiting a superlattice-like medium

Amplification in free-electron lasers exploiting media with periodically modulated refractive indices is studied in the regime of a large modulation. The conditions for realization of the large-modulation regime in a superlattice-like medium are established. The maximized gain, the corresponding saturation field and efficiency, as well as the optimal electron energy and propagation direction are determined. It is shown that the large-modulation regime makes it possible to extend significantly the operation frequency domain of the FEL employing a low-relativistic electron beam. Relationship with the Cherenkov and stimulated resonance-transition-radiation FELs is discussed. This research is partially supported by RFBR grant 97-02-17783.