Abstract

The laser gain G of the free-electron lasers exploiting media with periodically modulated refractive indices is studied in the regime of a large modulation. Such a medium can be realized as a superlattice-like structure or it can be created by a series of optical breakdowns in a gas produced by a train of pulses formed by an external laser. Criterion for existing of the large-modulation regime is determined. It requires that the period of modulation should exceed the speed of light devided by the maximum plasma frequency of the modulated medium. Thus, the largemodulation regime of the FEL can be realized under even if the modulation itself is rather small.

© 1996 IEEE