Abstract

The efficiency of a free-electron laser (FEL) is limited because of the loss of synchronism between beam and wave associated with the extraction of energy from the beam. Tapering the wiggler, a commonly accepted solution for maintaining synchronism, is not satisfactory because of two adverse effects: the small-signal gain is sharply reduced, as is the fraction of electrons trapped in a decelerating field. At IR and shorter wavelengths, only a few percent extraction efficiency has been achieved by tapering.

© 1987 Optical Society of America