Abstract

A self-consistent quantum electrodynamic (SCQED) theory of high voltage free electron lasers (FEL) is given. Spontaneous emission spectra and gain are predicted in the small signal gain regime and compared to FEL experimental data. The SCQED theory predicts line shift, spectral broadening, and gain reduction due to quantum mechanical effects which are not predicted by the classical/conventional FEL theories. Comparison with well accepted FEL experiments shows excellent agreement between the SCQED predictions and the data: much better than predicted by the classical/conventional FEL theories. Classical FEL theory is recovered as a subset of the SCQED theory in the classical limit of the SCQED FEL theory. It is found that the classical/conventional FEL theories are only valid in the limit of a short undulator containing a small number of periods. This limit results from the non-negligible finite electron state lifetime, and its associated spectral linewidth broadening (natural linewidth phenomena).

© 1989 Optical Society of America