  We consider the amplification in strong electric (magnetic) fields that are
uniform along the direction of the electron motion and are not uniform in the
transverse direction. It is shown that in such a system the gain is increased
compared with that of a magnetic undulator by a value of the order of gamma (
gamma is the relativistic factor). Numerical estimates are presented that
determine the possibility of amplification of a test wave in the optical and
near infrared bands.
