  After reviewing the pioneering work by Zel'Dovich in which radiation is
amplified perpendicular to the axis of a rotating conductor, we consider an
alternative scattering arrangement. We demonstrate superradiant amplification
of electromagnetic waves with orbital angular momentum, directed axially
towards a rotating conductor. Taking into account recent advances in optics and
condensed matter systems, our approach presents new possibilities for
rotational superradiance experiments. We discuss remaining challenges that must
be faced before a laboratory observation of the Zel'Dovich effect can be
considered feasible.
