  This article concerns the design of antireflection structures which, placed
on a photonic crystal surface, significantly diminish the fraction of energy
lost to reflected waves. After a review of the classes of these structures
proposed to date, a new method is presented in detail for the design of
antireflection gratings operating in a wide range of angles of incidence. The
proposed algorithm is illustrated by means of several examples, showing the
advantages and limitations.
