  We review recent results on the linear and non-linear optical response of
realistic quantum-wire structures. Our theoretical approach is based on a set
of generalized semiconductor Bloch equations, and allows a full
three-dimensional multisubband description of Coulomb correlation for any shape
of the confinement profile, thus permitting a direct comparison with
experiments for available state-of-the-art wire structures.
  Our results show that electron-hole Coulomb correlation removes the
one-dimensional band-edge singularities from the absorption spectra, whose
shape results to be heavily modified with respect to the ideal free-particle
case over the whole range of photoexcited carrier densities.
