  Ordered atomic arrays trapped in the vicinity of nanoscale waveguides offer
original light-matter interfaces, with applications to quantum information and
quantum non-linear optics. Here, we study the decay dynamics of a single
collective atomic excitation coupled to a waveguide in different
configurations. The atoms are arranged as a linear array and only a segment of
them is excited to a superradiant mode and emits light into the waveguide.
Additional atomic chains placed on one or both sides play a passive role,
either reflecting or absorbing this emission. We show that when varying the
geometry, such a one-dimensional atomic system could be able to redirect the
emitted light, to directionally reduce or enhance it, and in some cases to
localize it in a cavity formed by the atomic mirrors bounding the system.
