  We consider a quasi two-dimensional atomic Bose Einstein condensate
interacting with a near-resonant laser field that is back-reflected onto the
condensate by a planar mirror. We show that this single-mirror optical feedback
leads to an unusual type of effective interaction between the ultracold atoms
giving rise to a rich spectrum of ground states. In particular, we find that it
can cause the spontaneous contraction of the quasi two-dimensional condensate
to form a self-bound one-dimensional chain of mesoscopic quantum droplets, and
demonstrate that the observation of this exotic effect is within reach of
current experiments.
