  The realization of quantum functionalities with polaritons in an
all-semiconductor platform requires the control of the energy and spatial
overlap of the wave functions of single polaritons trapped in potentials with
precisely controlled shape and size. In this study, we reach the confinement of
microcavity polaritons in traps with an effective potential width down to 1 um,
produced by patterning the active region of the (Al,Ga)As microcavity between
two molecular beam epitaxy growth runs. We correlate spectroscopic and
structural data to show that the smooth surface relief of the patterned traps
translates into a graded confinement-potential characterized by lateral
interfaces with a finite lateral-width. We show that the structuring method is
suitable for the fabrication of arrays of proximal traps, supporting
hybridization between adjacent lattice sites.
