  Optically generated exciton-polaritons in cylindric semiconductor pillar
microcavity with embedded GaAs/AlGaAs quantum wells demonstrate a clear
polariton lasing regime. When exciting in the center of the pillar we detect a
ring-shaped emission, where the peak of intensity can be separated from the
excitation spot by more than 10 micrometers. The spatial coherence of the ring
emission is verified by interferometry measurements. These observations are
interpreted by drift of the exciton polariton condensate away from the
excitation spot due to its repulsion from the exciton reservoir and by its
spatial confinement by the pillar boundary.
