Polariton lasing is demonstrated on the zero dimensional states of single
GaAs/GaAlAs micropillar cavities. Under non resonant excitation, the measured
polariton ground state occupancy is found to be as large as 104. Changing
the spatial excitation conditions, competition between several polariton lasing
modes is observed, ruling out Bose-Einstein condensation. When the polariton
state occupancy increases, the emission blueshift is the signature of
self-interaction within the half-light half-matter polariton lasing mode.Comment: 5 pages, 4 figures, accepted for publication in Physical Review
Letter