  The authors show clear experimental evidence of lasing of exciton polaritons
confined in L3 photonic crystal cavities. The samples are based on an InP
membrane in air containing five InAsP quantum wells. Polariton lasing is
observed with thresholds as low as 120 nW, below the Mott transition, while
conventional photon lasing is observed for a pumping power one to three orders
of magnitude higher.
