Nonlinear emission of semiconductor microcavities in the strong coupling regime

We report on the nonlinear laserlike emission from semiconductor microcavities in the strong coupling regime. Under resonant continuous wave excitation we observe a highly emissive state. The energy, dispersion, and spatial extent of this state is measured and is found to be dispersionless and spatially localized. This state coexists with luminescence that follows the usual cavity-polariton dispersion. It is attributed to the amplification of luminescence by a parametric gain due to cavity-polariton scattering. Despite the resonant excitation at 1.6 K, we observe no sign of Bose-Einstein condensation nor Boser action.