Nonlinear emission of semiconductor microcavities in the strong coupling regime

We report on the nonlinear laserlike emission from semiconductor microcavit ies in the strong coupling regime; Under resonant continuous wave excitatio n we;observe a highly emissive state. The energy, dispersion, and spatial e xtent of this state is measured and is found to be dispersionless and spati ally localized. This state coexists with luminescence that follows the usua l cavity-polariton dispersion. It is attributed to the amplification of lum inescence by a parametric gain due to cavity-polariton scattering. Despite the resonant excitation at 1.6 K, we observe no sign of Bose-Einstein conde nsation nor Boser action.