LASER-EMISSION FROM SEMICONDUCTOR MICROCAVITIES - TRANSITION FROM NONPERTURBATIVE TO PERTURBATIVE REGIMES

We have demonstrated laser emission at densities below the saturation exciton density in a semiconductor microcavity by tuning the cavity re sonance to the low-energy side of the inhomogeneously broadened excito n distribution. Laser emission in this regime arises from population i nversion of localized excitons at the low-energy tail of the inhomogen eous distribution. Distinct spectral line shapes of laser emission and especially a large and abrupt change in the lasing threshold are obse rved when the composite system undergoes a transition from the nonpert urbative to the perturbative regimes. The abrupt threshold change is a ttributed to ionization of excitons occurring in the transition region .