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We investigate the photoluminescence polarization anisotropy of self-assembled individual lateral InGaAs/GaAs quantum dot molecules. In contrast to similarly grown single quantum dots, the dot molecules exhibit a remarkable degree of linear polarization, which remains almost unchanged when a lateral electric field is applied to tune the exciton wave function and, thus, the luminescence spectral properties. We discuss the nature of this polarization anisotropy and suggest possible causes based on the system's symmetry and heterostructure alloy composition. [ABSTRACT FROM AUTHOR]

Single lateral InGaAs quantum dot molecules have been embedded in a planar microcavity in order to increase the luminescence extraction efficiency. Using a combination of metal-organic vapor phase and molecular beam epitaxy samples could be produced that exhibit a 30 times enhanced single-photon emission rate. We also show that the single-photon emission is fully switchable between two different molecular excitonic recombination energies by applying a lateral electric field. Furthermore, the presence of a polarization fine structure splitting of the molecular neutral excitonic states is reported which leads to two polarization split classically correlated biexciton-exciton cascades. The fine structure splitting is found to be on the order of 10 μeV. [ABSTRACT FROM AUTHOR]

We investigated the photoluminescence from InP quantum dots incorporated in (Ga0.51In0.49)P microdisk structures. With increasing pump power we observe a transition to stimulated emission indicated by the S shape of the input-output curve. This transition is accompanied with a concentration of the emission to one or a few modes exhibiting quality factors on the order of 104 at transparency. Time-resolved measurements show that at the same time the photoluminescence decay time considerably decreases. Furthermore, in the transition regime the linewidth of the lasing mode is reduced and the second-order photon correlation function exhibits a reduction of fluctuations as previously reported for lasers with InAs quantum dots in photonic crystal, microdisk and micropillar cavities as the gain medium. The experimental findings are compared with the predictions of a microscopic theory. [ABSTRACT FROM AUTHOR]