The quantum-confined Stark effect of excitonic states in self-assembled (In,Ga)As∕GaAs quantum dots was studied by microphotoluminescence spectroscopy. A similar Stark-shift behavior for excitons, biexcitons, and a charged state was observed. Investigations suggest the absence of a permanent dipole moment in the lateral quantum dot plane. Values of the polarizability could be derived for all the investigated states. Furthermore, high-resolution Fabry-Pérot interferometry was applied to resolve the excitonic fine structure splitting and to investigate the influence of a lateral electric field. For a single dot, the splitting could be tuned to zero, thus affording the possibility to create electrically controlled entangled photon pairs.

We apply external uniaxial stress to tailor the optical properties of In(x)Ga(1-x)As/GaAs quantum dots. Unexpectedly, the emission energy of single quantum dots controllably shifts to both higher and lower energies under tensile strain. Theoretical calculations using a million atom empirical pseudopotential many-body method indicate that the shifting direction and magnitude depend on the lateral extension and more interestingly on the gallium content of the quantum dots. Our experimental results are in good agreement with the underlying theory.

This paper reviews the recent advances obtained by integrating semiconductor epitaxial films with embedded self-assembled quantum dots (QDs) on top of single-crystal piezoelectric substrates made of lead magnesium niobate-lead titanate (PMN-PT). This combination allows us to study in detail the effects produced by variable strains (up to about AE 0.2%) on the excitonic emission of single QDs and to add a powerful ''tuning knob'' to QDs. Biaxial stress can be used to reversibly shift the emission wavelength of QDs in a spectral range wider than 10 meV and to modify the relative binding energies of excitonic species. Anisotropic stress has instead a strong influence on the fine structure splitting of neutral excitons. Finally, we present experimental results on the effect of biaxial strain on the optical modes of microring optical resonators and show a simple approach enabling the compensation of piezo-creep via a closed-loop system. Schematic illustration of a QD membrane integrated on top of a PMN-PT substrate. Stress provided by the piezoelectric substrate allows broad range tuning of the emission properties of the overlying dots.