Dependence of the redshifted and blueshifted photoluminescence spectra of single InxGa1-xAs/GaAs quantum dots on the applied uniaxial stress

 We apply external uniaxial stress to tailor the optical properties of In_xGa_1-xAs/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.