Electrical control of fine-structure splitting in self-assembled quantum dots for entangled photon pair creation

The fine-structure splitting δ1 of the bright exciton doublet in self-assembled InGaAs/GaAs quantum dots is measured as a function of the applied in-plane electric field using time-resolved Kerr rotation. We observe a significant reduction of δ1 with increasing electric field, suggesting a symmetrizing of the electron and hole wave functions. For sufficiently high fields, it is shown that δ1 can be made less than the quantum dot homogeneous linewidth γ, which is calculated using an appropriate model. This may open the way for the electrical control of polarization-entangled photon pair creation through the radiative biexciton cascade.