Monitoring electrically driven cancellation of exciton fine structure in a semiconductor quantum dot by optical orientation.

We use optical orientation technique to monitor the degeneracy control of exciton states in a single InAs/GaAs quantum dot, achieved by applying an in-plane electric field. Under circularly polarized quasiresonant excitation, the exciton photoluminescence shows a pronounced maximum of circular polarization at electric field corresponding to zero fine structure splitting. By analyzing the width of this maximum we are able to determine the homogeneous linewidth of the excitonic transition. This experimental method is shown to be very efficient to test and possibly tune the photonic properties of an individual quantum dot for the emission of entangled photon pairs. [ABSTRACT FROM AUTHOR]