  The polarization splitting of the exciton ground state in two laterally
coupled quantum dots under an in-plane electric field is investigated and its
effective tuning is designed. It is found that there are significant Stark
effect and anticrossing in energy levels. Due to coupling between inter- and
intra-dot states, the absolute value of polarization splitting is significantly
reduced, and it could be tuned to zero by the electric field for proper
inter-dot separations. Our scheme is interesting for the research on the
quantum dots-based entangled-photon source.
