Controlled strong coupling and absence of dark polaritons in microcavities with double quantum wells

Abstract: We demonstrate an efficient switching between strong and weak exciton-photon coupling regimes in microcavity-embedded asymmetric double quantum wells, controlled by an applied electric field. We show that a fine tuning of the electric field leads to drastic changes in the polariton properties, with the polariton ground state being red-shifted by a few meV and having acquired prominent features of a spatially indirect dipolar exciton. We study the properties of dipolar exciton polaritons, called dipolaritons, on a microscopic level and show that, unlike recent findings, they are not dark polaritons but, owing to the finite size of the excition, are mixed states with comparable contribution of the cavity photon, bright direct, and long-living indirect exciton modes.