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

TL;DR

This paper demonstrates electric field-controlled switching between strong and weak exciton-photon coupling in microcavities with double quantum wells, revealing that dipolaritons are mixed states rather than dark polaritons.

Contribution

It introduces a method to control coupling regimes in microcavities and clarifies the nature of dipolaritons, showing they are not dark polaritons but mixed states.

Findings

Electric field enables switching between coupling regimes.

Polariton ground state is red-shifted and exhibits indirect dipolar exciton features.

Dipolaritons are mixed states with photon, direct, and indirect exciton contributions.

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.