Strong coupling of a quantum dot molecule to a photonic crystal cavity

Dynamically tunable light-matter interfaces are important for the success of emerging quantum technologies. Quantum dots embedded in photonic crystal membranes provide an attractive platform as the cavities have high quality factors, low mode volumes, and can be doped to provide limited voltage tuning of the exciton states. Here, the authors demonstrate that the versatility and applications of this architecture can be extended by replacing the quantum dot with a quantum dot molecule. Two tunnel-coupled quantum dots permit molecular exciton states that have voltage-tunable energies and dipole moments. Advantage is taken of the tunable dipole moments of mixed exciton states to demonstrate $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ tuning of the vacuum Rabi splitting as well as new polariton states with hybrid spin character.