Control of exciton-photon interactions in CuCl microcavities

Abstract

We have investigated the active-layer-thickness dependence of exciton-photon interactions in planar CuCl microcavities with HfO${}_{2}/$SiO${}_{2}$ distributed Bragg reflectors. The active layer thickness was changed from $\ensuremath{\lambda}/$32 to $\ensuremath{\lambda}/$4, while the cavity length was fixed at $\ensuremath{\lambda}/$2. We performed angle-resolved reflectance measurements and clearly detected three cavity-polariton modes, originating from the lower, middle, and upper polariton branches, in a strong-coupling regime of the ${Z}_{3}$ and ${Z}_{1,2}$ excitons and cavity photon. The incidence-angle dependence of the cavity-polariton modes was analyzed using a phenomenological Hamiltonian for the strong coupling. It was found that the interaction energies of the cavity-polariton modes, the so-called vacuum Rabi splitting energies, are systematically controlled from 22(37) to 71(124) meV for the ${Z}_{3}$(${Z}_{1,2}$) exciton by changing the active layer thickness from $\ensuremath{\lambda}/$32 to $\ensuremath{\lambda}/$4. The active-layer-thickness dependence of the Rabi splitting energy is quantitatively explained by a simple theory for quantum-well microcavities.