Control of Rabi Splitting Energies in CuCl Microcavities with HfO2/SiO2 Distributed Bragg Reflectors

The exciton-photon interaction in CuCl microcavities with HfO2/SiO2 distributed Bragg reflectors has been investigated from the viewpoint of the active-layer-thickness dependence of the interaction energy, the so-called vacuum Rabi splitting energy. The active layer thickness was changed from A/32 to A/5, where A corresponds to an effective resonant wavelength of the lowest-lying Z3 exciton. 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 Z3 and Z1,2 excitons, and cavity photon. The incidence-angle dependence of the cavity-polariton energies was analyzed with a phenomenological Hamiltonian for the strong coupling. The vacuum Rabi splitting energies are systematically controlled from 22 (37) to 68 (122) meV for the Z3 (Z1,2) exciton with an increase in the active layer thickness. The active-layer-thickness dependence of the Rabi splitting energy is quantitatively explained using a simple model for quantum-well microcavities.