Cavity-polariton interaction mediated by coherent acoustic phonons in semiconductor microcavities

The strong coupling between excitons in a quantum well (QW) and photons in a semiconductor microcavity leads to the formation of quasi-particles known as cavity-polaritons. In this contribution, we investigate their interaction with coherent acoustic phonons in the form of surface acoustic waves (SAWs) in a GaAs QW embedded in a (Al,Ga)As/AlAs microcavity. The periodic modulation introduced by the phonons folds the cavity-polariton dispersion within a mini-Brillouin zone (MBZ) defined by the phonon wave vector ($k_\mathrm{SAW}$). The appearance of well-defined mini-gaps at the edge of the MBZ as well as folded modes in the center of the MBZ are observed for different phonon densities and different cavity polariton detuning energies. The experimental results are in good agreement with calculations that take into account the modulation of the optical thickness of the microcavity spacer layer and the band-gap modulation of the GaAs QW caused by the SAW strain field.