Exciton polaritons confined in ZnO nanowires

ZnO is one of the most attractive materials for optical applications in the visible and the near UV range, ranging from large-scale white-light illumination to miniaturized lasers for the near UV. Furthermore, the unique properties of the semiconductor ZnO are of high interest in the field where advanced optics meets the nanoarea. Because of strong exciton transitions near the electronic band gap and an electron-hole binding energy of 60 meV, the optical properties are dominated by strong light-matter interaction, involving exciton polaritons. In macroscopic ZnO structures, light absorption and emission mediated by excitonpolaritons has been investigated in much detail. It was observed that exciton-photon coupling expressed as the longitudinal-transverse energy splitting is considerable stronger than in other II-VI or III-V semiconductors. In ZnO nanostructures, exciton-photon coupling can even be considerably enhanced due to photon confinement.