Plasmon-Enhanced Whispering Gallery Mode Lasing from Hexagonal Al/ZnO Microcavity

Wurtzite structural ZnO microrods with hexagonal cross section were fabricated by a simple vapor transport method and an individual ZnO microrod was employed as a whispering gallery microcavity. The obviously enhanced spontaneous and stimulated emissions were observed as the ZnO microrod was decorated with Al nanoparticles (NPs). Based on the absorption spectrum of Al NPs, the underlying mechanism was proposed and can be attributed to the resonant coupling between excitons of ZnO and surface plasmons (SPs) of Al NPs at the metal/ZnO interface on the surface of microcavity. In addition, the threshold of the ZnO microcavity decorated with Al NPs has reduced by half compared with that of the bare one, which provides additional evidence to support the energy coupling between the ZnO microrod and Al NPs. The controllability and improved emission properties of these types of microcavities are potentially important for designing highly efficient optoelectronic devices.