Synergistic graphene/aluminum surface plasmon coupling for zinc oxide lasing improvement

Collective oscillations of free electrons generate plasmons on the surface of a material. A whispering-gallery microcavity effectively confines the light field on its surface based on the total reflection from its internal wall. When these two kinds of electromagnetic waves meet each other, the stimulated emissions from an individual ZnO microrod were enhanced more than 50-fold and the threshold was reduced after the whispering-gallery microcavity was coated with a monolayer of graphene and Al nanoparticles. The improvement of the lasing performance was attributed to the synergistic energy coupling of the graphene/Al surface plasmons with ZnO excitons. The lasing characteristics and the coupling mechanism were investigated systematically.