Generation of exciton-polaritons in ZnO microcrystallines using second-harmonic generation

Abstract

We report an observation and detail mapping of exciton-polaritons (polaritons hereafter) on both lower-polariton and upper-polariton branches in ZnO microcrystallines using second-harmonic generation. Our investigations reveal that those polaritons can be well described by the dispersion curves of nanowires at certain diameter. The polaritons in the tree-like microcrystallines evolve as a function of incident wavelength in a similar fashion as that in a single nanowire. Hence, the origin of polaritons generated in the wire-based microcrystallines is the coupling between the excitons and the nanowire-cavities. The resonance profile of the polaritons reveals that the enhancement is due to the strong coupling between second-harmonic photons and the A, B and C excitons in ZnO. The high photon-polariton conversion efficiency suggests a new strategy for harvesting solar energy. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.