Coupling between the Mie Resonances of Cu₂O Nanospheres and the Excitons of Dye Aggregates

Although the resonance coupling between excitons and surface plasmons has been extensively investigated for decades, the coupling between excitons and the Mie resonances in dielectric/semiconductor nanostructures has remained largely unexplored. Herein we report on the preparation of single-crystalline Cu2O nanospheres with a moderate refractive index and the study of their coupling with organic dye aggregates. Colloidal Cu2O nanospheres of uniform diameters and good sphericity are obtained using a wet-chemistry growth method aided with mild etching. Unlike high-refractive-index dielectrics, Cu2O nanospheres possess spectrally overlapped electric and magnetic dipole modes. Rhodamine aggregates are coated onto the Cu2O nanospheres to investigate the variation of the scattering spectra induced by the resonance coupling. A clear anticrossing behavior with a mode splitting of 0.30 eV is experimentally observed. It is originated from the coupling between the overlapped dipolar Mie resonances in the Cu2O nanospheres and the excitons in the rhodamine aggregates.