Using multi-polar scattering and near-field plasmonic resonances to achieve optimal emission enhancement from quantum emitters embedded in dielectric pillars

Abstract

Recently, high refractive index micro-pillars have been widely used for enhancing the fluorescence of quantum emitters (vacancy/defect centers) embedded within the pillar. However, the maximum observed enhancement from these pillars has been limited to about a factor of 10. Within the dielectric pillars, the Purcell enhancement is restricted to around unity, and the fluorescence enhancement is mainly due to the enhancement of the collection efficiency of the dipole emission from inside the pillar if compared to a bulk substrate. Using multi-polar electromagnetic scattering resonances and near-field plasmonic field enhancement/confinement, here we report a simple metal–dielectric pillar resonator scheme to achieve a close to three orders of magnitude fluorescence enhancement from embedded solid state vacancy centers. The scheme comprises a silver (Ag) cylinder fabricated on top of a silicon-carbide (SiC) dielectric pillar, with both the SiC and Ag cylinders having the same diameter. A selective dipole orientation relative to the metal–dielectric interface for emitters close to the SiC pillar’s top surface leads to a large Purcell enhancement of the dipole’s emission. The Ag cylinder was found to function as an efficient resonator as well as an antenna, enhancing as well as directing a significant fraction of the dipole’s emission into far-field free space.