Observation of dipolar emission patterns from isolated Eu³⁺:Y₂O₃ doped nanocrystals: New evidence for single ion luminescence

We report results of emission pattern imaging experiments from single Eu³⁺:Y₂O₃ nanocrystals (3-12 nm size) designed to provide new insight on the luminescence dynamics of isolated rare-earth doped nano-phosphors. We observe dipolar emission patterns that are characteristic of single quantum emitters whose orientation appears fixed on the measurement time scale. We also show that the luminescence from single nanoparticles is linearly polarized, also characteristic of single quantum system behavior. Taken in combination with dynamical observations of blinking and discrete photobleaching, these experiments provide strong evidence for single ion luminescence, and confirm the dipolar nature of the optical transitions of Eu³⁺ in inorganic crystals.