Selective Control of Eu³⁺ Radiative Emission by Hyperbolic Metamaterials

In recent years the quest for novel materials possessing peculiar abilities of manipulating light at the nanoscale has been significantly boosted due to the strict demands of advanced nanophotonics and quantum technologies. In this framework radiative decay engineering of quantum emitters is of paramount importance for developing efficient single-photon sources or nanolasers. Hyperbolic metamaterials stand out among the best cutting-edge candidates for photoluminescence control owing to their potentially unlimited photonic density of states and their ability to sustain high-k modes that allow us to strongly enhance the radiative decay rate of quantum light emitters. The aim of the present paper is to show how Au/Al2O3 hyperbolic multilayers can be used to selectively control the photoluminescence of coupled Eu3+ emitters. We point out an enhancement of the Eu3+ transitions when they are in the hyperbolic regime of the metamaterials and a significant alteration of the ED and MD branching ratios by changing the emitter-metamaterial distance.