Spontaneous emission dynamics of Eu3+ions coupled to hyperbolic metamaterials

Abstract

Sub-wavelength nanostructured systems with tunable electromagnetic properties, such as hyperbolic metamaterials (HMMs), provide a useful platform to tailor spontaneous emission processes. Here, we investigate a system comprising Eu3+(NO3)3·6H2O nanocrystals on an HMM structure featuring a hexagonal array of Ag nanowires in a porous Al2O3 matrix. The HMM-coupled Eu3+ ions exhibit up to a 2.4 fold increase in their decay rate, accompanied by an enhancement of the emission rate of the 5D0 → 7F2 transition. Using finite-difference time-domain modeling, we corroborate these observations with the increase in the photonic density of states seen by the Eu3+ ions in the proximity of the HMM. Our results indicate that HMMs can serve as a valuable tool to control the emission from weak transitions and, hence, hint at a route toward more practical applications of rare-earth ions in nanoscale optoelectronics and quantum devices.