Giant Enhancement of Luminescence Down-Shifting by a Doubly Resonant Rare-Earth-Doped Photonic Metastructure

Phosphors based on rare earth ions are used to convert photons to useful wavelengths for a wide range of applications, but the improvement of their emission efficiency remains a key challenge in thin films. In this paper, we demonstrate theoretically and experimentally that a photonic crystal (PC) structure can efficiently enhance the luminescence properties of a down-shifting layer (DSL). Our new metastructure combines a DSL (Y2O3:Eu3+) and a two-dimensional (2D) planar PC (SiNx), the latter being specifically engineered to control simultaneously the absorption in the DSL and the emission into free space. A global emission enhancement of 77 times is obtained due to PC Bloch mode resonances. Additionally, this metastructure exhibits high transmission above 450 nm and favors the emission of converted light at specific angles, with an enhancement factor of up to 690. We explain how the slow and fast Bloch modes of the PC structure induce these giant absorption and extraction enhancements of light.