Upconversion enhancement based on mode hybridization in metamaterial absorber

Upconversion nanoparticles (UCNPs) can be used to harvest near-infrared (NIR) light and convert it into visible light. Although this improves optical device operating spectral range and efficiency, e.g., solar cells, typical UCNPs conversion efficiency is too low for practical devices. In this paper, we utilize mode hybridization to enhance the upconversion emission in a metamaterial absorber, which consists of metallic nanoring arrays, UCNPs and a metal film. Numerical and theoretical analysis results show that the maximum upconversion enhancement factor of 2.5 x 106 is achieved due to the mixture of gap plasmonic resonance mode and surface lattice resonance mode. Moreover, the electromagnetic field distribution shows that the anti-crossing behavior strongly impacts the mode distribution, making the mode energy contribute to upconversion. The designed metamaterial absorber is a novel approach in enhancing upconversion and promising for solar cells.