Nanophotonics for Photon Upconversion Enhancement

Lanthanide-based upconversion materials convert low-energy infrared photons into high-energy visible photons with much higher efficiency than two-photon absorption or second harmonic generation. Naturally, they have attracted much attention for potential applications in solar energy harvesting, photocatalysis, security, and biological imaging. Despite the high promise, the intrinsic conversion efficiency of upconversion materials remains low for most applications. The emergent nanophotonic technologies could provide a powerful tool to boost the upconversion efficiency and enable novel applications. In this chapter, we provide an in-depth review of the theoretical foundation for light-matter interaction, dynamics of luminescence upconversion process, and nanophotonic enhancement mechanisms. We then provide a comprehensive survey of recent progress in nanophotonic enhancement of upconversion. The use of plasmonic and dielectric nanostructures has led to 2–3 orders of magnitude improvements in upconversion efficiency. The accelerating pace of progress makes nanophotonically enhanced upconversion a highly promising platform for novel photonic applications.