Selective Polarization Modification of Upconversion Luminescence of NaYF₄:Yb³⁺,Er³⁺ Nanoparticles by Plasmonic Nanoantenna Arrays

Rare-earth ions doped upconversion nanoparticles (UCNPs) have received great attention for the promising applications ranging from bioimaging and sensing to lighting and displaying technology. Meanwhile, active control of polarization state of the upconversion luminescence (UCL) of UCNPs is also significant in the applications such as polarization microscopy and 3D display. Here, we report the polarization modification for the UCL of β-NaYF₄:Yb³⁺,Er³⁺ nanoparticles by selectively matching the localized surface plasmon resonance (LSPR) of the rectangular plasmonic slot nanoantenna array to the spectrum of the UCL. The plasmonic resonance band centered at 650 nm of the nanoantenna array realized a strong polarization nature of the selected UCL around 660 nm with the degree of linear polarization up to ∼80%, which stems from the interaction between the 660 nm emission band of UCNPs and the plasmonic modes of the rectangular slot nanoantenna array. Meanwhile, the UCL at 550 nm remained unpolarized due to the mismatch to the plasmonic modes. The experimental results are explained well by theoretical simulations based on the local surface plasmonic resonance. Our results provide an effective way to control the anisotropic UCL of UCNPs with the applications in polarization-based imaging and 3D display technologies and so forth.