title: Enhanced UV upconversion emission using plasmonic nanocavities.
abstract: Upconversion of near infrared (NIR) into ultraviolet (UV) radiation could lead to a number of applications in bio-imaging, diagnostics and drug delivery. However, for bare nanoparticles, the conversion efficiency is extremely low. In this work, we experimentally demonstrate strongly enhanced upconversion emission from an ensemble of β-NaYF4:Gd3+/Yb3+/Tm3+@NaLuF4core-shell nanoparticles trapped in judiciously designed plasmonic nanocavities. In doing so, different metal platforms and nanostructures are systematically investigated. Our results indicate that using a cross-shape silver nanocavity, a record high enhancement of 170-fold can be obtained in the UV band centered at a wavelength of 345 nm. The observed upconversion efficiency improvement may be attributed to the increased absorption at NIR, the tailored photonic local density of states, and the light out-coupling characteristics of the cavity.
authors.forename: Ahmed
authors.initials: A
authors.lastname: El Halawany
authors.forename: Sha
authors.initials: S
authors.lastname: He
authors.forename: Hossein
authors.initials: H
authors.lastname: Hodaei
authors.forename: Ahmed
authors.initials: A
authors.lastname: Bakry
authors.forename: Mir A N
authors.initials: MA
authors.lastname: Razvi
authors.forename: Ahmed
authors.initials: A
authors.lastname: Alshahrie
authors.forename: Noah J J
authors.initials: NJ
authors.lastname: Johnson
authors.forename: Demetrios N
authors.initials: DN
authors.lastname: Christodoulides
authors.forename: Adah
authors.initials: A
authors.lastname: Almutairi
authors.forename: Mercedeh
authors.initials: M
authors.lastname: Khajavikhan