Multiplasmons-Pumped Excited-State Absorption and Energy Transfer Upconversion of Rare-Earth-Doped Luminescence beyond the Diffraction Limit

Rare-earth-doped upconversion luminescence has attracted extensive attention due to its narrow-band and wide-range emission spectra, which cover biological and optical communication windows. For direct laser excitation, the photoluminescence of upconversion nanoparticles is inevitably involved in the excitation laser signals to luminescence, limiting its application due to high background noise, heating, and the low quantum yield of rare-earth-doped upconversion photoluminescence. Here, multiplasmons-excited upconversion luminescence was investigated by employing propagating surface plasmons polaritons on a monocrystalline silver microplate: pure plasmon near-field excitation without background photoluminescence. Due to near-field excitation, multisurface plasmons upconversion luminescence exhibit strong excited-state absorption and energy transfer upconversion, and more than 97-fold luminescence enhancement was obtained without background noise. It was found that multiplasmons-excited luminescence can be easily controlled by surface plasmons polaritons propagation and excitation modes and laser polarization directions, and a super-resolution luminescence of upconversion nanoparticles was achieved beyond the diffraction limit. The characterization of multiplasmon-excited luminescence helps not only enhance the understanding of light-matter interactions between rare-earth ions and plasmons in the near-field, but also benefits the development of bioimaging and the super-resolution of micro light sources.