Extraordinary upconversion enhancement in hybrid metasurface by simultaneous excitation/emission band match

Lanthanide doped upconversion nanoparticles (UCNPs) suffers a significant challenge of low quantum efficiency, which seriously limited their applications in photovoltaic device and bioimaging. In this work, we proposed a plasmonic pattern/UCNPs/metal film hybrid metasurface with ultrahigh upconversion enhancement factor. The plasmonic absorption bands can be precisely controlled to simultaneously match both the excitation and the emission wavelength of UCNPs. By constructing the efficient coupling between the local field and the UCNPs, the upconversion fluorescence can be enhanced by 4–6 orders of magnitude. It’s worth noting that such strategy almost covered the two major types of lanthanide doped UCNPs, which were sensitized by Yb3+ (excited under 980 nm) and Nd3+ (excited under 808 nm). The emission enhancement factor was found to be sensitive to the structural parameters and refractive index of the surroundings. Based on this effect, an upconversion intensity and spectra shift dual-mode sensing to environment refractive index can also be achieved. The proposed hybrid metasurface provided an effective way to achieve highly efficient upconversion emission, and the results can also be helpful in solar cells and biological detection.