Cavity controlled upconversion luminescence in Ag-capped NaYF4:Yb,Er micron rod

Ag-capped β-NaYF4:Yb,Er micron rods were designed and fabricated to enhance their upconversion luminescence (UCL), which is in strong demand for various practical applications. Micro-spectral measurement was used to characterize the UCL of single rods. UCL of the Ag-capped β-NaYF4:Yb,Er micron rods is enhanced by 4-fold compared to that of bare rods on glass, based on statistics from 32 rods, while UCL of rods on Ag film is only enhanced by 0.8-fold. Combination with back scattering spectra of several typical Ag-capped micron rods lead us to conclude that the stronger tailoring effect on UCL of Ag-capped rods can be explained by the stronger resonance confinement of light in the Ag-capped micron-rod cavities. UCL enhancement and strong fluctuations both in intensity and intensity ratio can be ascribed to modulation of radiative transition rates in different degrees, caused by variation of photonic mode densities around the emission wavelengths in various cavities.