Effect of excitation condition and Mn2+ doping on the red-to-green emission ratio in NaYF4:Er3+/Yb3+ phosphors

Rare earth ions doped up-conversion luminescent materials have attracted massive attention owing to their unique nonlinear optical properties of converting multiple low-energy photons into high-energy photons and potential application in many fields, especially in information storage and anti-counterfeiting. In this paper, the red-to-green emission ratio of NaYF4:Er3+/Yb3+ phosphors was adjusted through power density, pulse width and frequency. The results displayed that the red-to-green emission ratio enhanced with power density, pulse width and frequency increasing. The increase was not obvious with the increase of power density because of the combined effect of two-photon up-conversion processes and the increase rate of nonradiative relaxation process H-2(11/2)/S-4(3/2) -> F-4(9/2) (Er3+). The ratio changes with pulse width and frequency were originated to different non-steady-state up-conversion processes of red and green emissions. The ratio can also be changed from 0.75 to 0.98 by inducing Mn2+ ions in NaYF4:Er3+/Yb3+ phosphors, which is cause by the energy transfers among the energy levels H-2(11/2)/S-4(3/2) (Er3+), T-4(1) (Mn2+), and F-4(9/2) (Er3+). All methods of tuning the ratio of red-to-green emissions can be used in fields of information storage and optical encryption.

Automated summary

In this paper, the red-to-green emission ratio of NaYF4:Er3+/Yb3+ phosphors was adjusted through power density, pulse width, and frequency. It was found that the ratio increased with the increase of power density, pulse width, and frequency. The effect of power density on the ratio was not significant due to the combined effect of two-photon up-conversion processes and nonradiative relaxation process H-2(11/2)/S-4(3/2) -> F-4(9/2) (Er3+). The changes in ratio caused by pulse width and frequency were attributed to different non-steady-state up-conversion processes of red and green emissions.