Spectral variations and energy transfer processes on both Er3+ ion concentration and excitation densities in Yb3+–Er3+ codoped LaF3 materials

In comparison with the up-conversion spectra of Yb3+–Er3+ codopded systems reported previously, the interesting intensity changes of up-conversion luminescence between the violet, the blue, the green and the red on the both Er3+ ion concentration and excitation density with 978 nm laser diodes as an excitation source were observed in Yb3+–Er3+ codopded LaF3 powders. In order to clarify the change mechanisms, the up-conversion spectra of LaF3: 10 mol% Yb3+, 0.5 mol% Er3+ and LaF3: 10 mol% Yb3+, 1 mol% Er3+ were investigated and the results indicated that the cross-relaxation processes between Er3+ ions and the thermal population of the 2H11/2 level play significant roles.