Nonlinearity of the Upconversion Response of Er3+ in Y2TiO5:Er3+,Yb3+ Ceramics When Varying the Wavelength of Incident NIR Excitation Radiation.

Abstract

The upconversion response of Er3+ sensitized by Yb3+ in various crystalline hosts and illuminated with a laser light at around 980 nm revealed certain spectral shapes that are typical for each of the crystalline matrices containing the dopants. The purpose of this work was to measure the upconversion response of Er3+ as a dopant in Y2TiO5, sensitized by Yb3+, at different concentrations relative to the substituted Y3+ ion, and to reveal the subtleties of the mechanisms of the energy transfers between them and the lattice. Therefore, we synthesized Y2TiO5 ceramic samples doped with different concentrations of Er3+ and Yb3+, below 10% (mol), in order to minimize the distortion of the lattice. The oxide powders, obtained using the sol-gel method, as well as the ceramics were structurally and morphologically characterized using an X-ray diffraction analysis and scanning electron microscopy. When the ceramic samples were irradiated with an NIR laser light, it was found that, at a wavelength variation of only 2 nm of the incident radiation, from 973.5 nm to 975.5 nm, the upconversion spectra differed significantly. This nonlinearity is notable because it is not present in the case of other crystalline host matrices studied by us since the literature lacks information on this subject. We also correlated this effect with the simulated distribution of the average distances between Er3+ and Yb3+ ions in the host matrix.