Analysis of the upconversion processes of Nd3+ ions in transparent YAG ceramics

Optical properties of Nd3+ ions in YAG transparent ceramics have been analysed. The samples were prepared by a high temperature (1650 and 1680 °C) sintering followed by hot isostatic pressing (HIP) at 1650 or 1700 °C in order to obtain a well-homogeneous diffusion of the ions and functional transparency. The emission and luminescence decay curves from the 4F3/2 metastable laser level of these samples are very similar to the ones obtained on crystal samples grown with the Czochralski method. However, excitation upconversion spectra obtained detecting at 590 nm for the transparent ceramic samples present important differences compared to the bulk YAG crystal, which can be explained by a change in the upconversion mechanism involved and the different arrangements of the Nd3+ ions in the YAG matrix. The analysis of the upconversion excitation spectra is shown to be a good method to detect the differences between the positions occupied by the Nd3+ ions in different matrices.