TEMPERATURE-DEPENDENCE OF THE OPTICAL-PROPERTIES OF YB3+ IONS IN LINBO3 CRYSTALS

In this work the optical properties of Yb3+ ions in LiNbO3 crystals ar e studied as a function of temperature from 15 K to room temperature. The population of the upper Stark levels in each state increases with temperature and subsequently thermal bands appear in the absorption an d fluorescence spectra. The intensity of a thermally activated absorpt ion band fits well the Boltzmann profile. Efficient anti-Stokes photol uminescence is observed when pumping transitions starting from the exc ited Stark levels of the F-2(7/2) state. An increase of the decay time versus temperature is observed in the case of moderate Yb3+ concentra tion. It is related to a luminescence trapping mechanism since a diffe rent behaviour is observed for less doped samples. (C) 1998 Elsevier S cience B.V. All rights reserved.