Structural and optical spectroscopy of LiNbO3:Tm nanocrystals embedded in a SiO2 glass matrix

Abstract

Transparent SiO2:Li2O:Nb2O5 glass doped with Tm3+ has been prepared by the sol–gel method, and heat-treated in air (HT) at temperatures between 500 and 800 °C. X-ray diffraction (XRD) patterns and Raman spectroscopy show SiO2 and LiNbO3 phases in samples HT above 650 °C, and a NbTmO4 phase for T > 750 °C. The XRD SEM analysis show increasing particle size and number with the increase of HT temperature. Intra-4f12 transitions due to Tm3+ ion dispersed in the matrix are observed in samples with T > 650 °C. The luminescence is dominated by the 1G4 → 3F4 (∼650 nm), 1D2 → 3F3 (∼780 nm), 3H4 → 3H6 (∼800 nm), 3H5 → 3H6 (∼1200 nm) and 3H4 → 3F4 (∼1500 nm) transitions under resonant excitation to the ion levels.