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

Abstract Transparent SiO 2 :Li 2 O:Nb 2 O 5 glass doped with Tm 3+ 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 SiO 2 and LiNbO 3 phases in samples HT above 650 °C, and a NbTmO 4 phase for T > 750 °C. The XRD SEM analysis show increasing particle size and number with the increase of HT temperature. Intra-4f 12 transitions due to Tm 3+ ion dispersed in the matrix are observed in samples with T > 650 °C. The luminescence is dominated by the 1 G 4 → 3 F 4 (∼650 nm), 1 D 2 → 3 F 3 (∼780 nm), 3 H 4 → 3 H 6 (∼800 nm), 3 H 5 → 3 H 6 (∼1200 nm) and 3 H 4 → 3 F 4 (∼1500 nm) transitions under resonant excitation to the ion levels.