Spectroscopy and frequency upconversion of Er ions in fluorotellurite glasses

摘要

In this work we report the optical properties and upconversion luminescence of Er~(3+) ions in TeO_2-WO_3-PbO-BaF_2 and TeO_2-TiO_2-Nb_2O_5-BaF_2 fluorotellurite glasses and their comparison with those of TeO_2-TiO_2-Nb_2O_5 glass. The optical properties of Er~(3+) ions have been established in terms of absorption and emission spectra and lifetime measurements. The 1.5 μm emission cross-section has been determined from the line shape of the emission spectrum and the calculated emission probability for the ~4I_(13/2) level. The highest emission cross section (6.9 x 10~21 cm2) corresponds to the TeO_2-TiO_2-Nb_2O_5-BaF_2 glass with a figure of merit for the bandwidth of 524.4 cm2 nm. Upconversion emissions at 530, 548 nm, and 660 nm have been obtained under infrared excitation at 800 nm in the ~4I_(9/2) level and compared with those obtained under one photon excitation. The green emission corresponding to the ~4S_(3/2 → ~4I~(15/2) transition is dominant in all glasses. The excitation wavelength dependence of the upconverted luminescence together with its time evolution after infrared pulsed excitation suggest that energy transfer upconversion processes are responsible for the green upconversion luminescence.