Optical properties and luminescence of Er3+/Yb3+ co-doped La2O3–Nb2O5–Ga2O3 glasses prepared by aerodynamic levitation method

40La2O3–20Nb2O5–40Ga2O3 and xYb2O3–5Er2O3–(35-x) La2O3–20Nb2O5–40Ga2O3 (x = 0, 1, 5, 10) spherical transparent glasses were prepared by aerodynamic levitation method. Upconversion and near-infrared luminescence characteristics have been studied. Moreover, the thermal, mechanical, refractive index, transmittance properties of the glasses have also been discussed. Hardness and density of the glasses increase with the increase of Yb3+ concentration. The hardness of all samples are above 8.4 GPa, and density increase from 5.2504 g/cm3 to 5.817 g/cm3. The blank LNG glass has a refractive index of 2.0217 and Abbe number of 88.84, which is an excellent glass with high refractive index and low dispersion. Through DTA analysis, it is found that this series of glasses has excellent thermal stability. The glasses transition temperature (Tg) is about 800 °C. With the increase of Yb3+ concentration, Tg does not change obviously, but the crystallization initial temperature To and △T (△T = To−Tg) increase at first and then decrease. Upconversion fluorescence spectra show that green and red emission bands of 551 nm, 558 nm and 674 nm are obtained under the pump of 980 nm laser, which are two-photon emission processes. And in the near infrared region, the near-infrared emission with the emission center at 1559 nm is obtained, which corresponds to the transition from 4I13/2–4I15/2 of Er3+. The full width at half maximum (FWHM) of the prepared samples is about 120 nm, which is larger than that of ordinary glass. At the same time, with the increase of Yb3+ concentration, the change trend of fluorescence lifetime is consistent with that of near-infrared emission intensity.