Up-conversion luminescence in low phonon heavy metal oxide glass co-doped with Er3+/Ho3+ ions

In this paper, heavy metal oxide glasses co-doped with erbium and holmium ions have been synthesized. Glass composition, based on bismuth and germanium oxides, has been selected in terms of high thermal stability (Delta T = 125 degrees C), high refractive index (n = 2.19) and low maximum phonon energy (h nu(max) = 724 cm(-1)). Up-conversion luminescence spectra under the 980 nm laser diode excitation have been observed as a result of radiative transitions within the quantum energy level structures of Er3+ and Ho3+ ions. Optimization of rare earth ions content has been conducted, the highest emission intensity in the visible wavelength range has been observed in glass co-doped with molar concentration 0.5 Er2O3 / 0.5 Ho2O3.