Green and red upconversion luminescence in ytterbium-sensitized erbrium-doped novel lead-free germanium–bismuth–lanthanum glass

Abstract Structural and infrared-to-visible upconversion fluorescence properties in ytterbium-sensitized erbrium-doped novel lead-free germanium–bismuth–lanthanum glass have been studied. The structure of lead-free germanium–bismuth–lanthanum glass was investigated by peak-deconvolution of Raman spectrum, and the structural information was obtained from the peak wavenumbers. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 , and 4 F 9/2 → 4 I 15/2 , respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. This novel lead-free germanium–bismuth–lanthanum glass with low maximum phonon energy (∼ 751 cm −1 ) can be used as potential host material for upconversion lasers.