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

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 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, 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.