Structural and spectral characterisation of Er³⁺ and Nd³⁺ doped Ga-La-S-Se glasses

In this work, the spectroscopy of Er³⁺ and Nd³⁺ doped Se-GLS glasses was studied. A structural comparison between doped and non-doped samples was done to assess the differences between the glasses. For this comparison, Raman spectroscopy and thermal analysis were employed. The spectral properties of the samples were studied in order to identify the mechanisms responsible for quenching the fluorescence lifetime of the dopants. In particular, cross-relaxation and concentration quenching were observed in Nd³⁺ doped samples, whilst co-operative upconversion, radiation trapping and concentration quenching were observed in Er³⁺ doped samples. The results obtained demonstrated the fundamental role of the phonon energy in the mechanism of fluorescence. The low phonon energy of chalcogenides decreased the rate of non-radiative processes promoting co-operative upconversion. This effect could be exploited to design new lasers and sensitizers for solar energy harvesters.