Nd3+ sensitized blue upconversion luminescence in Nd3+/Pr3+ co-doped Ge–Ga–S–CsBr chalcohalide glasses

The effect of CsBr/Ga ratio on the blue upconverted emission from Nd3+/Pr3+ in Ge–Ga–S–CsBr chalcohalide glasses was investigated. When CsBr/Ga was smaller than unity, the energy transfer from Nd3+ to Pr3+ ions was dominant and blue emission centered at ∼ 495 nm (Pr3+:3P0 → 3H4) was observed. On the contrary, the intensity of the upconversion luminescence from Nd3+ increased at the expense of the blue emission when CsBr/Ga ratio exceeded unity. The possible relationship between the composition-dependent blue emission and the local environment of rare earth ions was discussed.