Compositional dependency of upconversion luminescence of Nd3 + doped Ge–Ga–S–CsBr chalcohalide glasses

• Intense green, orange and red upconversion from Ge–Ga–S–CsBr chalcohalide glass.
• The intensities and lifetimes increased with CsBr content, jumped when CsBr/Ga > 1.
• Low phonon energy surrounding of Nd3 + ions formed due to CsBr addition.

The effects of host glass composition on the upconversion luminescence of Nd3 + doped (1 − x)(Ge0.25Ga0.10S0.65)–x(CsBr) chalcohalide glasses were investigated. Bright upconversion luminescence was observed in the 535 nm, 602 nm and 665 nm bands, with weak blue emission. Luminescence intensity increased with CsBr content x, and jumped when x increased from 0.08 to 0.10. Lifetimes of 4G7/2 level and 4F3/2 intermediate levels of Nd3 + ions had similar dependency on CsBr content. Raman analysis proved that a [GaS3/2Br]− group formed due to CsBr addition. The effective phonon energy decreased from 375 cm− 1 ([Ga–S] bond vibration) to 245 cm− 1 ([Ga–Br] bond vibration) when CsBr/Ga ratio was > 1, which resulted in sudden changes in upconversion intensities and lifetimes. The results indicated that the chalcohalide glasses are promising candidates for use in applications that require efficient upconversion luminescence.