Compositional dependences on the mechanism of upconversion in Nd3+/Tm3+ co-doped chalcohalide glasses

Mechanisms of the compositional dependence of blue emission from Nd3+/Tm3+ co-doped Ge–Ga–S–CsBr chalcohalide glasses were investigated. The blue upconversion emissions (centered at 475 nm) due to the Tm3+: 1G4 → 3H6 transition decreased as the CsBr/Ga ratio in glasses while the other upconversion emissions from the Nd3+ ions increased. Changes in the local environment of rare-earth ions incurred by the CsBr addition significantly increased the excited state absorption within Nd3+ ions. This resulted in the decrease in the Nd3+ → Tm3+ energy transfer rates that led to the large decrease in blue upconversion emission.