Compositional dependence of infrared to blue and red conversion luminescence in oxyfluoride glass-ceramics co-doped with Tm³⁺ and Yb³⁺ ions

Abstract

The upconversion of infrared radiation into visible light has been studied in heavy metal oxyfluoride glass-ceramics co-doped with Yb³⁺ and Tm³⁺ ions at 300 K. The general composition of the compounds is 69.9PbF₂ + 7.5WO₃ + 7.5MO₂ + 15YbF₃ + 0.1TmF₃ (M = Si, Ge, Zr, Te, and Th). Two main upconversion emissions were observed. They are centered at 477 and 775 nm, corresponding to the ¹G₄ → ³H₆ and ³F₄ → ³H₆ transitions, respectively. Slopes of the emission intensity versus excitation power measurements indicate that the blue emission is due to three-photon absorption, while two-photon absorption processes are responsible for the red emission. A comparative method was used to measure the upconversion efficiencies under 16.5 mW/cm² excitation power. Measurements were made after the compounds were annealed at 450 °C for 4 h. The best conversion efficiencies were obtained for the compound having silicon (Si). They are 28 × 10⁻⁶ for the blue and 18 × 10⁻² for the red emission.