Blue Upconversion Luminescence in Tm³⁺/Yb³⁺-Codoped Lead Chloride Tellurite Glass

The upconversion properties of Tm³⁺/Yb³⁺-codoped lead chloride tellurite glass under 980 nm excitation were investigated. The intense blue (476 nm) emission and weak red (649 nm) emission corresponding to the ¹G₄ → ³H₆ and ¹G₄ → ³H₄ transitions of Tm³⁺ ions, respectively, were simultaneously observed at room temperature. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm³⁺/Yb³⁺-codoped lead chloride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.