High Efficiency Infrared to Visible Upconversion in Er³⁺/Yb³⁺-Doped Lead Halide Tellurite Glass

Strong upconversion luminescence of Er³⁺/Yb³⁺-doped lead halide tellurite glass under 976 nm excitation is demonstrated. Three emission bands centered at 525 nm, 545 nm, and 655 nm resulting from the transitions from the excited states ²H_11/2, ⁴S_3/2, and ⁴F_9/2 to the ground state ⁴I_15/2, respectively, are observed even at 60 mW pumping power. The power dependent intensity and the upconversion mechanisms responsible for the luminescences are evaluated and discussed. The obtained results might provide useful information for the developments of upconversion lasers.