Infrared to visible upconversion of Er³⁺and Er³⁺/Yb³⁺codoped lead-niobium-germanate glasses

Abstract

Infrared-to-visible upconversion processes have been investigated in Er³⁺-doped and Er³⁺/Yb³⁺ codoped lead-niobium-germanate glass (GeO₂-PbO-Nb₂O₅). Visible emissions at 526 nm, 547 nm, and 660 nm corresponding to the ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2 transitions respectively were observed under continuous wave excitation at 978 nm. Weak violet and blue emissions were also observed at 368 nm and 410 nm which are assigned to the ⁴G_9/2→⁴I_15/2 and ²H_9/2→⁴I_15/2 transitions respectively. An enhancement of the visible upconversion fluorescence in Er³⁺/Yb³⁺ codoped sample is confirmed due to efficient energy transfer from Yb³⁺ to Er³⁺ ions.