Frequency Upconversion Emission of Er³⁺-Doped Strontium--Lead--Bismuth Glasses

Er³⁺-doped strontium--lead--bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Under 975 nm excitation, intense green and red emissions centred at 525, 546, and 657 nm, corresponding to the transitions ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2, respectively, were observed at room temperature. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for 525 and 546nm emissions, and energy transfer upconversion for 657nm emission.