Characterization of cooperative upconversion and energy transfer of Er³⁺ and Yb³⁺/Er³⁺ doped phosphate glasses

Cooperative upconversion and Yb³⁺-Er³⁺ energy transfer in newly developed phosphate glasses were studied in this paper. The cooperative upconversion coefficients of ⁴I_13/2 level for different Er³⁺ concentrations were deduced from the pump intensity-dependent luminescence decay curves. Yb³⁺-Er³⁺ energy transfer efficiencies for different Yb³⁺ concentrations codoped with Er³⁺ (approximately 2×10²⁰ ions/cm³) were estimated from the lifetime measurements of ²F_5/2 level of Yb³⁺ ions. The small cooperative upconversion coefficients and high Yb³⁺-E³⁺ energy transfer efficiencies indicate these newly developed Er³⁺ and Yb³⁺/Er³⁺ doped phosphate glasses are excellent for amplifier and laser applications.