Vol. 35, Issue 4, pp. 837-842

Abstract

Energy transfer processes in lead borate glasses doubly doped with Yb–Tm and Yb–Er have been investigated at room temperature under excitation of Yb at 975 nm. The non-resonant energy transfer from ²F_5/2 state of Yb to ³H₅ state of Tm results in up-converted emission at 850 nm due to the ³H₄–³H₆ transition of thulium ions. The nearly resonant transfer from ²F_5/2 state of Yb to ⁴I_11/2 state of Er results in green up-conversion and near-infrared emission, which correspond to the ⁴S_3/2–⁴I_15/2 and ⁴I_13/2–⁴I_15/2 transitions of erbium ions, respectively. High Yb concentration in both co-doped samples is required for optimal energy transfer efficiency (h > 90%). Results with the singly Yb-doped samples are also presented to clarify the energy transfer process.