Rate equation analysis and energy transfer of Er3+-doped Ga2S3-GeS2-La2S3 glasses

Decay curves of 1.5 mm (4I13/2) and 1.0 mm (4I11/2) emissions from Er3+ ions in Ga2S3-GeS2-La2S3 glasses were measured by the excitation of a 1.5 mm and a 980 nm laser diode pump. The decay curves were simulated using rate equations for a model consisting of six levels of the Er3+ from the ground state. The rate equations contained five unknown parameters, i.e., excited state absorption cross sections of 4I13/2 yields 4I9/2 (sesa24) for 1.5 mm excitation and 4I11/2 yields 4F7/2 (sesa36) for 980 nm excitation, cooperative upconversion coefficients of (4I13/2, 4I13/2) yields (4I9/2, 4I15/2) (C2) and (4I11/2, 4I11/2) yields (4F7/2, 4I15/2) (C3), and an energy back-transfer coefficient of (4I9/2, 4I15/2) yields (4I13/2, 4I13/2) (C2r). These parameters were estimated by fitting the simulated curves to the measured ones. The obtained values were sesa24=0.3 x 10-20 cm2, sesa36=0.5 x 10-20 cm2, C2=30-40 x 10-18 cm3/s, C3=20-25 x 10-18 cm3/s, and C2r=5 x 10-18 cm3/s. 41 refs.