Er3+ and Yb3+ concentration effect in the spectroscopic properties and energy transfer in Yb3+/Er3+ codoped tellurite glasses

Spectroscopic properties of Yb3+/Er3+ codoped tellurite glasses as a function of Er3+ and Yb3+ concentration have been investigated. Under 970 nm excitation three strong up-conversion emission bands centred at 525, 546 and 656 nm were observed, and the characteristic near infrared emission band was centred at 1.53 mu m. With fluorescence and radiative lifetime the quantum efficiency (QE) of infrared (1.53 mu m) and visible upconversion (546 and 660 nm) emissions was calculated. The maximum stimulated emission cross section for I-4(13/2) -> I-4(15/2) transition of Er3+ is 9.7 x 10(-21) cm(2) for 3/0.5 mol%. The energy transfer (ET) efficiency from Yb3+ to Er3+ (F-4(5/2)) + (I-4(15/2)) -> (F-4(7/2)) + (I-4(13/2)) was calculated, being the maximum ET of 69% for 0.5 mol% of Er3+ with 4.5 mol% of Yb3+. The results indicate that both ET and QE depend mostly on Er3+ rather than on Yb3+ concentration.