Yb3+ effect on the spectroscopic properties of Er-Yb codoped SnO2 thin films

We have investigated the optical properties of sot-gel thin films of tin dioxide (SnO2) codoped with Er3+-Yb3+ as a function of Yb3+ concentration. The Judd-Ofelt model has been applied to absorption intensities of EP3+ (4f(11)) transitions to establish the so-called Judd-Ofelt intensity parameters: Omega(2), Omega(4), Omega(6). Various spectroscopic parameters were obtained to evaluate their dependence and the potential of the samples as a laser material in the eye-safe laser wavelength (1.53 mu m) as a function of Yb3+ concentration. An amelioration of the quality factor Omega(4)/Omega(6) was found with Yb content. Both the IR photoluminescence (PL) intensity and the up-conversion emission, from Er3+ ion in SnO2, were found to increase with Yb concentration. We show that the Yb3+ ion acts as sensitizer for Er3+ ion and contributes largely to the improvement of the spectroscopic properties of SnO2:Er. The mechanism of up-conversion emission is discussed and a model is proposed. The results showed that sol-gel SnO2 is promising gain media for developing the solid-state 1.5 mu m optical amplifiers and tunable up-conversion lasers. (C) 2011 Elsevier B.V. All rights reserved.