Er–Yb codoped phosphate glasses with improved gain characteristics for an efficient 1.55 µm broadband optical amplifiers

Abstract

We have investigated the optical properties of phosphate glasses codoped with Er3+–Yb3+ as a function of Yb3+concentration in order to evaluate their potential as both glass laser systems and amplifier materials. The results of differential scanning calorimetry (DSC) measurements indicate a good thermal stability of phosphate glasses. The Judd–Ofelt (JO) model has been applied to absorption intensities of Er3+ (4f11) transitions to establish the so-called Judd–Ofelt intensity parameters: Ω2, Ω4,Ω6. With the weak spectroscopic quality factors Ω4/Ω6 (0.38), we expect a relatively prominent Infrared laser emission. The intensity parameters are used to determine the spontaneous emission probabilities of some relevant transitions, the branching ratio and the radiative lifetimes of several excited states of Er3+ and compared to the equivalent parameters for other host glasses.Both the IR photoluminescence (PL) intensity and the PL decay time were found to largely increase with Yb3+concentration and the maximum quantum efficiency for the 1.55µm emission was found to be in the order of 91%. We show that the Yb3+ acts as sensitizer for Er3+ and contributes largely to the improvement of the spectroscopic properties of phosphate glasses codoped with Er3+–Yb3+.Using McCumber method, absorption cross-section and calculated emission cross-section, for the 4I13/2→ 4I15/2 transition, were determined and compared for the doped and codoped glasses. The phosphate glasses are promising gain media for developing the solid-state 1.55µm optical amplifiers.