Excited state absorption in Yb3+-Er3+-codoped phosphate glasses (ZnO-Al2O3-La2O3P2O5) around the I-4(13/2)-> I-4(15/2) emission spectral range

We are involved in Yb3+-Er3+-codoped phosphate glass research for eye-safe laser source near 1540 nm. Undoped and doped glasses of the composition: Zn O-Al2O3-La2O3-P2O5 have been synthesised. Absorption from the I-4(15/2) gro und state, emission spectra and decay time measurements have been performed at room temperature on these materials. In addition to the usual spectrosc opic characterisations, the excited state absorption I-4(13/2) --> I-4(9/2) Er3+ transition located at the long wavelength edge of the I-4(13/2) --> I -4(15/2) emission transition have also been investigated at room temperatur e. The excited state absorption spectra were obtained with a pump and probe technique employing a double modulation scheme in the infrared wavelength region from 1300 to 1900 nm. Furthermore, the line strength of the excited state absorption transition have been calculated in order to compare it wit h the experimental. (C) 1999 Elsevier Science B.V. All rights reserved.