Nanostructuring the Er-Yb distribution to improve the photoluminescence response of thin films

Thin films of amorphous aluminum oxide (a-Al2O3) codoped with Er3+ and Yb3+ ions have been in-depth nanostructured by distributing the rate earth (RE) ions in layers separated in the 0-3 nm range. The Yb to Er concentration ratio is varied from 0 to 3.6. The photoluminescence (PL) response at 1.53 mum exhibits an increase of up to two orders of magnitude with respect to that of films doped only with Er. The PL intensity is improved when Yb3+ and Er3+ ions are in separate layers and the results show that efficient Yb3+ to Er3+ energy transfer can be achieved for separations up to 3 nm. Furthermore, it is shown that designing an adequate RE distribution, for the same total RE content and Yb to Er concentration ratio, can enhance the PL intensity by a further factor of two. It is shown that the Er3+ PL response is improved because of a reduction of the RE clustering and an improvement of the energy transfer from Yb3+ to Er3+ ions. (C) 2004 American Institute of Physics.