Influence of Ce3+ doping on the structure and luminescence of Er3+-doped transparent glass-ceramics

Transparent glass-ceramics possess high thermal and mechanical properties, easy shaping allowing fibers elaboration and easy synthesis. However, previously studied Yb:Er-doped glass-ceramics do not appear efficient enough for optical amplification at 1.5 mu m in the telecommunication window. So, the addition of Ce3+ doping ions was performed. Oxyfluoride glasses (GeO2-PbO-PbF2) doped with ErF3, YbF3 and CeF3 were prepared and heated above glass transition temperature to obtain transparent glass-ceramics. Such treatment brings about the precipitation of fluorite-type nanocrystallites embedded into an amorphous oxide phase. Differential Thermal Analysis shows evidence that CeF3 acts as nucleating agent for the heterogeneous crystallization of the beta-PbF2 phase. Through Transmission Electron Microscopy the morphology of these glass-ceramics was studied. Energy dispersive X-ray microanalysis and unit cell parameter study show a segregation of the three rare-earth ions inside the fluorite crystallites, forming a solid solution Pb1-x-y-zErxYbyCezF2+x+y+z. The luminescence characteristics of the glass-ceramics doped with ErF3, YbF3 and CeF3 were compared to those of Yb:Er-doped glass-ceramics. CeF3 enables to dramatically decrease the up-conversion fluorescence of Er3+. The study of temporal dynamic of the I-4(13/2) level of Er3+ reveals a cross-relaxation process between Er3+ and Ce3+. Hence, the presence of Ce3+ enables to decrease the Er3+ up-conversion fluorescence at the benefit of the fluorescence of interest at 1.5 mu m, which is strongly enhanced. (c) 2005 Elsevier B.V. All rights reserved.