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Er-doped silica based wave-guides (EDFA) are of interest as Near IR signal laser-amplifiers operating at the for optic high-speed communication important wavelength of 1.5 m. It is desired to reduce the size of the present devices, but this requires an increased Er3+-ion concentration, which is difficult to achieve with conventional glass, physical or sol-gel techniques, due to the formation of Er-rich oxide clusters within the glass. Such clusters are detrimental to the optical properties since two Er3+-ions in close proximity interact to depopulate the desired exited level. By using a molecular heterometallic alkoxide precursor, ErAl3(OPri)12, with a single Er3+-ion surrounded by [Al(OR)4]- groups in a sol-gel process, we obtained highly homogenous ErAl3O6-TiO2-SiO2 planar wave-guide glasses, showing a very high maximum luminescence (at ca 1.5 micrometers) of 1 mol% compared to other techniques. These glasses were fairly stable even at 1000oC, according to the IR, Raman and TEM studies. But, although the flat wave-guide amplifiers receive much academic interest, fibre-amplifiers are still completely dominating the market. Therefore it is of great interest to investigate this sol-gel process also for fibre processing. A silica pre-form, internally coated with sol-gel processes using ErAl3(OPri)12. After heating to 1500oC the optical, TEM and XRD studies revealed that Er2Si2O7, Al6Si2O13 and Al2SiO5 had formed, and hence the designed atomic architecture was destroyed between 1000oC and 1500oC. Although quite good amplifiers could be made after fibre-drawing at ca 2200oC the atomic design concept was not applicable at least with the Er-Al system. It seems that the silica dissolved the Al-oxide to Er without the shield. Further studies tried out other well-characterised Er-precursors including the ErNb2(OPri)13 molecule. The Nb2O5 and Ta2O5 have very low solubility in silica and might possibly lead to more temperature stable glasses. However even though no Nb or Ta silicates were detected after heating to 1500oC, ErNbO4 and Nb2O5 particles formed in the glass which indicate that structural influencing by designed precursors is not an option for high temperature glass processing. |