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Abstract:The solid host of a laser dye modifies its spectroscopic properties with respect to its liquid host. During the Sol-Gel process the dye molecules suffer from changing their environment. Two parameters affect this matter, the change in the concentration due to the evaporation of the solvent (drying) and the caging of dye molecules inside the pores or attachment to the silica network. Rhodamine 6G absorption and fluorescence spectra with different concentrations, during Sol-Gel time processing, have been studied. Both, absorption and fluorescence spectra of the dye in the solid host, for different concentrations, show a blue-shift relative to its liquid phase.

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The Al co-doping in silica matrix doped with rare earth (RE) namely Er 3+ , Ho 3+ and Eu 3+ ions have been studied. The Al co-doping enhances the emission properties of the SolGel glass doped RE samples. FTIR measurements have been used in this study to probe the aluminum's behavior inside the silica network. The FTIR absorption bands 462.2, 810, 1103 cm -1 of the Si-O-Si and 685, 786 cm -1 of the Al-O bands have been used as principle absorption bands to explain the effect of increasing the Al :RE molar ratios, 4, 8, 10,as well as without Al co-dopant, on the doping process. The emission spectra of the prepared samples supported some concepts of the mechanism of aluminum action as co-dopant in the sol-gel silica matrices. The emission bands due to the ( 4 I 13/2 4 I 15/2 ~ 1536 nm) , ( 5 S 2 5 I 7 ~ 753 nm) and ( 5 D 0 7 F 2 ~ 619 nm) transitions of Er 3+ ,Ho 3+ and Eu 3+ ions, respectively , have been enhanced at Al :RE molar ratio of 10 comparing with 4 and 8. In contrast, the case of without Al co-doping shows strong quenched in these transitions.