Thesis (M.Sc.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Science and Interaction

Rare-earth ions are popular dopants for solid-state lasers due to their long upper-level lifetimes, ability to generate short pulses, and straight forward incorporation into host materials including glasses and crystals. The common characteristic of the rare earth (RE) metals is their partially-filled 4f shell. They often form trivalent ions whose properties are generally more important than those of neutral atoms. The most remarkable feature of the rare earth (RE) ions in solid-state host is the sharpness of many absorption and emission spectral lines which are as narrow as the spectra of free atoms. Among all lanthanide (III) ions interest is especially focused on Eu³⁺ and Sm³⁺ ions, europium has attracted significant attention as a luminescent active ion with an intense red emission coming from its 5D0 7F2 transition. The Eu³⁺ ion has the great advantage over other lanthanide ions with an even number of 4f⁶ electrons that the starting levels of the transitions in both the absorption and the luminescence spectrum are non-degenerate (J = 0). Moreover, the interpretation of the spectra is facilitated by the small total angular momentum J of the end levels in the transitions. The number of lines observed for the⁵D0 ⁷FJ transitions in the luminescence spectrum or the ⁵DJ 7F0 transitions in the absorption spectrum allows determining the site symmetry of the Eu³⁺ion. Sm³⁺ (4f⁵) ion is one of the most interesting ions to analyze the fluorescence properties because of its use in highdensity optical storage, under sea communication and color displays. Its emitting 4G5/2 level exhibits relatively high quantum efficiency and also shows different quenching emission channels. The sol-gel method has been reported to have more advantages over other wet chemistry and conventional glass processing methods because it has the potential to produce materials with high purity and homogeneity at low temperatures. It extends the traditional glass melting processes by allowing incorporation of semiconductor and rare-earth ions at low temperatures and predetermined concentrations in different hosts in such a way that the size and shape of the particles can be controlled during the growth and nucleation processes

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