Fluorescence properties of rare-earth doped sol-gel silica glasses

Rare earth doped silica glasses find numerous applications ranging from fiber amplifiers for optical communications to high power lasers for inertial confinement fusion research. The performance of rare earth doped optical devices would be improved by better understanding of relationships among glass structure, composition and dopant ion optical properties. The specific problem of rare earth ion clustering limits the efficiency of rare earth optical devices by limiting optimal rare earth ion concentrations.; The fluorescence properties of rare earth ions were studied in sol-gel silica in order to determine the mechanism of rare earth ion clustering and evaluate synthesis procedures designed to prevent clustering. Fluorescence line narrowing measurements were used to identify rare earth clustering. While aluminum co-doping in rare earth doped silica has been found to eliminate rare earth ion clusters, it has also been found to increase the residual hydroxyl content and hydroxyl quenching. The use of an alternate aluminum precursor expected to reduce the hydroxyl content in sol-gel silica and the use of other co-dopant ions to reduce rare earth ion clustering were considered.; Hydroxyl quenching due to the large residual hydroxyl content in sol-gel silica lowers optical efficiencies through non-radiative decay of ions in excited states. Excited state lifetime measurements were used to qualitatively assess the hydroxyl content of rare earth doped sol-gel silica with different compositions and prepared with different procedures. Fluorinated dopant ion precursors were used to produce in situ dehydroxylation in rare earth doped sol-gel silica. Additionally, rare earth doped hybrid organic/inorganic gels were prepared in an effort to reduce the hydroxyl content of the final silica glass. The influence of these synthesis schemes on rare earth ion clustering was also determined.; The effects of energy transfer between rare earth ions in sol-gel silica were examined with lifetime, fluorescence, and upconversion measurements. Rare earth ion clustering was expected to have a beneficial effect on upconversion. Green and red upconversion fluorescence was detected, and models of the upconversion processes were developed.