Enhancement of optical properties of Nd3+ doped fluorophosphate glasses by alkali and alkaline earth metal co-doping

Fluorophosphate glasses doped with trivalent Nd and using Li and Ba as network modifier cations are spectroscopically analyzed to understand the effects of these cations on the radiative and non-radiative process. The radiative properties of Nd3+ such as radiative transition probabilities, radiative decay times and stimulated emission cross-sections of the transitions from the F-4(3/2) level, and their dependence on network modifiers and active ion concentration are analyzed using the Judd-Ofelt theory. Results show that, eventhough stimulated emission cross-section is maximum in Li based glass, fluorescence quenching is higher, however it is considerably reduced by the presence of Ba. It is found that, Ba and LiBa based glasses yield higher quantum efficiency showing that Ba reduces the fluorescence quenching properties of the matrix. The stimulated emission cross-section of the emission band at 1.055 mum is higher than that of commercial laser glasses. On the other hand, quantitative estimation of the non-radiative processes such as multiphonon relaxation and quenching by water content shows that water content is far below the critical level of optimum laser performance. All these factors pertain to the fact that these Nd3+ doped fluorophosphate glasses can be effectively used for high power lasers in the 0.8 and 1.055 mum regions. (C) 2002 Elsevier Science B.V. All rights reserved.