FABRICATION AND CHARACTERIZATION OF NEODYMIUM-DOPED SILICA GLASS BY SOL-GEL PROCESS

Neodymium-doped silica glass possesses many properties ideal for high- power laser applications. These include low thermal expansion coeffici ent, high temperature stability, and low nonlinear index of refract;nn For the first time, the sol-gel process has been successfully employe d to prepare highly doped neodymia silica glass, up to 5wt% Nd for hom ogeneous dopant distribution. The optical characteristics of the silic a glass and its in-process gel. including the UV/VIS absorption spectr a, infrared absorption spectra, fluorescence emission spectrum and the fluorescence lifetime, are measured and analyzed. The structure of th e sample is also characterized by means of XRD and SEM. A porous gel i s observed to have formed when the heat treatment temperature reaches 300 degrees C. Wavelength shifts in the absorption peak corresponding to the I-4(9/2) to (4)Fg(5/2) transition have been observed during the densification process and for different Nd weight contents. The FTIR spectra have shown that high temperature heat treatment can greatly re duce the amount of OH groups and organic residue in the silica. We hav e also shown that a high OH content contributes to weak fluorescence i ntensity and short fluorescence lifetimes.