Micro and nanostructures in partially crystallised photothermorefractive glass
Abbreviated Journal Title
Phys. Chem. Glasses-Eur. J. Glass Sci. Technol. Part B
THERMO-REFRACTIVE GLASS; OPTICAL-PROPERTIES; SILICATE-GLASSES; FLUORINE; Chemistry, Physical; Materials Science, Ceramics
Na-Al-Zn-Br-F-silicate glass doped with Ce, Ag, Sb, and Sn is a photothermorefractive (PTR) glass. Ultraviolet exposed regions of this photosensitive glass undergo more extensive crystallisation of NaF nanocrystals than unexposed regions, giving rise to a (localised) permanent refractive index change. Although holographic optical elements produced in PTR glass have been used in laser systems, the detailed mechanism of phase transformation upon heating remains unknown. In this study, optical and scanning electron microscopies were used to investigate the microstructure of PTR glass, especially the diffusion zone surrounding dendritic NaF crystals in unexposed glass heat treated at temperatures exceeding 570 degrees C. As crystallisation evolves, the microstructure of the partially crystallised glass is non-uniform at the micrometre scale in terms of size and shape of NaF crystals, separated by regions of sodium/fluorine-depleted glass. A liquid-liquid phase separation structure with droplet-like morphology also appears at the submicron scale. The micron scale nonuniformities shown in the present study, developed at temperatures higher than those typically used to produce optical elements, indicate nanoscale nonuniformities of the same kind in the unexposed glass after low temperature photothermal processing, and should be considered in future studies aimed to unveil the origin of optical losses in PTR glass.
Physics and Chemistry of Glasses-European Journal of Glass Science and Technology Part B
"Micro and nanostructures in partially crystallised photothermorefractive glass" (2009). Faculty Bibliography 2000s. 2173.