Novel oxyfluoride glass and transparent glass-ceramics for fiber lasers and fiber amplifiers

Transparent glass-ceramics containing nano-crystals were prepared by controlled heat-treatment of conventionally melt-quenched NaF-YF(3)-Al(2)O(3)-SiO(2) oxyfluoride glass. The precipitated crystallites were composed of only cubic NaYF(4) and the average diameter was estimated as less than 10 nm from the X-ray diffraction analysis. The crystallites were so small that the transparency of the glass was kept after crystallization. NaYF(4) has a crystal structure of a fluorite type that cation sites were randomly occupied by Na(+) and Y(3+). It is expected that the Y(3+) sites can be substituted to other rare-earth ions which have the similar ionic radii. We have been prepared Tb(3+) and Yb(3+) co-doped glass and glass-ceramics. Green fluorescence was observed when the glass and glass-ceramics were excited by a 974 nm laser. The up-conversion intensity was enhanced by the crystallization.