Near infrared emissions of Cr3+ and Cr4+-doped glasses

Novel Cr-doped aluminosilicate and gallo-germinate glasses, which show strong emissions of both Cr3+ and Cr4+ ions, have been produced. The glasses are thermally stable and are ideal for fibre drawing. Room temperature emission can be seen in the region 1050-1300nm when pumped at 514nm and 1000-1475nm when pumped at 870 nm. The lifetime of Cr4+ emission for (3)A(2)-->T-3(1), transition has been measured, and the fast component of the decay is 200mus leading to a slow step which is 600mus long. The structure of the Cr-doped aluminosilicate has been analysed by MAS-NMR, TEM and Electron Energy Loss spectroscopy in TEM. The partially crystallised glass samples were analysed by an X-Ray diffraction technique. The analysis points out that the glasses contain Cr3+-ionic state, which undergoes a charge transfer to Cr4+ under excitation.