Improvement of fluorescence lifetime from Er-doped sol-gel silica glass by dehydration in CCl4

Monolithic Er-doped silica xerogels with erbium content of 5000 ppm were prepared by sol-gel technique. Samples were densified by thermal treatment in O-2/CCl4 environment. The 1.55 mum photoluminescence lifetimes after annealing at different temperatures were measured, together with the relative content of hydroxyl groups inside the samples. It was found that hydroxyl groups can be removed by CCl4 effectively. Consequently the photoluminescence lifetime of the samples increased significantly after the removal of hydroxyl groups. For sample treated in O-2/CCl4 at 900degreesC, fluorescence lifetime as long as 6ms was obtained and is pretty stable when the sample is kept in ambient air.