Saturation effect of up-conversion luminescence from erbium-doped, silica-titania sol-gel powders

The intensity of the visible up-conversion luminescence could be limited by a saturation effect produced by increased pump power. Visible up-conversion luminescence was obtained in erbium doped, silica-titania sol gel powders under dynamical pumping at 1532 nm. The saturation effect was studied for erbium radiative transitions 2H9/2→4I15/2 (410 nm), 2H11/2→4I15/2 (530 nm), 4S3/2→4I15/2 (550 nm), 2H9/2→4I13/2 (567 nm) and 4F9/2→4I15/2 (675 nm). The recorded up-conversion luminescence decreased when increasing excitation power. The results suggested that the saturation effect was determined by the pump power, the sample composition and the lifetimes of the corresponding first excited states.