Combinatorial Fluorescence Lifetime Measuring System for Developing Er-Doped Transparent Glass Ceramics

Fluorescence lifetime of Er3+ was measured for F-doped tellurite
glasses with parallel heat treatment under a temperature gradient
atmosphere in order to find the annealing condition to make transparent
glass ceramics in which Er3+ ions are located in the precipitated
crystals. The preparation and annealing of the samples were performed
in a vertical temperature gradient furnace, where molten glass was
sucked into a pre-heated Pyrex glass tube. The annealing temperature
range is between 350 degC and 800 degC. After the annealing
treatment, time-resolved fluorescence emission of Er3+ (1.55um;
excitation light source is 977nm) were measured sequentially along the
tube. The lifetime of the emission was about 2.6 msec for as-prepared
glass. We have found that the lifetime increased to 5.2 msec when the
glass was annealed at 470 degC for 5 min and 550 degC for 5 min
successively, although its transparency was lost. This increase implies
that the Er3+ ions are embedded in fluorine-rich phase to bring about
reduced non-radiative emission. We are now continuing to find the
condition to get transparent glass ceramics.