Collisional deactivation mechanism of luminescence in hydrogen-loaded Ge-doped fibers.
We report experimental results on the temperature and Ge-content dependencies of the decay times of the 3.1 eV emission of twofold-coordinated germaniums, excited at 3.51 eV, in both virgin and H2-loaded germanosilicate optical fibers. For T<110 K, the lifetimes are temperature invariant in the two kinds of fibers; at higher temperatures, they are progressively shortened in the H2-loaded fibers whereas they remain unaltered in the virgin fibers. On increasing the Ge content in the fiber core the lifetime decreases in the whole temperature range. We also found a direct correlation in H2-loaded samples between the dependencies on temperature of the emission lifetime and the diffusion lengths of H2 molecules in silica glass determined from earlier work. These experimental features are explained by assuming an elastic-collisional deactivation mechanism due to interaction with diffusing H2 molecules, described in terms of an Arrhenius law with activation energy approximately 64 meV that operates in competition with the normal radiative process.