Lifetime of thermally fixed holograms in LiNbO3 crystals doped with Mg and Fe

Decays of thermally fixed holograms in LiNbO3 crystals doped with 5.5 mol. % of Mg and 0.1 mol. % of Fe were measured at different temperatures. The analysis showed that the time decay is a thermally activated single process. The thermal activation energy depends on the Mg impurity and hydrogen concentration. Samples with moderate hydrogen concentration show an activation energy of 1.16 eV. Extrapolated room temperature hologram lifetimes as long as 540 years were determined. Samples with large amount of hydrogen impurity showed a lower activation energy and also lower room temperature lifetime.