Theoretical studies on nonvolatile two-step, two-color holographic recording sensitivity for LiNbO3:Fe

The effects of material and experimental parameters on the nonvolatile two-step, two-color holographic recording sensitivity for LiNbO3:Fe have been studied theoretically based on a two-center model. We have taken into account the direct electron transfer between the deep-trap center Fe2+/Fe3+ and the shallow-trap center NbLi4+/NbLi5+ due to the tunneling effect. The results show that the direct electron transfer between the Fe2+/Fe3+ and the NbLi4+/NbLi5+ centers plays a key role in the improvement of two-step, two-color holographic recording sensitivity. The near-stoichiometric LiNbO3:Fe has been confirmed theoretically to be of higher recording sensitivity and larger dynamic range than the congruent one in the low intensity region. A further improvement of the recording sensitivity can be achieved by employing appropriate doping concentration and thermal reduction treatment of Fe and/or selecting appropriate gating and recording wavelengths with large photo-excitation cross-sections.