Modeling of photorefractive two-step gated recording by long-life-time intermediate levels

Gated recording based on two-step excitation with metastable shallow traps is analyzed theoretically. A two-center model, including the tail of the conduction band into the bandgap, is suggested. The tail provides a way to model efficiently excitation from deep to shallow traps and long recombination times back into deep traps. The results are compared with experimental results performed with La₃Ga₅SiO₁₄, and good agreement is found. Further, the limiting material parameters determining the material sensitivity are identified.