The two photorefractive centres in iron doped nearly stoichiometric lithium niobate crystals

This paper investigates the photorefractive properties of iron doped lithium niobate with different [Li]/[Nb] ratios. The experimental results show two photorefractive centres for iron doped near-stoichiometric lithium niobate crystal. Besides Fe2+ and Fe3+ ions, small polarons and bipolarons are considered as another photoactive centre.