Photorefractive properties of lithium niobate crystals doped with manganese

The photorefractive properties of lithium niobate crystals doped with manganese (Mn) have been investigated. It is found that the effect of dark decay due to electron tunneling, which is the limiting factor of the highest practical doping level, is less in LiNbO_3:Mn than in LiNbO_3:Fe , and higher doping levels can be used in LiNbO_3:Mn to achieve larger dynamic range and sensitivity for holographic applications. The highest practical doping level in LiNbO_3:Mn has been found to be ~0.5 wt.% MnCO_3, and refractive-index changes and sensitivities up to 1.5X10^-3 and 1.3 cm/J are measured for extraordinarily polarized light of the wavelength 458 nm. It has been found that, in terms of both dynamic range (or refractive-index change) and sensitivity, the optimal oxidation state is highly oxidized. The distribution coefficient of Mn has been determined to be ~1. Absorption measurements are used to obtain more information about charge-transport parameters. The material is excellently suited for holographic recording with blue light. The hologram quality is outstanding because holographic scattering is much weaker compared with that in, e.g., iron-doped lithium niobate. Thermal fixing has been successfully demonstrated in LiNbO_3:Mn crystals