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 ϳ0.5 wt.% MnCO 3 , and refractive-index changes and sensitivities up to 1.5 ϫ 10 Ϫ3 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 ϳ1. 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.

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Utilizing a rotatable thin birefringent crystal and two polarizers, the three-dimensional (3D) wave front of any light wave can be measured conveniently. In first experiments phase-front distortions as small as 15 &mgr;m are detected with a dynamic range of 3 mm and a spatial resolution of 50 &mgr;m. Such a dynamic range and spatial resolution exceed the performance of conventional wave front sensors of, e.g., the Shack-Hartmann type, significantly. Furthermore, the new system is rather insensitive against mechanical instabilities in opposition to interferometric and holographic techniques.

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