Impact of the sublinear photoconductivity law on the interpretation of holographic results in BaTiO3

Thick holographic refractive index gratings are written in nominally pure and in iron doped BaTiO₃ crystals. The phase shift between refractive index grating and light pattern is studied as a function of an externally applied electric field by a direct phase shift measuring technique. The choice of the method is suggested by a theoretical analysis which allows for the effect of a nonlinear relation between photoconductivity and light intensity on the holographic writing process.