Anisotropic strong volume hologram in BaTiO₃

A photorefractive strong volume hologram by using anisotropic diffraction in a normal-cut BaTiO₃ is proposed and demonstrated. Experimental measurements fit the theoretical calculations well by using Kogelnik's formula with unclamped E-O coefficients. The maximum refractive index perturbation in the experiment is larger than 2.7 × 10^-4. In addition, we have observed that the output of the diffracted light are concentric circles. This pattern is shown as a good guide of the estimation of how large the refractive index perturbation is. The Bragg condition of the anisotropic strong volume hologram is so strict that an image-carried hologram cannot be directly read out. We proposed an address image method by erasure for solving this problem. Through this method, this anisotropic strong volume hologram has some potential for optical image storage.