High-sensitivity read-write volume holographic storage in Bi12SiO20 and Bi12GeO20 crystals

Bi12SiO20 and Bi12GeO20 present the best known photorefractive sensitivity for read-write volume holographic storage (S−1≃300 μJ/cm2) combined with high-quality image reconstruction. Recording processes by photocarrier diffusion (no applied field) and by photocarrier drift are identified. The high photosensitivity is attributed to photocarrier displacements comparable to or larger than fringe spacings. Saturation diffraction efficiency at light power densities larger than 600 μW/cm2 at λ=514.5 nm occurs from complete photocarrier trap filling.