Improvement of blue photorefractive properties in In-doped LiNbO ₃: Fe: Cu crystals

A high sensitivity and large dynamic range are observed in LiNbO ₃ : Fe : Cu and In-doped LiNbO₃ : Fe : Cu crystals at 488 nm wavelength based on the two-beam coupling experiment. The strong blue photorefraction is contributed by the two-centre effect and the remarkable characteristic of being in phase between the two gratings recorded in shallow and deep trap centres. The sensitivity S is measured up to 6.24 cm J ^-1, and simultaneously the dynamic range M/# is achieved to 34.2 in the In-doped LiNbO₃ : Fe : Cu crystal, which are enhanced significantly as compared with those of the LiNbO₃ : Fe : Cu crystal under the same experimental conditions. The damage-resistant dopants such as In³⁺ ions are no longer damage resistant, but they enhance the photorefractive properties at 488 nm wavelength. Experimental results definitely show that In-doped two-centre LiNbO₃ : Fe : Cu crystal is a promising candidate as a blue photorefraction material for volume holographic storage.