Volume holographic storage in near-stoichiometric LiNbO₃:Ce,Mn

Near-stoichiometric LiNbO₃:Ce,Mn exhibited a reversible photochromic effect at room temperature. Irradiation with ultraviolet (UV) light enhanced a visible absorption band, and the photorefractive sensitivity to 532 nm-green recording light was greatly improved after UV irradiation. Hologram multiplexing was performed with a continuous-wave 532 nm-green laser by the angle-multiplexing method without and with UV pre-exposure. An M/# of approximately 5 was obtained in a crystal of 2.55 mm-thickness in the absence of UV pre-exposure. In multiplexing after UV pre-exposure, however, the variable sensitivity and erasure-time constant made it very difficult to achieve a multiple hologram storage with nearly equivalent diffraction efficiency.