Fast photorefractive response in strongly reduced near-stoichiometric LiNbO_3 crystals

The photorefractive response time of LiNbO(3) crystal is of the order of minutes, and such a long response time limits the crystal's practical applications. We report the photorefractive properties of nominally pure near-stoichiometric LiNbO(3) crystal that is strongly reduced in vacuum. A short photorefractive response time of the order of 100 ms is measured at a wavelength of 514.5 nm, with incident light intensity of 1.6 W/cm (2) , and possible corresponding mechanisms are discussed. To our knowledge this is the first experimental evidence of a subsecond photorefractive response in pure LiNbO(3) crystals. The diffraction efficiency of a holographic grating written in this reduced crystal is low but can be enhanced by an externally applied electric field.