Thermal fixing of holograms and their electrically assisted development inbarium calcium titanate crystals

Photorefractive space-charge gratings in barium calcium titanate crystals a re studied with non-steady-state photoelectromotive force and holographic t echniques in the temperature range from 20 to 160 degreesC. Although the cr ystals undergo a ferroelectric-paraelectric phase transition at 100 degrees C, no sharp discontinuity of the space-charge field is observed. However, a slowly compensating grating is found, and thermal fixing is demonstrated. The behavior of the fixed grating is well described by a theory that was de veloped for lithium niobate. The lifetime of the fixed grating depends stro ngly on fringe spacing and temperature, and the diffraction efficiency of t he fixed grating can be drastically enhanced by application of an external electric field. (C) 2001 Optical Society of America.