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

Abstract

Photorefractive space-charge gratings in barium calcium titanate crystals are studied with non-steady-state photoelectromotive force and holographic techniques in the temperature range from 20 to 160 degreesC. Although the crystals undergo a ferroelectric-paraelectric phase transition at 100 degreesC, 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 developed for lithium niobate. The lifetime of the fixed grating depends strongly on fringe spacing and temperature, and the diffraction efficiency of the fixed grating can be drastically enhanced by application of an external electric field. (C) 2001 Optical Society of America.