THERMAL GRATINGS AND PYROELECTRICALLY PRODUCED CHARGE REDISTRIBUTION IN BATIO3 AND KNBO3

The influence of a pyroelectric charge-driving force on photorefractive currents is demonstrated experimentally for the first time to my knowledge. Illumination of photorefractive BaTiO3 and KNbO3 crystals by two intersecting coherent light pulses (light wavelength lambda(l) = 532 nm) induces thermal gratings. A spatially modulated pyroelectric field arises. Photoexcited carriers move in this field and tend to compensate for it. The pyroelectric field vanishes after termination of the pulse with a characteristic decay time, and redistributed charge remains. Measurements demonstrate that this pyroelectric charge-transport driving force can be much stronger than diffusion for fringe spacings greater than 2 mum. From this new charge-transport mechanism I derive a promising proposal for hologram writing and reading at the same wavelength without erasure.