Photoferroelectric imaging is the process of storing an image onto a piece of ferroelectric material by the aid of an applied electric pulse. Stored images are nonvolatile and selectively erasable.[1] Photoferroelectric image storage devices have the advantage of being "extremely simple and easy to fabricate".[2]
Photoferroelectric imaging uses a ferroelectric material's photosensitivity in conjunction with its ferroelectric properties. One type of medium which has been used for photoferroelectric imaging is lead lanthanum zirconate titanate (PLZT) ceramics,[1] which exhibit a good combination of properties for imaging: large electro-optic coefficients, high intrinsic and extrinsic photosensitivities, and nonvolatile memory.[3]
A description of a photoferroelectric imaging process (using PLZT material) is given in the McGraw-Hill Concise Encyclopedia of Science and Technology. In that process, a thin flat plate of transparent, optically polished PLZT material (around 0.25mm thick) was sputter-coated with indium tin oxide (ITO) on both sides, serving as electrodes. Then, the image was exposed onto one of the ITO surfaces, while a voltage pulse was simultaneously applied across the electrodes. The ferroelectric polarization thereby switched from one remanent state to another, and images were "stored both as spatial distributions of light-scattering centers in the bulk of the PLZT and as surface deformation strains which form a relief pattern of the image on the exposed surface."[1] The image may then be viewed directly or indirectly.[1]
This photoferroelectric effect is a type of electro-optic effect. In the example process, the ceramic was poled[a] to a saturation remanent polarization state by the light (charge carriers were photoexcited across the PLZT's bandgap). The polarization was then switched by the application of the electric field - a phenomenon called photoassisted domain switching.[4]
Photoferroelectric imaging may be useful in temporary image storage and display.[1] It also has potential applications in data storage[5][4] and holographic recording.[4]