Among the various methods to produce three-dimensional (3D) images, holography occupies a special niche. Indeed, holograms provide highly realistic 3D images with a large viewing angle capability without the need for special eyewear. Such characteristics make them valuable tools for a wide range of applications such as medical, industrial, military, and entertainment imaging. To be suitable for an updatable holographic display, a material needs to have a high diffraction efficiency, fast writing time, hours of image persistence, capability for rapid erasure, and the potential for large display area—a combination of properties that has not been realized before.Currently, there exist several media for recording holograms like photopolymers, silver halide films or dichromated gelatin, to name a few. However, in all of these media, the image is permanently written and cannot be refreshed. There also exist dynamic 3D display systems based on acousto-optic materials, liquid-crystals or microelectromechanical systems (MEMS), however they rely on massive wavefront computations that limit their image size capability. Inorganic crystals for hologram recording such as photorefractive crystals are extremely difficult to grow to larger than a few cubic centimeters in volume.Photorefractive polymers are dynamic holographic recording materials that allow for updating of images. They have been investigated over the last decade and have a wide range of applications including optical correlation, imaging through scattering media, and optical communication. Here, we report the details of the achievement of the first updatable holographic 3D display based on photorefractive polymers. With a 4$\times$4 in$^2$ size, this is the largest photorefractive 3D display to date and is capable of recording and displaying new images every few minutes. The holograms can be viewed for several hours without the need for refreshing, and can be completely erased and updated whenever desired.
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