Nonvolatile optical storage in photorefractive crystals

We discuss the state-of-the-art for optical holographic storage of information in photorefractive crystals. In particular, we have recently been successful in storing 3D images and 10 /spl mu/m optical interconnects. Holography is a common technique used to generate realistic 3D images. Photorefractive crystals are an ideal storage medium for recording holographic images because of several advantages, such as real-time exposure and display, a simple recording process in which no pre- or post-processing is required, low writing beam powers, and a potentially large storage volume. Recent experiments have clearly shown the potential of photorefractive crystals for 3D image storage and retrieval. In this paper, we report the first demonstration, to our knowledge, of the corresponding storage and retrieval of 3D color holograms in a photorefractive crystal. The 3D image reproduces the colors of the object and is visible over a wide perspective as demonstrated by moving one's head back and forth while viewing the hologram. The wide field-of-view of the hologram is also demonstrated using an imaging lens with a color CCD camera mounted on a goniometer to record various perspectives. In addition to storage of 3D images, we have also been successful at nonvolatile storage of two dimensional waveguides or optical interconnects in bulk crystals or potential substrates for electronic applications.