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Army Research Laboratory (1998)
3-D Holographic Display Using Strontium Barium Niobate

"An innovative technique for generating a three-dimensional holographic display using strontium barium niobate (SBN) is discussed. The resultant image is a hologram that can be viewed in real time over a wide perspective or field of view (FOV). The holographic image is free from system-induced aberrations and has a uniform, high quality over the entire FOV. The enhanced image quality resulted from using a phase-conjugate read beam generated from a second photorefractive crystal acting as a double-pumped phase-conjugate mirror (DPPCM). Multiple three-dimensional images have been stored in the crystal via wavelength multiplexing."

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"The proposed method employs a volume hologram recorded and read in real time in a photorefractive crystal to produce a 3-D image. This innovative technique is simple, and it differs from previous attempts at 3-D displays. We used a photorefractive material, Strontium Barium Niobate (SBN), to record a hologram, and a phase-conjugate read beam, which is generated from a double-pumped phase-conjugate mirror (DPPCM), to accurately reproduce the holographic image in space over a large perspective. The resultant holographic image is free from system-induced aberrations, may be viewed over a wide range of angles that can be expanded by the addition of a mosaic of crystals, and has uniform high quality over the entire Field of View (FOV)."

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Conclusions

A simple method for recording a real-time, 3-D hologram using Strontium Barium Niobate (SBN) has been demonstrated. The 3-D hologram is a realistic image that can be viewed over a large Field Of View (FOV). A Double-Pumped Phase-Conjugate Mirror (DPPCM) was used to produce a phase-conjugate read beam in order to view the hologram over the maximum perspective (FOV). We further increased the FOV of the hologram by storing the hologram in a mosaic of two SBN crystals. Multiple 3-D images have been stored and read out of the crystal via wavelength multiplexing. The holograms were also noted to persist without any external fixing mechanisms. During readout, the holograms persisted for hours. When the photorefractive storage crystal was kept in a dark environment, the holograms persisted for days.