A secure holographic memory system that uses fully phase encryption is presented. Two-dimensional arrays of data are phase encoded. Each array is then transformed into a stationary white-noise-like pattern by use of a random-phase mask located at the input plane and another at the Fourier plane. This encrypted information is then stored holographically in a photorefractive LiNbO3:Fe crystal. The original phase-encoded data can be recovered, by use of the two random-phase masks, with a phase-conjugate readout beam. This phase information can then be converted back to intensity information with an interferometer. Recording multiple images by use of angular multiplexing is demonstrated. The influence of a limited system bandwidth on the quality of reconstructed data is evaluated numerically. These computer simulation results show that a fully phase-based encryption system generally performs better than an amplitude-based encryption system when the system bandwidth is limited by a moderate amount.
© 2000 Optical Society of America
(070.4560) Fourier optics and signal processing : Data processing by optical means
(190.5330) Nonlinear optics : Photorefractive optics
(210.0210) Optical data storage : Optical data storage
(210.2860) Optical data storage : Holographic and volume memories
Xiaodi Tan, Osamu Matoba, Tsutomu Shimura, Kazuo Kuroda, and Bahram Javidi, "Secure Optical Storage that Uses Fully Phase Encryption," Appl. Opt. 39, 6689-6694 (2000)