Holographic Memories Using 2-Dimensional Phase-Code Multiplexing Method

Abstract

When implementing a phase-code multiplexing method in real holographic storage systems, there are several factors of cross-talk noise which degrade signal-to-noise ratio (SNR). To reduce such problems, we developed a new and practical phase-code multiplexing method using a 2-dimensional high-resolution phase-only spatial light modulator (P-SLM) which encodes a reference beam with orthogonal phase codes. Theoretically and experimentally, we found that removing a particular all 0 phase code which is always generated by Walsh-Hadamard matrices is quite effective in reducing the cross-talk noise. Moreover, we found that periodically tiled phase-code patterns reduce the cross-talk noise due to inhomogeneous illumination of the P-SLM in real systems. By combining these methods, we achieved bit error rates (BER) for multiplexed holograms on the order of 10 -4 –10 -3 without error correction.