Performance analysis of phase-code multiplexed holographic memory.

For analysis of effective phase-code multiplexing in a holographic memory system four types of phase code are generated and used as a reference beam. In computer simulations the size of the address beam is fixed at 32 x 32 pixels, and 0%, 5%, 10%, 15%, 20%, and 25% phase-error rates in a pixel are purposely added to the real phase values for consideration of the nonlinear phase-modulation characteristics of a practical spatial light modulator. Cross talk and signal-to-noise ratios (SNR's) are comparatively analyzed for these phase codes by calculation of the autocorrelation and the cross correlation. The pseudorandom code (PSR) has the lowest cross-correlation mean value of 0.067 among the four types of phase code, which means that the SNR of the PSR is higher than with other phase codes. Also, the standard deviation of the PSR, indicating the degree of recalled data degradation, has the lowest value, at 0.0113.