Unitary matrices for phase-coded holographic memories

Volume holographic data storage based on phase-code multiplexing is a promising technology for next generation optical storage devices. Volume holographic memories offer high storage capacities and short data access times through multiplexing and a page-oriented storage principle. Multiple holograms can be recorded in the storage media through various multiplexing techniques, such as angular, phase-code, wavelength or shift multiplexing. Among the different methods, deterministic phase-code multiplexing has been widely investigated since it entails several advantages. This method allows recording and retrieval of data pages without introducing moving parts or frequency-shifting elements into the setup, which results in a fast access speed. Crosstalk analyses have shown that the signal-to-noise ratio (SNR) of phase-code multiplexing is significantly higher than those of wavelength or angle multiplexing. In addition, phase-code multiplexing offers the potential of performing parallel optical operations of stored images, associative data search and enables powerful address based encryption techniques. this contribution, we present a novel type of matrices - unitary matrices (U-matrices) for phase-code multiplexed holographic memories.