Photorefractive optical processing for data security

Optical information processing techniques offer many advantages for data security applications. Optics offers many degrees of freedom like phase, spatial frequency, and polarization to encode data more securely. Being inherently two-dimensional, optical systems can process and relay two-dimensional information in parallel resulting in higher throughput rate compared to the electronic systems. The above advantages offered by optical information processing systems, coupled with advancements in enabling technologies like photorefractive crystals, spatial light modulators, charge coupled device cameras, and smart pixel technology have led to an increasing use of optoelectronic data processing techniques for security applications. Holographic memories that use photorefractive materials are attractive due to their high-density storage capacity, high-speed access to data, and rewritability. Thus photorefractive materials can be used for secured data storage and retrieval. Encrypted memory can be used in a secure communication network using ultrashort pulses. Encryption of amplitude and phase images, and storage of the subsequent encrypted image in photorefractive material has been achieved by various researchers. The present paper reviews various optical encryption techniques developed by us, based on photorefractive crystals. These techniques include double random encoding, fractional Fourier plane encoding, and fully phase encoding.