Refraction is a technique for the scattering or bending of light through transparent material. Refraction is responsible for many illusions including underwater objects appearing closer to the surface than they actually are.
Nonlinear Effects In Photorefractive Crystals
Photorefractive crystals are materials whose index of refraction is altered under the illumination of light. These crystals are both photoconductive and electro-optic. When a non-uniform light intensity pattern is present in the material, photocarriers are generated and redistributed, creating space charge electric fields which change the refractive index locally. These crystals are ideal media for real-time holography, and applications include wave amplification, image processing, phase conjugation, and laser beam steering for optical interconnects (Source).
Holographic Associative Memories
In optical and electronic computing, holographic memories are known for their ability to store a massive amount of nonlinear information in parallel such as images and associations. Hologram fixing techniques have been demonstrated in a wide variety of photorefractive materials including LiNbO3, BaTiO3, and KNbO3.
A liquid crystal spatial light modulator can be used to generate a unique pattern of light within an N x N matrix where analog data is filtered and modulated into binary elements for reading and writing. This type of signal processing is effective for numerous applications, including neural networks and optical arrays.
Implementations of neural network models based on the self-organizing features of the human brain are well suited to utilize the properties of light.