of the propagation of optical waves and the mixing of electromagnetic radiation in nonlinear optical media. In a progressive format that moves from the elementary to the complex, the book begins with the basics of electromagnetic waves and periodic structures, examining the physics of photorefractive effects and the mixing of waves in these media. Classical electrodynamics is used to describe the mixing of waves in photorefractive media. Concepts in elementary solid state physics are also used to clarify the discussion on the transport of charges in photorefractive crystals. Following chapters take an in-depth look at optical phase conjugators and photorefractive resonators. The fundamental principles of gratings and holograms are examined inchapters 7 and 8. The manifold applications in optical information processing, optical interconnection, and neural networks are clearly detailed in the following three chapters. The last chapter is devoted to a timely look at the higher order photorefractive effect in optical fi