Phase conjugation in photorefractive materials

Abstract

An optical wave that has passed through a distorter can be healed by phase conjugating the wave and passing it back through the distorter again. Phase conjugators that respond to weak optical waves (milliwatts) have been realized using a four-wave mixing geometry in photorefractive materials.1 If the material has a sufficiently large coupling strength it can become a self-pumped phase conjugator, and only the input wave is required.2