The effect of strong wave front distribution in optical wave conjugation by three-photon mixing

Information about phase distortion of an optical wave due to propagation can be obtained a priori through a feedback loop over the transmission medium. This will be conjugated and used to predistort the outgoing signal wave. Phase conjugation can be obtained through second- and third-order nonlinearities in optical materials. Quadratic conjugation lacks phase matching which leads to blurring, while cubic conjugation suffers from small cross section. Analysis of the Pockels effect in crystals to produce wave conjugation shows that long crystals can be used only if the laser intensity exceeds 10⁷W/cm². Spread in wave vectors of the distorted wave front leads to a stretched conjugate. This necessitates the use of wave front tracking.