Photorefarctive materials are by far the most suitable medium to generate optical phase conjugation. In particular, BaTiO3 is an attractive one among the candidates of photorefractive materials because of its large electrooptic coefficient that leads to strong coupling for two- and four-wave mixing. High phase conjugate reflectivity is always desired as well as diffraction efficiency for their different potential applications. This book contains the experimental observations of a unique enhancement of the transient diffraction efficiency and phase conjugate reflectivity with steady-state...