This is the third and final volume of a three volumes book series devoted to photorefractive effects, photorefractive materials and their applications. Since the publication of our first two Springer books on "Photorefractive Materials and Their Applications" (Topics in Applied Physics, Vols 61 and 62) almost 20 years ago a lot of research has been done in this area. New and often unexpected effects have been discovered, theoretical models developed, known effects could be finally explained and novel applications had been proposed. We believe that the field has now reached a high level of maturity, even if research continues in all areas mentioned above and with new discoveries arriving quite regularly. We therefore have decided to invite some of the top experts in the field to put together the state of the art in their respective fields. This after we had been encouraged to do so for more than ten years by the publisher, due to the fact that the former volumes were out of print since long time. The first volume is devoted to the description of the basic effects leading to photoinduced refractive index changes in electro-optical materials. In the second volume the status of the most recent developments in the field of photorefractive materials is reviewed and the parameters, which govern the photorefractive nonlinearity are highlighted. This third volume deals with the applications of the photorefractive effects and of materials. Starting about 35 years ago the attractivity of the photorefractive effect for data storage, for optical metrology, optical signal processing and nonlinear optical applications has been recognized. One of the main reasons for this is the large nonlinearity or refractive index change, which can be induced by low light intensities by using the photoinduced space-charge fields in electro-optical materials. Many new concepts have been demonstrated in the laboratories over all these years. Several of these concepts have been proved useful also in other areas of nonlinear optics. Particularly interesting was the observation of a large energy from pump beams to the signal beam in two- and fourwave mixing experiments. This effects lead to coherent amplification of a waveform covering spatial information and to self-pumped optical phase conjugation with applications in the area of wavefront correction of self-induced optical resonators. In this third volume a series of applications of photorefractive nonlinear optics and of optical data storage are presented in several chapters. This and the other two volumes on photorefractive effects, materials and applications have been prepared mainly for researchers in the field, but also for physics, engineering and materials science students. Several chapters contain sufficient introductory material for those not so familiar with the topic to obtain a thorough understanding of the photorefractive effect. We hope that for researchers active in the field these books should provide a useful reference source for their work.