It is now well established that a unique feature of coherent optical beams is their
capability to transmit, to process and to interconnect in parallel a large number
of high bandwidth information channels. However, although a considerable
potential exists for these techniques, their development depends critically on
the availability of nonlinear optical materials that work at high speed and low
incident optical power. At present, these requirements are stimulating a great
deal of research in materials science and are challenging existing technologies,
in particular high speed electronics. This volume devoted to photorefractive
crystals and their applications presents a detailed account of materials and
device issues. Starting from the large index nonlinearities observed in several
photorefractive crystals, the authors present and analyse a variety of new applications
based on all-optical interactions between the incident laser beams.
Photorefractive crystals permit beam interactions with a large gain at low
power levels. A remarkable consequence is the demonstration of complex signal
processing functions using the amplification and feedback concepts for performing
tasks comparable to electronics, but now on optical wavefronts containing
spatial information. These concepts are clearly outlined and developed in the
different chapters of this book which cover theory and experiments relevant
to image amplification, phase conjugation, self-induced optical resonators and
associative memories. This collection of articles provides a broad survey of the
current research on the applications of photorefractive crystals. We hope that,
together with the significant results already demonstrated, it will stimulate
further research into the optimization of photorefractive crystals as well as the
investigation of new effects and the invention of new devices and device architectures.