Preface

I was introduced to the photorefractive effect in organic compounds in 1994 when I started my career at the Centre Spatial de Liege (Belgium). The objective of the program was to develop nondestructive testing technology to analyze aerospace structures and payloads. At the time, that class of materials had just been discovered and was a scientific hot topic. While the science was interesting, the figures of merit of the materials were marginal, and, unfortunately for me, no application could be developed in the short duration of the project. Leaving Belgium for the United States, I had the chance to work with one of the most active groups in the field of photorefractive polymers at the University of Arizona. There, Professors Peyghambarian and Marder had assembled a team of scientists ranging the span from organic chemistry through optical characterization and theoretical modeling. That kind of team formed the critical mass necessary to make significant advances in science. During that time, I witnessed the diffraction efficiency and sensitivity of the material multiplied a hundredfold, while the response time decreased by the same order of magnitude. Compositions were being optimized for different regions of the spectrum where proof-of-concept applications were demonstrated. Theories were formulated to explain the behaviors observed in the laboratory, and the predictions of these theories were being tested in quasi real time. Thanks to that effort, and many similar ones all around the world, photorefractive organic materials are now fairly well understood from a theoretical point of view and their properties substantially more developed than they were a decade ago. Today, it is possible to synthesize a stable photorefractive compound with close to 100% diffraction efficiency, several hundred cm 1 of gain, and sub-millisecond response time. The first chapter of this book (Blanche and Lynn) provides a scientific history of these exciting discoveries, from mathematical modeling to the development of specific organic molecules and compounds, as well as the manufacturing of reliable devices and characterization procedures. Labeled as an introduction, it is an overview of the techniques and progress the field of photorefractive material has experienced the last 25 years.