Many years spent in an industrial engineering laboratory have convinced me that there is ever-increasing need to present recent and current research in forms which can be easily assimilated by engineers, technical managers, and others concerned with applications and the development of new tech­ nology. There is a forbidding gap between the typical research paper, addressed by specialists to other specialists, and the popular-level account addressed to the layman. The second does not adequately prepare the engi­ neer for profitably studying the first; it does not impart sufficient depth of understanding to the manager who must make decisions on the relative merits of various approaches to a problem or on the potential contributions various specialists might make to his program. This book is the outgrowth of a review prepared to fill this need for engineers in a large corporation who were concerned with the industrial application of lasers. That review was written hurriedly, on a fixed budget, to a deadline; consequently, it contained oversimplifications and errors, not all of which were trivial. Nevertheless, the favorable response proved that such a review is indeed needed. It is hoped that this more finished work will prove useful to a wide variety of potential users of laser-centered devices and systems, and may even stimulate the generation of useful ideas.