Nearly a decade aga a general review article on the evaluation of optical radia tion hazards was published in Applied Optics (Sliney and Freasier, 1973). This arti cle received many favorable comments but also prompted many inquiries regarding specific optical hazard problems. From this it became evident that a monograph rather than a supplemental and expanded article was needed to fill this literature gap relating to laser and optical radiation hazards. The present work is designed to fill that gap, and is structured to permit either classroom or self-study use. Much of the material in this book was developed in eonnection with short courses on laser safety and radiometry in which we have participated, as weIl as from our previous articles. In particular, the sequenee of chapters is based upon the experiences which we have had in lecturing in courses with different schedules. One of the great difficulties in developing a text of this nature is that a broad, multidisciplinary background must be included in order that the reader can comprehend all of the subjeet matter readily. For this reason, the material presented on anatomy and physiology is orien ted toward the engineer or physical scientist, while the review material on basic optical physics is intended more for the physician or life scientist.

Although scarcely 20 years have passed since the creation of the first laser, laser engineering has enjoyed a variety of applications in science and in practice. Among these applications, a special pI ace is held by those related to the propagation of laser radiation in the atmosphere. Some, such as laser communication and information-transmission systems, locating and teleme tering systems, and mapping and navigation systems, require access to quantitative data on the effects of the atmosphere on the parameters of the laser beam serving as the carrier of useful information, since the efficacy of any such system depends significantly on the influence of the atmosphere. Another set of laser applications associated with the propagation of coherent radiation in the atmosphere requires the solution of both direct and inverse problems related to this complex subject. The kind of applica tion in question is the use of lasers for long-range monitoring of various physical parameters of the atmosphere-a new and highly promising direc tion in science and engineering.

Unique properties of laser radiation including its monochromatic properties, polarization, high spectral intensity, coherence, narrow beam divergence, the possibility of controlling the pulse duration and radiation spectrum and, finally, the fact that extremely high power and energy create very favorable conditions for the extensive application of lasers to communi cation systems, systems for the lidar sensing and ultra-high-precision ranging, navigation, remote monitoring of the environment, and many other systems operating in the atmosphere. The operative efficiency of the above systems depends significantly on the state of the atmosphere and the corresponding behavior of laser radia tion propagating through it. This circumstance has stimulated the studies of the above regularities during the passt 10-15 years. For the investiga tions to be carried out the scientists were forced to develop new theories and methods for studying the problem experimentally. Moreover, during such investigations some previously unknown phenomena were observed, among them the nonlinear effects accompanying high-power laser radiation propagating through the atmosphere are of paramount importance. Among the nonlinear effects caused by high-power laser radiation inter action with the atmosphere, the effects accompanying the propagation of high-power radiation through the atmospheric aerosols are of particular interest. Aerosols always occur in the atmosphere. It should be noted that the microphysical and optical characteristics of atmospheric aerosols vary widely, this fact causes a great variety in the features of their inter action with radiation.

This is a comprehensive tutorial on the emerging technology of free-space laser communications (FSLC). The book offers an all-inclusive source of information on the basics of FSLC, and a review of state-of-the-art technologies. Coverage includes atmospheric effects for laser propagation and FSLC systems performance and design. Free-Space Laser Communications is a valuable resource for engineers, scientists and students interested in laser communication systems designed for the atmospheric optical channel.

Free space optics is a telecommunications technique which is already being used for everyday exchange of information and has many advantages over other techniques (bandwidth, low cost, mobility of the equipment, security, etc.); within the next decade, it is likely to become an integral and essential part of data-processing architectures and telecommunications. A history of wireless optical telecommunications is given, together with a recapitulation of the application of the principles of electromagnetism to free-space optics. Coverage is also given to the transmitters and receivers of optical beams, whih are the basis of any optical communication system. These devices were responsible for the first truly significant advances in the performance of these systems. Special attention is given to the problems associated with the propagation of photons, both in the presence and absence of obstacles, since these are key issues in gaining an understanding of future telecommunication systems based on wireless optics. Finally, the authors considwer standards, as well as safety and confidentiality issues.