A typical optical system is composed of three basic components: a source, a detector, and a medium in which the optical energy propagates. Many textbooks cover sources and detectors, but very few cover propagation in a comprehensive way, incorporating the latest progress in theory and experiment concerning the propagating medium. This book fulfills that need. It is the first comprehensive and self-contained book on this topic. It is useful reference book for researchers, and a textbook for courses like Laser Light Propagation, Solid State Optics, and Optical Propagation in the Atmosphere.