Over the last two decades, such new technologies as laser-aided material processing, optical communication, holography, and optical measurement techniques have advanced from laboratory curiosities to commercially available engineering tools. Faced with these developments, engineers must now apply in their practice many concepts of physics that in the past were considered outside the boundaries of classical engineering. Advanced levels of electromagnetic theory and of quantum mechanics are now required to answer fundamental questions about interference, diffraction, or polarization of light and their applications. For example: How does radiation interact with gases, liquids, and solids? How does one obtain optical gain? When should a laser be used, and when would an ordinary light source suffice? How can a laser beam be produced and focused? Answers to these questions are essential for selecting an optical technique for measuring the properties of gas, liquid, or solid phases, or when designing a laser system for material processing, surgery, communication, or entertainment. Although most engineering students attend two or three undergraduate courses in physics, they seldom acquire the proficiency required to fully understand the intricacies of modern optics or laser applications. Similarly, midlevel engineers who obtained their formal education before many new techniques were developed may find an increasing gap between the knowledge acquired in undergraduate physics classes and the requirements of professional practice.