In a very short period of time, lasers have advanced from a mere research interest to an increasingly useful, commercially available tool for material processing, precision measurements, surgery, communication, and entertainment. This book provides the background in theoretical physics necessary to understand the engineering applications of lasers. It summarizes relevant theories of geometrical optics, physical optics, quantum optics, and laser physics while tying them to applications in such areas as fluid mechanics, combustion, surface analysis, material processing, and laser machining. The author clearly and thoroughly explains advanced topics such as laser Doppler velocimetry, laser-induced fluorescence, and holography. The book includes numerous examples and advanced problems that simulate real-world research and encourage independent reading and analysis. The book will benefit researchers and students across all branches of engineering.