In modern optics, the photon concept is indispensable for an ever-increasing range of applications, including many that are now prominent in twenty-first-century technology. To fully appreciate these applications, it is essential to understand the quantum principles and the mechanisms involved. This book, written by two widely published experts in the area, aims to provide a sound and up-to-date description of the theory and applications of photon science. It concisely explains substantial theory with a light touch, and the text is illustrated with original color figures.