Authored by one of the founders and major players in this field of research, this is a thorough and comprehensive approach to the quantum mechanical output coupling theory of lasers – an important area of optical physics that has so far been neglected in the scientific literature. Clearly structured, the various sections cover one-dimensional optical cavity, laser, and microcavity laser with output coupling, atom-field interaction in a free-dimensional space, 3D analysis of spontaneous emission in a planar microcavity with output coupling, plus two-atom spontaneous emission. With numerous end-of-chapter problems, this is vital reading for theoretical physicists, laser specialists, and physicists in industry, as well as students and lecturers in physics.