This graduate-level text presents the fundamental physics of solid-state lasers, including the basis of laser action and the optical and electronic properties of laser materials. After an overview of the topic, the first part begins with a review of quantum mechanics and solid-state physics, spectroscopy, and crystal field theory; it then treats the quantum theory of radiation, the emission and absorption of radiation, and nonlinear optics; concluding with discussions of lattice vibrations and ion-ion interactions, and their effects on optical properties and laser action. The second part...