ABSTRACT
Lasers are essentially quantum devices. The process of stimulated emission is a quantum phenomenon. Stimulated emission is essential to the generation of spatially and spectrally coherent radiation, which are also quantum phenomena. Thus, albeit initially a macroscopic device, the laser emits radiation that is intrinsically quantum in character. The chapter considers a first and essential step in the creation of a laser: laser excitation. The word laser has its origin in an acronym of the words light amplification by stimulated emission of radiation. However, the laser is readily associated with the spatial and spectral coherence characteristics of its emission. A laser is a device that transforms electrical energy, chemical energy, or incoherent optical energy into coherent optical emission. Laser optics, as defined in Duarte, refers to the individual optics elements that comprise laser cavities, to the optics ensembles that comprise laser cavities, and to the physics that results from the propagation of laser radiation.
