Laser Fundamentals

This chapter presents an overview of the operational basics of lasers and the properties and characteristic parameters that define a laser system as well as the major types that are less or more commonly used in the military domain. It discusses the operational principle of a laser and associated topics such as two-level laser, three-level laser and four-level laser, different parts that make up a laser system and modes of a laser. All particles, big or small, according to the basic rules of quantum mechanics, have discrete energy levels or states. A typical laser comprises of three main parts; namely the active medium, the pumping source and the resonant structure. Monochromaticity is one of the essential requirements for the laser radiation to be coherent. Coherence is the most important property that distinguishes the laser radiation from the ordinary light. The directionality of laser radiation has its origin in the coherence of the stimulated emission process.