The theoretical basis of laser

The word 'laser' is a free translation of LASER'. LASER was originally a specialized term composed of the prefix Light amplification by stimulated emission of radiation. In 1964, Academician Qian Xuesen proposed the name 'Laser　　1) Theoretical basis of laser　　 In 1916, Einstein published 'Quantum Theory on Radiation' based on Bohr's work. The article puts forward the theory of laser radiation, which is the core foundation of laser theory. Therefore Einstein is considered the father of laser theory. In this paper, Einstein distinguished three kinds of processes: stimulated absorption, spontaneous emission, and stimulated emission. Spontaneous radiation means that atoms in high-energy states spontaneously radiate photons and migrate to low-energy states. The characteristic of this type of radiation is that the transition of each atom is spontaneous and independent, and the process is completely free of external influences. It doesn't matter. Therefore, the state of the photons emitted by them is different. This kind of light has poor coherence and scattered directions, while stimulated emission is the opposite. Stimulated emission means that atoms at high energy levels are stimulated by 'or induced' by photons, transition to low energy levels and radiate a photon with the same frequency as the incident photon. This is like a rooster crowing in the morning, when one rooster croaks, the other roosters will make the same sound when they are stimulated.' The characteristic of stimulated radiation is that the photon produced by the stimulated radiation has exactly the same state as the original photon that caused the stimulated radiation. They have the same frequency and the same direction, and it is impossible to distinguish the difference between the two. In this way, one photon becomes two identical photons through one stimulated radiation. This means that the light is strengthened, or light is amplified. This is the basic process of producing laser light. (The above is edited by laser cutting machine for details, please refer to www.gnlaser.com)