The term LASER stands for

The term LASER is an acronym for Light Amplification by Stimulated Emission of Radiation [2]. Unlike conventional light sources that rely on spontaneous emission, where atoms emit radiation randomly in various directions and phases, a laser operates on the principle of stimulated emission [1]. This process occurs when an incoming photon interacts with an atom in an excited state, forcing it to transition to a lower energy level and emit a second photon that is identical in wavelength, phase, and direction. This mechanism allows for the production of a coherent, monochromatic, and highly directional beam of light. The concept was theoretically predicted by Albert Einstein in 1917 and first realized experimentally by T.H. Maiman in 1960. The process requires a gain medium, a population inversion of electron states, and an optical resonator to facilitate amplification [2].

Sources

1. [1] https://www.sciencedirect.com/topics/engineering/light-amplification-by-stimulated-emission-of-radiation
2. [2] https://lasers.llnl.gov/education/nifs-guide-how-lasers-work