Core Laser Principles Learning Path

Laser terminology and maser distinction

The topic distinguishes laser terminology from maser terminology by tracing the origin of the acronyms and the frequency ranges they cover. “Maser” originally stood for “microwave amplification by stimulated emission of radiation,” referring to devices that use stimulated emission to amplify electromagnetic radiation at microwave frequencies. When similar principles were applied to optical (higher-frequency) devices, the term “optical maser” was used initially, but the acronym was updated by replacing “microwave” with “light,” yielding “laser” (“light amplification by stimulated emission of radiation”). In modern usage, devices operating at frequencies higher than microwaves (roughly above 300 GHz, including infrared, ultraviolet, X-ray, and gamma-ray lasers) are called lasers, while devices operating at microwave or lower radio frequencies are called masers. The terms “to lase” and “lasing” are also used for producing coherent light via stimulated emission, and both laser/maser terminology can extend to naturally occurring coherent emissions (e.g., astrophysical masers and atom lasers).

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Coherence as defining laser property

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