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Publisher Summary LASER is an acronym for light amplification by stimulated emission of radiation. A laser is a device that produces radiant energy predominantly by stimulated emission. All lasers have three basic characteristics: a material medium, population inversion of electron states, and a resonant structure. The material medium can be either a solid, liquid, or gas. The medium is excited by a variety of methods to achieve an electronic population inversion, a phenomenon whereby more electrons are in an excited state than in a lower level state. Finally, the medium is placed in a resonant structure so that stimulated emission can make multiple passes through the excitation region. All lasers require an operating medium in which to achieve population inversion. This medium can be a gas, liquid, or solid material. Common gas lasers include helium-neon and carbon dioxide lasers. These gas lasers incorporate other gases to improve their efficiency, because when a mixture of gases is used to improve excitation, population inversion and depletion of lower band levels are improved. |
