laser
Americannoun
noun
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a source of high-intensity optical, infrared, or ultraviolet radiation produced as a result of stimulated emission maintained within a solid, liquid, or gaseous medium. The photons involved in the emission process all have the same energy and phase so that the laser beam is monochromatic and coherent, allowing it to be brought to a fine focus
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any similar source producing a beam of any electromagnetic radiation, such as infrared or microwave radiation
verb
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to use a laser on (something), esp as part of medical treatment
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(often foll by off) to remove (a tattoo, fat, etc) with laser treatment
noun
Closer Look
A laser emits a thin, intense beam of nearly monochromatic visible or infrared light that can travel long distances without diffusing. Most light beams consist of many waves traveling in roughly the same direction, but the phases and polarizations of each individual wave (or photon) are randomly distributed. In laser light, the waves are all precisely in step, or in phase, with each other, and have the same polarization. Such light is called coherent. All of the photons that make up a laser beam are in the same quantum state. Lasers produce coherent light through a process called stimulated emission. The laser contains a chamber in which atoms of a medium such as a synthetic ruby rod or a gas are excited, bringing their electrons into higher orbits with higher energy states. When one of these electrons jumps down to a lower energy state (which can happen spontaneously), it gives off its extra energy as a photon with a specific frequency. But this photon, upon encountering another atom with an excited electron, will stimulate that electron to jump down as well, emitting another photon with the same frequency as the first and in phase with it. This effect cascades through the chamber, constantly stimulating other atoms to emit yet more coherent photons. Mirrors at both ends of the chamber cause the light to bounce back and forth in the chamber, sweeping across the entire medium. If a sufficient number of atoms in the medium are maintained by some external energy source in the higher energy state—a condition called population inversion—then emission is continuously stimulated, and a stream of coherent photons develops. One of the mirrors is partially transparent, allowing the laser beam to exit from that end of the chamber. Lasers have many industrial, military, and scientific uses, including welding, target detection, microscopic photography, fiber optics, surgery, and optical instrumentation for surveying.
Etymology
Origin of laser
1955–60; l(ightwave) a(mplification by) s(timulated) e(mission of ) r(adiation)
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
When a laser shines on an atom to trigger the release of a photon, the process can also produce extra, unwanted photons.
From Science Daily
These systems trap laser light between two mirrors, causing the light to bounce back and forth before some of it eventually escapes.
From Science Daily
Two such condensates were separated by a narrow optical barrier formed by a focused laser beam.
From Science Daily
The team is exploring faster laser sources, including VCSELs, and testing whether narrowing the sweep range can further improve performance.
From Science Daily
Anderson went on to spend nearly a decade at Aurora and led development of a Lidar system that bounces lasers off objects to capture surroundings in 3-D.
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
