laser

[ley-zer]

noun

Physics.

1. a device that produces a nearly parallel, nearly monochromatic, and coherent beam of light by exciting atoms to a higher energy level and causing them to radiate their energy in phase.

laser

¹

/ ˈleɪzə /

noun

1. 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

2. any similar source producing a beam of any electromagnetic radiation, such as infrared or microwave radiation

verb

1. to use a laser on (something), esp as part of medical treatment

2. (often foll by off) to remove (a tattoo, fat, etc) with laser treatment

Laser

²

/ ˈleɪzə /

noun

1. a type of dinghy, designed to be sailed by one person

laser

1. Short for light amplification by stimulated emission of radiation. A device that creates and amplifies electromagnetic radiation of a specific frequency through the process of stimulated emission. The radiation emitted by a laser consists of a coherent beam of photons, all in phase and having the same polarization. Lasers have many uses, such as cutting hard or delicate substances, reading data from compact disks and other storage devices, and establishing straight lines in geographical surveying.

laser

1. A device that produces a very narrow, highly concentrated beam of light. Lasers have a variety of uses in such areas as surgery, welding and metal cutting, and sound and video recording and reproduction. The name is an acronym for l ight a mplification by s timulated e mission of r adiation.

Word History and Origins

Origin of laser¹

1955–60; l(ightwave) a(mplification by) s(timulated) e(mission of ) r(adiation)

Word History and Origins

Origin of laser¹

C20: from l ight a mplification by s timulated e mission of r adiation

A 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.

Example Sentences

This week it is announcing it will test sensors to detect laser threats in space.

From BBC

On Tuesday, the Department of Homeland Security announced that they had arrested “four criminal illegal aliens” who allegedly conducted laser strikes on a Border Patrol helicopter “in an attempt to temporarily blind the pilot.”

From Los Angeles Times

But this time Stafford finished the deal with a laser pass to Adams.

From Los Angeles Times

However, Prof Ali believes we can potentially boost collagen output and maintain elasticity in our skin by using special techniques such as laser collagen stimulation and microneedling.

From BBC

The Hunter's Return is a vast canvas depicting a war zone, with toppled trees and craters lit up by a fiery sky, and with green military laser beams emerging from the smoke.

From BBC

Related Words

• bar 
• glow 
• radiation 
• ray 
• shaft