A laser beam used for welding.
Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". [1] [2] The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.

A laser differs from other sources of light in that it emits light coherently, spatially and temporally. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances ( collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.

Among their many applications, lasers are used in optical disk drives, laser printers, and barcode scanners; DNA sequencing instruments, fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed; and laser lighting displays in entertainment.


Modern telescopes use laser technologies to compensate for the blurring effect of the Earth's atmosphere. [3]

Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, which is diffraction-limited. Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance.

Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively great distance (the coherence length) along the beam. [4] A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase that vary randomly with respect to time and position, thus having a short coherence length.

Lasers are characterized according to their wavelength in a vacuum. Most "single wavelength" lasers actually produce radiation in several modes having slightly differing frequencies (wavelengths), often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously. There are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all such devices are classified as "lasers" based on their method of producing light, i.e., stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.


Laser beams in fog, reflected on a car windshield

The word laser started as an acronym for "light amplification by stimulated emission of radiation". In this usage, the term "light" includes electromagnetic radiation of any frequency, not only visible light, hence the terms infrared laser, ultraviolet laser, X-ray laser, gamma-ray laser, and so on. Because the microwave predecessor of the laser, the maser, was developed first, devices of this sort operating at microwave and radio frequencies are referred to as "masers" rather than "microwave lasers" or "radio lasers". In the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser; this term is now obsolete. [5]

A laser that produces light by itself is technically an optical oscillator rather than an optical amplifier as suggested by the acronym. It has been humorously noted that the acronym LOSER, for "light oscillation by stimulated emission of radiation", would have been more correct. [6] With the widespread use of the original acronym as a common noun, optical amplifiers have come to be referred to as "laser amplifiers", notwithstanding the apparent redundancy in that designation.

The back-formed verb to lase is frequently used in the field, meaning "to produce laser light," [7] especially in reference to the gain medium of a laser; when a laser is operating it is said to be "lasing." Further use of the words laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser and atom laser.

Other Languages
Afrikaans: Laser
Ænglisc: Lēohtfȳsend
العربية: ليزر
asturianu: Láser
azərbaycanca: Lazer
বাংলা: লেজার
башҡортса: Лазер
беларуская: Лазер
беларуская (тарашкевіца)‎: Лазэр
български: Лазер
Boarisch: LASER
bosanski: Laser
brezhoneg: Laser
català: Làser
čeština: Laser
Cymraeg: Laser
dansk: Laser
Deutsch: Laser
eesti: Laser
Ελληνικά: Λέιζερ
español: Láser
Esperanto: Lasero
euskara: Laser
فارسی: لیزر
français: Laser
Frysk: Laser
Gaeilge: Léasar
galego: Láser
贛語: 激光
ગુજરાતી: લેસર
한국어: 레이저
Հայերեն: Լազեր
hrvatski: Laser
Bahasa Indonesia: Laser
íslenska: Leysir
italiano: Laser
עברית: לייזר
Basa Jawa: Laser
ಕನ್ನಡ: ಲೇಸರ್
ქართული: ლაზერი
қазақша: Лазер
Kreyòl ayisyen: Lazè
Latina: Laser
latviešu: Lāzers
lietuvių: Lazeris
magyar: Lézer
македонски: Ласер
മലയാളം: ലേസർ
Bahasa Melayu: Laser
монгол: Лазер
မြန်မာဘာသာ: လေဆာရောင်ခြည်
Nederlands: Laser (licht)
日本語: レーザー
norsk: Laser
norsk nynorsk: Laser
oʻzbekcha/ўзбекча: Lazer
ਪੰਜਾਬੀ: ਲੇਜ਼ਰ
پنجابی: لیزر
پښتو: لېزر
Patois: Lieza
polski: Laser
português: Laser
română: Laser
русиньскый: Ласер
русский: Лазер
Scots: Laser
Seeltersk: Laser
shqip: Lazeri
sicilianu: Laser
සිංහල: ලේසර්
Simple English: Laser
slovenčina: Laser
slovenščina: Laser
کوردی: لەیزەر
српски / srpski: Ласер
srpskohrvatski / српскохрватски: Laser
suomi: Laser
svenska: Laser
Tagalog: Laser
தமிழ்: சீரொளி
татарча/tatarça: Лазер
తెలుగు: లేజర్
ತುಳು: ಲೇಸರ್
Türkçe: Lazer
українська: Лазер
اردو: لیزر
ئۇيغۇرچە / Uyghurche: لازېر نۇرى
Tiếng Việt: Laser
Võro: Lasõr
Winaray: Laser
吴语: 激光
ייִדיש: לאזער
粵語: 激光
中文: 激光