Light Amplification by Stimulated Emission of Radiation

Laser science or laser physics is a branch of

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...

that describes the theory and practice of

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...

s. Laser science is principally concerned with

quantum electronics Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have ...

, laser construction,

optical cavity An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors or other optical elements that forms a cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and prov ...

design, the physics of producing a

population inversion In science, specifically statistical mechanics, a population inversion occurs while a system (such as a group of atoms or molecules) exists in a state in which more members of the system are in higher, excited states than in lower, unexcited energy ...

in laser media, and the temporal evolution of the light field in the laser. It is also concerned with the physics of laser beam propagation, particularly the physics of

Gaussian beam In optics, a Gaussian beam is a beam of electromagnetic radiation with high monochromaticity whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile. Thi ...

s, with

laser applications Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow ...

, and with associated fields such as

nonlinear optics Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in ''nonlinear media'', that is, media in which the polarization density P responds non-linearly to the electric field E of the light. The non-linearity is typic ...

and

quantum optics Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have ...

History

Laser science predates the invention of the laser itself.

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...

created the foundations for the laser and

maser A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, James ...

in 1917, via a paper in which he re-derived

Max Planck Max Karl Ernst Ludwig Planck (, ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical p ...

’s law of radiation using a formalism based on probability coefficients ( Einstein coefficients) for the

absorption Absorption may refer to: Chemistry and biology *Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which s ...

spontaneous emission Spontaneous emission is the process in which a quantum mechanical system (such as a molecule, an atom or a subatomic particle) transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount ...

, and

stimulated emission Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to th ...

of electromagnetic radiation. The existence of stimulated emission was confirmed in 1928 by

Rudolf W. Ladenburg Rudolf Walter Ladenburg (June 6, 1882 in Kiel – April 6, 1952 in Princeton, New Jersey) was a German atomic physicist. He emigrated from Germany as early as 1932 and became a Brackett Research Professor at Princeton University. When the wave of ...

.Steen, W. M. "Laser Materials Processing", 2nd Ed. 1998. In 1939, Valentin A. Fabrikant made the earliest laser proposal. He specified the conditions required for light amplification using stimulated emission. In 1947,

Willis E. Lamb Willis Eugene Lamb Jr. (; July 12, 1913 – May 15, 2008) was an American physicist who won the Nobel Prize in Physics in 1955 "for his discoveries concerning the fine structure of the hydrogen spectrum." The Nobel Committee that year awarded hal ...

and R. C. Retherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission; in 1950,

Alfred Kastler Alfred Kastler (; 3 May 1902 – 7 January 1984) was a French physicist, and Nobel Prize laureate. Biography Kastler was born in Guebwiller (Alsace, German Empire) and later attended the Lycée Bartholdi in Colmar, Alsace, and École Normale S ...

(Nobel Prize for Physics 1966) proposed the method of

optical pumping Optical pumping is a process in which light is used to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher one. It is commonly used in laser construction to pump the active laser medium so as to achieve pop ...

, experimentally confirmed, two years later, by Brossel, Kastler, and Winter. The theoretical principles describing the operation of a microwave laser (a maser) were first described by Nikolay Basov and

Alexander Prokhorov Alexander Mikhailovich Prokhorov (born Alexander Michael Prochoroff, russian: Алекса́ндр Миха́йлович Про́хоров; 11 July 1916 – 8 January 2002) was an Australian-born Soviet-Russian physicist known ...

at the ''All-Union Conference on Radio Spectroscopy'' in May 1952. The first maser was built by

Charles H. Townes Charles Hard Townes (July 28, 1915 – January 27, 2015) was an American physicist. Townes worked on the theory and application of the maser, for which he obtained the fundamental patent, and other work in quantum electronics associated wit ...

James P. Gordon James Power Gordon (March 20, 1928 – June 21, 2013) was an American physicist known for his work in the fields of optics and quantum electronics. His contributions include the design, analysis and construction of the first maser in 1954 ...

, and

Herbert J. Zeiger Herbert J. Zeiger (b. 16 March 1925 in the Bronx, New York City, United States; d. 14 January 2011) was an American physicist and co-developer of the first maser. Zeiger graduated from the City College of New York with a bachelor's degree in 194 ...

in 1953. Townes, Basov and Prokhorov were awarded the

Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

in 1964 for their research in the field of stimulated emission.

Arthur Ashkin Arthur Ashkin (September 2, 1922 – September 21, 2020) was an American scientist and Nobel laureate who worked at Bell Laboratories and Lucent Technologies. Ashkin has been considered by many as the father of optical tweezers, "LaserFest – t ...

Gérard Mourou Gérard Albert Mourou (; born 22 June 1944) is a French scientist and pioneer in the field of electrical engineering and lasers. He was awarded a Nobel Prize in Physics in 2018, along with Donna Strickland, for the invention of chirped pulse a ...

, and

Donna Strickland Donna Theo Strickland (born 27 May 1959) is a Canadian optical physicist and pioneer in the field of pulsed lasers. She was awarded the Nobel Prize in Physics in 2018, together with Gérard Mourou, for the practical implementation of chirped ...

were awarded the Nobel Prize in Physics in 2018 for groundbreaking inventions in the field of laser physics. The first working laser (a pulsed

ruby laser A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960. Ruby lasers produce pulses of ...

) was demonstrated on May 16, 1960, by Theodore Maiman at the

Hughes Research Laboratories Hughes may refer to: People * Hughes (surname) * Hughes (given name) Places Antarctica * Hughes Range (Antarctica), Ross Dependency * Mount Hughes, Oates Land * Hughes Basin, Oates Land * Hughes Bay, Graham Land * Hughes Bluff, Victori ...

References

External links

A very detailed tutorial on lasers
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History

See also

References

External links