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 optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

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'' originated as an acronym for light amplification by stimulated emission of radi ...

s. Laser science is principally concerned with

quantum electronics Quantum optics is a branch of atomic, molecular, and optical physics and quantum chemistry that studies the behavior of photons (individual quanta of light). It includes the study of the particle-like properties of photons and their interaction w ...

laser construction A laser is constructed from three principal parts: *An energy source (usually referred to as the ''Laser pumping, pump'' or ''pump source''), *A ''gain medium'' or ''Active laser medium, laser medium'', and *Two or more mirrors that form an ''o ...

optical cavity An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors or other optical elements that confines light waves similarly to how a cavity resonator confines microwaves. Optical cavities are a major component of lasers, ...

design, the physics of producing a

population inversion In physics, specifically statistical mechanics, a population inversion occurs when 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 an idealized beam of electromagnetic radiation whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile. This fundamental (or ...

s, with laser applications, and with associated fields such as

nonlinear optics Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in Nonlinearity, 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 ...

and

quantum optics Quantum optics is a branch of atomic, molecular, and optical physics and quantum chemistry that studies the behavior of photons (individual quanta of light). It includes the study of the particle-like properties of photons and their interaction ...

History

Laser science predates the invention of the laser itself.

Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...

created the foundations for the laser and

maser A maser is a device that produces coherent electromagnetic waves ( microwaves), through amplification by stimulated emission. The term is an acronym for microwave amplification by stimulated emission of radiation. Nikolay Basov, Alexander Pr ...

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 physics, theoretical physicist whose discovery of energy quantum, quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial con ...

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

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

, 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 ...

of electromagnetic radiation. The existence of stimulated emission was confirmed in 1928 by Rudolf W. Ladenburg.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 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 German-born French physicist and Nobel laureate in Physics. He is known for the development of optical pumping. Biography Kastler was born in Guebwiller (Alsace, at the time part of the Germ ...

(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 popu ...

, 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 Nikolay Gennadiyevich Basov (; 14 December 1922 – 1 July 2001) was a Russian Soviet physicist and educator. For his fundamental work in the field of quantum electronics that led to the development of laser and maser, Basov shared the 1964 Nobe ...

and

Alexander Prokhorov Alexander Mikhailovich Prokhorov (born Alexander Michael Prochoroff, ; 11 July 1916 – 8 January 2002) was an Australian-born Russian physicist and researcher on lasers and masers, in the former Soviet Union. He shared the Nobel Prize in P ...

at the ''All-Union Conference on Radio Spectroscopy'' in May 1952. The first maser was built by Charles H. Townes, James P. Gordon, and Herbert J. Zeiger in 1953. Townes, Basov and Prokhorov were awarded the

Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...

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 Labs. Ashkin has been considered by many as the father of optical tweezers, "LaserFest – the 50th anniversary of the firs ...

, Gérard Mourou, and Donna Strickland 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 Theodore Harold Maiman (July 11, 1927 – May 5, 2007) was an American engineer and physicist who is widely credited with the invention of the laser.Johnson, John Jr. (May 11, 2008). "Theodore H. Maiman, at age 32; scientist created the first L ...

at the Hughes Research Laboratories.

References

External links

A very detailed tutorial on lasers
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History

See also

References

External links