A report on LaserStimulated emission and Photon

Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers
Laser light is a type of stimulated emission of radiation.
Photons are emitted by a cyan laser beam outside, orange laser beam inside calcite and its fluorescence
A laser beam used for welding
Photoelectric effect: the emission of electrons from a metal plate caused by light quanta – photons.
The cone shows possible values of wave 4-vector of a photon. The "time" axis gives the angular frequency (rad⋅s−1) and the "space" axis represents the angular wavenumber (rad⋅m−1). Green and indigo represent left and right polarization
A helium–neon laser demonstration. The glow running through the center of the tube is an electric discharge. This glowing plasma is the gain medium for the laser. The laser produces a tiny, intense spot on the screen to the right. The center of the spot appears white because the image is overexposed there.
Thomas Young's double-slit experiment in 1801 showed that light can act as a wave, helping to invalidate early particle theories of light.
Spectrum of a helium–neon laser. The actual bandwidth is much narrower than shown; the spectrum is limited by the measuring apparatus.
In 1900, Maxwell's theoretical model of light as oscillating electric and magnetic fields seemed complete. However, several observations could not be explained by any wave model of electromagnetic radiation, leading to the idea that light-energy was packaged into quanta described by . Later experiments showed that these light-quanta also carry momentum and, thus, can be considered particles: The photon concept was born, leading to a deeper understanding of the electric and magnetic fields themselves.
Lidar measurements of lunar topography made by Clementine mission.
Up to 1923, most physicists were reluctant to accept that light itself was quantized. Instead, they tried to explain photon behaviour by quantizing only matter, as in the Bohr model of the hydrogen atom (shown here). Even though these semiclassical models were only a first approximation, they were accurate for simple systems and they led to quantum mechanics.
Laserlink point to point optical wireless network
Photons in a Mach–Zehnder interferometer exhibit wave-like interference and particle-like detection at single-photon detectors.
Mercury Laser Altimeter (MLA) of the MESSENGER spacecraft
Stimulated emission (in which photons "clone" themselves) was predicted by Einstein in his kinetic analysis, and led to the development of the laser. Einstein's derivation inspired further developments in the quantum treatment of light, which led to the statistical interpretation of quantum mechanics.
Aleksandr Prokhorov
Different electromagnetic modes (such as those depicted here) can be treated as independent simple harmonic oscillators. A photon corresponds to a unit of energy E = hν in its electromagnetic mode.
Charles H. Townes
LASER notebook: First page of the notebook wherein Gordon Gould coined the acronym LASER, and described the elements required to construct one. Manuscript text: "Some rough calculations on the feasibility / of a LASER: Light Amplification by Stimulated / Emission of Radiation. /
Conceive a tube terminated by optically flat / [Sketch of a tube] / partially reflecting parallel mirrors..."
Graph showing the history of maximum laser pulse intensity throughout the past 40 years.
Wavelengths of commercially available lasers. Laser types with distinct laser lines are shown above the wavelength bar, while below are shown lasers that can emit in a wavelength range. The color codifies the type of laser material (see the figure description for more details).
A 50 W FASOR, based on a Nd:YAG laser, used at the Starfire Optical Range
A 5.6 mm 'closed can' commercial laser diode, such as those used in a CD or DVD player
Close-up of a table-top dye laser based on Rhodamine 6G
The free-electron laser FELIX at the FOM Institute for Plasma Physics Rijnhuizen, Nieuwegein
Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments.
The US–Israeli Tactical High Energy weapon has been used to shoot down rockets and artillery shells.
Laser application in astronomical adaptive optics imaging

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

- Laser

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.

- Stimulated emission

Such a gain medium, along with an optical resonator, is at the heart of a laser or maser.

- Stimulated emission

The photon concept has led to momentous advances in experimental and theoretical physics, including lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics.

- Photon

An electron in an atom can absorb energy from light (photons) or heat (phonons) only if there is a transition between energy levels that matches the energy carried by the photon or phonon.

- Laser

The laser is an extremely important application and is discussed above under stimulated emission.

- Photon
Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers

3 related topics with Alpha


Einstein in 1921, by Ferdinand Schmutzer

Albert Einstein

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German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time.

German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time.

Einstein in 1921, by Ferdinand Schmutzer
Einstein at the age of three in 1882
Albert Einstein in 1893 (age 14)
Einstein's Matura certificate, 1896
Albert Einstein and Mileva Marić Einstein, 1912
Einstein in 1904 (age 25)
Olympia Academy founders: Conrad Habicht, Maurice Solovine and Albert Einstein
The New York Times reported confirmation of "the Einstein theory" (specifically, the bending of light by gravitation) based on 29 May 1919 eclipse observations in Principe (Africa) and Sobral (Brazil), after the findings were presented on 6 November 1919 to a joint meeting in London of the Royal Society and the Royal Astronomical Society. (Full text)
Einstein with his second wife, Elsa, in 1921
Einstein's official portrait after receiving the 1921 Nobel Prize in Physics
Albert Einstein at a session of the International Committee on Intellectual Cooperation (League of Nations) of which he was a member from 1922 to 1932.
Albert Einstein (left) and Charlie Chaplin at the Hollywood premiere of City Lights, January 1931
Cartoon of Einstein after shedding his "pacifism" wings (Charles R. Macauley, c. 1933)
Albert Einstein's landing card (26 May 1933), when he landed in Dover (United Kingdom) from Ostend (Belgium) to visit Oxford.
Portrait of Einstein taken in 1935 at Princeton
Einstein accepting US citizenship certificate from judge Phillip Forman
Einstein in 1947
Albert Einstein (right) with writer, musician and Nobel laureate Rabindranath Tagore, 1930
Albert Einstein with his wife Elsa Einstein and Zionist leaders, including future President of Israel Chaim Weizmann, his wife Vera Weizmann, Menahem Ussishkin, and Ben-Zion Mossinson on arrival in New York City in 1921
Eddington's photograph of a solar eclipse
Einstein with Millikan and Georges Lemaître at the California Institute of Technology in January 1933.
Einstein at his office, University of Berlin, 1920
The photoelectric effect. Incoming photons on the left strike a metal plate (bottom), and eject electrons, depicted as flying off to the right.
Einstein during his visit to the United States
Newspaper headline on 4 May 1935
Einstein and Niels Bohr, 1925
The 1927 Solvay Conference in Brussels, a gathering of the world's top physicists. Einstein is in the center.
Einstein (second from left) at a picnic in Oslo during the visit to Denmark and Norway in 1920. Heinrich Goldschmidt (left), Ole Colbjørnsen (seated in center) and Jørgen Vogt behind Ilse Einstein.

He also investigated the thermal properties of light and the quantum theory of radiation, which laid the foundation of the photon theory of light.

In 1917, at the height of his work on relativity, Einstein published an article in Physikalische Zeitschrift that proposed the possibility of stimulated emission, the physical process that makes possible the maser and the laser.

Atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy vol. 1 (1808)


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Smallest unit of ordinary matter that forms a chemical element.

Smallest unit of ordinary matter that forms a chemical element.

Atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy vol. 1 (1808)
The Geiger–Marsden experiment:
Left: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.
Right: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus.
The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete.
The binding energy needed for a nucleon to escape the nucleus, for various isotopes
A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
This diagram shows the half-life (T½) of various isotopes with Z protons and N neutrons.
These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. Do not forget that even the top of the diagram is lower than an unbound electron state.
An example of absorption lines in a spectrum
Graphic illustrating the formation of a Bose–Einstein condensate
Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them (See surface reconstruction).
Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process.

The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state.

If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level.

This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band.

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.


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Electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

Electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.
The electromagnetic spectrum, with the visible portion highlighted
Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily
Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.
Hong Kong illuminated by colourful artificial lighting.
Pierre Gassendi.
Christiaan Huygens.
Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.

Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and particles.

Emission can also be stimulated, as in a laser or a microwave maser.