A report on Laser

Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers
A laser beam used for welding
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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.
Spectrum of a helium–neon laser. The actual bandwidth is much narrower than shown; the spectrum is limited by the measuring apparatus.
Lidar measurements of lunar topography made by Clementine mission.
Laserlink point to point optical wireless network
Mercury Laser Altimeter (MLA) of the MESSENGER spacecraft
Aleksandr Prokhorov
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

Device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

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

153 related topics with Alpha

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First prototype ammonia maser and inventor Charles H. Townes. The ammonia nozzle is at left in the box, the four brass rods at center are the quadrupole state selector, and the resonant cavity is at right. The 24 GHz microwaves exit through the vertical waveguide Townes is adjusting. At bottom are the vacuum pumps.

Maser

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Device that produces coherent electromagnetic waves through amplification by stimulated emission.

Device that produces coherent electromagnetic waves through amplification by stimulated emission.

First prototype ammonia maser and inventor Charles H. Townes. The ammonia nozzle is at left in the box, the four brass rods at center are the quadrupole state selector, and the resonant cavity is at right. The 24 GHz microwaves exit through the vertical waveguide Townes is adjusting. At bottom are the vacuum pumps.
A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below)
A hydrogen maser.

The laser works by the same principle as the maser but produces higher frequency coherent radiation at visible wavelengths.

Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes.

Optical amplifier

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Device that amplifies an optical signal directly, without the need to first convert it to an electrical signal.

Device that amplifies an optical signal directly, without the need to first convert it to an electrical signal.

Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes.
Schematic diagram of a simple Doped Fiber Amplifier

An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed.

Laser light is a type of stimulated emission of radiation.

Stimulated emission

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Process by which an incoming photon of a specific frequency can interact with an excited atomic electron , causing it to drop to a lower energy level.

Process by which an incoming photon of a specific frequency can interact with an excited atomic electron , causing it to drop to a lower energy level.

Laser light is a type of stimulated emission of radiation.
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Such a gain medium, along with an optical resonator, is at the heart of a laser or maser.

A glass nanoparticle is suspended in an optical cavity

Optical cavity

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Arrangement of mirrors that forms a standing wave cavity resonator for light waves.

Arrangement of mirrors that forms a standing wave cavity resonator for light waves.

A glass nanoparticle is suspended in an optical cavity
Types of two-mirror optical cavities, with mirrors of various curvatures, showing the radiation pattern inside each cavity.
Stability diagram for a two-mirror cavity. Blue-shaded areas correspond to stable configurations.
Alignment of a folded cavity using an autocollimator

Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light.

Photons are emitted by a cyan laser beam outside, orange laser beam inside calcite and its fluorescence

Photon

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Elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

Elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

Photons are emitted by a cyan laser beam outside, orange laser beam inside calcite and its fluorescence
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
Thomas Young's double-slit experiment in 1801 showed that light can act as a wave, helping to invalidate early particle theories of light.
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.
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.
Photons in a Mach–Zehnder interferometer exhibit wave-like interference and particle-like detection at single-photon detectors.
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.
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.

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.

A ruby laser head. The photo on the left shows the head unassembled, revealing the pumping cavity, the rod and the flashlamps. The photo on the right shows the head assembled.

Laser pumping

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A ruby laser head. The photo on the left shows the head unassembled, revealing the pumping cavity, the rod and the flashlamps. The photo on the right shows the head assembled.
Various laser pumping cavity configurations.
Laser pumping lamps. The top three are xenon flashlamps while the bottom one is a krypton arc lamp
External triggering was used in this extremely fast discharge. Due to the very high speed, (3.5 microseconds), the current is not only unable to fully heat the xenon and fill the tube, but is still in direct contact with the glass.
The spectral outputs for flashlamps using various gases, at a current density approaching that of greybody radiation.
Optical pumping of a laser rod (bottom) with an arc lamp (top). Red: hot. Blue: cold. Green: light. Non-green arrows: water flow. Solid colors: metal. Light colors: fused quartz.
These gas-discharge lamps show the spectral line outputs of the various noble gases.
A dye laser tuned to 589nm (amber yellow), pumped with an external, frequency-doubled Nd:YAG laser @ 532nm (yellowish-green). The closeness between wavelengths results in a very small Stokes shift, reducing energy losses.

Laser pumping is the act of energy transfer from an external source into the gain medium of a laser.

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Population inversion

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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 states.

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 states.

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A three-level laser energy diagram.
A four-level laser energy diagram.

This concept is of fundamental importance in laser science because the production of a population inversion is a necessary step in the workings of a standard laser.

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

Light

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

Fig.1. Simplified scheme of levels a gain medium

Active laser medium

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Fig.1. Simplified scheme of levels a gain medium
Laser rods (from left to right): Ruby, Alexandrite, Er:YAG, Nd:YAP

The active laser medium (also called gain medium or lasing medium) is the source of optical gain within a laser.

Charles H. Townes

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American physicist.

American physicist.

Daughters of Townes in Sweden in 1964
Townes (right) receiving the 1964 Nobel Prize
Townes (right) receiving the 2006 Vannevar Bush Award

Townes worked on the theory and application of the maser, for which he obtained the fundamental patent, and other work in quantum electronics associated with both maser and laser devices.