Laser

A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical source composed of a resonant optical cavity and a gain medium.

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The resonant cavity contains a coherent beam of light

Related Topics:
Coherent - Light

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between reflective surfaces

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so that each photon passes through the gain medium multiple times

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before being emitted from the output aperture or lost to

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diffraction or absorbtion.

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The gain medium is a material of controlled purity, size, and shape,

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which uses a quantum mechanical effect

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called stimulated emission (discovered by Einstein while researching the photoelectric effect) to amplify the beam.

Related Topics:
Stimulated emission - Einstein - Photoelectric effect

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The output of a laser may be a continuous, constant-amplitude output (known as CW or continuous wave), or pulsed, by using the techniques of Q-switching, modelocking, or gain-switching. In pulsed operation, much higher peak powers can be achieved. A laser medium can also function as an optical amplifier when seeded with light from another source. The amplified signal can be very similar to the input signal in terms of wavelength, phase, and polarization; this is particularly important in optical communications. The verb "to lase" means "to produce coherent light" or possibly "to cut or otherwise treat with coherent light", and is a back-formation of the term laser.

Related Topics:
Continuous wave - Q-switching - Modelocking - Gain-switching - Optical amplifier - Wavelength - Phase - Polarization - Optical communications - Back-formation

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Common light sources, such as the incandescent light bulb, emit photons in almost all directions, usually over a wide spectrum of wavelengths. Most light sources are also incoherent; i.e., there is no fixed phase relationship between the photons emitted by the light source. By contrast, a laser generally emits photons in a narrow, well-defined, polarized, coherent beam of near-monochromatic light, consisting of a single wavelength or hue.

Related Topics:
Light source - Incandescent light bulb - Photons - Spectrum - Wavelength - Incoherent - Polarized - Monochromatic - Hue

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Some types of lasers, such as dye lasers and vibronic solid-state lasers can produce light over a broad range of wavelengths; this property makes them suitable for the generation of extremely short pulses of light, on the order of a femtosecond (10-15 seconds). A great deal of quantum mechanics and thermodynamics theory can be applied to laser action (see laser science), though in fact many laser types were discovered by trial and error.

Related Topics:
Quantum mechanics - Thermodynamics - Laser science - Trial and error

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