Laser

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

Uses of lasers

At the time of their invention in 1960, lasers were called "a solution looking for a problem". Since then, they have become ubiquitous, finding utility in thousands of highly varied applications in every section of modern society from vision correction to guidance for transportation and spacecraft to thermonuclear fusion. They have been widely regarded as one of the most influential technological achievements of the 20th century.

Related Topics:
Vision correction - Guidance for transportation - Spacecraft - Thermonuclear fusion

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The exceptional utility which lasers have found in scientific, industrial and commercial applications stems from their coherency, high monochromaticity, capability for reaching extremely high powers, or a confluence of these factors. For instance, a laser beam's coherence potentially allows it to be focused down to its diffraction limit, which at visible wavelengths corresponds to only a few hundred nanometers. This property is what allows a laser to record gigabytes of information in the microscopic pits of a DVD. It is also what allows a laser of modest power to be focused to very high intensities and used for cutting, burning or even vaporizing materials. For example, a frequency doubled neodymium yttrium aluminum garnet () laser emitting 532 nanometer (green) light at 10 watts output power is theoretically capable of achieving an intensity of megawatts per square centimeter. In reality however, perfect focusing of a beam to its diffraction limit is very difficult. See: Laser applications for more information.

Related Topics:
Coherency - Monochromaticity - Diffraction limit - DVD - Power - Intensities - Frequency doubled - Neodymium - Megawatt - Square centimeter - Laser applications

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Additionally, laser light can be highly intense—able to cut steel and other metals. While the beam emitted by a laser often has a very small divergence (highly collimated), a perfectly collimated beam cannot be created, due to the effect of diffraction. Nonetheless, a laser beam will spread much less than a beam of light generated by other means. A beam generated by a small laboratory laser such as a helium-neon (HeNe) laser spreads to approximately 1 mile (1.6 kilometres) in diameter if shone from the Earth's surface to the Moon. Some lasers, especially semiconductor lasers due to their small size, produce very divergent beams. However, such a divergent beam can be transformed into a collimated beam by means of a lens. In contrast, the light from non-laser light sources cannot be collimated by optics as well or much. Using a waveguide such as an optical fibre though, diffraction laws governing divergence no longer apply. Other interesting effects happen in nonlinear optics.

Related Topics:
Steel - Divergence - Diffraction - Helium - Neon - (HeNe) laser - Earth - Moon - Lens - Waveguide - Optical fibre - Nonlinear optics

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See Directed-energy_weapon#Lasers for use of lasers as weapons.

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