LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The emitted laser light is noted for its high degree of spatial and temporal coherence, which is unattainable using other technologies.
Laser amplifiers are used in industrial, medical, military, and commercial applications.
Spatial coherence is typically expressed through the output being a narrow beam which is diffraction-limited, often a so-called "pencil beam." Laser beams can be focused to very tiny spots, achieving a very high irradiance. They can also be launched into a beam of very low divergence in order to concentrate their power at large distances.
Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively large distance, the coherence length, along the beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase which vary randomly with respect to time and position, and therefore, has a short coherence length.
Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.
Gordon Gould and Laser
Gordon Gould (July 17, 1920 – September 16, 2005), born in New York City, was an American physicist who is widely credited, but not wholly, with the invention of the laser. He coined the word LASER. Gould is best known for his 38 years fight with the US Patent and Trademark Office to secure patents for the laser. He also fought with laser manufacturers in court battles to enforce the patents he subsequently did obtain.
More on LASER's History
The term "laser beam" is an extremely intense narrow parallel beam of light. Earlier, Gordon Gould has been mentioned as inventor of laser, but because of controversies, he was not universally credited for its invention.
In 1917, Albert Einstein said that it should be possible to make rays of light of the correct frequency on an atom for it to release energy in the form of light. However, according to Ireland's handy book of inventors, it was until 1958 that the right calculations were made by A.L. Schawlow and C.H. Townes.
Despite many experimental failures, in 1960, Schawlow and Townes eventually succeeded in generating the first laser beam by using a type of ruby.
The laser has been used in high-powered versions for cutting through metal, delicate surgery scuh as in eye operations. And notably, it's greatly used on special effects at stage concerts, as well as public Christmas light displays.
Sources:
LASER, Wikipedia.Org
Who Invented, Discovered, Made the First..? by Kenneth Ireland. Great Britain: Ravette Books, 1988.
Image:
LASER, by Jeff Keyzer, (Beams reflected in Fog and Car Windshield), Wikimedia Commons
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