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Lasers and Light
Lasers are finding increasing application in many areas of scientific research and engineering
A laser is a source of optical radiation having four special properties. The radiation is:
 | bright
| monochromatic
| coherent
| unidirectional | |
All laser applications are a direct result of one of more of these special properties.
The word laser is an acronym for Light Amplification by Stimulated Emission of Radiation.
A laser is a light amplifier. It makes use of stimulated emission to produce a stream of photons having, identical frequency, phase and direction. This process takes place within an optical cavity similar to a Fabry-Perot interferometer. The cavity resonates by reflection giving rise to further stimulated emission of photons and consequent amplification of the radiation in the cavity. A small fraction of the radiation is permitted to escape through one of the cavity mirrors this escaping. radiation forms the usable output of the laser.
Principles of the laser were first described by Schawlow and Townes in 1958. The first operational was built by Maiman of the Hughes Aircraft Company in 1961.
All lasers depend for their operation on the phenomenon of stimulated emission of radiation.
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