Wednesday, March 4, 2009

Back To Basics - Laser


The word laser is an acronym (an abbreviation pronounced as an ordinary word) of Light Amplification by Stimulated Emission of Radiation. Lasers are devices that produce or amplify a beam of narrow, low-divergence light with a well-defined wavelength within the optical region of the electromagnetic spectrum, covering the infrared, the visible and the ultraviolet.
Lasers have a variety of uses in such areas as surgery, welding and metal cutting, and sound and video recording and reproduction.

Historically, the laser is very different from other 20th century inventions as it first appeared as an imaginary literary creation.

Even before the invention of the first laser in 1960, and when only a handful of specialists were aware of Einstein's prediction of stimulated emission (1917), the term “laser” was already well-known. In particular, numerous science-fiction writers had imagined an extremely powerful beam, capable of destroying anything in its path. These devices were generally controlled by aggressive intergalactic beings bent on wreaking havoc on the world.

Since the discovery of the first real laser in 1961, many others have been developed each year. Current research is focused on the development of solid state lasers (diode lasers, crystal or amorphous solids doped with active ions, optic fibre lasers) with the aim of obtaining much shorter pulses (the present limit is 4.5 fs or 4.5 10-15 seconds) and much greater power (emissions of about 10 kilowatts are now common).

Some important dates:
1961: Javan, Bennet and Herriot build the first gas helium-neon laser operating
continuously at 1.15. In fact, this laser can emit over a whole range of discrete wavelengths, from green to infrared via orange and red (633 nm).
1962: First red helium-neon laser.
1965: First semiconductor lasers.
1966: First coloured pulsed lasers (red, orange, yellow).
1970: First coloured continuous-wave lasers (red, orange, yellow).

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