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Lasers are devices which produce pure, intense beams of light and radiation. When they were first invented in 1960, nobody knew what to do with them. Though they seem likely to be useful, they were for a while called “a solution waiting for a problem”.

A laser is a machine for making and concentrating light waves into a very intense beam. The letters LASER stand for Light Amplification by Stimulated Emission of Radiation. The light made by a laser is much more intense than ordinary light. With ordinary light, all the light waves are of different lengths. With lasers, all the light waves have the same length, and this increases the intensity.

Atoms are made of neutrons, electrons and protons. The electrons circle round the protons and neutrons. In a laser, the electrons are “excited” to a high energy level. As the electrons fall back from their “excited” state to their normal state, they give off energy. This energy is given off as light which can be seen. A number of materials have this property including some gases, liquids, solids and semiconductors. Thus a number of different types of lasers have been developed.

Lasers are now used for many scientific, medical and industrial purposes. The thin beam of light gives a lot of heat and it is used to join metal when a very small joint is needed. The beam can also be used as a drill, to make holes in steel, or even in diamonds. Because the beam is so small, it’s very important in delicate surgery and is used in eye operations.

Semiconductor quantum generators have been developed at Lebedev Institute of Physics in 1962. They occupy a special place among the optical generators. While the size of the ruby crystal laser comes to tens of centimeters and that of the gas generator is about a meter long, the semiconductor laser is a few tens of a millimeter long, the density of its radiation being hundreds of thousands of times greater than that of the best ruby laser.

But the most interesting thing about the semiconductor laser is that it is able to
transform electrical energy directly into the light wave one. As the efficiency
approaches 100 percent as compared to a maximum of about 1 percent of other types, the semiconductor laser opens up new possibilities of producing extremely economical sources of light.

The beam of a laser can be focused very precisely. Its accuracy as a means of
measurement has allowed the scientists to calculate the speed of light more precisely than ever before and with the use of laser reflectors, placed on the Moon by American astronauts, to determine its exact distance from the Earth.

Surgeons performing operations have found the laser as a surgical knife, able to make bloodless incisions and it is invaluable in delicate eye surgery.

But it is in the field of communication that the laser will find its most extensive
application in future. Scientists foresee the day when a single laser beam will be
employed to carry simultaneously millions of telephone conversations or a thousand of television programs. It will serve for fast communications across continents, under the sea, between the Earth and spaceships and between men traveling in space.

The potential importance of these applications continues to stimulate new developments in laser technology.


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