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THE LASER1 TODAY AND TOMORROW

The laser has become a multipurpose tool. It has caused a real revolution in technology.

Atoms emit rays of different length, which prevents the forming of an intense beam of light. The laser forces its atoms to emit rays having the same length and travelling in the same direction. The result is a narrow, extremely intense beam of light that spreads out very little and is therefore able to travel very great distances.

The most common laser is the helium-neon laser in the laser tube, containing 10 per cent helium gas and 90 per cent neon gas. At the end of the tube there is a mirror, and at the other end there is a partial mirror[2]. The electrons get energy from a power supply[3] and become " excited", giving off energy as light. This tight is reflected by the mirror at one end of the tube. It can only escape through the partial mirror at the other end of the tube.

The first laser was built in I960. Since then scientists have developed several types of the laser which make use of luminescent crystals, luminescent glass, a mixture of various gases and finally semiconductors.

Having been developed at Lebedev Institute of Physics in 1962, semiconductor quantum generators occupy a special place among the optical generators. While the size of the ruby crystal laser comes to tens of centimetres and that of the gas generator is about a metre long, the semiconductor laser is a few tens of a millimetre 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 light wave energy. With an efficiency approaching 100 per cent as compared to a maximum of about 1 per cent of other types, the semiconductor laser opens up new possibilities of producing extremely economical sources of light.

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 cany simultaneously millions of telephone conversations or a thousand of television programmes. It will serve for fast communications across continents, under the sea, between the Earth and spaceships and between men travelling in space.

The potential importance of these applications continues to stimulate new development in the laser field.

Ответьте на вопросы.

1. What is the laser?

2. What is the function of the laser?

3. What beam of plight does the laser produce?

4. When was the first laser built?

5. What types of quantum generators did scientists develop after I960?

6. What type of the laser is the most common one at present?

7. Where will the laser find the most extensive applications in future?