UNIT 15 LASERS AND MASERS

1. Read the text:

  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 emitted 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, i.e. it is monochromatic, and this increases the intensity or it can be said that it is amplified. Another its peculiarity is a small divergence of its light beam.

     Atoms are made up of electrons and nuclei. 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.

  There are lasers which use luminescent crystals, for example, the crystal of synthetic ruby, a mixture of various gases and finally semiconductors. Scientists of the Lebedev Institute of Physics have first succeeded to develop a laser on the basis of a gallium arsenide semiconductor in 1962.

  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.

Lasers are also used in holography. A hologram is a three-dimen­sional image, a bit like a photograph. It's different from a photograph because it looks solid. As you walk round a hologram, it changes, as if it were real. Now holography is used for testing engineering ideas. An engineer can use a hologram to build up and check a new building such as a bridge. He can find out all about it before he builds it.

The word MASER is also an acronym for Microwave Amplifi­cation by Stimulated Emission of Radiation. The maser is operated on the same principle as the laser except that the wavelengths generated are much longer and therefore the energy jumps involved are smaller. The excited bodies in a maser are molecules rather than atomic electrons and the beam generated is a coherent beam of microwaves, which is not visible to the eye.

Masers have made revolutionary advance possible in a number of different fields. They are up to 1.000 times more sensitive than any other type of amplifiers. Maser amplifiers mounted on radio tele­scopes can increase their range by a factor of 10, allowing us to reach out to the bounds of the known universe. Because of the very constant frequency with which masers can be made to oscillate they can be used as master controls for atomic clocks of unbelievable accuracy; an error not exceeding 1 second in 10.000 years has already been achiev­ed.

The idea of using stimulated emission of radiation for ampli­fication of very short waves belongs to A. Prokhorov and N. Basov of the Lebedev Institute in Moscow.

 

2. In the text find equivalents to the following phrases:

- очень сильный пучок;

- с малым расхождением пучка;

- мазер работает на тех же принципах,

- атомы состоят из электронов и ядер;

- энергия излучается в виде видимого света;

- погрешность, не превышающая 1 секунду в …;

- трехмерное изображение;

- когерентный пучок микроволн;

- в 1,000 раз более чувствительные;

- увеличить в 10 раз;

- выйти за границы изученной вселенной

 

TALKING POINT

3. Discuss in pairs:

· the peculiar properties of a laser beam;

· the scope of laser application;

· fields of science and technology where the use of masers is highly promising.

VOCABULARY STUDY

4. Translate the following word combinations (compound nouns) into Russian:

current oscillation, wave length, signal feed,

quantum amplifiers, semiconductor laser, ruby crystal,

pulsed laser, power efficiency, power generation,

long distance communication, semiconductor quantum generators,

light wave energy, miniature radio stations, optic quantum generators,

high frequency radiation, superspeed computers, luminescent crystal lasers,

transmission band frequency, small divergence beam,

radio frequency quantum generator, decimeter wave radio receiver.

 

5. Read the text and put the verbs in the appropriate form:

About sixty years ago, neither laser installations nor the very word laser … 1 (to be) in existence. Today the field of laser applications … 2 (to expand) very rapidly. Lasers …3 (to use) in electronics, medicine, engineering, communications, the automobile and aircraft industry, agricultural machine building, and other fields of the economy and science. Let us point out only a few uses of the laser such as micro weld­ing, resistor trimming, etc., something that can …4 (to perform) perfectly well today.

Laser radiation …5 (to have) the property of selective excitation of atoms and molecules, enabling laser isolation of isotopes. The first successful experiment in separating isotopes by laser was performed in our country at the Institute of Spectroscopy of the USSR Academy of Sciences, in 1972. This work … 6 (to regard) by specialists as highly promising for power engineering and production of superpure materials.

The use of laser technology …7 (to increase) considerably the reso­lution and sensitivity of the spectroscopic methods. Without the laser beam, there could be no optical electronics which computer specialists use as to make high-speed and small-size computers. Optical electronic instru­ments for recording, storing and processing information …8 (to use) a laser beam. Lasers can quickly record and read out information, with record­ing density being 100 times higher than in the most advanced magnetic system used in computers of old generations. It is evident that it is due to lasers that centralized archives …9 (to set up) allowing us to display any required information on a home TV screen.

We …10 (to succeed) in designing a new information carrier which can be used for multiple recording of light signals, similar to the magne­tic tape recording,

Great importance …11 (to give) today to the use of lasers in medicine. Lasers have been successfully used in eye treatment.

Thus the laser today comes in handy in solving process and quality control problems, in medicine, communications and computer techno­logy. High-power lasers …12 (to use) now for long-distance space communications. It can do hundreds of jobs; the number …13 (to increase) constantly, and is becoming a customary and indispensable assistant in most professions.

6. Read the following text and answer the questions:

a) What was the idea suggested by specialists of the quantum radiophysics labo­ratory?

b) How is the distance to the Moon measured?

Laser at Work

In a department of the Lebedev Physics Institute of the USSR Academy of Sciences (FIAN) scientists from the quantum radiophysics laboratory have suggested the idea of laser-controlled thermonuclear fusion and obtained priority results in this field. Experiments in heating and condensing plasma to receive thermonuclear fusion are being con­ducted at one of the world's biggest laser thermonuclear installations "Delfin" (Dolphin).

The Institute carries out research in developing new types of lasers, studying the interaction of coherent radiation with matter, in laser thermonuclear fusion and in optoelectronics.

The results of this fundamental research find wide application in the development of new instruments and technological processes, in the evolvement of substances with new properties in medicine, in metrology and in the latest methods of information processing.

What's more, lasers are being used for very important and interest­ing explorations, such as measuring the distance to the Moon. Power lasers send very short light pulses to the Moon. There are targets, or angle light reflectors, installed in five different places there, able to reflect the incident light in a precisely reverse direction. As with radar, the distance to the Moon is estimated by measuring the time signal takes to reach the target and return.

In the 70th of the XXth century scientists of FIAN’s observation station in the Crimea built Laser range finder complexes. They measured the distance to the Moon with an error of not more than one or two centimeters. This precision has allowed the laser measurement of distances to the Moon to become a new method for exploring the Earth-Moon system. Compared with other methods, laser measurements of many basic geometric and dynamic characteristics of the Earth-Moon system offer precision several factors higher and enable more delicate geodynamic phenomena to be explored, and geodetic constructions to be performed with high degree of precision. It gives us better understanding of the laws governing the movements of the Earth and the Moon.

Note : laser range finder – лазерное устройство для измерения расстояний

 

7. Form phrases by matching the words from 1-10 with the words a-k:

1. pulsed      2. thermonuclear  3. interesting  4. laser   5. delicate

6. degree of     7. better  8. wide 9. information    10. fundamental

 

a) precision  b) surgery  c) fusion  d) laser  e) research  f) application

g) measurement    h) exploration  i) understanding   k) processing

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