Lasers and Masers

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1. 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 different lengths. With lasers, all the light waves have the same length, and this increases the intensity.

2. Atoms are made up 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.

3. 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.

4. Lasers are also used in holography. A hologram is a three-dimensional image, a bit like¹ 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.

5. The word MASER is also an acronym – for Microwave Amplification by Stimulated Emission of Radiation. The maser is operated on the same principle² 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.

6. Masers have made revolutionary advance possible in a number of different fields. They are up to 1.000 times more sensitive³ than any other type of amplifiers. Maser amplifiers mounted on radio telescopes can increase even their great 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.

7. The idea of using stimulated emission of radiation for amplification of very short waves came, from A.Prokhorov and N.Basov of the Lebedev Institute in Moscow.

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