Joshua Reitz, age 9, of Sioux Falls, S.D., for his question:
HOW DOES A LASER WORK?
A laser is a device that strengthens or amplifies light. A laser will produce a thin beam of light that can burn a hole in a diamond or carry the signals of many different TV pictures at the same time.
Laser stands for "light amplification by stimulated emission of radiation."
To understand how a laser works, it is necessary to know something about the nature of atoms and how they interact with light and other forms of energy.
Light is a form of energy that is released from individual atoms or molecules. The amount of energy in an atom depends on the motion of the electrons that orbit the atom's nucleus.
The basic parts of a laser include a power source and a light amplifying substance. Stimulated emission results when energy from the power source interacts with excited atoms in the substance.
The total energy produced by a laser is always less than the energy produced by the power source. But the laser produces a much more intense light.
Solid lasers are the most widely used type of laser. Their light amplifying substance may be a crystal, glass or semiconductor. A semiconductor conducts electricity, but not so well as true conductors, such as copper or iron.
Light produced by an ordinary electric light bulb or the sun is called incoherent light. The light has different frequencies and travels in different directions.
Light produced from a laser is called coherent light. The light is produced by stimulated emission that has the same frequency as the triggering light. It travels in the same direction and so it combines with and amplifies the triggering light.
In other words, laser light travels in only one direction. It travels in a narrow beam, and the sides of the beam stay almost parallel.
Because it produces a highly directional beam, a laser can transmit information with little interference. A laser beam can be directed to fall solely on the desired laser receiving equipment. Because the equipment receives only the laser beam directed at it, most interference is eliminated.
A laser can transmit voice messages and television signals with ease. It has great advantages over ordinary electronic transmitters because the high frequency of laser light enables a laser beam to carry much more information than radio waves can.
A laser also serves as an efficient long distance transmitter because of its highly directional beams.