Rusty Marshall, age 13 of Stuttgart, Ark., for his question:
WHO DISCOVERED THE LASER?
A laser is a device that strengthens or amplifies light. A laser produces a thin beam of light that can burn a hole in a diamond or carry the signals of many different television pictures at the same time.
The word "laser" stands for light amplification by stimulated emission of radiation.
Two physicists from the United States, Arthur Schawlow and C.H. Townes, first proposed the idea of the laser in 1958. In the same year, similar ideas were developed by two Russian physicists, N.G. Basov and A.M. Prokhorov.
Laser research grew out of earlier studies of microwave amplifying devices called masers. As a result, early lasers were also called optical masers because they amplified light in much the same way masers amplified microwaves.
A scientist from the United States named Theodore Maiman built the first laser, a ruby laser, and operated it for the first time in 1960.
In 1961, Ali Javan, another United States physicist, operated the first continuous laser.
Semiconductor lasers were first operated in 1962 by three separate teams of American scientists. The first liquid laser was operated in 1966 by another American, Peter Sorokin.
The laser truly went into outer space in 1969 when the astronauts on the Apollo II space flight placed a mirrored device called a laser reflector on the moon. Scientists use this device to measure precisely the distance between the earth and the moon. They do so by measuring the time needed for the laser beam to travel to the reflector and back.
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 that produced by the power source.
Solid lasers are the most widely used type of laser. Their light amplifying substance may be a crystal, glass or a semiconductor. A semiconductor conducts electricity, but not as well as true conductors, such as copper or iron.
Crystal lasers have fluorescent crystals, such as that of a ruby, as their light amplifying substance. The power for a ruby laser comes from a flash tube, which may be coiled around the crystal.
The flash tube produces a brilliant flash of light. The flash excites a large number of chromium ions, which are electrically charged atoms, in the ruby. This process of using a flash to excite the atoms is called optical pumping.
In communications, lasers are used to transmit voice messages and television signals.