Laser Magic

Ever since lasers--a word and an instrument stemming from Light Amplification by Stimulated Emission of Radiation--were first perfected, their fierce, pure gleam has been one of the most revolutionary tools of advancing science. By stimulating the atoms of a synthetic ruby with brief bursts from a powerful strobe lamp, scientists demonstrated that they could produce spurts of "coherent" light --pure red light that is all of the same wavelength, all polarized in the same direction, and all traveling in phase in almost perfectly parallel beams. Such light can be focused so sharply that its energy is concentrated on a tiny spot, and laser experimenters love to show how an in stantaneous flash of their innocent-looking red light can burn a hole in a thin sheet of steel.

But the fact that lasers can blast holes in razor blades would hardly explain the excitement that they have stirred up. There is more to them than that. In their ruby hearts, lasers hold the secrets of new industrial and communication techniques, new sonar-like underwater detection systems. They may supply the means for the most precise measurements ever made of the speed of light.

Blue Puff. Physicist Kiyo Tomiyasu, 42, technical director of General Electric Co.'s laser lab, is particularly proud of the ease with which one of his lasers has drilled holes in a pea-sized black synthetic diamond. Diamonds, which are the hard est things known to man, have been drilled before, but the process is difficult and time consuming. Dr. Tomiyasu (Nevada-born; Harvard doctorate) did the job on his diamond with laser light. Each hole was drilled by a flash that lasted only one two-thousandth of a second. Pinpointed by a lens on the crystallized carbon of diamond, which has the highest vaporizing temperature of any solid substance, laser light produces a blue puff of vapor that is close to 18,000DEG F., about twice the temperature of the sun's white-hot surface.

Dr. Tomiyasu and his colleagues have also learned how to make laser light carry information. Modulated in much the same manner as radio waves, its high frequencies can handle far more intelligence than any microwave beam. Each five-thousandth-of-a-second burst of light can theoretically be made to transmit coded information that would be the equivalent of 200,000 words.

For most purposes there are handier ways to communicate, but Dr. Tomiyasu has his eye on a notoriously difficult communication problem. When a missile nose cone or a spaceship slams down through the atmosphere, it surrounds itself with a sheath of plasma (hot, ionized gases) that repels radio waves. Space scientists well remember that during the most critical period of Colonel John Glenn's return to earth from his orbital flight, the radios of his Mercury capsule were blacked out for seven minutes by the plasma sheath. Laser light, if strong enough, can penetrate plasma, and Dr. Tomiyasu believes that returning space vehicles of the future, such as Apollo moon capsules or Dyna-Soar gliders, will use laser burst-communication to talk to the earth despite the flaming meteor trails around them.

Time or Light? Most laser light is deep red (from synthetic ruby), or infrared, but there seems to be no reason why it could not be manufactured in other colors too. Dr. Tomiyasu is especially interested in blue-green light, which penetrates sea water better than other colors; he hopes to generate it in a laser that uses a fluorescent liquid instead of synthetic ruby.

Blue-green laser light would be a boon to underwater exploration. Shot out in a thin beam from a submarine or an oceanographic surface ship, it could probe the ocean floor, look for wrecks or obstacles as far as 1,000 ft. away, much farther than ordinary light could penetrate. It could also carry messages between friendly submarines.

Dr. Tomiyasu also envisions far more exotic applications for the laser. Scientists have long considered the speed of light to be a changeless constant of the universe, but recent measurements have made light seem to be traveling slightly faster than it did 20 years ago. If accurate measurements with the laser's coherent light confirm this apparent change, scientists will have to face up to a touchy problem. Is it the speed of light that is actually changing, or time itself? The units with which man measures time (and speed) are traditionally derived from the various movements of the earth. If the earth were slowly slowing down, time, measured in this way, would be stretching out, and that changeless constant, the speed of light, would seem to be getting faster.

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