Think of a laser simply as a tool. One that uses light instead of mechanical energy. And a tool that allows its user to control the form and amount of energy directed at a particular place. The laser can cut through a two-inch-thick sheet of steel or detect a single atom. It can perform a task as dramatic as igniting a thermonuclear fusion reaction or as seemingly mundane as drilling a hole in a baby-bottle nipple.

What Is a Laser?

A laser is a device that produces a very special kind of light. You can think of it as a super flashlight. But the beam that is emitted by a laser differs from the light that comes out of a flashlight in four basic ways:

Laser light is intense. Yet only a few lasers are powerful. That's not the contradiction you might think. Intensity is a measure of power per unit area, and even a laser that emits only a few milliwatts can produce a lot of intensity in a beam that's only a millimeter in diameter. In fact, it can produce an intensity equal to that of sunlight. An ordinary lightbulb emits more light than a small laser like this, but that light spreads out all over the room. Some lasers can produce many thousands of watts continuously; others can produce trillions of watts in a pulse only a billionth of a second long.

Laser beams are narrow and will not spread out like ordinary light beams. This quality is called directionality. You know that even the most powerful flashlight beam will not travel far. Aim one at the sky, and its beam seems to disappear quickly. The beam begins to spread out as soon as it leaves the flashlight, eventually dispersing so much as to be useless. On the other hand, beams from lasers with only a few watts of power were bounced off the moon, and the light was still bright enough to be seen back on the earth. One of the first laser beams shot at the moon-in 1962-spread out only two and a half miles on the lunar surface. Not bad when you consider that it traveled a quarter of a million miles!

Laser light is coherent. This means that all the light waves coming out of a laser are lined up with each other. An ordinary light source, such as a lightbulb, generates light waves that start at different times and head in different directions. It's like throwing a handful of pebbles into a lake. You cause some tiny splashes and a few ripples, but that's about all. But if you take the same pebbles and throw them one by one, at exactly the right rate, at the same spot, you can generate a more sizable wave in the water. This is what a laser does, and this special property is useful in a variey of ways. Put another way, a lightbulb or a flashlight is like a shotgun; a laser is like a machine gun.

Lasers produce light of only one color. Or, to say it in a more technical way, the light is monochromatic. Ordinary light comes in all the colors of visible light (that is, the spectrum). Mixed together, they come out white. Laser beams have been produced in every color of the rainbow (red is the most common laser color), as well as in many kinds of invisible light, but each laser can emit one color and one color only. There are such things as tunable lasers, which can be adjusted to produce several different colors, but even they can emit only one color at a time. A few lasers can emit several monochromatic wavelengths at once-but not a continuous spectrum containing all the colors of visible light as a lightbulb does. And then there are many lasers that project invisible light, such as infrared and ultraviolet light.

What Are Lasers Good For?

The range of uses for the laser is striking, going far beyond the original ideas of the scientists who developed the first models.

The wide variety of lasers is also striking. At one end of the scale there are lasers made from tiny semiconductor chips similar to those used in electronic circuits, no larger than grains of salt. At the other end, building- size laser weapons are being tested by the military.

The tasks that lasers perform are usually difficult or impossible with any other tool. Lasers are relatively expensive tools and are often brought in to do a job only because they can deliver the required type and amount of energy to the desired spot. Charles H. Townes, one of the inventors of the laser and a Nobel Prize winner, said recently that he believes the laser "is going to touch on a very great number of areas. The laser will do almost anything. But it costs. That is the only limitation."

The $50,000 Scalpel and Television Fibers

A typical surgical laser, for example, costs from $30,000 to $50,000 and up, or about a thousand times more than a good conventional scalpel. And to be honest, for many operations a scalpel may be better than a laser. But if you have a detached retina, a condition that could lead to blindness, you may be happy that these expensive scalpels exist. A laser can do what a knife can't: weld the retina back to the eyeball. No incision is required for this delicate surgery, which can be performed right in the doctor's office. The laser beam shines through the lens of the patient's eye and is focused on the retina, producing a small lesion that helps hold it to the eyeball. Exotic as this sounds, a similar laser treatment has become a standard way of curing blindness caused by diabetes.

Laser medicine probably hasn't touched you personally (you'd know if it had), but laser communication has undoubtedly served you already. If you watched the Olympics or some of the major football games on television recently, you probably saw signals that were transmitted part of the way to your home by lasers. Lasers carry telephone signals in dozens of places around the countty. In both cases, light from the lasers is carried through hair-thin fibers of glass-fiber optics-a technology that could ultimately bring a multitude of new communication services into your home.

Death Rays, Drills, Nuclear Fusion

Lasers are already commonplace items among our military, but probably not in the way you think. Their main function in the business of war is that of range finder and target designator, not ray gun. Lasers are used to measure the distances to targets or pinpoint them with a "bull's-eye," helping either guns or missiles to home in on the enemy. And yes, in an offshoot of H. G. Wells's idea, the U.S. military is also spending about $300 million a year trying to build lasers able to destroy targets ranging from helicopters to ballistic missiles and satellites. The Soviet Union has a comparable program and is believed to have already used a laser to temporarily blind the sensitive electronic "eyes" of a U.S. spy satellite.

In factories around the world, lasers are now used routinely to drill holes in diamonds, label automotive parts, and weld battery cases for heart pacemakers. Laser quality-control "inspectors" sit ever-vigilant on assembly lines, making sure that the sizes of parts do not deviate from an acceptable range.

One of the hopes for ending our energy problems is thermonuclear fusion, the process by which energy is generated by the sun. One way of creating fusion here on earth is to heat and compress pellets containing hydrogen to the temperatures and pressures needed to fuse the nuclei of the hydrogen atoms together, creating tiny hydrogen bombs and thus generating incredible power. What can compress these pellets? Lasers, of course.

Three-Dimensional Images and Super Readers

Lasers are what make holograms possible-those three-dimensional images that seem to float before you, suspended in space. But holography has many seemingly mundane applications as well, from testing the quality of aircraft tires to measuring heat flow to aiding in the design of such things as hair dryers.

Lasers have made new art and new entenainment forms possible, even beyond holography. Laser light shows, the best known of which is Laserium, have been seen by millions of people around the world. A laser is also at the heart of one type of videodisk player, which plays back movies and television programs prerecorded on phonographlike disks.

Lasers can read. Those cryptic bar codes on food packages in super-markets are read by scanning them with a laser beam. The pattern of reflected light is decoded to tell a computer in the back of the store what the label says. This not only tabulates the price on the cash register but automatically registers it in the computer's inventory memory. Lasers also read special typewriter faces, so that manuscripts can be typeset automatically, without human aid.

And lasers can write. It’s simple for a computer to control a laser, making it write on film, special paper, or the drum of a copying machine, for later transfer to paper. Lasers expose printing plates for newspapers and print statements for insurance companies and mutual funds.

A Billion Dollars a Year

Lasers also serve the interests of pure scientific research, aiding in numerous and complicated experiments. Lasers can cause and control chemical reactions and someday might even propel rockets and aircraft.

The laser's catalogue of wonders is growing larger each day, as is the thriving laser industry. The market for lasers and related equipment hit $1 billion for the first time in 1980. That figure, which doesn't include sizable efforts in the Soviet Union and China, is nearly double the 1977 total sales figure.

But the laser has a long way to go. Its potential is only just beginning to be exploited. While the $1 billion figure may sound impressive, it is far less than the annual sales of many companies you've never heard of. To pick a familiar name, the RCA Corporation alone sold $7.5 billion worth of merchandise and services in 1979.

There are still many problems to be overcome regarding the use of the laser. These obstacles demand sophisticated and elaborate techniques-or the simple, brilliant insight that leads to breakthroughs. However, similar obstacles have been faced and overcome before. That's how we got to where we are now.

Jeff Hecht and Dick Teresi