The transistor burst upon the electronic scene in the 1950s. Almost
overnight the size of new models of radios, television sets, and a host
of other electronic devices shrank like deflating balloons. Suddenly the
hard-of-hearing could carry their sound amplifiers in their ears.
Teenagers could listen to favorite music wherever they went. Everywhere
we turned the transistor was making its mark. There was even a proposal
before Congress to require that every home have a transistor radio in
case of emergency.
The next development to fire the imagination of scientists and engineers
was the laser—an instrument that produces an enormously intense
pencil-thin beam of light. Most of us have heard so much about this
invention it seems hard to believe that the first one was built only a
few years ago. We were told that the laser was going to have an even
greater effect on our lives than the transistor. It was going to replace
everything from dentists’ drills to electric wires. The whole world, it
seemed, eventually would be nothing but a gigantic collection of lasers
that would do everything anyone wanted. Roads would be blazed through
jungles at one sweep; our country would be safe once and for all from
intercontinental ballistic missiles; cancer would be licked; computers
would be small enough to carry in a purse; and so on and on.
Yet for the first couple of years the laser seemed able to do nothing
but blaze holes in razor blades for TV commercials. Somehow the device
never seemed to emerge from the laboratory, prompting one cynic to call
it “an invention in search of an application”.
Many of the wild claims came from misunderstandings on the part of the
press, others from exaggerations by a few manufacturers who wanted free
publicity. But with even less exotic devices than lasers, the road from
the laboratory to the marketplace may often be long and hard. Price,
efficiency, reliability, convenience—these are all factors that must be
considered. It soon became clear that with something as new as the
laser, much improvement was necessary before it could be used in science
and medicine, and even more before it could be used in industry.
It now seems, however, that the turning point has been reached. We have
seen laser equipment put on the market for performing delicate surgery
on the eye, spot-welding tiny electronic circuits (Figure 1), and
controlling machine tools with amazing accuracy (Figure 2).
[Illustration: Figure 1 _A commercial laser microwelder. A
microscope is needed for accurate placement of beam energy._]
The pace is quickening. At least a dozen manufacturers have announced
that they are designing laser technology into their products. These are
not laboratory experiments but practical products for measurement and
testing, and for industrial, military, medical, and space uses. The
Army, for example, has announced that it will purchase its first
equipment for use in the field: a portable, highly accurate range finder
for artillery observation.
Still, this hardly accounts for the $100,000,000 spent in one recent
year on laser research and development by some 500 laboratories in the
United States. The U. S. Government alone has spent about $25,000,000 on
laser research in a single year. Dozens, and perhaps hundreds, of other
applications are on the fire—simmering or boiling as the case may be.
Some require particular technical innovations such as greater power or
higher efficiency. Others are entirely new applications. One of the most
exciting of these is holography (pronounced ho LOG ra phy).
Holography involves a completely different approach to photography. In
addition to more immediate applications in microscopy, information
storage and retrieval, and interferometry, it promises such bonuses as
3-dimensional color movies and TV someday.
You have to see the holographic process in operation to believe it. One
moment you are looking at what appears to be an underexposed or lightly
smudged photographic plate. Then suddenly a true-to-life image of the
original object springs into being behind the negative—apparently
suspended in midair! Not only is the full effect of “roundness” and
depth there, but you can also see anything lying behind the object’s
image by moving your head, exactly as if the original scene containing
the object were really there.
Still another important field of application is that of communications.
Perhaps because it is less spectacular than burning holes in razor
blades, we haven’t heard as much about it. Yet there are probably more
physicists and engineers working on adapting the laser for use in
communications than on any other single laser project.
The reason for this is the fact that existing communications facilities
are becoming overloaded. Space on transoceanic telephone lines is
already at a premium, with waiting periods sometimes running into hours.
Radio “ham” operators have been threatened with loss of some of their
best operating frequencies to meet the demand of emerging nations of
Africa for new channels. Television programs must compete for space on
cross-country networks with telephone, telegraph, and transmission of
data. The increasing use of computers in science, business, and industry
will strain our facilities still further. Communication satellites will
help, but they will not give us the whole answer; and much development
work remains to be done on satellites.
[Illustration: Figure 2 _Precision control of a machine tool by
laser light._]
Why the interest in the laser for communications? In a recent experiment
all seven of the New York TV channels were transmitted over a single
laser beam. In terms of telephone conversations, one laser system could
theoretically carry 800,000,000 conversations—four for each person in
the United States.
In this booklet we shall learn what there is about the laser that gives
it so much promise. We shall investigate what it is, how it works, and
the different kinds of lasers there are. We begin by discussing some of
the more familiar kinds of radiation, such as radio and microwaves,
light and X rays.