CONTENTS

INTRODUCTION 1

THE ELECTROMAGNETIC SPECTRUM 5

RADIO WAVES 9

LIGHT AND THE ATOM 14

WHAT’S SO SPECIAL ABOUT COHERENT LIGHT? 19

CONTROLLED EMISSION 25

A LASER IS BORN 29

LASING—A NEW WORD 32

SOME INTERESTING APPLICATIONS 34

A MULTITUDE OF LASERS 42

COMMUNICATIONS 48

A LASER IN YOUR FUTURE? 52

SUGGESTED REFERENCES 53

United States Atomic Energy Commission Division of Technical Information

Library of Congress Catalog Card Number: 68-60742 1968; 1969(rev.)

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Nothing about lasers is more astonishing than their ability to produce holograms, under arrangements such as shown above. Two laser beams (of different colors) emerge from the curtain (rear). They are optically combined (left center) and the combined beam is then divided by prisms, mirrors and lenses so that part of it shines on the figurines (foreground) and part on the square holographic plate (right center). When the plate is developed (like an ordinary photographic film), it will seem to have only a dull gray surface until it is viewed with spatially coherent light (such as from a laser or a beam through a pinhole) shining through it. Then an amazing, multi-colored, three-dimensional image of the figurines will be visible. (See page 19 and Figure 13.)

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By HAL HELLMAN