Understanding Lasers E-Book

Jeff Hecht

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: IEEE Press Understanding Science & Technology Series
• Sprache: Englisch

Seitenzahl: 673

Veröffentlichungsjahr: 2011

Beschreibung

Updated to reflect advancements since the publication of the previous edition, Understanding Lasers: An Entry-Level Guide, 3rd Edition is an introduction to lasers and associated equipment. You need only a minimal background in algebra to understand the nontechnical language in this book, which is a practical, easy-to-follow guide for beginners. By studying the conceptual drawings, tables, and multiple-choice quizzes with answers provided at the back of the book you can understand applications of semiconductor lasers, solid-state lasers, and gas lasers for information processing, medicine, communications, industry, and military systems.

Leseprobe

Contents

PREFACE

CHAPTER 1 INTRODUCTION AND OVERVIEW

ABOUT THIS CHAPTER

1.1 THE IDEA OF THE LASER

1.2 WHAT IS A LASER?

1.3 LASER MATERIALS AND TYPES

1.4 OPTICAL PROPERTIES OF LASER LIGHT

1.5 HOW LASERS ARE USED

1.6 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 1

CHAPTER 2 PHYSICAL BASICS

ABOUT THIS CHAPTER

2.1 ELECTROMAGNETIC WAVES AND PHOTONS

2.2 QUANTUM AND CLASSICAL PHYSICS

2.3 INTERACTIONS OF LIGHT AND MATTER

2.4 BASIC OPTICS AND SIMPLE LENSES

2.5 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 2

CHAPTER 3 HOW LASERS WORK

ABOUT THIS CHAPTER

3.1 BUILDING A LASER

3.2 PRODUCING A POPULATION INVERSION

3.3 RESONANT CAVITIES

3.4 LASER BEAMS AND RESONANCE

3.5 WAVELENGTH SELECTION AND TUNING

3.6 LASER EXCITATION TECHNIQUES

3.7 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 3

CHAPTER 4 LASER CHARACTERISTICS

ABOUT THIS CHAPTER

4.1 COHERENCE

4.2 LASER WAVELENGTHS

4.3 BEHAVIOR OF LASER BEAMS

4.4 LASER POWER

4.5 LASER EFFICIENCY

4.6 DURATION OF EMISSION

4.7 POLARIZATION

4.8 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 4

CHAPTER 5 OPTICS AND LASER ACCESSORIES

ABOUT THIS CHAPTER

5.1 CLASSICAL OPTICAL DEVICES

5.2 TRANSPARENT OPTICAL MATERIALS

5.3 OPTICAL SURFACES, COATINGS, AND FILTERS

5.4 NONLINEAR OPTICS

5.5 BEAM INTENSITY AND PULSE CONTROL

5.6 BEAM DIRECTION AND PROPAGATION

5.7 MOUNTING AND POSITIONING EQUIPMENT

5.8 OPTICAL MEASUREMENT

5.9 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 5

CHAPTER 6 TYPES OF LASERS

ABOUT THIS CHAPTER

6.1 LASER OSCILLATORS AND OPTICAL AMPLIFIERS

6.2 LASER MEDIA

6.3 THE IMPORTANCE OF GAIN

6.4 BROADBAND AND WAVELENGTH-TUNABLE LASERS

6.5 LASER-LIKE LIGHT SOURCES

6.6 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 6

CHAPTER 7 GAS LASERS

ABOUT THIS CHAPTER

7.1 THE GAS LASER FAMILY

7.2 GAS-LASER BASICS

7.3 HELIUM–NEON LASERS

7.4 ARGON- AND KRYPTON-ION LASERS

7.5 METAL-VAPOR LASERS

7.6 CARBON DIOXIDE LASER

7.7 EXCIMER LASERS

7.8 CHEMICAL LASERS

7.9 OTHER GAS LASERS

7.10 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 7

CHAPTER 8 SOLID-STATE AND FIBER LASERS

ABOUT THIS CHAPTER

8.1 WHAT IS A SOLID-STATE LASER?

8.2 SOLID-STATE LASER MATERIALS

8.3 OPTICAL PUMPING

8.4 RUBY LASERS

8.5 NEODYMIUM LASERS

8.6 VIBRONIC AND TUNABLE SOLID-STATE LASERS

8.7 ERBIUM AND OTHER EYE-SAFE LASERS

8.8 RARE-EARTH-DOPED FIBER LASERS

8.9 RARE-EARTH-DOPED FIBER AMPLIFIERS

8.10 RAMAN FIBER LASERS AND AMPLIFIERS

8.11 WHAT WE HAVE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 8

CHAPTER 9 SEMICONDUCTOR DIODE LASERS

ABOUT THIS CHAPTER

9.1 BASICS OF SEMICONDUCTOR DIODE LASERS

9.2 SEMICONDUCTOR BASICS

9.3 LIGHT EMISSION AT JUNCTIONS

9.4 LAYERS AND CONFINEMENT IN DIODE LASERS

9.5 CONFINEMENT IN THE JUNCTION PLANE

9.6 EDGE-EMITTING DIODE LASERS

9.7 SURFACE-EMITTING DIODE LASERS

9.8 QUANTUM WELLS AND DOTS

9.9 QUANTUM CASCADE LASERS

9.10 OPTICAL PROPERTIES OF DIODE LASERS

9.11 DIODE LASER MATERIALS AND WAVELENGTHS

9.11.5 InGaAs Pump Lasers

9.12 SILICON LASERS

9.13 PACKAGING AND SPECIALIZATION OF DIODE LASERS

9.14 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 9

CHAPTER 10 OTHER LASERS AND RELATED SOURCES

ABOUT THIS CHAPTER

10.1 TUNABLE DYE LASERS

10.2 EXTREME-ULTRAVIOLET SOURCES

10.3 FREE-ELECTRON LASERS

10.4 SILICON LASERS

10.5 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 10

CHAPTER 11 LOW-POWER LASER APPLICATIONS

ABOUT THIS CHAPTER

11.1 ADVANTAGES OF LASER LIGHT

11.2 READING WITH LASERS

11.3 OPTICAL DISKS AND DATA STORAGE

11.4 LASER PRINTING AND MARKING

11.5 FIBER-OPTIC COMMUNICATIONS

11.6 LASER MEASUREMENT

11.7 LASER POINTERS, ART, AND ENTERTAINMENT

11.8 LOW-POWER DEFENSE APPLICATIONS

11.9 SENSING AND SPECTROSCOPY

11.10 HOLOGRAPHY

11.12 WHAT HAVE WE LEARNED?

WHAT’S NEXT?

QUIZ FOR CHAPTER 11

CHAPTER 12 HIGH-POWER LASER APPLICATIONS

ABOUT THIS CHAPTER

12.1 HIGH- VERSUS LOW-POWER LASER APPLICATIONS

12.2 ATTRACTIONS OF HIGH-POWER LASERS

12.3 MATERIALS WORKING

12.4 ELECTRONICS MANUFACTURING

12.5 THREE-DIMENSIONAL MODELING

12.6 LASER MEDICAL TREATMENT

12.7 PHOTOCHEMISTRY AND ISOTOPE SEPARATION

12.8 LASER-DRIVEN NUCLEAR FUSION

12.9 HIGH-ENERGY LASER WEAPONS

12.10 FUTURISTIC HIGH-POWER LASER IDEAS

12.11 WHAT HAVE WE LEARNED?

QUIZ FOR CHAPTER 12

CHAPTER 13 LASERS IN RESEARCH

ABOUT THIS CHAPTER

13.1 LASERS OPEN NEW OPPORTUNITIES

13.2 LASER SPECTROSCOPY

13.3 MANIPULATING TINY OBJECTS

13.4 ATOM LASERS AND BOSE–EINSTEIN CONDENSATES

13.5 SLOW LIGHT

13.6 NANOSCALE LASERS

13.7 PETAWATT LASERS

13.8 ATTOSECOND PULSES

13.9 LASER ACCELERATION

13.10 OTHER EMERGING RESEARCH

13.11 WHAT WE HAVE LEARNED?

QUIZ FOR CHAPTER 13

ANSWERS TO QUIZ QUESTIONS

APPENDIX A: LASER SAFETY

A.1 POWER SUPPLY HAZARDS

A.2 LASER BEAM HAZARDS

APPENDIX B: HANDY NUMBERS AND FORMULAS

PHYSICAL CONSTANTS

CONVERSIONS

SYMBOLS TO REMEMBER

IMPORTANT FORMULAS

APPENDIX C RESOURCES AND SUGGESTED READINGS

FURTHER READING

GLOSSARY

INDEX

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To the memory of family, friends, and members of the laser community who have passed away since the last edition: My parents, George T. and Laura Hecht; Howard Rausch, who taught me how to write about lasers; laser pioneers Theodore Maiman, Gordon Gould, and Arthur Schawlow; and my friend and editor Heather Messenger.

PREFACE

“For Credible Lasers, See Inside.”

THE LASER IS LESS THAN three years younger than the space age. Just days after the Soviet Union launched Sputnik I on October 4, 1957, Charles Townes and Gordon Gould had two crucial discussions at Columbia University about the idea that would become the laser. As the United States and Soviets launched the space race, Townes and Gould went their separate ways and started their own race to make the laser. On May 16, 1960, Theodore Maiman crossed the laser finish line, demonstrating the world’s first laser at Hughes Research Laboratories in California.

Bright, coherent, and tightly focused, laser beams were a new kind of light that excited the imagination. Science fiction writers turned their fictional ray guns into lasers with a stroke of the pen. Science writers inhaled deeply of the technological optimism of the early 1960s and wrote breathless predictions about the future of “the incredible laser.” An article in the November 11, 1962 issue of the Sunday newspaper supplement This Week revealed U.S. Army schemes for equipping soldiers with a “death-ray gun . . . small enough to be carried or worn as a side-arm.” It quoted Air Force Chief of Staff Curtis E. LeMay predicting that ground-based lasers could zap incoming missiles at the speed of light.

The reality was something else. A bemused Arthur Schawlow, who had worked with Townes on the laser, posted a copy of “The Incredible Laser” on his door at Stanford University, along with a note that read, “For credible lasers, see inside.” Irnee D’Haenens, who had helped Maiman make the first laser, called the laser “a solution looking for a problem,” a joke that summed up the real situation. The infant laser had tremendous potential, but it had to grow up first.

D’Haenens’s joke lasted many years. So did the popular misconception that lasers were science-fictional weapons. If you told your neighbors you worked with lasers in the 1970s, they inevitably thought you were building death rays. That began to change as supermarkets installed laser scanners to automate checkout in the early 1980s. Then lasers began playing music on Compact Discs. Laser printers, laser pointers, CD-ROMs, and DVD players followed. Laser surgery became common, particularly to treat eye disease. Surveyors, farmers, and construction workers used lasers to draw straight lines in their work. Lasers marked serial numbers on products, drilled holes in baby-bottle nipples, and did a thousand obscure tasks in industry. Lasers transmitted billions of bits per second through optical fibers, becoming the backbone of the global telecommunications network and the Internet.

The incredible laser has become credible, a global business with annual sales in the billions of dollars. Lasers have spread throughout science, medicine and industry. Lasers are essential components in home electronics, buried inside today’s CD and DVD players, and vital to tomorrow’s high-definition disk systems. It’s a rare household that doesn’t own at least one laser. Yet lasers have not become merely routine; they still play vital roles in Nobel-grade scientific research.

This book will tell you about these real-world lasers. To borrow Schawlow’s line, “For credible lasers, see inside.” It will tell you how lasers work, what they do, and how they are used. It is arranged somewhat like a textbook, but you can read it on your own to learn about the field Each chapter starts by saying what it will cover, ends by reviewing key points, and is followed by a short multiple-choice quiz.

We start with a broad overview of lasers. The second chapter reviews key concepts of physics and optics that are essential to understand lasers. You should review this even if you have a background in physics, especially to check basic optical concepts and terms. The third and fourth chapters describe what makes a laser work and how lasers operate. The fifth chapter describes the optical accessories used with lasers. Try to master each of these chapters before going on to the next.

The sixth through tenth chapters describe various types of lasers. Chapter 6 gives an overview of laser types and configurations, and explains such critical concepts as the difference between laser oscillation and amplification, the importance of laser gain, and tunable lasers. Chapter 7 describes the workings of gas lasers and important types such as the helium–neon and carbon-dioxide lasers. Chapter 8 covers solid-state and fiber lasers, including neodymium lasers and fiber lasers and amplifiers. Chapter 9 covers the hot area of semiconductor diode lasers, including the important new blue diode lasers. Chapter 10 describes other types of lasers, including tunable dye lasers, extreme ultraviolet sources, free-electron lasers, and efforts to develop silicon lasers.

The final three chapters cover laser applications, divided into three groups. Chapter 11 describes low-power applications, including communications, measurement, and optical data storage. Chapter 12 covers high-power applications, including surgery, industrial materials processing, and laser weapons. Chapter 13 focuses on research and emerging developments in areas including spectroscopy, slow light, laser cooling, and extremely precise measurements. The appendices, glossary, and index are included to help make this book a useful reference.

To keep this book to a reasonable length, we concentrate on lasers and their workings. We cover optics and laser applications only in brief, but after reading this book you may want to study them in more detail.

I met my first laser in college and have been writing about laser technology since 1974. I have found it fascinating, and I hope you will, too.

JEFF HECHT

Auburndale, Massachusetts

January 2008

CHAPTER 1

INTRODUCTION AND OVERVIEW

ABOUT THIS CHAPTER

This chapter will introduce you to lasers. It will give you a basic idea of their use, their operation, and their important properties. This basic understanding will serve as a foundation for the more detailed descriptions of lasers and their operation in later chapters.

1.1 THE IDEA OF THE LASER

Optics was a sleepy backwater of physics when Theodore Maiman demonstrated the first laser in 1960. His announcement made headlines, and for many years afterward, lasers were novelties that attracted attention. Today, lasers are commonplace in developed countries. Thanks in large part to the laser, optics has become a dynamic field, expanding far beyond the binoculars, cameras, and spectacles that were the main products of the optical industry half a century ago.

We take lasers almost for granted today, as just another wonder of our technological age along with satellites and electronic chips. Most of us think of lasers as cylindrical devices that emit pencil-thin beams of red or green light, and shine bright spots on the wall. The first kind of laser to come to your mind is likely to be the pen-like laser pointers you can buy for $10 or less at an electronics or stationary store.

But lasers come in many other sizes, shapes, and forms. Most of them are tiny semiconductor chips that we never see because they are hidden inside electronic equipment such as CD players, CD-ROM drives, and DVD, or Blu-Ray players. Others are tubes filled with gas that emit laser light. Some are boxes the size of a filing cabinet or a refrigerator that emit powerful beams to cut or drill holes in metal or plastic. The largest lasers fill the interior of a building and generate pulses of light that for a fleeting billionth or trillionth of a second can deliver more power than the whole U.S. electric power grid. Laser output may not be visible; many lasers emit at infrared or ultraviolet wavelengths invisible to the human eye.

What makes them all lasers is that they generate light in the same way, by a process called “light amplification by the stimulated emission of radiation.” The word “LASER” is an acronym for that phrase. It is the process of amplifying stimulated emission that makes laser light special. The sun, light bulbs, flames, and other light sources emit light in a different way, spontaneously. That leads to important differences between laser light and other kinds of light, which we will explain later.

Most of us also are familiar with fictional weapons that resemble lasers and sometimes are called lasers. The deadly heat rays used by the Martian invaders of Earth in The War of theWorlds seem uncannily like lasers, emitting beams of invisible infrared light. Yet H. G. Wells wrote the book in 1896, long before anyone had thought of stimulated emission or lasers. Wells just imagined a searchlight beam that could burn rather than illuminate.

Pulp science fiction writers soon churned out tales of ray guns or death rays, which fired deadly beams of light or other (often undefined) forms of radiation. The writers may have heard rumors that legendary inventor Nikola Tesla and a handful of other scientists were working on death rays in the 1920s and 1930s, but there was no real science behind their weapons. They were just futuristic props to avoid arming 25th century heroes with six-shooters. But thanks to those stories, when the laser was invented the public thought of it as a “death ray,” much to the annoyance of the people working with real lasers.

It is true that military researchers are trying to develop laser weapons. That is not new; it has been going on since the 1960s and so far has consumed many billions of dollars to shoot down a few targets. As you will learn in Section 12.8, laser weapons are big, and they try to destroy targets by focusing a lot of light energy on them. In short, it is not easy to make lasers into weapons.

This book is about real lasers, so we will start by looking at the fundamental concepts behind real-world laser technology, briefly explaining what they are and how they developed.

1.2 WHAT IS A LASER?

You have already seen than the word “laser” is shorthand for the phrase “light amplification by the stimulated emission of radiation.” Each part of that phrase has a special meaning, so we will look at it piece by piece, starting from the end.