Military Laser Technology for Defense E-Book

Alastair D. McAulay

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 431

Veröffentlichungsjahr: 2011

Beschreibung

Recent advances in ultra-high-power lasers, including the free-electron laser, and impressive airborne demonstrations of laser weapons systems, such as the airborne laser, have shown the enormous potential of laser technology to revolutionize 21st century warfare. Military Laser Technology for Defense, includes only unclassified or declassified information. The book focuses on military applications that involve propagation of light through the atmosphere and provides basic relevant background technology. It describes high-power lasers and masers, including the free-electron laser. Further, Military Laser Technology for Defense addresses how laser technology can effectively mitigate six of the most pressing military threats of the 21st century: attack by missiles, terrorists, chemical and biological weapons, as well as difficulty in imaging in bad weather and threats from directed beam weapons and future nuclear weapons. The author believes that laser technology will revolutionize warfare in the 21st century.

Leseprobe

Contents

Cover

Title Page

Copyright

Preface

Acknowledgments

About the Author

Part I: Optics Technology for Defense Systems

Chapter 1: Optical Rays

1.1 Paraxial Optics

1.2 Geometric or ray optics

1.3 Optics for Launching and Receiving Beams

Chapter 2: Gaussian Beams and Polarization

2.1 Gaussian Beams

2.2 Polarization

Chapter 3: Optical Diffraction

3.1 Introduction to Diffraction

3.2 Uncertainty principle for Fourier transforms

3.3 Scalar Diffraction

3.4 Diffraction-limited imaging

Chapter 4: Diffractive Optical Elements

4.1 Applications of DOEs

4.2 Diffraction Gratings

4.3 Zone Plate Design and Simulation

4.4 Gerchberg–Saxton Algorithm for Design of DOEs

Chapter 5: Propagation and Compensation for Atmospheric Turbulence

5.1 Statistics Involved

5.2 Optical Turbulence in the Atmosphere

5.3 Adaptive Optics

5.4 Computation of Laser Light Through Atmospheric Turbulence

Chapter 6: Optical Interferometers and Oscillators

6.1 Optical Interferometers

6.2 Fabry–Perot Resonators

6.3 Thin-film Interferometric Filters and Dielectric Mirrors

Part II: Laser Technology for Defense Systems

Chapter 7: Principles for Bound Electron State Lasers

7.1 Laser Generation of Bound Electron State Coherent Radiation

7.2 Semiconductor Laser Diodes

7.3 Semiconductor Optical Amplifiers

Chapter 8: Power Lasers

8.1 Characteristics

8.2 Solid-state Lasers

8.3 Powerful Gas Lasers

Chapter 9: Pulsed High Peak Power Lasers

9.1 Situations in Which Pulsed Lasers May be Preferable

9.2 Mode-locked Lasers

9.3 Q-Switched Lasers

9.4 Space and Time Focusing of Laser Light

Chapter 10: Ultrahigh-Power Cyclotron Masers/Lasers

10.1 Introduction to Cyclotron or Gyro Lasers and Masers

10.2 Gyrotron-type Lasers and Masers

10.3 Vircator Impulse Source

Chapter 11: Free-Electron Laser/Maser

11.1 Significance and Principles of Free-Electron Laser/Maser

11.2 Explanation of Free-Electron Laser Operation

11.3 Description of High- and Low-Power Demonstrations

Part III: Applications to Protect Against Military Threats

Chapter 12: Laser Protection from Missiles

12.1 Protecting from Missiles and Nuclear-Tipped ICBMs

12.2 The Airborne Laser Program for Protecting from ICBMs

12.3 Protecting from Homing Missiles

12.4 Protecting Assets from Missiles

Chapter 13: Laser to Address Threat of New Nuclear Weapons

13.1 Laser Solution to Nuclear Weapons Threat

13.2 Description of National Infrastructure Laser

Chapter 14: Protecting Assets from Directed Energy Lasers

14.1 Laser Characteristics Estimated by Laser Warning Device

14.2 Laser Warning Devices

Chapter 15: Lidar Protects from Chemical/Biological Weapons

15.1 Introduction to Lidar and Military Applications

15.2 Description of Typical Lidar System

15.3 Spectrometers

15.4 Spectroscopic Lidar Senses Chemical Weapons

Chapter 16: 94 GHz Radar Detects/Tracks/Identifies Objects in Bad Weather

16.1 Propagation of Electromagnetic Radiation Through Atmosphere

16.2 High-Resolution Inclement Weather 94 GHz Radar

16.3 Applications, Monitoring Space, High Doppler, and Low Sea Elevation

Chapter 17: Protecting from Terrorists with W-Band

17.1 Nonlethal Crowd Control with Active Denial System

17.2 Body Scanning for Hidden Weapons

17.3 Inspecting Unopened Packages

17.4 Destruction and Protection of Electronics

Bibliography

Index

Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada

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Preface

In 1832, Carl Von Clausewitz [22] wrote: “War is an extension of politics.” Historically, war erupts when groups cannot resolve their conflicts politically. Consequently, every group must prepare to defend itself against reasonable future threats.

Laser technology is ideal for defense against modern weapons because laser beams can project energy over kilometers in microseconds, fast enough to eliminate most countermeasure responses. This book includes only unclassified or declassified information and focuses on military applications that involve propagation through the atmosphere. Chapters 1–6 provide background material on optical technologies. Chapters 7–11 describe laser technologies including efficient ultrahigh-power lasers such as the free-electron laser that will have a major impact on future warfare. Chapters 12–17 show how laser technologies can effectively mitigate six of the most pressing military threats of the 21st century. This includes the use of lasers to protect against missiles, future nuclear weapons, directed beam weapons, chemical and biological attacks, and terrorists and to overcome the difficulty of imaging in bad weather conditions.

Understanding these threats and their associated laser protection systems is critical for allocating resources wisely because a balance is required between maintaining a strong economy, an effective infrastructure, and a capable military defense. A strong defense discourages attackers and is often, in the long run, more cost-effective than alternatives. I believe laser technology will revolutionize warfare in the 21st century.

Alastair D. McAulay

Lehigh University, Bethlehem, PA

Acknowledgments

I thank my wife Carol-Julia, for her patience and help with this book. Also my thanks to my son Alexander and his wife Elizabeth. I wish to acknowledge the too-many-to-name researchers in this field whose publications I have referenced or with whom I have had discussions. This includes appreciation for the International Society for Optical Engineering (SPIE), the Optical Society of America (OSA), and IEEE. I also thank Lehigh University for providing me with the environment to write this book.

About the Author

Alastair McAulay received a PhD in Electrical Engineering from Carnegie Mellon University, and an MA and BA in Mechanical Sciences from Cambridge University. Since 1992, he is a Professor in the Electrical and Computer Engineering Department at Lehigh University; he was Chandler-Weaver Professor and Chair of EECS at Lehigh from 1992 to 1997 and NCR Distinguished Professor and Chair of CSE at Wright State University from 1987 to 1992. Prior to that, he was in the Corporate Laboratories of Texas Instruments for 8 years, where he was program manager for a DARPA optical data flow computer described in his book “Optical Computer Architectures” that was published by Wiley in 1991. Prior to that, he worked in the defense industry on projects such as the Advanced Light Weight Torpedo that became the Mk. 50 torpedo. Dr McAulay can be contacted via network Linked In.

Part I

Optics Technology for Defense Systems

Chapter 1

Optical Rays

Geometric or ray optics [16] is used to describe the path of light in free space in which propagation distance is much greater than the wavelength of the light—normally microns (see Section 1.2.3 for more exact conditions). Note that we cannot apply ray theory if the media properties vary noticeably in distances comparable to wavelength; for such cases, we use more computationally demanding finite approximation techniques such as finite-difference time domain (FDTD) [154] or finite elements [78, 79]. Ray theory postulates rays that are at right angles to wave fronts of constant phase. Such rays describe the path along which light emanates from a source and the rays track the Poynting vector of power in the wave. Geometric or ray optics provides insight into the distribution of energy in space with time. The spread of neighboring rays with time enables computation of attenuation, which provides information analogous to that provided by diffraction equations but with less computation. Ray optics is extensively used for the passage of light through optical elements, such as lenses, and inhomogeneous media for which refractive index (or dielectric constant) varies with position in space.

In Section 1.1, we derive the paraxial equation that reduces dimensionality when light stays close to the axis. In Section 1.2, we study geometric or ray optics: Fermat's principle, limits of ray theory, the ray equation, rays through quadratic media, and matrix representations. In Section 1.3, we consider thin lens optics for launching and/or receiving beams: magnification, beam expanders, beam compressors, telescopes, microscopes, and spatial filters.

1.1 Paraxial Optics

In 1840, Gauss proposed the paraxial approximation for propagation of beams that stay close to the axis of an optical system. In this case, propagation is, say, in the z direction and the light varies in transverse x and y directions over only a small distance relative to the distance associated with the radius of curvature of a spherically curved surface in x and y (Figure 1.1). The region of the spherical surface near the axis can be approximated by a parabola. The spherical surface of curvature R is

(1.1)

Using the binomial theorem to eliminate the square root,

(1.2)

which is the equation for a parabola.

Figure 1.1 Illustrates the paraxial approximation.

1.2 Geometric or ray optics

1.2.1 Fermat's Principle

In 1658, Fermat introduced one of the first variational principles in physics, the basic principle that governs geometrical optics [16]: A ray of light will travel between points and by the shortest optical path ; no other path will have a shorter optical path length. The optical path length is the equivalent path length in air for a path through a medium of refractive index n. Equivalently, because the refractive index is (v is the phase velocity, and c is the velocity of light), , this is also the shortest time path. As the optical path length or time differs for each path, our optimization to determine the shortest (a minimum extremum) is that of a length or time function among many path functions, that is a function of a function (a functional), and this requires the use of calculus of variations [42]. Fermat's principle is written for minimum optical path length or, equivalently, for minimum time:

(1.3)

Fermat's principle lends itself to geometric optics in which light is considered to be rays that propagate at right angles to the phase front of a wave, normally in the direction of the Poynting power vector. Note that electromagnetic waves are transverse, and the electric and magnetic fields in free space oscillate at right angles to the direction of propagation and hence to the ray path. When valid, a wave can be represented more simply by a single ray.

1.2.2 Fermat's Principle Proves Snell's Law for Refraction

Fermat's principle can be used to directly solve problems of geometric optics as illustrated by our proof of Snell's law of refraction, the bending at an interface between two media of different refractive indices and , where is the dielectric constant and is the relative permeability (Figure 1.2). From Fermat's principle, the optical path from to intercepts the dielectric interface at R so that the optical path length through R is the least for all possible intercepts at the interface. Because at an extremum the function in equation (1.3) has zero gradient, moving the intercept point a very small variational distance along the interface to Q will not change the optical path length. From , the change in optical path length when moving from the path through to the path through is