Military Laser Technology for Defense: Technology for Revolutionizing 21st Century Warfare

Preface xiii

Acknowledgments xv

About The Author xvii

I Optics Technology for Defense Systems 1

1 Optical Rays 3

1.1 Paraxial Optics 4

1.2 Geometric or Ray Optics 5

1.2.1 Fermat’s Principle 5

1.2.2 Fermat’s Principle Proves Snell’s Law for Refraction 5

1.2.3 Limits of Geometric Optics or Ray Theory 6

1.2.4 Fermat’s Principle Derives Ray Equation 6

1.2.5 Useful Applications of the Ray Equation 8

1.2.6 Matrix Representation for Geometric Optics 9

1.3 Optics for Launching and Receiving Beams 10

1.3.1 Imaging with a Single Thin Lens 10

1.3.2 Beam Expanders 13

1.3.3 Beam Compressors 14

1.3.4 Telescopes 14

1.3.5 Microscopes 17

1.3.6 Spatial Filters 18

2 Gaussian Beams and Polarization 20

2.1 Gaussian Beams 20

2.1.1 Description of Gaussian Beams 21

2.1.2 Gaussian Beam with ABCD Law 24

2.1.3 Forming and Receiving Gaussian Beams with Lenses 26

2.2 Polarization 29

2.2.1 Wave Plates or Phase Retarders 31

2.2.2 Stokes Parameters 33

2.2.3 Poincaré Sphere 34

2.2.4 Finding Point on Poincaré Sphere and Elliptical Polarization from Stokes Parameters 35

2.2.5 Controlling Polarization 36

3 Optical Diffraction 38

3.1 Introduction to Diffraction 38

3.1.1 Description of Diffraction 39

3.1.2 Review of Fourier Transforms 40

3.2 Uncertainty Principle for Fourier Transforms 42

3.2.1 Uncertainty Principle for Fourier Transforms in Time 42

3.2.2 Uncertainty Principle for Fourier Transforms in Space 45

3.3 Scalar Diffraction 47

3.3.1 Preliminaries: Green’s Function and Theorem 48

3.3.2 Field at a Point due to Field on a Boundary 48

3.3.3 Diffraction from an Aperture 50

3.3.4 Fresnel Approximation 51

3.3.5 Fraunhofer Approximation 54

3.3.6 Role of Numerical Computation 56

3.4 Diffraction-Limited Imaging 56

3.4.1 Intuitive Effect of Aperture in Imaging System 56

3.4.2 Computing the Diffraction Effect of a Lens Aperture on Imaging 57

4 Diffractive Optical Elements 61

4.1 Applications of DOEs 62

4.2 Diffraction Gratings 62

4.2.1 Bending Light with Diffraction Gratings and Grating Equation 63

4.2.2 Cosinusoidal Grating 64

4.2.3 Performance of Grating 66

4.3 Zone Plate Design and Simulation 67

4.3.1 Appearance and Focusing of Zone Plate 67

4.3.2 Zone Plate Computation for Design and Simulation 68

4.4 Gerchberg–Saxton Algorithm for Design of DOEs 73

4.4.1 Goal of Gerchberg–Saxton Algorithm 73

4.4.2 Inverse Problem for Diffractive Optical Elements 73

4.4.3 Gerchberg–Saxton Algorithm for Forward Computation 74

4.4.4 Gerchberg–Saxton Inverse Algorithm for Designing a Phase-Only Filter or DOE 74

5 Propagation and Compensation for Atmospheric Turbulence 77

5.1 Statistics Involved 78

5.1.1 Ergodicity 79

5.1.2 Locally Homogeneous Random Field Structure Function 80

5.1.3 Spatial Power Spectrum of Structure Function 80

5.2 Optical Turbulence in the Atmosphere 82

5.2.1 Kolmogorov’s Energy Cascade Theory 83

5.2.2 Power Spectrum Models for Refractive Index in Optical Turbulence 85

5.2.3 Atmospheric Temporal Statistics 86

5.2.4 Long-Distance Turbulence Models 86

5.3 Adaptive Optics 86

5.3.1 Devices and Systems for Adaptive Optics 86

5.4 Computation of Laser Light Through Atmospheric Turbulence 89

5.4.1 Layered Model of Propagation Through Turbulent Atmosphere 90

5.4.2 Generation of Kolmogorov Phase Screens by the Spectral Method 92

5.4.3 Generation of Kolmogorov Phase Screens from Covariance Using Structure Functions 94

6 Optical Interferometers and Oscillators 99

6.1 Optical Interferometers 100

6.1.1 Michelson Interferometer 101

6.1.2 Mach–Zehnder Interferometer 105

6.1.3 Optical Fiber Sagnac Interferometer 108

6.2 Fabry–Perot Resonators 109

6.2.1 Fabry–Perot Principles and Equations 110

6.2.2 Fabry–Perot Equations 110

6.2.3 Piezoelectric Tuning of Fabry–Perot Tuners 116

6.3 Thin-Film Interferometric Filters and Dielectric Mirrors 116

6.3.1 Applications for Thin Films 117

6.3.2 Forward Computation Through Thin-Film Layers with Matrix Method 118

6.3.3 Inverse Problem of Computing Parameters for Layers 122

II Laser Technology for Defense Systems 125

7 Principles for Bound Electron State Lasers 127

7.1 Laser Generation of Bound Electron State Coherent Radiation 128

7.1.1 Advantages of Coherent Light from a Laser 128

7.1.2 Basic Light–Matter Interaction Theory for Generating Coherent Light 129

7.2 Semiconductor Laser Diodes 133

7.2.1 p–n Junction 133

7.2.2 Semiconductor Laser Diode Gain 136

7.2.3 Semiconductor Laser Dynamics 139

7.2.4 Semiconductor Arrays for High Power 140

7.3 Semiconductor Optical Amplifiers 140

8 Power Lasers 143

8.1 Characteristics 144

8.1.1 Wavelength 144

8.1.2 Beam Quality 144

8.1.3 Power 145

8.1.4 Methods of Pumping 146

8.1.5 Materials for Use with High-Power Lasers 147

8.2 Solid-State Lasers 148

8.2.1 Principles of Solid-State Lasers 148

8.2.2 Frequency Doubling in Solid State Lasers 150

8.3 Powerful Gas Lasers 158

8.3.1 Gas Dynamic Carbon Dioxide Power Lasers 158

8.3.2 COIL System 160

9 Pulsed High Peak Power Lasers 165

9.1 Situations in which Pulsed Lasers may be Preferable 165

9.2 Mode-Locked Lasers 167

9.2.1 Mode-Locking Lasers 167

9.2.2 Methods of Implementing Mode Locking 169

9.3 Q-Switched Lasers 170

9.4 Space and Time Focusing of Laser Light 171

9.4.1 Space Focusing with Arrays and Beamforming 171

9.4.2 Concentrating Light Simultaneously in Time and Space 173

10 Ultrahigh-Power Cyclotron Masers/Lasers 177

10.1 Introduction to Cyclotron or Gyro Lasers and Masers 178

10.1.1 Stimulated Emission in an Electron Cyclotron 178

10.2 Gyrotron-Type Lasers and Masers 179

10.2.1 Principles of Electron Cyclotron Oscillators and Amplifiers 180

10.2.2 Gyrotron Operating Point and Structure 182

10.3 Vircator Impulse Source 184

10.3.1 Rationale for Considering the Vircator 184

10.3.2 Structure and Operation of Vircator 184

10.3.3 Selecting Frequency of Microwave Emission from a Vircator 186

10.3.4 Marx Generator 186

10.3.5 Demonstration Unit of Marx Generator Driving a Vircator 188

11 Free-Electron Laser/Maser 191

11.1 Significance and Principles of Free-Electron Laser/Maser 192

11.1.1 Significance of Free-Electron Laser/Maser 192

11.1.2 Principles of Free-Electron Laser/Maser 192

11.2 Explanation of Free-Electron Laser Operation 193

11.2.1 Wavelength Versatility for Free-Electron Laser 194

11.2.2 Electron Bunching for Stimulated Emission in Free-Electron Laser 197

11.3 Description of High- and Low-Power Demonstrations 199

11.3.1 Proposed Airborne Free-Electron Laser 199

11.3.2 Demonstration of Low-Power System for Free-Electron Maser at 8–12 GHz 200

11.3.3 Achieving Low Frequencies with FELs 200

11.3.4 Range of Tuning 203

11.3.5 Design of Magnetic Wiggler 203

III Applications to Protect Against Military Threats 205

12 Laser Protection from Missiles 207

12.1 Protecting from Missiles and Nuclear-Tipped ICBMs 208

12.1.1 Introducing Lasers to Protect from Missiles 208

12.1.2 Protecting from Nuclear-Tipped ICBMs 209

12.2 The Airborne Laser Program for Protecting from ICBMs 212

12.2.1 Lasers in Airborne Laser 212

12.2.2 Incorporating Adaptive Optics for Main Beam Cleanup into Airborne Laser 213

12.2.3 Incorporating Adaptive Optics to Compensate for Atmospheric Turbulence in ABL 215

12.2.4 Illuminating Lasers for Selecting Target Aim Point 215

12.2.5 Nose Turret 217

12.2.6 Challenges Encountered in the ABL Program 217

12.2.7 Modeling Adaptive Optics and Tracking for Airborne Laser 219

12.3 Protecting from Homing Missiles 223

12.3.1 Threat to Aircraft from Homing Missiles 223

12.3.2 Overview of On-Aircraft Laser Countermeasure System 224

12.3.3 Operation of Countermeasure Subsystems 227

12.3.4 Protecting Aircraft from Ground-Based Missiles 228

12.4 Protecting Assets from Missiles 228

13 Laser to Address Threat of New Nuclear Weapons 231

13.1 Laser Solution to Nuclear Weapons Threat 231

13.1.1 Main Purpose of U.S. and International Efforts 231

13.1.2 Benefits of Massive Laser Project 232

13.1.3 About the NIF Laser 232

13.2 Description of National Infrastructure Laser 233

13.2.1 Structure of the NIF Laser 233

14 Protecting Assets from Directed Energy Lasers 237

14.1 Laser Characteristics Estimated by Laser Warning Device 238

14.2 Laser Warning Devices 239

14.2.1 Grating for Simultaneously Estimating Direction and Frequency 240

14.2.2 Lens for Estimating Direction Only 242

14.2.3 Fizeau Interferometer 243

14.2.4 Integrated Array Waveguide Grating Optic Chip for Spectrum Analysis 245

14.2.5 Design of AWG for Laser Weapons 249

15 Lidar Protects from Chemical/Biological Weapons 251

15.1 Introduction to Lidar and Military Applications 252

15.1.1 Other Military Applications for Lidar 252

15.2 Description of Typical Lidar System 253

15.2.1 Laser 253

15.2.2 Cassegrain Transmit/Receive Antennas 254

15.2.3 Receiver Optics and Detector 254

15.2.4 Lidar Equation 255

15.3 Spectrometers 257

15.3.1 Fabry–Perot-Based Laboratory Optical Spectrum Analyzer 258

15.3.2 Diffraction-Based Spectrometer 258

15.3.3 Grating Operation in Spectrometer 260

15.3.4 Grating Efficiency 261

15.4 Spectroscopic Lidar Senses Chemical Weapons 262

15.4.1 Transmission Detection of Chemical and Biological Materials 262

15.4.2 Scattering Detection of Chemical and Bacteriological Weapons Using Lidar 263

16 94 GHz Radar Detects/Tracks/Identifies Objects in Bad Weather 265

16.1 Propagation of Electromagnetic Radiation Through Atmosphere 266

16.2 High-Resolution Inclement Weather 94 GHz Radar 267

16.2.1 94 GHz Radar System Description 267

16.2.2 Gyroklystron with Quasi-Optical Resonator 269

16.2.3 Overmoded Low 94 GHz Loss Transmission Line from Gyroklystron to Antenna 271

16.2.4 Quasi-Optical Duplexer 272

16.2.5 Antenna 273

16.2.6 Data Processing and Performance 273

16.3 Applications, Monitoring Space, High Doppler, and Low Sea Elevation 274

16.3.1 Monitoring Satellites in Low Earth Orbit 274

16.3.2 Problem of Detecting and Tracking Lower Earth Orbit Debris 275

16.3.3 Doppler Detection and Identification 276

16.3.4 Low Elevation Radar at Sea 276

17 Protecting from Terrorists with W-Band 277

17.1 Nonlethal Crowd Control with Active Denial System 278

17.2 Body Scanning for Hidden Weapons 279

17.3 Inspecting Unopened Packages 282

17.3.1 Principles for Proposed Unopened Package Inspection 283

17.4 Destruction and Protection of Electronics 284

17.4.1 Interfering or Destroying Enemy Electronics 285

17.4.2 Protecting Electronics from Electromagnetic Destruction 286

Bibliography 289

Index 299