LASERS Anthony E. Siegman Professor of Electrical Engineering Stanford University University Science Books Mill Valley, California
CONTENTS Preface xili Units and Notation XV List of Symbols xvii BASIC LASER PHYSICS 1.An Introduction to Lasers 1 2. Stimulated Transitions:The Classical Oscillator Model 80 3. Electric Dipole Transitions in Real Atoms 118 4. Atomic Rate Equations 176 5. The Rabi Frequency 221 6. Laser Pumping and Population Inversion 243 7.Laser Amplification 264 8. More On Laser Amplification 307 9. Linear Pulse Propagation 331 10. Nonlinear Optical Pulse Propagation 362 11. Laser Mirrors and Regenerative Feedback 398 12. Fundamentals of Laser Oscillation 457 13. Oscillation Dynamics and Oscillation Threshold 491 OPTICAL BEAMS AND RESONATORS 14.Optical Beams and Resonators:An Introduction 558 15.Ray Optics and Ray Matrices 581 16. Wave Optics and Gaussian Beams 626 17.Physical Properties of Gaussian Beams 663 18. Beam Perturbation and Diffraction 698 19. Stable Two-Mirror Resonators 744 20. Complex Paraxial Wave Optics 777 21. Generalized Paraxial Resonator Theory 815 22. Unstable Optical Resonators 858 23.More on Unstable Resonators 891 LASER DYNAMICS AND ADVANCED TOPICS 24.Laser Dynamics:The Laser Cavity Equations 923 25.Laser Spiking and Mode Competition 954 26.Laser Q-Switching 1004 27.Active Laser Mode Coupling 1041 28. Passive Mode Locking 1104 29. Laser Injection Locking 1129 30.Hole Burning and Saturation Spectroscopy 1171 31.Magnetic-Dipole Transitions 1213
LIST OF TOPICS Preface xiii Units and Notation xV List of Symbols xvii BASIC LASER PHYSICS Chapter 1 An Introduction to Lasers 1.1 What Is a Laser? 1.2 Atomic Energy Levels and Spontaneous Emission 6 1.3 Stimulated Atomic Transitions 18 1.4 Laser Amplification 1.5 Laser Pumping and Population Inversion 1.6 Laser Oscillation and Laser Cavity Modes 059 1.7 Laser Output-Beam Properties 1.8 A Few Practical Examples 6 1.9 Other Properties of Real Lasers 1.10 Historical Background of the Laser 74 1.11 Additional Problems for Chapter 1 76 Chapter 2 Stimulated Transitions:The Classical Oscillator Model 2.1 The Classical Electron Oscillator 80 2.2 Collisions and Dephasing Processes 89 2.3 More on Atomic Dynamics and Dephasing 97 2.4 Steady-State Response:The Atomic Susceptibility 102 2.5 Conversion to Real Atomic Transitions 110 Chapter 3 Electric Dipole Transitions in Real Atoms 3.1 Decay Rates and Transition Strengths in Real Atoms 118 3.2 Line Broadening Mechanisms in Real Atoms 126 3.3 Polarization Properties of Atomic Transitions 135 3.4 Tensor Susceptibilities 143 3.5 The“Factor of Three" 150 3.6 Degenerate Energy Levels and Degeneracy Factors 153 3.7 Inhomogeneous Line Broadening 157 Chapter 4 Atomic Rate Equations vi 4.1 Power Transfer From Signals to Atoms 176
LIST OF TOPICS vii 4.2 Stimulated Transition Probability 181 4.3 Blackbody Radiation and Radiative Relaxation 187 4.4 Nonradiative Relaxation 195 4.5 Two-Level Rate Equations and Saturation 204 4.6 Multilevel Rate Equations 211 Chapter 5 The Rabi Frequency 5.1 Validity of the Rate Equation Model 221 5.2 Strong Signal Behavior:The Rabi Frequency 229 Chapter 6 Laser Pumping and Population Inversion 6.1 Steady-State Laser Pumping and Population Inversion 243 6.2 Laser Gain Saturation 252 6.3 Transient Laser Pumping 257 Chapter 7 Laser Amplification 7.1 Practical Aspects of Laser Amplifiers 264 7.2 Wave Propagation in an Atomic Medium 266 7.3 The Paraxial Wave Equation 276 7.4 Single-Pass Laser Amplification 279 7.5 Stimulated Transition Cross Sections 286 7.6 Saturation Intensities in Laser Materials 292 7.7 Homogeneous Saturation in Laser Amplifiers 297 Chapter 8 More On Laser Amplification 8.1 Transient Response of Laser Amplifiers 307 8.2 Spatial Hole Burning,and Standing-Wave Grating Effects 316 8.3 More on Laser Amplifier Saturation 323 Chapter 9 Linear Pulse Propagation 9.1 Phase and Group Velocities 331 9.2 The Parabolic Equation 339 9.3 Group Velocity Dispersion and Pulse Compression 343 94 Phase and Group Velocities in Resonant Atomic Media 351 9.5 Pulse Broadening and Gain Dispersion 356 Chapter 10 Nonlinear Optical Pulse Propagation 10.1 Pulse Amplification With Homogeneous Gain Saturation 362 10.2 Pulse Propagation in Nonlinear Dispersive Systems 375 10.3 The Nonlinear Schrodinger Equation 387 10.4 Nonlinear Pulse Broadening in Optical Fibers 388 10.5 Solitons in Optical Fibers 392 Chapter 11 Laser Mirrors and Regenerative Feedback 11.1 Laser Mirrors and Beam Splitters 398 11.2 Interferometers and Resonant Optical Cavities 408 11.3 Resonance Properties of Passive Optical Cavities 413
vii LIST OF TOPICS 11.4 "Delta Notation"for Cavity Gains and Losses 428 11.5 Optical-Cavity Mode Frequencies 432 11.6 Regenerative Laser Amplification 440 11.7 Approaching Threshold:The Highly Regenerative Limit 447 Chapter 12 Fundamentals of Laser Oscillation 12.1 Oscillation Threshold Conditions 457 12.2 Oscillation Frequency and Frequency Pulling 462 12.3 Laser Output Power 473 12.4 The Large Output Coupling Case 485 Chapter 13 Oscillation Dynamics and Oscillation Threshold 13.1 Laser Oscillation Buildup 491 13.2 Derivation of the Cavity Rate Equation 497 13.3 Coupled Cavity and Atomic Rate Equations 505 13.4 The Laser Threshold Region 510 13.5 Multiple-Mirror Cavities and Etalon Effects 524 13.6 Unidirectional Ring-Laser Oscillators 532 13.7 Bistable Optical Systems 538 13.8 Amplified Spontaneous Emission and Mirrorless Lasers 547 OPTICAL BEAMS AND RESONATORS Chapter 14 Optical Beams and Resonators:An Introduction 14.1 Transverse Modes in Optical Resonators 559 14.2 The Mathematics of Optical Resonator Modes 565 14.3 Build-Up and Oscillation of Optical Resonator Modes 569 Chapter 15 Ray Optics and Ray Matrices 15.1 Paraxial Optical Rays and Ray Matrices 581 15.2 Ray Propagation Through Cascaded Elements 593 15.3 Rays in Periodic Focusing Systems 599 15.4 Ray Optics With Misaligned Elements 607 15.5 Ray Matrices in Curved Ducts 614 15.6 Nonorthogonal Ray Matrices 616 Chapter 16 Wave Optics and Gaussian Beams 16.1 The Paraxial Wave Equation 626 16.2 Huygens'Integral 16.3 Gaussian Spherical Waves 16.4 Higher-Order Gaussian Modes 新嫩 16.5 Complex-Argument Gaussian Modes 16.6 Gaussian Beam Propagation in Ducts 652 16.7 Numerical Beam Propagation Methods 656