Laser Physics

PETER W. MILONNI is currently Laboratory Fellow and Laboratory Associate in the Complex Systems Group of the Theoretical Division, Los Alamos National Laboratory and Research Professor of Physics at the University of Rochester. Dr. Milonni is the author or coauthor of several books and has published research and review papers on both pure and applied physics. He has served for many years on a number of editorial boards, and was the recipient of the Max Born Award of the Optical Society of America in 2008. His research interests are in the areas of quantum optics and electrodynamics, especially in connection with the quantum and fluctuation properties of electromagnetic radiation and its interaction with matter. JOSEPH H. EBERLY is currently Andrew Carnegie Professor Physics and Professor of Optics at the University of Rochester. A past president of the Optical Society of America, he has contributed to the research literature on theoretical quantum optics and laser physics, with interests in multipulse propogation, high-field atomic physics, quantum entanglement, cavity QED, and relaxation dynamics. Dr. Eberly received the Smoluchowski Medal of the Physical Society of Poland in 1987 and the Charles Hard Townes Award of the Optical Society of America in 1994. He is the coauthor of two books and coeditor of several conference proceedings. He is the founding editor of Optics Express and has served on a number of editorial and advisory boards.

• Preface xiii1 Introduction to Laser Operation 11.1 Introduction 11.2 Lasers and Laser Light 31.3 Light in Cavities 81.4 Light Emission and Absorption in Quantum Theory 101.5 Einstein Theory of Light–Matter Interactions 111.6 Summary 142 Atoms, Molecules, and Solids 172.1 Introduction 172.2 Electron Energy Levels in Atoms 172.3 Molecular Vibrations 262.4 Molecular Rotations 312.5 Example: Carbon Dioxide 332.6 Conductors and Insulators 352.7 Semiconductors 392.8 Semiconductor Junctions 452.9 Light-Emitting Diodes 492.10 Summary 55Appendix: Energy Bands in Solids 56Problems 643 Absorption, Emission, and Dispersion of Light 673.1 Introduction 673.2 Electron Oscillator Model 693.3 Spontaneous Emission 743.4 Absorption 783.5 Absorption of Broadband Light 843.6 Thermal Radiation 853.7 Emission and Absorption of Narrowband Light 933.8 Collision Broadening 993.9 Doppler Broadening 1053.10 The Voigt Profile 1083.11 Radiative Broadening 1123.12 Absorption and Gain Coefficients 1143.13 Example: Sodium Vapor 1183.14 Refractive Index 1233.15 Anomalous Dispersion 1293.16 Summary 132Appendix: The Oscillator Model and Quantum Theory 132Problems 1374 Laser Oscillation: Gain and Threshold 1414.1 Introduction 1414.2 Gain and Feedback 1414.3 Threshold 1434.4 Photon Rate Equations 1484.5 Population Rate Equations 1504.6 Comparison with Chapter 1 1524.7 Three-Level Laser Scheme 1534.8 Four-Level Laser Scheme 1564.9 Pumping Three- and Four-Level Lasers 1574.10 Examples of Three- and Four-Level Lasers 1594.11 Saturation 1614.12 Small-Signal Gain and Saturation 1644.13 Spatial Hole Burning 1674.14 Spectral Hole Burning 1694.15 Summary 172Problems 1735 Laser Oscillation: Power and Frequency 1755.1 Introduction 1755.2 Uniform-Field Approximation 1755.3 Optimal Output Coupling 1785.4 Effect of Spatial Hole Burning 1805.5 Large Output Coupling 1835.6 Measuring Gain and Optimal Output Coupling 1875.7 Inhomogeneously Broadened Media 1915.8 Spectral Hole Burning and the Lamb Dip 1925.9 Frequency Pulling 1945.10 Obtaining Single-Mode Oscillation 1985.11 The Laser Linewidth 2035.12 Polarization and Modulation 2075.13 Frequency Stabilization 2155.14 Laser at Threshold 220Appendix: The Fabry-Pérot Etalon 223Problems 2266 Multimode and Pulsed Lasing 2296.1 Introduction 2296.2 Rate Equations for Intensities and Populations 2296.3 Relaxation Oscillations 2306.4 Q Switching 2336.5 Methods of Q Switching 2366.6 Multimode Laser Oscillation 2376.7 Phase-Locked Oscillators 2396.8 Mode Locking 2426.9 Amplitude-Modulated Mode Locking 2466.10 Frequency-Modulated Mode Locking 2486.11 Methods of Mode Locking 2516.12 Amplification of Short Pulses 2556.13 Amplified Spontaneous Emission 2586.14 Ultrashort Light Pulses 264Appendix: Diffraction of Light by Sound 265Problems 2667 Laser Resonators and Gaussian Beams 2697.1 Introduction 2697.2 The Ray Matrix 2707.3 Resonator Stability 2747.4 The Paraxial Wave Equation 2797.5 Gaussian Beams 2827.6 The ABCD Law for Gaussian Beams 2887.7 Gaussian Beam Modes 2927.8 Hermite–Gaussian and Laguerre–Gaussian Beams 2987.9 Resonators for He–Ne Lasers 3067.10 Diffraction 3097.11 Diffraction by an Aperture 3127.12 Diffraction Theory of Resonators 3177.13 Beam Quality 3207.14 Unstable Resonators for High-Power Lasers 3217.15 Bessel Beams 322Problems 3278 Propagation of Laser Radiation 3318.1 Introduction 3318.2 The Wave Equation for the Electric Field 3328.3 Group Velocity 3368.4 Group Velocity Dispersion 3408.5 Chirping 3518.6 Propagation Modes in Fibers 3558.7 Single-Mode Fibers 3618.8 Birefringence 3658.9 Rayleigh Scattering 3728.10 Atmospheric Turbulence 3778.11 The Coherence Diameter 3798.12 Beam Wander and Spread 3888.13 Intensity Scintillations 3928.14 Remarks 395Problems 3979 Coherence in Atom-Field Interactions 4019.1 Introduction 4019.2 Time-Dependent Schrödinger Equation 4029.3 Two-State Atoms in Sinusoidal Fields 4039.4 Density Matrix and Collisional Relaxation 4089.5 Optical Bloch Equations 4149.6 Maxwell–Bloch Equations 4209.7 Semiclassical Laser Theory 4289.8 Resonant Pulse Propagation 4329.9 Self-Induced Transparency 4389.10 Electromagnetically Induced Transparency 4419.11 Transit-Time Broadening and the Ramsey Effect 4469.12 Summary 451Problems 45210 Introduction to Nonlinear Optics 45710.1 Model for Nonlinear Polarization 45710.2 Nonlinear Susceptibilities 45910.3 Self-Focusing 46410.4 Self-Phase Modulation 46910.5 Second-Harmonic Generation 47110.6 Phase Matching 47510.7 Three-Wave Mixing 48010.8 Parametric Amplification and Oscillation 48210.9 Two-Photon Downconversion 48610.10 Discussion 492Problems 49411 Some Specific Lasers and Amplifiers 49711.1 Introduction 49711.2 Electron-Impact Excitation 49811.3 Excitation Transfer 49911.4 He–Ne Lasers 50211.5 Rate Equation Model of Population Inversion in He–Ne Lasers 50511.6 Radial Gain Variation in He–Ne Laser Tubes 50911.7 CO2 Electric-Discharge Lasers 51311.8 Gas-Dynamic Lasers 51511.9 Chemical Lasers 51611.10 Excimer Lasers 51811.11 Dye Lasers 52111.12 Optically Pumped Solid-State Lasers 52511.13 Ultrashort, Superintense Pulses 53211.14 Fiber Amplifiers and Lasers 53711.15 Remarks 553Appendix: Gain or Absorption Coefficient for Vibrational-Rotational Transitions 554Problems 55812 Photons 56112.1 What is a Photon 56112.2 Photon Polarization: All or Nothing 56212.3 Failures of Classical Theory 56312.4 Wave Interference and Photons 56712.5 Photon Counting 56912.6 The Poisson Distribution 57312.7 Photon Detectors 57512.8 Remarks 585Problems 58613 Coherence 58913.1 Introduction 58913.2 Brightness 58913.3 The Coherence of Light 59213.4 The Mutual Coherence Function 59513.5 Complex Degree Of Coherence 59813.6 Quasi-Monochromatic Fields and Visibility 60113.7 Spatial Coherence of Light From Ordinary Sources 60313.8 Spatial Coherence of Laser Radiation 60813.9 Diffraction of Laser Radiation 61013.10 Coherence and the Michelson Interferometer 61113.11 Temporal Coherence 61313.12 The Photon Degeneracy Factor 61613.13 Orders of Coherence 61913.14 Photon Statistics of Lasers and Thermal Sources 62013.15 Brown–Twiss Correlations 627Problems 63414 Some Applications of Lasers 63714.1 Lidar 63714.2 Adaptive Optics for Astronomy 64814.3 Optical Pumping and Spin-Polarized Atoms 65814.4 Laser Cooling 67114.5 Trapping Atoms with Lasers and Magnetic Fields 68514.6 Bose–Einstein Condensation 69014.7 Applications of Ultrashort Pulses 69714.8 Lasers in Medicine 71814.9 Remarks 728Problems 72915 Diode Lasers and Optical Communications 73515.1 Introduction 73515.2 Diode Lasers 73615.3 Modulation of Diode Lasers 75415.4 Noise Characteristics of Diode Lasers 76015.5 Information and Noise 77415.6 Optical Communications 782Problems 79016 Numerical Methods for Differential Equations 79316.A Fortran Program for Ordinary Differential Equations 79316.B Fortran Program for Plane-Wave Propagation 79616.C Fortran Program for Paraxial Propagation 799Index 809