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Laser Fundamentals

Book Description

Laser Fundamentals provides a clear and comprehensive introduction to the physical and engineering principles of laser operation and design. Simple explanations, based throughout on key underlying concepts, lead the reader logically from the basics of laser action to advanced topics in laser physics and engineering. Much new material has been added to this second edition, especially in the areas of solid-state lasers, semiconductor lasers, and laser cavities. This 2004 edition contains a new chapter on laser operation above threshold, including extensive discussion of laser amplifiers. The clear explanations, worked examples, and many homework problems will make this book invaluable to undergraduate and first-year graduate students in science and engineering taking courses on lasers. The summaries of key types of lasers, the use of many unique theoretical descriptions, and the extensive bibliography will also make this a valuable reference work for researchers.

Table of Contents

  1. Coverpage
  2. Laser Fundamentals
  3. Title page
  4. Copyright page
  5. Dedication
  6. Contents
  7. Preface to the Second Edition
  8. Preface to the First Edition
  9. Acknowledgments
  10. 1 INTRODUCTION
    1. OVERVIEW
    2. Introduction
    3. Definition of the Laser
    4. Simplicity of a Laser
    5. Unique Properties of a Laser
    6. The Laser Spectrum and Wavelengths
    7. A Brief History of the Laser
    8. Overview of the Book
  11. SECTION 1. FUNDAMENTAL WAVE PROPERTIES OF LIGHT
    1. 2 WAVE NATURE OF LIGHT – THE INTERACTION OF LIGHT WITH MATERIALS
      1. OVERVIEW
      2. 2.1 Maxwell’s Equations
      3. 2.2 Maxwell’s Wave Equations
        1. Maxwell’s Wave Equations for a Vacuum
        2. Solution of the General Wave Equation – Equivalence of Light and Electromagnetic Radiation
        3. Wave Velocity – Phase and Group Velocities
        4. Generalized Solution of the Wave Equation
        5. Transverse Electromagnetic Waves and Polarized Light
        6. Flow of Electromagnetic Energy
        7. Radiation from a Point Source (Electric Dipole Radiation)
      4. 2.3 Interaction of Electromagnetic Radiation (Light) with Matter
        1. Speed of Light in a Medium
        2. Maxwell’s Equations in a Medium
        3. Application of Maxwell’s Equations to Dielectric Materials – Laser Gain Media
        4. Complex Index of Refraction – Optical Constants
        5. Absorption and Dispersion
        6. Estimating Particle Densities of Materials for Use in the Dispersion Equations
      5. 2.4 Coherence
        1. Temporal Coherence
        2. Spatial Coherence
        3. REFERENCES
        4. PROBLEMS
  12. SECTION 2. FUNDAMENTAL QUANTUM PROPERTIES OF LIGHT
    1. 3 PARTICLE NATURE OF LIGHT – DISCRETE ENERGY LEVELS
      1. OVERVIEW
      2. 3.1 Bohr Theory of the Hydrogen Atom
        1. Historical Development of the Concept of Discrete Energy Levels
        2. Energy Levels of the Hydrogen Atom
        3. Frequency and Wavelength of Emission Lines
        4. Ionization Energies and Energy Levels of Ions
        5. Photons
      3. 3.2 Quantum Theory of Atomic Energy Levels
        1. Wave Nature of Particles
        2. Heisenberg Uncertainty Principle
        3. Wave Theory
        4. Wave Functions
        5. Quantum States
        6. The Schrödinger Wave Equation
        7. Energy and Wave Function for the Ground State of the Hydrogen Atom
        8. Excited States of Hydrogen
        9. Allowed Quantum Numbers for Hydrogen Atom Wave Functions
      4. 3.3 Angular Momentum of Atoms
        1. Orbital Angular Momentum
        2. Spin Angular Momentum
        3. Total Angular Momentum
      5. 3.4 Energy Levels Associated with One-Electron Atoms
        1. Fine Structure of Spectral Lines
        2. Pauli Exclusion Principle
      6. 3.5 Periodic Table of the Elements
        1. Quantum Conditions Associated with Multiple Electrons Attached to Nuclei
        2. Shorthand Notation for Electronic Configurations of Atoms Having More Than One Electron
      7. 3.6 Energy Levels of Multi-Electron Atoms
        1. Energy-Level Designation for Multi-Electron States
        2. Russell–Saunders or LS Coupling – Notation for Energy Levels
        3. Energy Levels Associated with Two Electrons in Unfilled Shells
        4. Rules for Obtaining S, L, and J for LS Coupling
        5. Degeneracy and Statistical Weights
        6. j–j Coupling
        7. Isoelectronic Scaling
        8. REFERENCES
        9. PROBLEMS
    2. 4 RADIATIVE TRANSITIONS AND EMISSION LINEWIDTH
      1. OVERVIEW
      2. 4.1 Decay of Excited States
        1. Radiative Decay of Excited States of Isolated Atoms – Spontaneous Emission
        2. Spontaneous Emission Decay Rate – Radiative Transition Probability
        3. Lifetime of a Radiating Electron – The Electron as a Classical Radiating Harmonic Oscillator
        4. Nonradiative Decay of the Excited States – Collisional Decay
      3. 4.2 Emission Broadening and Linewidth Due to Radiative Decay
        1. Classical Emission Linewidth of a Radiating Electron
        2. Natural Emission Linewidth as Deduced by Quantum Mechanics (Minimum Linewidth)
      4. 4.3 Additional Emission-Broadening Processes
        1. Broadening Due to Nonradiative (Collisional) Decay
        2. Broadening Due to Dephasing Collisions
        3. Amorphous Crystal Broadening
        4. Doppler Broadening in Gases
        5. Voigt Lineshape Profile
        6. Broadening in Gases Due to Isotope Shifts
        7. Comparison of Various Types of Emission Broadening
      5. 4.4 Quantum Mechanical Description of Radiating Atoms
        1. Electric Dipole Radiation
        2. Electric Dipole Matrix Element
        3. Electric Dipole Transition Probability
        4. Oscillator Strength
        5. Selection Rules for Electric Dipole Transitions Involving Atoms with a Single Electron in an Unfilled Subshell
        6. Selection Rules for Radiative Transitions Involving Atoms with More Than One Electron in an Unfilled Subshell
        7. Parity Selection Rule
        8. Inefficient Radiative Transitions – Electric Quadrupole and Other Higher-Order Transitions
        9. REFERENCES
        10. PROBLEMS
    3. 5 ENERGY LEVELS AND RADIATIVE PROPERTIES OF MOLECULES, LIQUIDS, AND SOLIDS
      1. OVERVIEW
      2. 5.1 Molecular Energy Levels and Spectra
        1. Energy Levels of Molecules
        2. Classification of Simple Molecules
        3. Rotational Energy Levels of Linear Molecules
        4. Rotational Energy Levels of Symmetric-Top Molecules
        5. Selection Rules for Rotational Transitions
        6. Vibrational Energy Levels
        7. Selection Rule for Vibrational Transitions
        8. Rotational–Vibrational Transitions
        9. Probabilities of Rotational and Vibrational Transitions
        10. Electronic Energy Levels of Molecules
        11. Electronic Transitions and Associated Selection Rules of Molecules
        12. Emission Linewidth of Molecular Transitions
        13. The Franck–Condon Principle
        14. Excimer Energy Levels
      3. 5.2 Liquid Energy Levels and Their Radiation Properties
        1. Structure of Dye Molecules
        2. Energy Levels of Dye Molecules
        3. Excitation and Emission of Dye Molecules
        4. Detrimental Triplet States of Dye Molecules
      4. 5.3 Energy Levels in Solids – Dielectric Laser Materials
        1. Host Materials
        2. Laser Species – Dopant Ions
        3. Narrow-Linewidth Laser Materials
        4. Broadband Tunable Laser Materials
        5. Broadening Mechanism for Solid-State Lasers
      5. 5.4 Energy Levels in Solids – Semiconductor Laser Materials
        1. Energy Bands in Crystalline Solids
        2. Energy Levels in Periodic Structures
        3. Energy Levels of Conductors, Insulators, and Semiconductors
        4. Excitation and Decay of Excited Energy Levels – Recombination Radiation
        5. Direct and Indirect Bandgap Semiconductors
        6. Electron Distribution Function and Density of States in Semiconductors
        7. Intrinsic Semiconductor Materials
        8. Extrinsic Semiconductor Materials – Doping
        9. p–n Junctions – Recombination Radiation Due to Electrical Excitation
        10. Heterojunction Semiconductor Materials
        11. Quantum Wells
        12. Variation of Bandgap Energy and Radiation Wavelength with Alloy Composition
        13. Recombination Radiation Transition Probability and Linewidth
        14. REFERENCES
        15. PROBLEMS
    4. 6 RADIATION AND THERMAL EQUILIBRIUM –ABSORPTION AND STIMULATED EMISSION
      1. OVERVIEW
      2. 6.1 Equilibrium
        1. Thermal Equilibrium
        2. Thermal Equilibrium via Conduction and Convection
        3. Thermal Equilibrium via Radiation
      3. 6.2 Radiating Bodies
        1. Stefan–Boltzmann Law
        2. Wien’s Law
        3. Irradiance and Radiance
      4. 6.3 Cavity Radiation
        1. Counting the Number of Cavity Modes
        2. Rayleigh–Jeans Formula
        3. Planck’s Law for Cavity Radiation
        4. Relationship between Cavity Radiation and Blackbody Radiation
        5. Wavelength Dependence of Blackbody Emission
      5. 6.4 Absorption and Stimulated Emission
        1. The Principle of Detailed Balance
        2. Absorption and Stimulated Emission Coefficients
        3. REFERENCES
        4. PROBLEMS
  13. SECTION 3. LASER AMPLIFIERS
    1. 7 CONDITIONS FOR PRODUCING A LASER –POPULATION INVERSIONS, GAIN, AND GAIN SATURATION
      1. OVERVIEW
      2. 7.1 Absorption and Gain
        1. Absorption and Gain on a Homogeneously Broadened Radiative Transition (Lorentzian Frequency Distribution)
        2. Gain Coefficient and Stimulated Emission Cross Section for Homogeneous Broadening
        3. Absorption and Gain on an Inhomogeneously Broadened Radiative Transition (Doppler Broadening with a Gaussian Distribution)
        4. Gain Coefficient and Stimulated Emission Cross Section for Doppler Broadening
        5. Statistical Weights and the Gain Equation
        6. Relationship of Gain Coefficient and Stimulated Emission Cross Section to Absorption Coefficient and Absorption Cross Section
      3. 7.2 Population Inversion (Necessary Condition for a Laser)
      4. 7.3 Saturation Intensity (Sufficient Condition for a Laser)
      5. 7.4 Development and Growth of a Laser Beam
        1. Growth of Beam for a Gain Medium with Homogeneous Broadening
        2. Shape or Geometry of Amplifying Medium
        3. Growth of Beam for Doppler Broadening
      6. 7.5 Exponential Growth Factor (Gain)
      7. 7.6 Threshold Requirements for a Laser
        1. Laser with No Mirrors
        2. Laser with One Mirror
        3. Laser with Two Mirrors
        4. REFERENCES
        5. PROBLEMS
    2. 8 LASER OSCILLATION ABOVE THRESHOLD
      1. OVERVIEW
      2. 8.1 Laser Gain Saturation
        1. Rate Equations of the Laser Levels That Include Stimulated Emission
        2. Population Densities of Upper and Lower Laser Levels with Beam Present
        3. Small-Signal Gain Coefficient
        4. Saturation of the Laser Gain above Threshold
      3. 8.2 Laser Beam Growth beyond the Saturation Intensity
        1. Change from Exponential Growth to Linear Growth
        2. Steady-State Laser Intensity
      4. 8.3 Optimization of Laser Output Power
        1. Optimum Output Mirror Transmission
        2. Optimum Laser Output Intensity
        3. Estimating Optimum Laser Output Power
      5. 8.4 Energy Exchange between Upper Laser Level Population and Laser Photons
        1. Decay Time of a Laser Beam within an Optical Cavity
        2. Basic Laser Cavity Rate Equations
        3. Steady-State Solutions below Laser Threshold
        4. Steady-State Operation above Laser Threshold
      6. 8.5 Laser Output Fluctuations
        1. Laser Spiking
        2. Relaxation Oscillations
      7. 8.6 Laser Amplifiers
        1. Basic Amplifier Uses
        2. Propagation of a High-Power, Short-Duration Optical Pulse through an Amplifier
        3. Saturation Energy Fluence
        4. Amplifying Long Laser Pulses
        5. Amplifying Short Laser Pulses
        6. Comparison of Efficient Laser Amplifiers Based upon Fundamental Saturation Limits
        7. Mirror Array and Resonator (Regenerative) Amplifiers
        8. REFERENCES
        9. PROBLEMS
    3. 9 REQUIREMENTS FOR OBTAINING POPULATION INVERSIONS
      1. OVERVIEW
      2. 9.1 Inversions and Two-Level Systems
      3. 9.2 Relative Decay Rates – Radiative versus Collisional
      4. 9.3 Steady-State Inversions in Three- and Four-Level Systems
        1. Three-Level Laser with the Intermediate Level as the Upper Laser Level
        2. Three-Level Laser with the Upper Laser Level as the Highest Level
        3. Four-Level Laser
      5. 9.4 Transient Population Inversions
      6. 9.5 Processes That Inhibit or Destroy Inversions
        1. Radiation Trapping in Atoms and Ions
        2. Electron Collisional Thermalization of the Laser Levels in Atoms and Ions
        3. Comparison of Radiation Trapping and Electron Collisional Mixing in a Gas Laser
        4. Absorption within the Gain Medium
        5. REFERENCES
        6. PROBLEMS
    4. 10 LASER PUMPING REQUIREMENTS AND TECHNIQUES
      1. OVERVIEW
      2. 10.1 Excitation or Pumping Threshold Requirements
      3. 10.2 Pumping Pathways
        1. Excitation by Direct Pumping
        2. Excitation by Indirect Pumping (Pump and Transfer)
        3. Specific Pump-and-Transfer Processes
      4. 10.3 Specific Excitation Parameters Associated with Optical Pumping
        1. Pumping Geometries
        2. Pumping Requirements
        3. A Simplified Optical Pumping Approximation
        4. Transverse Pumping
        5. End Pumping
        6. Diode Pumping of Solid-State Lasers
        7. Characterization of a Laser Gain Medium with Optical Pumping (Slope Efficiency)
      5. 10.4 Specific Excitation Parameters Associated with Particle Pumping
        1. Electron Collisional Pumping
        2. Heavy Particle Pumping
        3. A More Accurate Description of Electron Excitation Rate to a Specific Energy Level in a Gas Discharge
        4. Electrical Pumping of Semiconductors
        5. REFERENCES
        6. PROBLEMS
  14. SECTION 4. LASER RESONATORS
    1. 11 LASER CAVITY MODES
      1. OVERVIEW
      2. 11.1 Introduction
      3. 11.2 Longitudinal Laser Cavity Modes
        1. Fabry–Perot Resonator
        2. Fabry–Perot Cavity Modes
        3. Longitudinal Laser Cavity Modes
        4. Longitudinal Mode Number
        5. Requirements for the Development of Longitudinal Laser Modes
      4. 11.3 Transverse Laser Cavity Modes
        1. Fresnel–Kirchhoff Diffraction Integral Formula
        2. Development of Transverse Modes in a Cavity with Plane-Parallel Mirrors
        3. Transverse Modes Using Curved Mirrors
        4. Transverse Mode Spatial Distributions
        5. Transverse Mode Frequencies
        6. Gaussian-Shaped Transverse Modes within and beyond the Laser Cavity
      5. 11.4 Properties of Laser Modes
        1. Mode Characteristics
        2. Effect of Modes on the Gain Medium Profile
        3. REFERENCES
        4. PROBLEMS
    2. 12 STABLE LASER RESONATORS AND GAUSSIAN BEAMS
      1. OVERVIEW
      2. 12.1 Stable Curved Mirror Cavities
        1. Curved Mirror Cavities
        2. ABCD Matrices
        3. Cavity Stability Criteria
      3. 12.2 Properties of Gaussian Beams
        1. Propagation of a Gaussian Beam
        2. Gaussian Beam Properties of Two-Mirror Laser Cavities
        3. Properties of Specific Two-Mirror Laser Cavities
        4. Mode Volume of a Hermite–Gaussian Mode
      4. 12.3 Properties of Real Laser Beams
      5. 12.4 Propagation of Gaussian Beams Using ABCD Matrices– Complex Beam Parameter
        1. Complex Beam Parameter Applied to a Two-Mirror Laser Cavity
        2. REFERENCES
        3. PROBLEMS
    3. 13 SPECIAL LASER CAVITIES AND CAVITY EFFECTS
      1. OVERVIEW
      2. 13.1 Unstable Resonators
      3. 13.2 Q-Switching
        1. General Description
        2. Theory
        3. Methods of Producing Q-Switching within a Laser Cavity
      4. 13.3 Gain-Switching
      5. 13.4 Mode-Locking
        1. General Description
        2. Theory
        3. Techniques for Producing Mode-Locking
      6. 13.5 Pulse Shortening Techniques
        1. Self-Phase Modulation
        2. Pulse Shortening or Lengthening Using Group Velocity Dispersion
        3. Pulse Compression (Shortening) with Gratings or Prisms
        4. Ultrashort-Pulse Laser and Amplifer System
      7. 13.6 Ring Lasers
        1. Monolithic Unidirectional Single-Mode Nd:YAG Ring Laser
        2. Two-Mirror Ring Laser
      8. 13.7 Complex Beam Parameter Analysis Applied to Multi-Mirror Laser Cavities
        1. Three-Mirror Ring Laser Cavity
        2. Three- or Four-Mirror Focused Cavity
      9. 13.8 Cavities for Producing Spectral Narrowing of Laser Output
        1. Cavity with Additional Fabry–Perot Etalon for Narrow-Frequency Selection
        2. Tunable Cavity
        3. Broadband Tunable cw Ring Lasers
        4. Tunable Cavity for Ultranarrow-Frequency Output
        5. Distributed Feedback (DFB) Lasers
        6. Distributed Bragg Reflection Lasers
      10. 13.9 Laser Cavities Requiring Small-Diameter Gain Regions – Astigmatically Compensated Cavities
      11. 13.10 Waveguide Cavities for Gas Lasers
        1. REFERENCES
        2. PROBLEMS
  15. SECTION 5. SPECIFIC LASER SYSTEMS
    1. 14 LASER SYSTEMS INVOLVING LOW-DENSITY GAIN MEDIA
      1. OVERVIEW
      2. 14.1 Atomic Gas Lasers
        1. Introduction
        2. Helium–Neon Laser
        3. General Description
        4. Laser Structure
        5. Excitation Mechanism
        6. Applications
        7. Argon Ion Laser
        8. General Description
        9. Laser Structure
        10. Excitation Mechanism
        11. Krypton Ion Laser
        12. Applications
        13. Helium–Cadmium Laser
        14. General Description
        15. Laser Structure
        16. Excitation Mechanism
        17. Applications
        18. Copper Vapor Laser
        19. General Description
        20. Laser Structure
        21. Excitation Mechanism
        22. Applications
      3. 14.2 Molecular Gas Lasers
        1. Introduction
        2. Carbon Dioxide Laser
        3. General Description
        4. Laser Structure
        5. Excitation Mechanism
        6. Applications
        7. Excimer Lasers
        8. General Description
        9. Laser Structure
        10. Excitation Mechanism
        11. Applications
        12. Nitrogen Laser
        13. General Description
        14. Laser Structure and Excitation Mechanism
        15. Applications
        16. Far-Infrared Gas Lasers
        17. General Description
        18. Laser Structure
        19. Excitation Mechanism
        20. Applications
        21. Chemical Lasers
        22. General Description
        23. Laser Structure
        24. Excitation Mechanism
        25. Applications
      4. 14.3 X-Ray Plasma Lasers
        1. Introduction
        2. Pumping Energy Requirements
        3. Excitation Mechanism
        4. Optical Cavities
        5. X-Ray Laser Transitions
        6. Applications
      5. 14.4 Free-Electron Lasers
        1. Introduction
        2. Laser Structure
        3. Applications
        4. REFERENCES
    2. 15 LASER SYSTEMS INVOLVING HIGH-DENSITY GAIN MEDIA
      1. OVERVIEW
      2. 15.1 Organic Dye Lasers
        1. Introduction
        2. Laser Structure
        3. Excitation Mechanism
        4. Applications
      3. 15.2 Solid-State Lasers
        1. Introduction
        2. Ruby Laser
        3. General Description
        4. Laser Structure
        5. Excitation Mechanism
        6. Applications
        7. Neodymium YAG and Glass Lasers
        8. General Description
        9. Laser Structure
        10. Excitation Mechanism
        11. Applications
        12. Neodymium: YLF Lasers
        13. General Description
        14. Laser Structure
        15. Excitation Mechanism
        16. Applications
        17. Neodymium: Yttrium Vanadate (Nd:YVO4 Lasers
        18. General Description
        19. Laser Structure
        20. Excitation Mechanism
        21. Applications
        22. Ytterbium:YAG Lasers
        23. General Description
        24. Laser Structure
        25. Excitation Mechanism
        26. Applications
        27. Alexandrite Laser
        28. General Description
        29. Laser Structure
        30. Excitation Mechanism
        31. Applications
        32. Titanium Sapphire Laser
        33. General Description
        34. Laser Structure
        35. Excitation Mechanism
        36. Applications
        37. Chromium LiSAF and LiCAF Lasers
        38. General Description
        39. Laser Structure
        40. Excitation Mechanism
        41. Applications
        42. Fiber Lasers
        43. General Description
        44. Laser Structure
        45. Excitation Mechanism
        46. Applications
        47. Color Center Lasers
        48. General Description
        49. Laser Structure
        50. Excitation Mechanism
        51. Applications
      4. 15.3 Semiconductor Diode Lasers
        1. Introduction
        2. Four Basic Types of Laser Materials
        3. Laser Structure
        4. Frequency Control of Laser Output
        5. Quantum Cascade Lasers
        6. p-Doped Germanium Lasers
        7. Excitation Mechanism
        8. Applications
        9. REFERENCES
  16. SECTION 6. FREQUENCY MULTIPLICATION OF LASER BEAMS
    1. 16 FREQUENCY MULTIPLICATION OF LASERS AND OTHER NONLINEAR OPTICAL EFFECTS
      1. OVERVIEW
      2. 16.1 Wave Propagation in an Anisotropic Crystal
      3. 16.2 Polarization Response of Materials to Light
      4. 16.3 Second-Order Nonlinear Optical Processes
        1. Second Harmonic Generation
        2. Sum and Difference Frequency Generation
        3. Optical Parametric Oscillation
      5. 16.4 Third-Order Nonlinear Optical Processes
        1. Third Harmonic Generation
        2. Intensity-Dependent Refractive Index – Self-Focusing
      6. 16.5 Nonlinear Optical Materials
      7. 16.6 Phase Matching
        1. Description of Phase Matching
        2. Achieving Phase Matching
        3. Types of Phase Matching
      8. 16.7 Saturable Absorption
      9. 16.8 Two-Photon Absorption
      10. 16.9 Stimulated Raman Scattering
      11. 16.10 Harmonic Generation in Gases
        1. REFERENCES
  17. Appendix
  18. Index