This third edition, motivated by the numerous and significant developments in the laser field since the publication of the second edition in 1982, is a substantially revised version of the previous edition. The basic philosophy has, however, remained the same, namely, to provide a broad and unified descrip­ tion of laser behavior at the simplest level that is compatible with a correct physical understanding. The basic organization of the book has also remained the same. The book is therefore aimed at both classroom teaching and self-study by students in electrical engineering, physics, and chemistry who have an interest in understanding the principles of laser operation. The major additions to this edition are the following: 1. New sections dealing with laser types, in particular x-ray lasers and new solid-state lasers, including alexandrite devices, and a greatly extended description of semiconductor lasers. 2. A more extended treatment of laser mode-locking, including new sections on cavity dumping and pulse compression. 3. A more extended and greatly simplified description of the coherence and statistical properties of laser light as opposed to those of conven­ tional light. 4. A greatly extended discussion of the physics of gas discharges. Other important additions include a discussion of some topics from conven­ tional optics (e.g., ray matrix methods, Fabry-Perot interferometers, and multilayer dielectric mirrors), Gaussian beam propagation (e.g., the ABeD law), and the theory of relaxation oscillations and active mode-locking.

1. Introductory Concepts.- 1.1. Spontaneous and Stimulated Emission, Absorption.- 1.2. The Laser Idea.- 1.3. Pumping Schemes.- 1.4. Properties of Laser Beams.- 1.5. Organization of the Book.- Problems.- 2. Interaction of Radiation with Matter.- 2.1. Introduction.- 2.2. Summary of Blackbody Radiation Theory.- 2.3. Absorption and Stimulated Emission.- 2.4. Spontaneous Emission.- 2.5. Nonradiative Decay.- 2.6. Saturation.- 2.7. Decay of a Many-Atom System.- 2.8. Degenerate Levels.- 2.9. Molecular Systems.- Problems.- References.- 3. Pumping Processes.- 3.1. Introduction.- 3.2. Optical Pumping.- 3.3. Electrical Pumping.- Problems.- References.- 4. Passive Optical Resonators.- 4.1. Introduction.- 4.2. Some Topics from Geometrical and Wave Optics.- 4.3. Photon Lifetime and Cavity Q.- 4.4. Plane-Parallel Resonator.- 4.5. Confocal Resonator.- 4.6. Gaussian Beam Propagation and the ABCD Law.- 4.7. Generalized Spherical Resonator.- 4.8. Unstable Resonators.- Problems.- References.- 5. Continuous Wave and Transient Laser Behavior.- 5.1. Introduction.- 5.2. Rate Equations.- 5.3. CW Laser Behavior.- 5.4. Transient Laser Behavior.- 5.5. Concluding Remarks.- Problems.- References.- 6. Types of Lasers.- 6.1. Introduction.- 6.2. Solid-State Lasers.- 6.3. Gas Lasers.- 6.4. Liquid Lasers (Dye Lasers).- 6.5. Chemical Lasers.- 6.6. Semiconductor Lasers.- 6.7. Color-Center Lasers.- 6.8. The Free-Electron Laser.- 6.9. X-Ray Lasers.- 6.10. Summary of Performance Data.- Problems.- References.- 7. Properties of Laser Beams.- 7.1. Introduction.- 7.2. Monochromaticity.- 7.3. Complex Representation of Polychromatic Fields.- 7.4. Statistical Properties of Laser Light and Thermal Light.- 7.5. First-Order Coherence.- 7.6. Directionality.- 7.7. Laser Speckle.- 7.8. Brightness.- 7.9. Comparison BetweenLaser Light and Thermal Light.- 7.10. Higher-Order Coherence.- Problems.- References.- 8. Laser Beam Transformation: Propagation, Amplification, Frequency Conversion, Pulse Compression.- 8.1. Introduction.- 8.2. Transformation in Space: Gaussian Beam Propagation.- 8.3. Transformation in Amplitude: Laser Amplification.- 8.4. Frequency Conversion: Second-Harmonic Generation and Parametric Oscillation.- 8.5. Transformation in Time: Pulse Compression.- Problems.- References.- Appendixes.- A Semiclassical Treatment of the Interaction of Radiation with Matter.- B Space-Dependent Rate Equations.- C Theory of Active Mode Locking for a Homogeneous Line.- D Physical Constants.- Answers to Selected Problems.