This third edition of the popular text, while retaining nearly all the material of the previous edition, incorporates material on important new developments in lasers and quantum electronics. The book covers phase-conjugate optics and its myriad applications, the long wavelength quaternary semiconductor laser, and our deepened understanding of the physics of semiconductor lasers - especially that applying to their current modulations and limiting bandwidth, laser arrays and the related concept of supermodes, quantum well semiconductor lasers, the role of phase amplitude coupling in laser noise, and free-electron lasers. In addition, the chapters on laser noise and third-order nonlinear effects have been extensively revised. The previous edition of this book was published in 1975.