Since Fall of 1993, when we completed the manuscript of our book \"Semi­ conductor-Laser Physics\" [W. W. Chow, S. W. Koch, and M. Sargent III (Springer, Berlin, Heidelberg, 1994)] many new and exciting developments have taken place in the world of semiconductor lasers. Novel laser and ampli­ fier structures were developed, and others, for example, the VCSEL (vertical cavity surface emitting laser) and monolithic MOPA (master oscillator power amplifier), made the transition from research and development to production. When investigating some of these systems, we discovered instances when de­ vice performance, and thus design depend critically on details of the gain medium properties, e. g., spectral shape and carrier density dependence of the gain and refractive index. New material systems were also introduced, with optical emission wave­ lengths spanning from the mid-infrared to the ultraviolet. Particularly note­ worthy are laser and light-emitting diodes based on the wide-bandgap group-III nitride and II | Semiconductor-Laser Fundamentals by Weng W. Chow, Hardcover | Indigo Chapters