The first half of the book presents basic concepts, such as the semiconductor physics needed to understand the operation of lasers, p-n junction theory, alloys, heterostructures, quantum nanostructures, theory, waveguides, resonators, filters, and optical processes. The remainder of the book describes various lasers, including double heterostructure, quantum wire, quantum dot, quantum cascade, vertical-cavity surface-emitting, single-mode and tunable, nitride, group IV, and transistor lasers. This textbook equips students to understand the latest progress in the research and development of semiconductor lasers, from research into the benefits of quantum wire and quantum dot lasers to the application of semiconductor lasers in fiber-optic communications. Each chapter incorporates reading lists and references for further study, numerous examples to illustrate the theory, and problems for hands-on exploration.