Book excerpt: Semiconductor Lasers and Heterojunction LEDs presents an introduction to the subject of semiconductor lasers and heterojunction LEDs. The book reviews relevant basic solid-state and electromagnetic principles; the relevant concepts in solid state physics; and the p-n junctions and heterojunctions. The text also describes stimulated emission and gain; the relevant concepts in electromagnetic field theory; and the modes in laser structures. The relation between electrical and optical properties of laser diodes; epitaxial technology; binary III-V compounds; and diode fabrication are also considered. The book further tackles the heterojunction devices of alloys other than GaAs-AlAs; the devices for special applications; distributed-feedback lasers; and the transient effects in laser diodes. Students taking courses in semiconductor lasers and heterojunction LEDs will find the book useful.