This chapter discusses the spontaneous emission and optical gain in semiconductor lasers. Spontaneous emission which initiates lasing, optical gain which is essential to achieve lasing, and other processes involved in lasing all use quantum processes at the level of single atoms and electrons within the lasing material. Without simplifications, the physics and mathematics necessary to describe such atomic systems fully is too complicated, certainly for the level of this book. The simplification and approximations must, however, be done in a way which is adapted to the requirements of semiconductor lasers, and the limitations must be understood. The results and implications of quantum physics are discussed here but there are only illustrative outlines of any derivations.

Inspec keywords: quantum optics; spontaneous emission; optical losses; semiconductor lasers

Other keywords: optical gain; loss; semiconductor lasers; spontaneous emission; quantum physics

Subjects: Lasing action in semiconductors