This chapter has set the scene for the operation and fabrication of semiconductor lasers, emphasising why the authors see lasers with grating reflectors as so important. The earliest lasers were examined, showing that a key requirement is to confine the photons and electrons to the same physical region. A geometrical factor Γ, known as the confinement factor, expresses the degree to which this has achieved. The simplest requirements for lasing were put forward so that the reader understands the importance, just as in electronic feedback oscillators, of the round-trip gain and phase in achieving a stable oscillation. The importance of single-mode lasers for modern optical communication along silica fibres over many tens of kilometres was noted. A variety of different types of laser were outlined, and in particular it was observed that to gain a stable single mode the favoured technology is to incorporate some form of Bragg grating. The fundamentals of gratings were introduced and the elements of different laser designs with gratings buried in their structures were presented.

Inspec keywords: optical elements; optical communication equipment; Bragg gratings; optical fabrication; semiconductor lasers; silicon compounds; laser modes; optical fibre communication

Other keywords: stable oscillation; silica fibres; Bragg grating; semiconductor diode laser; laser design; laser fabrication; grating reflectors; single-mode lasers; confinement factor; optical communication; round-trip gain

Subjects: Lasing action in semiconductors