Theory of spontaneous emission noise in multisection semiconductor lasers

Calculations of spontaneous emission noise in semiconductor lasers are mainly based on a fundamental theory developed by Henry in 1986, which is useful for simple systems, together with a formulation in terms of transfer matrices by Makino and others, which facilitates application of the theory to more complicated multisection systems. The aim of this review is to present a unified account of this theoretical work in a transparent form intended to encourage its further use in complex systems. The opportunity is taken to strengthen the existing theory by including the effects of differing optical wave vectors in different sections and the consequent reflections at interfaces, which are important in some applications. Sample calculations are presented for a range of systems with one, two, three, and four sections and the predictions compared with other theoretical and experimental results.